Winter, spring options for winter annual weed control in wheat

There are several herbicide options for controlling winter annual broadleaf weeds in wheat. Generally, fall applications will provide the best control of winter annual weeds with any herbicide, as long as the weeds have emerged. The majority of winter annual weeds usually will emerge in the fall, although you can still have some emergence in the spring, especially if precipitation after planting is limited in the fall. However, winter annual weeds that emerge in the spring often are not very competitive with the crop, at least in years when there is a decent crop.

Some herbicides can work well even when applied during the dormant part of the season, while others perform best if the crop and weeds are actively growing. The key difference relates to the degree of soil activity provided by the herbicide. Herbicides that have good residual activity, such as Glean, Finesse, Amber and Rave can generally be applied in January and February when plants aren’t   actively growing and still provide good weed control, assuming you have proper conditions for the application. Most other herbicides, which depend more on foliar uptake, will not work nearly as well during the mid-winter months, when the wheat and weeds aren’t actively growing, as compared to a fall or early spring application. This might be especially true this year due to the colder temperatures and dieback of foliage this winter.

Spring herbicide applications can be effective for winter annual broadleaf weed control as well, but timing and weather conditions are critical to achieve good control. Spring applications generally are most effective on winter annual broadleaf weeds soon after green-up when weeds are still in the rosette stage of growth, and during periods of mild weather. Once weeds begin to bolt and wheat starts to develop more canopy, herbicide performance often decreases dramatically.

Spring-germinating summer annual weeds often are not a serious problem for a good healthy stand of wheat coming out of the winter. However, if wheat stands are thin and the wheat is late developing, early-germinating summer annual weeds such as kochia, Russian thistle and wild buckwheat might be a problem, especially at harvest time. Many of these weeds can be controlled by residual herbicides applied earlier in the season. If not, post-emergence treatments should be applied soon after weed emergence and before the wheat gets too large in order to get good spray coverage and achieve the best results.

Another important consideration with herbicide application timing is crop tolerance at different application timings. For example, 2,4-D should not be applied in the fall or until wheat is fully tillered in the spring. On the other hand, any herbicide containing dicamba can be applied after wheat has two leaves, but should not be applied once the wheat gets close to jointing in the spring. Herbicides containing dicamba include Banvel, Clarity, Rave, Pulsar, Agility SG and several generic dicamba products. Dicamba is one of the most effective herbicides for kochia control, but if the wheat is starting to joint, it shouldn’t be applied. At that point, Starane Ultra or other herbicides containing fluroxypyr would be a safer option and could still provide good kochia control. Most other broadleaf herbicides in wheat can be sprayed from the time wheat starts tillering until the early jointing stages of growth, but the label should always be consulted to confirm the recommended treatment stages before application.

The best advice regarding crop safety with herbicide-fertilizer combinations and application timing is to follow the label guidelines. We generally see minimal crop injury and no yield loss from top-dress fertilizer/residual herbicide applications during the winter months. However, these combinations can often cause considerable burn to the wheat if applied when the crop is actively growing and with warmer weather. The foliar burn is generally temporary in nature, and the wheat usually will recover if good growing conditions persist.

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Wheat varieties hard or soft, red or white, winter or spring?

After eons of farmers and then scientists isolating and encouraging the genetic development of more “user friendly” characteristics, there are over 30,000 varieties of wheat today, each with its own merits. Most simply, we can classify current wheat varieties as some combination of each of the following: hard or soft, red or white, winter or spring.

Hard wheat

 has a higher protein content than soft wheat and thus produces more gluten, the elastic component of a dough that can capture and hold carbon dioxide (CO2). Therefore, hard wheat is critical for yeast-leavened baked goods, but is also appropriate for a wide range of baking.Hard winter wheat

is planted in the fall, mainly in Texas, Oklahoma, Kansas, Nebraska, and other prairie states. It grows until it’s about five inches tall, and then with the onset of winter and cold weather, it becomes dormant under snow cover, and continues growing the following spring. It’s harvested in late spring and early summer. The protein content of hard winter wheat ranges between 10–12%.Hard spring wheat

grows predominantly in the Dakotas, Minnesota, and Montana, as well as in Canada, where the climate is more severe. It’s planted in the spring and harvested in late summer and early fall. Generally, the farther north you go, the more spring wheat you’ll find and the greater the levels of protein—generally 12–14%.Soft wheat

has a larger percentage of carbohydrates and thus less gluten-forming protein. Soft wheat can be red or white, and is almost always winter wheat. Soft winter wheat is grown primarily east of the Mississippi, from Missouri and Illinois east to Virginia and the Carolinas in the South and New York in the North. There are also important crops of soft white wheat in the Pacific Northwest. Soft wheat is used to make cake and pastry flour.

the color of wheat

The color of wheat relates to pigments found primarily in the bran. Both hard and soft wheat can be either red or white. White wheat varieties simply lack the pigment that gives red wheat its dark color.

