Legumes&Nitrogen Fixation

One of the most significant contributions that legume cover crops make to the soil is the nitrogen (N) they contain. Legume cover crops fix atmospheric N in their plant tissues in a symbiotic or mutually beneficial relationship with rhizobium bacteria. In association with legume roots, the bacteria convert atmospheric N into a form that plants can use. As cover crop biomass decomposes, these nutrients are released for use by cash crops. Farmers should make an effort to understand this complex process because it will help them to select the proper legumes for their cropping plan, calculate when to incorporate cover crops and plant cash crops that follow, and plan fertilizer rates and schedules for those cash crops. Above all, they need to inoculate legume seed before planting with the appropriate Rhizobium species.

The N associated with cover crop biomass undergoes many processes before it is ready to be taken up for use by cash crops. The process begins with biomass N, which is the nitrogen contained in mature cover crops. From 75 to 90 percent of the nitrogen content in legume cover crops is contained in the above ground portions of the plant, with the remaining N in its roots and nodules (Shipley et al., 1992).

When legume or grass cover crops are killed and incorporated into the soil, living microorganisms in the soil go to work to decompose plant residues. The biomass nitrogen is mineralized and converted first to ammonium (NH4) and then to nitrate compounds (NO3) that plant roots can take up and use. The rate of this mineralization process depends largely on the chemical composition of the plant residues that are involved (Clement et al., 1995), and on climatic conditions.

Determining the ratio of carbon to nitrogen (C:N) in the cover crop biomass is the most common way to estimate how quickly biomass N will be mineralized and released for use by cash crops. As a general rule, cover crop residues with C:N ratios lower than 25:1 will release N quickly. In the southeastern U. S., legume cover crops, such as hairy vetch and crimson clover, killed immediately before corn planting generally have C:N ratios of 10:1 to 20:1 (Ranells and Wagger, 1997). Residues with C:N ratios greater than 25:1, such as cereal rye and wheat, decompose more slowly and their N is more slowly released.

A study conducted in 1989 reported that 75 to 80 percent of the biomass N produced by hairy vetch and crimson clover residues was released eight weeks after the cover crops were incorporated into the soil (Wagger, 1989a). This amounted to 71 to 85 pounds of N per acre. However, not all of the released N was taken up by the subsequent corn crop. The corn utilized approximately 50 percent of the N released by both residues. (This value may be con-sidered the N uptake efficiency of corn from legume residues. This value is similar to the N uptake efficiency of corn from inorganic fertilizer sources, such as ammonium nitrate.) The N not taken up by the following crops may still contribute to soil health. Living microbes in the soil may use the nitrogen to support population growth and microbial activity in the soil.

(Source – http://www.cefs.ncsu.edu/resources/organicproductionguide/covercropsfinaljan2009.pdf)

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THE PROTECTIVE EFFECT OF HUMATES

 The increase in ionized radiation and pollution of our environment with herbicides, pesticides, heavy metal compounds, and other toxic mutagenic and carcinogenic substances presents a real danger to living organisms today and their progeny in the future.  Considering the soil pollution by water soluble heavy metal salts in the industrial regions and the long-term excessive use of mineral fertilizer, pesticides, and herbicides in agricultural regions, the crops, particularly vegetables and root-crops, accumulate excess amounts of harmful admixtures.  That is why the creation of pure agricultural technologies is one of the most important tasks of our time.

The protective effect of humates develop in the following directions:

  1. Protection from radioactive irradiation and its consequences.

  2. Protection from harmful admixtures in the atmosphere, soil, and subsoil waters in technogenic districts.

  3. Protection from the consequences of the pesticides and other chemicals used in agriculture.

  4. Protection from unfavorable environmental factors in zones of risky agriculture.

  5. Decrease in content of the nitrates that form when nitrogen fertilizer is used.

     Long-term research showed that humic substances bond many organic and non-organic substances into poorly soluble or insoluble compounds, which prevents their penetration from soil into subsoil waters and growing plants.  It reduces the toxic effect of residual amounts of herbicides, soil polluting radio nuclides, heavy metals, and other harmful substances, as well as radiation and chemical contamination.  Tests showed that even after 50% affection of the plant, its vital functions are completely restored due to the humic preparation effect.  This unique quality of humates is particularly important for the regions in Russia, Byelorussia, and Ukraine that are contiguous to the Chernobyl region.   In the future it could be used to gradually restore contaminated land.

     Modern floriculture is not possible without the use of different chemicals necessary to fight weed, pest, and plant disease.  It is widely known, however, that the use of those chemicals causes a number of negative effects due to their accumulation in the soil.  The infamous fact of DDT accumulation led to its complete banning.  However, DDT appearance still occasionally occurs in crops.  Science proved that sodium humate reduces the damaging effect of the pesticide atrazine by increasing its decomposition, which leads to an increase in the crop capacity of barley.

     The use of humates in zones of risky agriculture is particularly important.  Unfortunately, most territories of Russia can be considered risky.  In the south, the humates help to fight the effect of droughts, since it has been established that the humate treatment of plants ensures their drought resistance.  In Siberia and in the north of Russia, humate treatment can save the plants from late frosts.  In the 1960s, a corn crop was saved by colleagues of Irkutsk university, after an unexpected frost.  In 1996, in the Angarsk region, a strong frost happened on the 19th of June.  The parts of the potato fields that had been treated with the humates were the only undamaged parts.

