With harvest underway or fast approaching, you may be trying to estimate the number of bushels in a partially filled bin and how much capacity is remaining.
Use the following calculation to estimate the bushels of grain in a round bin.
Bushels = 0.628 x D2 x H
D is the diameter of the bin, in feet.
H is the height of the grain mass in the bin (depth of grain) , in feet.
0.628 is a conversion constant.
1. Calculate the number of bushels of corn in a 30-foot diameter bin with the eave 18 feet above the concrete foundation with the drying floor, 1 foot above the foundation. This would make the maximum grain depth 17 feet when the bin is full.
In this case, to calculate the bushels of grain contained from drying floor to the eave:
Bushels = 0.628 x D2 x H
Bushels = 0.628 x (30 x 30) x 17
Bushels = 9,608
2. If you have peaked grain at the top of the bin, the bushels in the peak can be estimated by using a different conversion constant in the equation.
Bushels = 0.209 x D2 x H
D is the diameter of the bin, in feet.
H is the height of the grain peak above the eave, in feet.
0.209 is a conversion constant for bushels in a cone-shaped pile of grain that extends to the bin wall.
For example, if the top of the peak is 6 feet above the normal depth of grain in the bin, the volume of the peaked grain is calculated as follows.
Bushels = 0.209 x D2 x H
Bushels = 0209 x (30 x 30) x 6 = 1,128 bu
Add the totals from example equation 1 and equation 2. Total grain in the bin is 10,736 bushels (9,608 + 1,128)
Rectangular, Flat Storage Buildings
For rectangular flat storage buildings, the math is simpler. Multiply length (ft) by width (ft) by grain depth (ft) by 0.8 bushels per cubic foot.
Let’s calculate the amount of grain in a flat storage building that is 40 feet by 60 feet and has a grain depth of 10 feet.
Much of wheat’s yield potential is determined at planting. Attain top yields by having a uniform stand that has time to achieve significant growth before winter dormancy.
Ideally, winter wheat is planted while the soil and air temperatures are still warm to insure the seedling can emerge quickly and uniformly in plenty of time to develop multiple tillers and a strong root system. In fact, beginning in mid- to late September, potential wheat yields tend to slip at least one bushel for every day planting is delayed. This relationship may not hold, however, once the calendar reaches late October as soil and weather conditions tend to play a more important role.
While the Hessian fly no longer poses a significant threat to wheat in Michigan, the fly-free-date is still a useful reference. The fly-free-date is during the first week of September in the northern Lower Peninsula, around mid-September in mid-state areas and approximately the third or fourth week of September for southern Michigan. Highest yields are often attained when seedings are made within two weeks following the posted fly-free-date. When wheat is planted within a few days of the fly-free-date, seeding rates and fall-applied nitrogen rates should be reduced.
Attaining a consistent seed depth is important because it will increase the probability of even emergence. Usually, a planting depth of 1 to 1.5 inches is sufficient in heavy soil. Deeper seed placement may have an advantage when some types of winter stresses occur, but usually this is outweighed by the advantage in more rapid emergence posed by more shallowly placed seed. Where planting depths of 2 inches or greater may be advantageous is when a coarse soil is very dry. In this case, seed should be planted as deep as possible in order to come in contact with moisture.
Michigan State University Extension’s recommendation is to plant between 1.4 and 2.2 million seeds per acre. Seeding rates on the lower end of the range should be reserved for fields being planted within a week of the fly-free-date. Using high seeding rates are discouraged when seeding relatively early as it may lead to overly thick stands that tend to lodging as the plant approach maturity.
As the calendar advances, seeding rates should become progressively higher. If planting continues into the second half of October, the seeding rate should be increased to at least 1.8 million seeds per acre. The seeding rates should also be adjusted upward when seed is of questionable quality.
Table 1 identifies the pounds of seed needed based on the number of seeds per pound and your population target. For example, if the seed bag specifies 14,000 seeds per pound and the target seeding rate is 1.8 million seeds per acre, 129 pounds of seed would be needed per acre.
Table 2 is useful for assessing the number of seeds being dropped by each row unit (7.5-inch row spacing) and for evaluating actual emergence.