Hard red winter wheat

 has ample protein content to yield the necessary amounts of gluten, the elastic component of a dough that can capture and hold carbon dioxide (the gas produced by yeast that raises your dough) for most yeast bread baking, yet is mellow enough to use in other baked goods including muffins and scones. Planted in the fall in the prairie states, hard red winter wheat lies dormant under snow cover during the winter and continues growing until harvest in late spring. It gets its red color from pigmentation in the bran layer of the wheat berry.Hard white spring wheat

has a high protein content and thus is good at producing gluten, the elastic component of a dough that can capture and hold carbon dioxide (the gas produced by yeast that raises your dough). Unlike red wheat, white wheat lacks some of the pigmentation in the bran layer of the wheat berry; since that pigment carries an astringent flavor, white wheat is lighter in both color and flavor. It’s planted in spring and harvested in late fall/early winter.Hard red spring wheat

 is typically higher in protein content than hard red winter wheat and thus is very good at producing gluten, the elastic component of a dough that can capture and hold carbon dioxide (the gas produced by yeast that raises your dough), making it ideal for breads, rolls, and pizza. Planted in the spring in the Dakotas, Minnesota, Montana, and Canada, hard red spring wheat is harvested in late summer and early fall. It gets its red color from pigmentation in the bran layer of the wheat berry.
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Crop responses to climatic variation

Crop responses to climatic variability and extremes

The yield productivity of many crops has risen over the past 40 years. Rates of yield increase in Europe have ranged from 0.8% (oats; Avena sativa) to 2.6% (triticale; Triticosecale) per year (Ewert et al. 2005). Rates of increase in wheat yields differ between European countries, but regional variation about the linear trend is less clear. More southerly European countries have lower rates of wheat yield increase than more northern ones, suggesting that weather factors such as temperature and precipitation play a more determining role in yield than in the north.. The fact that there have been lower rates of increase in yields in areas of Europe with more extreme conditions and that deviations from a linear trend have increased, points to the conclusion that warming since the start of the 1990s (Schär et al. 2004) has started to affect European wheat yields.

For crops, both changes in the mean and variability of temperature can affect crop processes, but not necessarily the same processes. Some crop processes, mostly related to growth such as photosynthesis and respiration, show continuous and mainly nonlinear changes in their rates as temperature increases. Rates of development and progression through a crop life cycle more often show linear responses to temperature. Both growth and developmental processes show temperature optima, whereby process rates increase over a range but thereafter flatten and decrease. For example, the light-saturated photosynthesis rate of C3 crops such as wheat and rice is at a maximum for temperatures from about 20–32 °C; total crop respiration, the sum of the growth and maintenance components, shows a steep nonlinear increase for temperatures from 15–40 °C followed by a rapid and nearly linear decline. The threshold developmental responses of crops to temperature are often well defined, changing direction over a narrow temperature range, as will be seen later.

An experimental study of climatic variability and wheat

Physiological responses to temperature changes in plants may occur at short or long time-scales (Wollenweber et al. 2003). Rapid changes in enzymatic reactions caused by differential thermosensitivity of various enzymes can deplete or result in accumulation of key metabolites. In addition, short-term effects involving altered gene expression, such as heat-shock protein synthesis, are likely to occur. Longer-term responses include alterations in the rate of carbon dioxide (CO2) assimilation and electron transport per unit leaf area, and impaired cell anaplerotic carbon metabolism, sucrose synthesis and carbon (C) and nitrogen (N) partitioning within and between organs (Jagtap et al. 1998). Altered carbon availability brought about by these events will affect uptake, transport and assimilation of other nutrients, disturb lipid metabolism and injure cell membranes (Maheswari et al. 1999), resulting in changes in growth rates and grain yield (Al Khatib & Paulsen 1999). However, temperature responses for specific physiological processes do not always relate directly to growth, because the latter is an integration of the effects of temperature on total metabolism (Bowes 1991).