     Watering soil with a 0.01% humate solution substantially increases the biological activity of the soil and boosts plants resistance against the harmful waste in technogenic zones of chemical and coking industries.  In 1998, in Buryatia, wide scale tests were carried out in treating of saline soils with humates.  The results showed a 214% increase in crops of green herbage, in comparison with the control group.

     The ability of humates to create complexes and their high sorption activity are used to bond the ions of heavy metals in contaminated soil.  That is why increased amount of humates (up to 20-30 kg per hectare) should be used on contaminated soil to ensure the contact and create favorable conditions for forming of complexes.

Humates accelerate water-exchange processes and physiological processes in the cell and participate in oxidation processes at the cell level.  They are conducive to complete assimilation of mineral nutrients in the plant, particularly in abnormal cases, such as saline soils, drought, and other unfavorable environmental factors. 

     An important quality of humates is their ability to decrease the level of nitrate nitrogen in produce.  It was proven by tests on a variety of crops (oats, corn, potatoes, root-crops, lettuce, cucumbers) that humate use decreases the nitrate content by 50% on average.  At the Dnepropetrovsk agricultural institute, field tests were carried out on chernozem soils.  Two crop cultures were tested – corn and barley (as second in the crop rotation).  The herbicide atrazine (4 kg per hectare) was used on the corn.  The results showed that atrazine reduced the growth of weeds by 80% and increased the crop capacity of the corn by 19%-20%.  However, the residual amounts of  the herbicide reduced the crop capacity in barley, which was sown after the corn in crop rotation, by 16%.  The use of sodium humate considerably changed the situation.  It stimulated corn growth and increased the crop capacity by an additional 10%, while the nitrates content (NO3) in the corn of honey and pearl ripeness decreased from 280.1 mg/kg to 199.7 mg/kg in laboratory tests and to 707 mg/kg in field tests.  Barley grown after the corn was noted to improve its germination, growth, and mass gaining, while containing less atrazine and more chlorophyll in the leaves.  The crop capacity of the barley increased by 5.2 centner per hectare, with a total crop capacity reaching 30.9 centner per hectare.  It was also noted that the atrazine content in the final produce decreased by 52%-71%, which made it an ecologically pure produce.

Thus, humic preparations are the reliable protection for plants and crops against harmful admixtures from our environment (soil, subsoil waters, rain-water, and the atmosphere), which is more polluted each day.  They also protect crops from unfavorable environmental factors (drought, ionizing radiation, etc.).

(Source – http://www.teravita.com/Humates/Chapter5.htm)

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Cover and Green Manure Crop Benefits to Soil Quality

Soil Quality and Resource Management

Soil is one of the five resources—soil, water, air, plants, and animals—that NRCS deals with in resource planning. Soil is intimately related to the other four resources, and its condition can either negatively or positively impact the other resources. For example, if the soil surface is functioning adequately, the soil will allow water to infiltrate, thus reducing the potential for erosion and increasing the amount of water stored for plant use. This function of soil affects water quality, plant growth, and the health of animals. In addition, protection of the surface layer resists wind erosion, thus protecting the air resource. Soil Quality is a critical factor in the management of natural resources, and the protection or enhancement of soil quality is the key component of all resource management assistance activities in the NRCS.

What is Soil Quality?

Soil quality is the capacity of a specific kind of soil to function within natural or managed ecosystem boundaries to:

* sustain plant and animal productivity

* maintain or enhance water and  air quality

* support human health and habitation.

As defined, the terms soil quality, soil health, and soil condition are interchangeable.

Effects of Conservation Practices

One of the goals of conservation planning is to consider the effects of conservation practices and systems on soil quality. This is the first technical note in a series on how conservation practices affect soil quality. This technical note is designed to compliment local or regional information on the specific nature of cover crops. Cover and Green Manure Crop Benefits to Soil Quality

1. EROSION – Cover crops increase vegetative and residue cover during periods when erosion energy is high, especially when main crops do not furnish adequate cover. Innovative planting methods such as aerial seeding, interseeding with cyclone seeder, or other equipment may be needed, when main crop harvest, delays conventional planting of cover crops during recommended planting dates.

2. DEPOSITION OF SEDIMENT – Increase of cover reduces upland erosion, which in turn reduces sediment from floodwaters and wind.

3. COMPACTION – Increased biomass, when decomposed, increases organic matter promoting increased microbial activity and aggregation of soil particles. This increases soil porosity and reduces bulk density. Caution: plant cover crops when soils are not wet, or use other methods such as aerial seeding.

4. SOIL AGGREGATION AT THE SURFACE – Aggregate stability will increase with the addition of and the decomposition of organic material by microorganisms.

5. INFILTRATION – Surface cover reduces erosion and run-off. Cover crop root channels and animal activities, such as earthworms, form macropores that increase aggregate stability and improve infiltration. Caution: Macropores can result in an increase in leaching of highly soluble pesticides if a heavy rain occurs immediately after application. However, if only sufficient rainfall occurs to move the pesticide into the surface soil after application, the risks for preferential flow are minimal. Cover crops, especially small grains, utilize excess nitrogen.

6. SOIL CRUSTING – Cover crops will provide cover prior to planting the main crop. If conservation tillage is used, benefits will continue after planting of main crop. Increases of organic matter, improved infiltration, and increased aggregate stability reduce soil crusting.

7. NUTRIENT LOSS OR IMBALANCE – Decomposition of increased biomass provides a slow release of nutrients to the root zone. Legume cover crops fix atmospheric nitrogen and provide nitrogen for the main crop. Legumes utilize a higher amount of phosphorus than grass or small grains. This is useful in animal waste utilization and management. Small grains are useful as catch crops to utilize excess nitrogen, which reduces the potential for nitrogen leaching. Caution: To prevent nutrient tie ups, cover crops should be killed 2-3 weeks prior to planting main crop. Tillage tools are used to kill and bury cover crops in conventional tillage systems. However, with conservation tillage systems, cover crops are killed with chemicals and left on or partially incorporated in the soil.

Caution: Research has shown that incorporation of legume cover crops results in more rapid mineralization. However, due to delay in availability of nitrogen from legume cover crop in conservation tillage, a starter fertilizer should be applied at planting. (Reeves, 1994). An ARS study done in Morris, Minnesota reported dramatically higher carbon losses through C02 remissions under moldboard plow plots as compared to no-till. It was reported that carbon was lost as C02 in 19 days following moldboard plowing of wheat stubble that was equal to the total amount of carbon synthesized into crop residues and roots during the growing season. Long-term studies indicate that up to 2 percent of the residual organic matter in soils are oxidized per year by moldboard plowing” (Schertz and Kemper, 1994).

8. PESTICIDE CARRYOVER – Cover crops reduce run-off resulting in reduced nutrient and pesticide losses from surface runoff and erosion. Increased organic matter improves the environment for soil biological activity that will increase the breakdown of pesticides.

9. ORGANIC MATTER – Decomposition of increased biomass results in more organic matter. Research shows cover crops killed 2-3 weeks prior to planting main crop, results in adequate biomass and reduces the risk of crop losses from soil moisture depletion and tie up of nutrients.

10. BIOLOGICAL ACTIVITY – Cover and green manure crops increase the available food supply for microorganisms resulting in increased biological activity.

11.WEEDS AND PATHOGENS – Increased cover will reduce weeds. Caution: Research has shown reductions in yield are possible in conservation tillage cotton systems following winter cover crops. Reductions are attributed to interference from residue (poor seed/soil contact), cool soil temperatures at planting, increased soil borne pathogens, and increased insects and other pests. Harmful effects from the release of chemical compounds of one plant to another plant (allelopathic) are possible with crops like cotton, but losses can be reduced by killing the cover crop 2-3 weeks prior to planting main crop, and achieving good seed/soil contact with proper seed placement. Cover crops have shown some allelopathic effects on weeds reducing weed populations in conservation tillage (Reeves, 1994).

12. EXCESSIVE WETNESS – Cover and green manure crops may remove excess moisture from wet soils, resulting in reduction of “waterlogging” in poorly drained soils. Caution: transpiration of water can be a detriment in dry climates. Planners should adjust the kill date of cover crops to manage soil water.

 Summary

Cover and Green Manure Crops as a conservation practice can improve soil health. Soil quality benefits such as increased organic matter, biological activity, aggregate stability, infiltration, and nutrient cycling accrue much faster under no-till than other tillage practices that partially incorporate the residue.

One example comes from the Jim Kinsella farming operation near Lexington, Illinois. He reports that organic matter levels have increased from 1.9 percent 6.2 percent after 19 years of continuous no-till (Schertz and Kemper, 1994). Future technical notes will deal with other conservation practice effects on soil quality. The goal of the Soil Quality Institute is to provide this information to field offices to enable them to assist landusers in making wise decisions when managing their natural resources.

(Sources – http://soils.usda.gov/sqi/management/files/sq_atn_1.pdf)

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Comparison of the effect of liquid humic fertilizers

Maize (Zea mays L.) is one of the most highly consumed  crops, and the most important foodstuff after wheat and  rice around the world. The global production of maize is 604 million tons, with a planting area of up to 140 million hectares. Iran produces 2 million tons of maize on 350000 hectares of land. However, the production from hybrid maize seeds in Iran is highly limited (FAO, 2002).

This plant, photosynthetically, is of C4 type and thrives in tropical and semitropical climates (Emam, 2008) and is native for central and southern America (Khodabandeh, 1998). Based on its role in production of grain and forage and providing food for livestock, as well as its industrial use, maize has become an important crop in Iran, as well as in other parts of the world. Expanding the area under  maize cultivation in Iran in order to become self-sufficient is one the most important goal pursued by the government and as a result of implementing programs designed to increase grain maize production over the last few years, this crop has seen a very fast growth in terms of planting area and yield.

Humic substances (HS) are the result of organic decomposition of the natural organic compounds comprising 50 to 90% of the organic matter of peat, lignites, sapropels, as well as of the non-living organic matter of soil and water ecosystems. Authors believe that humic substances can be useful for living creatures in developing organisms (as substrate material or food source, or by enzyme-like activity); as carrier of nutrition; as catalysts of biochemical reactions; and in antioxidant activity (Kulikova et al., 2005). Yang et al. (2004) argued that humic substances can both directly and indirectly

affect the physiological processes of plant growth. Soil organic matter is one of the important indices of soil fertility, since it interacts with many other components of the soil. Soil organic matter is a key component of land ecosystems and it is associated with the basic ecosystem processes for yield and structure(Pizzeghello et al., 2001).