The developmental stage of the crop exposed to increased temperatures has an important effect on the damage experienced by the plant (Slafer & Rawson 1995), but experimental studies of the effects of temperature variability on crop productivity are rare. This is mainly because of the difficulties in establishing and maintaining a temperature regime where a mean climatic value can be held constant between treatments that vary the amplitude of temperature (Moot et al. 1996). A solution to this is to examine the effects of extreme conditions at particular developmental stages (Ferris et al. 1998), in which the extreme conditions are defined with reference to literature (Porter & Gawith 1999). Wollenweber et al. (2003) tested the null hypothesis that wheat plants react to two separate periods of high temperature as if they were independent of each other. The chosen stages were the double-ridge stage of the apical meristem, which is close in time to the transition from vegetative to reproductive development of the apical meristem, and anthesis when extreme temperature events interfere with the development of fertile grains, as meiosis and pollen growth are affected (Wallwork et al. 1998). The experimental design, and the extreme temperature conditions were defined as a heat period of eight days of 25 °C at the double-ridge stage and/or a heat event of 35 °C at anthesis. Biomass accumulation, photosynthesis and the components of grain yield were analysed. While a high temperature event of 25 °C at the double-ridge stage is not a stress event sensu strictu for wheat, reproductive spikelet initiation can be impaired (Porter & Gawith 1999) and 25 °C is 13 °C higher than mean daily temperatures measured over 30 years at the experimental site in Denmark.

Grain yields were significantly lower in the treatments with high temperatures at anthesis and at both developmental stages. The major yield component reduced by the treatments was the harvest index; that is, the proportion of total dry matter invested in grain. The harvest index was lower in plants experiencing heat periods because their grain number per plant was reduced by 60% . However, there was no significant difference in the grain yield of plants as between those warmed at anthesis and those at double ridges and anthesis, meaning that the plants experienced the warming periods as independent and that critical temperatures of 35 °C for a short-period around anthesis had severe yield reducing effects. The conclusions from such results for climate change are that yield damaging weather signals for cereals such as wheat are in the form of absolute temperature thresholds, are linked to particular developmental stages and can be effective over short time-periods. This means that yield damage estimates of coupled crop–climate models need to have a maximum temporal resolution of a few days and incorporate models of crop phenology to deal with the overlap between such extreme weather events and crop sensitivity to them.

In contrast to the effects on developmentally linked processes, no significant differences were seen in the relation between light-saturated photosynthesis and leaf internal CO2 concentration for the heat treatments. A heat episode during DR increased the rates of light-saturated photosynthesis (Asat) in green leaves slightly. There were no significant differences in Asat and carboxylation efficiency, reinforcing the conclusion that the principal effects of high temperatures are on developmental processes, such as flowering and the formation of sinks for assimilated carbon, which in itself either is stimulated or is little affected by short-term warming. An extreme heat episode during vegetative development does not seem subsequently to affect the growth and developmental response of wheat to a second heat event at anthesis, and high-temperature episodes seem to operate independently of each other.

Crop temperature thresholds

In addition to the linear and nonlinear responses of crop growth and development processes described above, short-term extreme temperatures can have large yield-reducing effects on major crops. These effects were reviewed for wheat by Porter & Gawith (1999) and, for annual crops in general, by Wheeler et al. (2000). A general point arising from these reviews were that temperature thresholds are well defined as absolute threshold temperatures above which particularly the formation of reproductive sinks, such as seeds and fruits, are adversely affected, as seen in the experiment described above.

The largest standard error found was 5.0 °C for the maximum temperature for root growth, followed by 3.7 °C for the optimum temperature of root growth. Others, such as the base and optimum temperatures for shoot growth, the optimum temperature for leaf initiation and base temperature for anthesis have standard errors of less than 0.5 °C. Thus, the consensus is that functionally important temperatures for wheat are conservative when compared between different studies.