Classically, humic substances are defined as a general group of heterogeneous organic materials which occur naturally and are characterized by yellow through dark colors with high molecular weight (Kulikova et al., 2005).  Shahryari et al. (2011) experienced the effect of two types of humic fertilizers (peat and leonardite derived) on germination and seedling growth of maize genotypes. They reported that interaction of “genotype × solutions (peat and leonardite based humic fertilizers and control) was significant in terms of the length of primary roots.

Application of leonardite based humic fertilizer had a remarkably more effect on relative root growth of Single Cross 794 and ZP 434 than other genotypes. In their experiment, the relation between germination rate and primary roots was positively significant under the condition of application of both types of humic fertilizers; but there was not the same relation for control treatment.

They argued that all types of various humic substances as a biological fertilizer can have an either similar or different effect in early growth stages of maize, as peat and leonardite based fertilizers that they applied produced more seedling roots than control, however the length of coleoptiles was higher in treatment with application of leonardite based humic fertilizer and control than treatment with application of peat based humic fertilizer. They believe that if used in lower quantity these natural fertilizers can have a lot of effect on plant growth.

Hence, in order to recognize how effective they might be, investigations should be considered based on various amounts of humic fertilizers. Finally, they suggested that both peat and leonardite based humic fertilizers could be used to stimulate growth of primary roots in maize which are critical for an optimal establishment of maize in the field.

Gadimov et al. (2009) claimed that humic substances are natural technological products with a miraculous biological effect on crops and concluded that a scientific and practical program is required to make use of this technology in the world, particularly in developing countries. Also, Shahryari et al. (2009) concluded that potassium humate is a miraculous natural material for increasing both quantity and quality of wheat and can be used to produce organic wheat. Thus, application of biological products such as humic fertilizers to provide nutrition for crops can be one of the useful methods to achieve some of the objects of organic crop production.

In addition, Shahryari et al. (2011) studied the response of various maize genotypes against chlorophyll content of the leaves at the presence of the two types of humic fertilizers. In their experiment, solutions (two types of peat and leonardite based liquid humic fertilizers and control) and interaction of “genotypes × solutions” produced significant difference at 1% probability level in terms of chlorophyll content of the leaves. Genotypes such as Single Cross 704 and 505 had the highest index for chlorophyll content when treated by leonardite based humic fertilizer. Peat based humic fertilizer decreased the index for chlorophyll content in genotypes such as 500, OS499 and 505, while leonardite based humic fertilizer decreased the index for chlorophyll content of the leaves in genotypes such as Golden West and Single Cross 704. However, peat based humic fertilizer did not have such an effect on these two maize genotypes.

Meanwhile, leonardite based humic fertilizer had no effect on index for chlorophyll content of leaves in genotypes such as 500, OS499 and 505. Genotypes such as ZP677 and ZP434 produced no response against the application of the two types of humic fertilizers. This study was aimed to compare the effect of liquid peat and leonardite based humic fertilizers on the yield of maize genotypes in Ardabil Region.

MATERIALS AND METHODS

This experiment was conducted at Agriculture Research Station of Islamic Azad University, Ardabil Branch (5 km west of Ardabil City) in 2009 – 2010 cropping year. The region has a semiarid and cold climate, where the temperature during winter season usually drops below zero. This region is located 1350 m above the sea level with longitude and latitude being 48.2°E and 38.15°N, respectively.

Average annual minimum and maximum temperatures are -1.98and 15.18°C, respectively; whereas maximum absolute temperature is 21.8°C; and mean annual precipitation has been reported to be 310.9 mm. The soil of the field was alluvial clay with a pH ranging from 7.8 to 8.2.

Vegetative materials included six maize genotypes prepared from the Agriculture and Natural Resources Research Center of Ardabil Province. The Experiment was conducted as split plot in the basisof randomized complete block design with three replications. The main factor included three conditions (peat based humic fertilizer; leonardite based humic fertilizer; without the application of humic fertilizer) and the sub factor included six maize genotypes (ZP677, Golden west, OS499, ZP434, Ns540 and Single Cross 704). Each of experimental blocks included 3 plots, 320 cm length in rows, with80 cm from each other containing plants at 20 cm distances.

Pretreatment of seeds were done on the basis of 220 ml per 10 L of water to be applied for 1 ton of seeds. Moreover, irrigation was done in flooding manner. Weed-fighting was done both mechanically and manually during all growth stages. Liquid humic fertilizer was prepared and applied based on 400 ml per 50 L of water for 1 ha of maize plantation. The prepared solution was sprayed upon the aerial part of the plants during 5th leaf stage, appearance of reproductive organs, flowering and grain filling stages. All the samples were taken randomly from competitive plants at middle rows. Study traits included grain number per ear row, number of grain row per ear, ear number, weight of 1000 grains, biological yield, vegetative yield and grain yield.

Statistical analysis

Analysis of variance of data and mean comparison of them was done using MSTATC and SPSS programs. Mean comparison was done using Duncan’s multiple range test, at 5% probability level. Due to abnormality of data for ear number and its high coefficient of variation, square root conversion was used to normalize it.

RESULTS AND DISCUSSION

Results from analysis of variance for study traits suggest that there was a significant difference  between experimental conditions in terms of grain yield and biological yield at 1 and 5% probability levels, respectively. In addition, there was a nonsignificant difference between study genotypes in terms of all evaluated traits except for number of grain row per ear and wet biomass at 1% probability level. Furthermore, there was no difference observed between the interaction of genotype and experimental conditions for any trait being studied, and this was in agreement with the report of Shahryari et al. (2009). This means that under study genotypes had the same responses to potassium humate.

Moreover, results from mean comparison of data (Table 2) for studied genotypes indicate that genotype OS499 (110.70 g) had the highest 1000 grain weight, whereas genotype Single Cross (81.20 g) had the lowest 1000 grain weight on average. Based on mean comparison of 1000 grain weight, genotypes OS499 and ZP434 were placed in the same group as NS540, whereas genotype ZP677 was placed in the same group as Golden West. Genotype ZP677 (with a mean value of 15.48) and genotype ZP434 (with a mean value of 13.49) had the highest and lowest values of number per ear, respectively; and genotypes such as Golden West and Single Cross were placed in  the same group as NS540 and had no difference in terms of this trait. Genotype ZP677 (with a mean value of 20.89 ton/ha) and genotype OS499 (with a mean value of 16.93 ton/ha) had the highest and lowest biological yield respectively and genotype OS499 was placed in the same group as ZP434, whereas genotypes such as Golden West and Single Cross were placed in the same group as NS540. Genotype ZP677 (with a mean value of 108.68 ton/ha) was the best among other genotypes in terms of wet biomass, whereas ZP434 (with a mean value of 77.52 ton/ha) had the lowest value for wet biomass. ZP677 was placed in the same group as NS540, whereas genotypes Golden West and OS499 were placed in the same group as ZP434 and had no difference in terms of this trait.

Shahryari and Shamsi (2009a) reported that potassium humate increased the rate of biological yield of wheat from 3.26 to 3.72 g/plant; but it had no effect on harvest index. Also, they found that uses of potassium humate increased grain yield. Results from mean comparison of data  for experimental conditions being studied indicate that application of leonardite based liquid humic fertilizer produced the highest biological yield(21.99 ton/ha on average), whereas no application of humic fertilizer produced the lowest biological yield(14.97 ton/ha on average). In this respect, both types of applied humic fertilizers had similar effects. Application of leonardite based liquid humic fertilizer produced the highest grain yield (7.09 ton/ha on average) among the conditions being studied, whereas under the condition of without humic fertilizer obtained the lowest value(4.07 ton/ha).

Ayas and Gulser (2005) reported that humic acid leads to increased growth and height and subsequently increased biological yield through increasing nitrogen content of the plant. It has also been reported that application of humic acid in nutritional solution led to increased content ofnitrogen within aerial parts and growth of shoots and root of maize (Tan, 2003). In another investigation, the application of humic acid led to increased phosphorus and nitrogen content of bent grass plant and increased the accumulation of dry materials (Mackowiak et al.,2001). Humic acid leads to increased plant yield through positive physiological effects such as impact on metabolism of plant cells and increasing the

concentration of leaf chlorophyll (Naderi et al., 2002).

Also, spraying humic acid on wheat crop increased its yield by 24% (Delfine et al., 2002). In general, the results from this study indicate that the application of leonardite based humic fertilizer increased biological yield by 46.89% compared to control, whereas peat based humic fertilizer increased biological yield by 34.47% compared to control. Seyedbagheri (2008)evaluated commercial humic acid products derived from lignite and leonardite in different cropping systems from 1990 to 2008. The results of those evaluations differed as a result of the source, concentration, processing, quality, types of soils and cropping systems. Under their research, crop yield increased from a minimum of 9.4%to a maximum of 35.8%. However, application of humic fertilizer in this study increased the biological yield by 40.68% on average. Application of leonardite based humic fertilizer increased the grain yield of maize by 74%.

Also, peat based humic fertilizer increased the grain yield by 44.7%. Overall, the mean increase for grain yield under the condition of application of humic fertilizers was as high as 59.45%. Similar results were also presented by Shahryari et al. (2009b) on wheat. They reported increase of grain yield (by 45%) from 2.49 ton/ha to 3.61 ton/ha affected potassium humate derived from sapropel in normal irrigation conditions.

Conclusion

Results from this experiment indicate that the application of liquid humic fertilizer can positively affect the maize yield and some agronomic traits related to it. These desirable effects can be a consequence of its effect on the physiology of the maize. In general, application of humic acid can lessen the need for chemical fertilizers and subsequently reduce environmental pollution, and compared with other chemical and biological fertilizers, they are affordable. Finally, it can be said that application of humic fertilizer not only increases the yield of maize, but also can play a significant role in achieving the goals of sustainable agriculture

( Source http://www.academicjournals.org/ajb/PDF/pdf2012/13Mar/Khaneghah%20et%20al.pdf)

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Agroecological Efficiency Of Composts And Humic Fertilizers

Fertilizing ability of composts

In this connection researches of fertilizing ability of composts from various organic  components, including unconventional, in their influence on change of fertility and soil ecological conditions, and also in agricultural crops productivity and quality are actual.

In Russia researches of efficiency of composts from containing organic matter waste in system soil-plant have been lead in Moscow area on the Central experimental station of the All-Russia scientific research institute of agrochemistry named after D.N. Pryanishnikov.

In microfield experiment on sod-podsolic heavy loamy soil the action of composts from sewage deposits and wood waste (coniferous trees sawdust) on perennial cereal grasses (Dactylis glomerata L.) crop was studied.