A crop that is important in the developing world is groundnut (Arachis hypogaea L.). This is an important food crop of the semi-arid tropics, including Africa, and can experience temperatures above 40 °C for periods during the growing season (Vara Prasad et al. 2000). The harvestable seeds of groundnut are formed following flowering and fruiting periods. When exposed for short-periods at high temperatures of up to 42 °C just after flowering, a clear relationship between fruit set and mean floral temperature was found (Vara Prasad et al. 2000). From between 32 and 36 °C and up to 42 °C, the percentage fruit set fell from 50% of flowers to zero and the decline in rate was linear, illustrating once more the sharpness of response of crop plants to temperatures between 30 and 35 °C during the flowering and fruiting periods.

Various literature sources have identified similar patterns for other important food crops such as maize and rice. For example, maize exhibits reduced pollen viability for temperatures above 36 °C; rice grain sterility is brought on by temperatures in the mid-30s °C and similar temperatures can lead to a reverse of the vernalizing effects of cold temperatures in wheat. What is perhaps more surprising than the consistent damaging effects of high temperatures in food crops is that cold-blooded animals also exhibit threshold temperature responses for various activities. As with plants, the lethal limits are the widest, followed by activity limits, development and growth with the reproductive limits being the narrowest from 24 to 30 °C, the upper value interestingly close to the limits seen for many crop plants, but this is presumably a coincidence. It would be very useful to have equivalent diagrams for the major crop plants in the world and thereby provide specific quantitative information on the probability and consequences, in other words the risk, from crop damaging climate change at the regional or country level. This would further be the linkage between crop physiology, crop agronomy and climate science (Porter 2005).

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Spectrum of the Pests on Cereal Crops and Influence of Soil Fertilisation

Different biotic factors such as predators, parasitoids and different pathogens affect the pests of cereals. Also affecting them are the abiotic factors temperature, rainfall, humidity, wind and sunshine (Sehgal 2006).

Climatically, the slowly rising temperatures are very important for the spectrum of pests. Winters are shorter, temperatures below freezing occur on average on fewer days than before and the soil is frozen to shallower depths. This results in pest species occurring at northern localities, whereas  before they had appeared only at lower latitudes (Gallo 2002).

Past research has shown that fertilisation of the soil affects a pest’s presence. Fertilisation had a positive effect on the crops, especially on their height and density, leading to a higher presence of pests. Stimulation of plant growth and development is the main goal of fertilisation. Regeneration of the plants is important if the pests damage the plants.

Organic fertilisation is very important because it suppresses the plant pathogens and also affects the frequency of pests (Sokolov 1991). Healthy vital plants are preferred by many pests on cereal species (Price 1991; Breton & Addicott 1992; Preszler & Price 1995).

The variety of a crop can also affect the occurrence of a pest. Ovipositonal behaviour, variability of eggs, growth and survival of the young larvae of the cereal leaf beetle were adversely affected by the trichome density on wheat leaves(Schillinger& Gallun 1968). Eggs per plant and larval survival decreased asthe length and density of trichomes increased (Hoxie et al. 1975).

Differences in the yields between the varieties and the year’s volume in the same level of the damage were detected. Later varieties were better able to compensate for the damage than earlier varieties in years with similar weather (Šedivý 1995).

Influence of a new farming system on pests and their natural enemies has began a few years ago (Khamraev 1990; Pfiffner 1990; Xie et al. 1995).

Material And Methods

Our research was conducted at Nitra-Dolná Malanta. The whole area (530 m2 ) used in the tree-year experiment (2004–2006) was split into 8 identical plots (each of 60 m2 ) separated by a 1 m belt where soil was superficially cultivated.

Pests were monitored on spring barley cvs. Jubilant (2004) and Annabell (2005, 2006), and on winter wheat cvs. Samanta (2004) and Solara (2005, 2006). At every sampling date 5 m2 of winter wheat and spring barley was swept using a standard sweeping net. Collecting began at the shooting phase, ended at wax ripeness of cereal crops and was done every 7–10 days, depending on the weather.

The insects collected from each crop were determined. Spiders were removed from samples, and aphids were excluded from the analysis at they were used in another study. We determined the influence of fertilisation and nutrition on the pests in the control variants(0) without fertilisation, and variants fertilised (F) with manure (40 t/ha) + fertilisers(winter wheat for 7 t yield: 70 kg N/ha, 30 kg P/ha, 0 kg K/ha; spring barley for 6 t yield: 30 kg N/ha, 30 kg P/ha, 0 kgK/ha).Climatic data were provided by the meteorological station nearthe Slovak University of Agriculture at Nitra, Slovak Republic. All results were evaluated with mathematical-statistic analysis Statgraphics.