The sewage deposits came from Kurianovskaya aeration station of Moscow and differed in storage periods. Compost 1 was prepared from sewage deposits after 10 years remaining on drying beds, compost 2 – from a deposit received directly from the aeration station filter-press in year of a trial establishment.

The deposits composting was carried out with addition of wood sawdust in quantity of 10  % of the mix dry weight. For composts efficiency comparative studying the great cattle manure on straw bedding had been used.

Organic fertilizers – both compost and manure – were applied in the soil in the first year of experiment in two dozes: 10 and 35 t/ha of dry substance. In the next years of researches we studied their aftereffect. Mineral fertilizers in treatment N180P60K100 were applied annually: a full doze of phosphorus and half doze of nitrogen and potassium in spring, second half of nitrogen and potassium doze – after the first hay cutting of perennial grasses.

Initial agrochemical parameters values of soil properties in a layer of 0-20 cm were the following: рHKCl – 4, the amount of organic carbon – 0,8 %, mobile phosphorus and potassium (Kirsanov) accordingly – 118 and 119 mg/kg. Investigated organic fertilizers differed on a chemical compound.

These data show that composts from sewage deposits have high fertilizing ability and contain especially much phosphorus – over 5 %. Manure contains less general phosphorus then deposits, but more potassium and organic substance.

The compost from long storage deposit is more polluted by heavy metals, especially Cd and Zn. The general content of heavy metals in this compostе is two times higher than in compostе from a fresh deposit.

In described experiment the application of various dozes of different composts had influenced ambiguously on agrochemical properties of sod-podsolic soil.

In a year of fertilizers application the maximal рH values – 4,5 and 4,7 have been received accordingly in treatments with use of composts made of filter-press deposit, or new deposit, and manure in the raised dozes (35 t/ha). Mineral fertilizers application had not changed reaction of the soil solution; pH value did not differ from the control treatment.

Next year the insignificant increase of pH value in all treatments with organic fertilizers application was observed. In the fifth year of organic fertilizers aftereffect sewage deposit composts and manure in 35 t/ha dozes had the greatest influence on the soil acidity, the shift of рH was accordingly 0,9 and 0,8 units. In a treatment with mineral fertilizers рH did not change during all years of researches.

Thus, usage of composts on the basis of sewage deposits (both new, and old, i.e. 10-years storage) as fertilizer did not influence negatively on acidity of the soil: in all treatments with application of organic fertilizers the increase of рH value was observed, it can be explained with high amount of calcium in them, which at a gradual mineralization of organic substance passed in a soil solution.

Amount of the soil organic substance in the year of fertilizers application had risen in comparison with the control on treatments with high dozes of both investigated composts, and also on both treatments with manure. In the aftereffect of fertilizers in these treatments the amount of organic substance had also increased, deposit compost from a filter-press had been as good as and traditional manure in this parameter.

In treatments of low composts dozes (10 t/ha of dry weight) from the moment of fertilizers application to the fifth year of aftereffect the decrease of organic substance amount in the soil occurred due to its intensive mineralization.

Annual application of mineral fertilizers reduced the amount of organic substance in soil in comparison with the control during first two years of researches. In the fifth year of aftereffect this parameter was at a level of the control.

It is characteristic that in the year of organic fertilizers entering in all treatments the increase of phosphorus amount in soil was observed. At entering deposit composts of different periods of storage in a doze of 10 t/ha the quantity of phosphorus increased in comparison with a control treatment in 1,3-1,5 times in a year of action.

In process of organic substance mineralization the amount of mobile phosphorus had decreased, that was connected with its consumption by plants. The same law was noted in the treatment with a low doze of manure.

Other character of phosphate regime was observed at increasing of organic fertilizers dozes. At entering a high doze of deposit compost from the filter-press amount of mobile phosphorus in the soil had rose over 3 times in comparison with the control and remained stable in all years of experiment.

Usage of composts from a long storage deposit in the increased doze had led to gradual increase in the amount of phosphorus in soil from 220 mg/kg in a year of entering up to 260 mg/kg in the fi fth year of fertilizers aftereffect. Herewith, amount of phosphorus in soil had lower values than in treatments with compost from the fi lter-press deposit in the same doze.

Amount of mobile potassium in soil had decreased in all treatments with application of organic fertilizers, though higher values of this parameter have been received at entering farmyard manure in a doze of 35 t/ha.

In the lead experiment high efficiency of investigated composts had been established by analysis of perennial cereal grasses productivity. For 7 years of experiment average increase of perennial grasses crop dry weight in relation to the treatment without fertilizers had generated, at entering new and old deposit  composts in a dry weight doze of 10 t/ha, accordingly 27 and 23,3 %, and in the raised doze of 35 t/ha increased up to 75,4 and 49,1 %.

An important agroecological aspect of fertilizers usage is their influence on accumulation of heavy metals in soil and plants. According to experiment, entering of composts from sewage deposits raised the amount of  cadmium in soil in comparison with control (without fertilizers) and treatment with manure. More distinctly this dependence was found out at entering drying beds deposit compost in a high doze – 35 t/ha.

Increase of nickel and lead amount in soil was observed only at entering high doze compost from a new deposit. The amount of copper and zinc in soil increased at entering both composts in both dozes.