Results and disscusion

Spring barley

In 2004, insects were first collected in the last decade of April; during next 2 years collecting began in the first decade of May. The beginning of collecting was affected by the weather during the years. The last insects occurred in the first decade of July. The date of the maximum occurrence of the pests changed during the research. Maximum of the insects was recorded between the May and (307pieces/5m2 ) a June (357pieces/5 m2) in 2004.The abundance of the insects decreased at about 45% after this time. The lowest abundance of insects was in May during the low average day temperatures. Maximum occurrence of total insects was in the last decade of May and in the first decade of June. Our results are similar to results of Gallo (2002), who maximum of the insects recorded in the first decade of May and June. Only one maximum of occurrence was recorded in 2004.Only one maximum was recorded in 2006 too. Two maximum of occurrence were recorded in 2005.

The maximum occurrence of the pests(89 pieces/5 m2 ) was recorded on spring barley at the beginning of the June in 2006. Phyllotreta (18 pieces/5m2 ), Thysanoptera (21 pieces per 5 m2 ) and Oulema gallaeciana (12 pieces/5 m2 )were dominant pests. Other authors presented the same spectrum of dominant pests (Gallo & Pekár 1999). There were no insects recorded on spring barley in July. The spring barley was in the wax ripeness. Abundance of the natural enemies increased at about 28% in the second decade of June but it decreased compared to the first decade about 80% by the end of month.

Different occurrence of the insectswasin20.The maximum of the collected insects (102 pieces per 5 m2 ) was at the end of June. The total number of insects 114 pieces/5 m2 was recorded in the first decade of June and from which there were 84pieces/5m2 pests. There was recorded maximum amount of natural enemies(14 pieces/5 m ). The second maximum of total insects(262 pieces/5m2) and also pests (177 pieces/5 m2 ) was recorded in the last decade of May. The collecting was realised in the first decade of July in 2005. The amount of the pests decreased at about 34% and natural enemies at about 63% in 2005. During the three years study the effect of fertilisation was monitored in the spring barley (Figure 2).According the results, more pests were recorded on fertilised variants.The more pests were recorded on the non-fertilised variants only in 2004. Our results are different from results of Samsonova (1991), according which the fertilisation had no effect on the occurrence of the pests. Levine (1993) results are similar to ours.

The occurrence of the insects had the similar character on fertilised and non-fertilised variants. The relation between fertilised and non-fertilised variants had not statistically significant difference

Total amount of collected insects on spring barley had increasing tendency during the all years. Total amount of the pests was 1630 pieces per 5 m2 collected during the entire period in2004.

This number decreased at about 55%in 2006.The amount of natural enemies had also decreasing tendency. While 66 pieces/5 m2 of natural enemies were collected in 2004, this amount decreased at about 67% in 2006 (Table 1). This drop could be caused by higher temperature during the year 2006.

According to Honěk (2003), McAvoy and Kok (2004), the temperature influenced occurrence and development of the pests in crops. Difference between the year 2004 and the other years 2005 and 2006 was statistically evident.

Winter wheat

The beginning of collecting was realised in the second decade of April and the last collections were realised in the first decade of July during the years 2004–2006.The last collection was realised atthe end of June in 2006.The beginning was affected by the weather during the years.

The first maximum of the pests was recorded in the last decade of April(247 pieces/5 m2 )in 2004. The second maximum was recorded at the end of May (350 pieces/5 m2 ) and at the beginning of June(285 pieces/5 m2 ).Thrips (44 pieces/5 m2 ) had the highest occurrence. The cereal leaf beetle was recorded at most in April. It was found occasionally in the crops in the next time. Aphids(58 pieces/5 m2) were recorded in the crops in June. Maximum occurrence of the pests was recorded in the last decade of May (284 pieces/5 m2 ), the second one in the second decade of June (314 pieces/5 m2 ) in 2005. There were trips (26 pieces/5 m2 ) and flea beetle (38 pieces/5 m2 ) and also cereal leaf beetle(15 pieces/5 m2).The aphids were not recorded in this year. During the terms with the highest level of the pests, there were also recorded the highest occurrence of the natural enemies (53pieces/5 m2).

Our results were similar to the results of Gallo and Pekár (1999, 2001),which presented the same spectrum of the pests. The high occurrence of the pests was recorded also in the first(266 pieces/5 m2) and in the second (197 pieces/5 m2 ) decade of June. The highest occurrence had again thrips (18 pieces per 5 m2 ), flea beetle (24 pieces/5 m2) and cereal leaf beetle (10 pieces/5 m2). Frittfly Oscinella fritt was recorded (6 pieces/5 m2) during the entire year.

The higher occurrence ofthe pests could be caused by higher temperature during the year. According to Petr et al. (1987), and McAvoy and Kok (2004), the temperature influenced occurrence and development of the pests in the crops. The influence of the fertilisation was study during three years research on winter wheat.

According to our results, the higher occurrence of the pests was recorded on fertilised variants. The higher occurrence of the pests was recorded on the non-fertilised variants only in the year 2004. Our results are different from the results of the other author according which the fertilisation had no influence at the pests (Samsonova 1991).The similar results reached Levine (1993) and Gallo and Pekár (1999).The occurrence of the insects had the similar character on fertilised and non-fertilised variants. Maximum amount of the pests was recorded one decade sooner on the fertilised variants than on the non-fertilised variants. Relation between fertilised and non-fertilised variants had not statistically significant difference.

The total number of insects had a decreasing tendency during the three years and in both variants of fertilisation. While 3259/5 m2 of insects were collected in 2004, this number decreased by about 51% in 2006. This decrease was expressive on the non-fertilised variantsin 2006, it began on the fertilised variants after the first year. The same decreasing tendency had also pests and their natural enemies. Their occurrence decreased at about 59%during the study. Difference between the year 2006 and the other years 2005 and 2004 was statistically evident.

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Humates and chemical fertilizers

 Intensive agricultural systems demand the use of large quantities of mineral fertilizers in order to supply the plants with basic micro-elements, such as nitrogen, phosphorus, and potassium.  In doing so, we often forget that mineral fertilizer is for plants what illegal drugs are for sportsmen – you can immediately see high results but tend to ignore the future consequences.  The higher the amount of mineral fertilizer used, the more intensive is the erosion of the soil, the poorer the soil’s humus content, and the environment is more polluted.  The problem of effective mineral fertilizer assimilation is central in plant-growing.  The difficulty of its solution lies in the fact that water soluble potassium and nitrogen fertilizers are easily washed out of the soil, while phosphorus fertilizers, on the contrary, bond with ions of Ca, Mg, Al, and Fe that are present in soil and form inert compounds, which are inaccessible to plants.  The presence of humic substances, however, substantially increases effective assimilation of all mineral nutrition elements.  It was shown in the tests of barley that humate treatment (with NPK) improved its growth, development, and the crop capacity while decreasing the use of mineral fertilizer. (V. Kovalenko, M. Sonko, 1973.)  The tests on wheat showed that one-way use of nitrogen fertilizers on winter wheat crops did not have a high positive effect on the crop capacity, while its use along with humates and super phosphate achieved an expected positive effect. (L. Fot, 1973.)  Interestingly, the mechanism of interaction between humates and micro-elements of mineral nutrition is specific for each of them.  The positive process of Nitrogen assimilation occurs due to an intensification of the ion-exchange processes, while the negative processes of “nitrate” formulation decelerates.  Potassium assimilation accelerates due to a selective increase in the penetrability of cell membranes.  As for phosphorus, humates bond ions of Ca, Mg, and Al first, which prevents the formation of insoluble phosphates.  That is why the increase of humate content leads to an increase of the plant’s phosphorus consumption. (Lee & Bartlett, 1973.)

Therefore, the combination of humates and mineral fertilizer guarantees their effective assimilation by plants.  