Amount of heavy metals in plants depended on a composts doze, however in all treatments it did not exceed standards existing in Russia. It is important to note, that forage value of perennial grasses was enough high, especially in such parameter, as phosphorus.  At entering composts from both kinds of sewage deposits with wood waste the appreciable increase of this important element in grassy forages was marked.

Thus, on the basis of conducted experiment it is possible to conclude, that one of effective ways of city sewage deposits recycling is preparation of composts on their basis with subsequent usage as organic fertilizers in forage production.

Composts, prepared from fermented deposits of city sewage with addition of wood waste (sawdust), were characterized by high fertilizing ability and could be used for the major forage crops, fi rst of all for perennial cereal grasses of intensive usage.

Efficiency of plants growth regulators

In a number of field experiments organized by institute in various regions of Russia efficiency of plants growth regulators in the form of humates was studied. The positive effect of humates application at cultivation of grain crops had been received in Krasnodar Territory.

It had been established, that at processing seeds of a winter wheat by K and Na humates in recommended concentration the production process became more active due to increase of tillering intensity and shares of productive stalks in general haulm stand. In turn it created opportunity to mobilize almost insoluble salts and to transform them in accessible forms for plants. As a result reliable increase of a grain yield had been received in treatments with application humates in relation to the control.

The even greater effect was reached at carrying out of double processing with humates – seeds and plants of winter wheat. Potassium humate turned out to be the most effective among studied growth regulators. At processing only seeds of winter wheat with potassium humates the 13 % increase of a grain yield in relation to the control was achieved, at processing only plants – 11,9 %, and at double application of humates, i.e. at processing  by it both seeds, and plants, it reached 15,5 %.

Conclusion

Thus, generalizing results of researches in the fi eld experiments, it is possible to ascertain,  that application both traditional, and unconventional organic fertilizers by optimization of their dozes and combinations to mineral fertilizers, and also regulators of growth in the form of humates, provides increase of productivity of agricultural crops, improves their quality, promotes preservation of soil fertility and preservation of the environment from pollution.

(Source – http://www.ramiran.net/doc08/RAMIRAN_2008/Merzlaya.pdf)

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Green-manure crops

Green-manure crops – also known as cover crops – play an important part in field-crop production in both agriculture and horticulture.

They can be used to break up pest and disease life cycles, increase soil fertility and nutrient levels, suppress the growth of weeds and improve soil structure.

Green manures can be easily incorporated into a growing system either field-wide or inter-row depending on the crops being grown. They are particularly useful in tree production where plants are in place for a number of years and demand access to good levels of soil nutrients. Lifting and selling trees affects soil structure and green manures can help to stabilize these areas.

Some green manures are best sown in the autumn and can therefore be effectively fitted in between some crops. They can provide good control over any potential nitrate leaching, which can occur on bare soils, particularly over the winter months. For crops such as Sudan grass, tagetes or brassicas, planting should occur when the risk of frost has gone — during late spring and summer months.

1. Grazing rye

For the prevention of nitrate leaching over the winter months, grazing rye is one of the best green manures to sow. It establishes quickly and will grow year-round even in the cooler months. When rye is subsequently incorporated, it is important that the following crop is planted as soon as possible afterwards to maximize the available mineral nitrogen and prevent leaching.

2. Leguminous plants

Legumes, such as lupins and vetch, will produce nitrogen during their growing stages that results in significant levels of soil mineral N available to crops that follow. It is important, therefore, to time the sowing — and subsequent incorporation — of a legume crop to maximize on the amount of nitrogen that is produced.

3. Phacelia

Phacelia has vigorous and highly branched roots that penetrate the soil and help to break it down. It is a valuable green manure for soils with poor structure. Its roots quickly reach their maximum development when the plant is in flower, usually around two months after sowing.

It produces dense foliage that can reach about 45cm in height, which can protect the soil from the impact of rain and smother weeds. Damage by frost (at -5°C or below) results in foliage collapse that then provides good soil cover — particularly useful on capped soils.

As phacelia decomposes, it releases high levels of accessible forms of minerals, particularly phosphorus, calcium and magnesium, which are then available for the following crop. When incorporated into the soil, the foliage and stems quickly release high levels of nitrogen one or two months after decomposition begins. Planted in autumn, it can help to reduce nitrate leaching in mild winters, retaining up to as much as 50 per cent of nitrogen produced by cultivation.

The bright-blue flowers attract hoverflies, which will predate on aphids on nearby crops. Bees are also attracted to this crop. It can be sown on all soil types — March to September — and grows in most climate ranges in the UK.

4. Sudan grass (Sorghum spp.)

This crop is heat-tolerant, drought-resistant and can grow in a wide range of soils. It produces a deep, penetrating network of roots throughout its life. This can be increased further by cutting the top growth part-way through the growing season.

Sudan grass does not produce flowers but forms a large, dense canopy layer that suppresses weed growth and prevents erosion. Soil nematode populations and Verticillium wilt propagules may be reduced in an infested soil after growing this crop. The plant produces a harmless glucoside called dhurrin, which when the plant is damaged by cutting, frost or drought is converted into hydrogen cyanide.

During growth, roots will also exude dhurrin, providing some initial control. Young tissue produces the greater amount of hydrogen cyanide but it must be incorporated and sealed immediately after flail-cutting for maximum effect.

5. Marigolds (Tagetes spp.)

Tagetes species have the added benefit of being able to produce flowers and can be sown in between crops such as field-grown trees. The plant roots contain naturally-occurring broad-spectrum biocides that act as nematicides, fungicides and bacteriocides. Levels of organic matter incorporated into soils depend on the variety used.