     Thus, the idea of combined use of humates and mineral fertilizer naturally comes to mind.  Creation of such a combined fertilizer is a new step in plant-growing development.  It was no coincidence when over ten years ago an Italian company, “ Vineta Mineraria,” published a project, ”Umex: a new technological tool at service for agriculture of 2000.”  This project was about establishing the production of humate-coated granulated nitrogen, potassium, and phosphorus fertilizers.  From 1988 to 1990, in Byelorussia, the vegetation field tests and production experiences were carried out to comparatively study new humate-coated forms of mineral fertilizers, such as urea, super phosphate, and potassium chloride, produced in Italy and Russia.  The tests showed that use of humate-coated urea in the production experiences with potatoes increased the crop capacity by an average of 28-31 centner/hectare, whilst at the same time decreasing the nitrate content by 40%, in comparison with the control group (urea). For root-crops, the crop capacity reached 200-220 centner/hectare, with an improvement in the quality of the produce. However, in spite of the impressive results, this project was not developed further, and these new preparations did not appear on the international markets.  Perhaps, the high cost of the humates, in comparison with the mineral base, was the reason, so the new type of fertilizer was not competitive.  However, with the new manufacturing technologies today, these materials can be cost-effective in modern agriculture.

     Field tests (M. Butyrin, 1996) showed that use of humate-coated urea increased the crop capacity of potatoes by 20% and that of oats  by 50%.

     Other important components of plants’ nutrition are micro-elements – Fe, Cu, Zn, B, Mn, Mo, Co.  Plants use a very small amount of them, measured in one thousandth or one hundred thousandth of a percent.  Nevertheless, they are vital to plants’ development.  For instance, boron resists certain diseases and increases the amount of ovaries and vitamin content in fruit.  Manganese is vital for the photosynthesis process and the formulation of vitamin C and sugars.  Copper assists in albumen synthesis, which ensures drought and frost resistance in plants, as well as their resistance to fungal and viral infections.  Zinc is part of many vegetable ferments participating in fertilization, breathing, albumen, and carbohydrates synthesis.  Molybdenum and cobalt are important to nitrogen assimilation from the atmosphere.  Considering what was said in previous chapters, the readers might pay attention to our explanations of similar effect.  We explained it was due to humate use.  But if you consider that the humates transport micro-elements to plants most efficiently and form complexes with micro-elements that are easily assimilated by plants, the seeming contradiction is easily resolved.

     Humic acids form complexes naturally.  For thousands of years, they accumulated vital elements.  When applied, humic acids also extract these vital elements from the soil in an accessible way for plants to form.  For example, iron and manganese, according to respected professor D. Orlov, are assimilated only in humic complex form.  Research by A. Karpukhin showed that the presence of these complexes determine the mobility of most macro- and micro-elements and their supply and travel inside plants’ organs.

Therefore, treating vegetating plants with humates ensures their continuous nutrition with vital macro- and micro-elements.

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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.


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 –

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The Rice-Wheat Consortium’s Example

The Indo-Gangetic Plains of Pakistan, India, Nepal and Bangladesh are endowed with plentiful natural resources, deep productive soils, sufficient good quality water, climatic conditions that permit multiple cropping, high population densities and relatively good infrastructure. The Green Revolution (GR) of the 1970s and 1980s radically changed the traditional agricultural system of this region. Now, about 13.5 million hectares of land are in continuous rotation of irrigated rice and wheat, providing food and livelihoods for many millions. Between 1960 and 1995 rice yields increased from 1.55 to 2.66 tonnes/ha and wheat yields from 0.84 to 2.34 tonnes/ha.

The majority of the farm households have less than 5 ha of land, whilst a minority have more than 20 ha. All farmers use improved varieties of wheat with fertiliser. In rice, some farmers still grow traditional, fine quality varieties like Basmati as they fetch higher market prices. Mechanisation levels are high, especially in the western regions, with resource-poor farmers renting tractors and threshers for tilling and harvesting. Animal power is still common in the eastern regions, but farmers complain of the increasing costs of maintaining draught bullocks. Many farmers are moving to contract ploughing with tractors; dairy cows are acquired in place of draught bullocks.

The main factors for the initial success of the GR and the emergence of the ricewheat system were the introduction of high-yielding, semi-dwarf varieties and chemical fertilisers. Pesticides, investments in irrigation infrastructure, political commitment and policy support played a lesser role. Free irrigation water, cheap agrochemicals, subsidised power supply and low-interest farm credit were some of the crucial supports provided by South Asian governments that made intensive ricewheat production profitable and a safe system for farmers.

However, in the past several years the productivity growth of wheat and rice has declined and the expansion of rice and wheat area has halted due to many reasons (Hobbs and Morris, 1996). Ecological degradation of the natural resource base has occurred as farmers using conventional technologies harvest up to 10 tonnes of cereal per year. Long-term rice-wheat experiments have shown that yield growth declines at constant input levels. Unbalanced use of fertiliser and delayed planting of crops are cited as major factors. Profitability has dropped as more inputs are needed to get the same yield. Input subsidies that favoured the GR have lacked farmlevel incentives for efficient input use. The price of rice and wheat has declined steadily over the last 30 years. Partial removal of subsidies and ecological problems have put stress on the economy of farmers.

Resource degradation in the rice-wheat system can take many forms: loss of organic matter; mining of soil nutrients; build-up of weeds, diseases and pests; waterlogging, salinity and sodicity. Additional problems that reduce system productivity are: low nutrient and water use efficiency associated with delayed crop establishment, driven in turn by inappropriate tillage practices  (delays in sowing wheat after rice can reduce yields as much as 1.5% per day); flat sowing and flood irrigation causing nutrient leaching; puddling leading to formation of a ploughpan, reduced soil permeability and enhanced soil cracking; and restriction of plant root and shoot growth and chlorosis due to temporary water stagnation. To compound these problems, Phalaris minor, the major weed in wheat has developed strong resistance to the commonly used herbicides and farmers have had to shift to new, more expensive herbicides. Excessive pumping from wells is leading to declining water tables in fresh water aquifer zones, while inadequate drainage is causing waterlogging and salinity in others… <more>


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Phosphorus Nutrition of Wheat

Spring and winter wheat represent a dominant crop in rotation across large areas of North America. Improvements in plant genetics, pest management, fertilizer management, and agronomic practices have all contributed to progressively increasing wheat yields. Since 1960,
average wheat yield has increased by 0.38 bu/A/year in the U.S. and 0.31 bu/A/year in Canada.

Phosphorus (P) fertilization is a major input in crop production in many areas, because some soils lack sufficient P to optimize crop yields and quality. Effective nutrient management requires that nutrients be available in adequate amounts when needed by the plant. Ensuring that P is plant available early in the growing season is of particular importance. Phosphorus is critical in the metabolism of plants, playing a role in cellular energy transfer, respiration, and photosynthesis.

Wheat takes up P throughout the growing season. Total P uptake by wheat is about 0.68 lb P2O5/bu. Harvesting grain removes P at a rate of about 0.50 lb P2O5/bu. Banding near the seed provides ready access to P supplies during early season growth. Maintaining adequate
P supplies throughout the soil ensures P is sufficient to meet plant needs during the remainder of the season.

Wheat produces two kinds of stems—the main stem and a variable number of tillers. Early in its life cycle, wheat “decides” which tillers to develop. Factors such as P or N deficiency, hard soil, or planting too deep can create stresses that reduce the initiation of tillers. Early season limitations in P availability can result in restrictions in crop growth from which the plant will not recover, even if P supply is later increased to adequate levels.

Of all the tillers formed, grain from the T1 and T2 tillers (originating from the bases of the first and second leaves, respectively) accounts for about half of the final yield. The other half comes from grain from the main stem. Tillers originating from the base of the third and fourth leaves (T3 and T4) generally have little to no impact on final grain yield. Early in the season, when wheat is “deciding” how many tillers to initiate, P from fertilizer may account for more than 50% of the total P in the plant. If P supplies in the plant become deficient, the initiation of T1 and T2 tillers can be significantly inhibited, cutting into sources of approximately half of the final yield.

Soil testing calibration research has been conducted throughout North America to establish the general relationship between relative yield (percent of yield attainable when P is sufficient) and soil test levels. These data come primarily from studies examining broadcast applications of P. Note the close similarity between relative yield and P for both spring wheat and winter wheat (Figure 3). For both crops, wheat yield is optimized when soils are in the 15 to 20 ppm P range (Olsen). If P fertility is built to these levels, continued applications of P will be necessary to maintain soil levels. As a first approximation, apply a rate equal to crop removal, then check periodically to see if soil tests are staying in the desired range.

Although higher soil fertility levels are important for season-long P nutrition, early season P supplies must be accessible to the limited root system of the young wheat plant. For this reason, P placed near the seed at planting (starter P) has proven effective, especially in cold soils. The response of wheat to low rates of starter P is often referred to as the “pop-up effect”, and is marked by improved leaf and root growth, tiller formation, and yield. Research from North Dakota provides indications that starter P can provide benefits even at higher soil test levels, probably because of its superior positional availability… <more>


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