6. Mustards

There are several varieties on the market but the Caliente brand from Plant Solutions has shown significant promise abroad and in the UK. A wide range of soil diseases can be reduced including Verticillium wilt, silver scurf, Sclerotinia and nematode damage, onion pink root, Sclerotinia minor in lettuce, Pythium in carrots, Fusarium in tomatoes and Sclerotinia, Pythium and Fusarium in beans. A significant amount of organic matter is also produced that can be incorporated into the soil to release a similar product to the Sudan grass.

Flowering time and incorporation depend on variety and sowing date. A period of 21 days after incorporation is recommended prior to planting a new crop to prevent the risk of poor seed germination.

Caliente Brand Mustard 119 is a good all-round variety for sowing in spring or late summer for quick crops or mid autumn for overwintered crops in milder parts of the UK.

Caliente Brand Mustard 99 provides the best biofumigant action from its high glucosinolate levels (30 per cent more than 119). Requires good growing conditions including additional fertiliser and irrigation in dry periods.

Caliente Brand Mustard 61 is a large-leaved variety producing high levels of biomass under ideal conditions. Requires a longer season to grow and is the slowest to flower. It needs good warm weather and irrigation in dry conditions, so is suitable for midsummer UK growing.

7. Nemat (Eruca sativa)

A white-flowered rocket (pictured) that has shown similar biofumigant properties to the mustards. It can also be used as a trap crop for various nematodes including some root knot and cyst species. The roots contain the highest glucosinolate levels.

The dense foliage produced will provide a good level of biomass for incorporation. Mowing the crop before it flowers can extend the growing — and trapping — period. It is tolerant of a range of temperatures, can take a light frost and is relatively drought-tolerant once established.

(Source  – http://www.hortweek.com/News/1181031/Green-manure-crops/)

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Nitrogen Use Efficiency and Recovery from N Fertilizer under Rice-Based Cropping Systems

Nitrogen fertilization is widely adopted to enhance grain production and improve nitrogen utilization in rice all over the world. Rice is produced under both upland and lowland ecosystems with about 76% of the global rice produced from irrigated-lowland rice systems. Improved nitrogen use efficiency, particularly for N, is an important goal in cropping system development. Determination of N use efficiency in cereal based agro-ecosystems enabled broad assessment of agronomic management and environmental factors related to N use, Grain yield and N accumulation, N in aboveground, N harvest index, and grain N accumulation are the key indicators of N use efficiency. Soil N and biological nitrogen fixation (BNF) by associated organisms are major sources of N for lowland rice. Soil organic N is continually lost through plant removal, leaching, denitrification and ammonia volatilization. An additional concern is that the capacity of soil to supply N may decline with continuous intensive rice cropping under wetland conditions, unless it is replenished by biological N fixation. More than 50% of the N used by flooded rice receiving fertilizer N is derived from the combination of soil organic N and BNF by free-living and rice plant-associated bacteria. The remaining N requirement is normally met with fertilizer. Legumes are used commonly in agricultural systems as a source of N for subsequent crops and for maintaining soil N levels and reducing energy requirements by adding significant amounts of N to the soil (Entz et al., 2002). Reducing fertilizer N use in lowland rice systems while maintaining the native soil N resource and enhancing crop N output is desirable from both environmental and economic perspectives. This may be possible by obtaining N on the land through legume BNF, minimizing soil N losses, and by improved recycling of N through plant residues. Sustainable cropping systems are essential for agronomic, economic, and environmental reasons. Thus the management of indigenous soil N and N derived in situ through legume BNF poses potentials for enhancing the N nutrition and N use efficiency of crops and total N output from a lowland rice-based cropping system. The ability of legumes to fix N and their residual impact on soil N status has long been recognized, but many farmers also realize that the accrued N benefits will vary between different legume systems. To date the fate of N in green manure and productivity of dual-purpose dry season legumes and their effects on soil N dynamics and their contributions to the yield and N uptake of the following rice crop has been studied only a few instances. Cropping systems that include legumes have the potential for contributing N to following crops and may moderate NO3 levels in the soil to avoid potential for NO3 leaching. Grain and forage legumes grown in dry season and their residues could supplement some sort of N source for succeeding crop. Broad bean is used as a winter or spring cover crop, green manure, vegetable and an expensive food legume. It is capable of producing large amounts of dry matter and accumulating large quantities of nitrogen (N) and fixed substantial quantities of N for subsequent crops. Several international studies suggest vetches are efficient N-fixers and accumulate large amounts of N during growth. Hairy vetch not only supply N fixed by leguminous bacteria to the soil but also inhibits the weed growth and decrease the density of insect pest by allelopathy. Broad bean and hairy vetch are used in the rice-based cropping systems in Japan, but scientific information is very little. Therefore the present study was undertaken to the following objectives: (i) to determine N accumulation and quantify N fixed by broad bean and hairy vetches using the 15N natural abundance and N difference method (ii) to quantify N recoveries from rice after broad bean and hairy vetch systems and inorganic fertilizer sources using 15N labeled fertilizer and (iii) to determine the amount of fertilizer N required to optimize rice yield when broad bean and hairy vetch are included in the system…<more>

(Source– http://www.cropj.com/motior_3_6_2009_336_351.pdf )

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