Table 1. Relating seed size and seeding rates to the amount of seed required per acre
Seed size (seeds/ lb.)
Target seeding rates (millions of seeds per acre)
Amount of seed required (lbs./acre)
* Seeds per acre / seeds per lb. = lbs. of seed per acre
Table 2. Relating target seeding rate per acre to seed and seedling numbers (for 7.5-inch row spacing)
Covers crops grown between periods of primary cash crop production can offer many benefits to the sustainability of cropping systems. Improvements in soil quality resulting from cover crops may include increases in soil organic matter, reduced soil compaction, or increased soil microbial activity. Cover crops can be an important management tool to reduce environmental pollution from soil erosion, leaching, and surface runoff. Past research in other regions has found mixed results ranging from increases in corn and sorghum yields after summer legume cover crops to no yield advantage following non-legume or winter legume cover crops.
An ongoing study is being conducted by researchers at K-State to determine how long-term effects of legume and non-legume summer and winter cover crops grown before grain sorghum impact nitrogen (N) availability and the response of sorghum yield to N fertilization.
The crop rotation was wheat-grain sorghum-soybean. Treatments included four different cover crops (see below), double crop soybeans (DSB) as a cash crop alternative, and a chemical fallow (CF) check. These treatments were imposed following wheat harvest so grain sorghum is the crop in the rotation most likely to be affected. The four cover crop treatments included:
Summer legume (SL) – forage soybean
Summer non-legume (SNL) – sorghum-sudangrass
Winter legume (WL) –crimson clover
Winter non-legume (WNL) – daikon radish
Nitrogen fertilizer was applied after grain sorghum planting in a subsurface band at 0, 40, 80, 120, and 160 lb N/acre.
After three cycles of cover crops, yields of grain sorghum with no N fertilizer applied were highest following the summer legume cover crop treatment (Figure 1). A minimum of about 35 lb N/acre of added N fertilizer would be required for sorghum yields to reach similar yield levels with the CF and other cover crop treatments.
Figure 1. Sorghum response to 3rd cycle of cover crops (3-year average, 2014 to 2016)
Sorghum yield response to cover crops over an 8-year average is shown in Table 1. Grain sorghum planted after the summer legume and double-crop soybean cover crops produced significantly greater yields than the other treatments when no fertilizer N was added. There is potential to replace a portion of the cash crop N requirement with summer legume cover crops. The summer legume cover crop contributed an average of 33 lb N/acre to the grain sorghum during the growing season. Double-crop soybean contributed an average of 19 lb N/acre.
On the other extreme, sorghum sudangrass, a summer non-legume, removed an average of 47 lb N/acre from the plant-available soil N pool (Table 1). Sorghum sudangrass has a relatively high carbon-to-nitrogen (C:N) ratio which leads to immobilization (tie-up) of available soil N. For cover crops with high C:N ratios, additional N input by the grower may be necessary to maintain sorghum or corn yields.
Table 1. Nitrogen fertilizer replacement value and sorghum yield (8-year average)
Although there was no significant improvement in yield or N supply from winter cover crops, these plants may reduce N loss by leaching over the winter through N uptake before it moves out of the rooting zone as well as a providing residue to protect the soil surface and help reduce erosion.
The agronomically optimum fertilizer rate for sorghum after an 8-year average of yield data was approximately 80 lb N/acre for all treatments except where a summer non-legume cover crop (sorghum-sudangrass) was used. With the summer non-legume cover crop, the agronomically optimum fertilizer rate was 120 lb N/acre.
Appropriate management adjustments will need to be made if you are incorporating cover crops into your wheat-grain sorghum or similar cropping system. Cover crops are likely to affect N availability and uptake by the subsequent crop. Fertilizer N applications should be adjusted according to specific cover crop species and management to maximize yield.
No-till alfalfa should be part and parcel of a no-till system. The threat of soil erosion is very substantial if alfalfa is established in tilled soil. A stand can be partially lost due to erosion, or rills and gullies can form in a new seeding. These rills and gullies will be present for many years and can compromise operation of field equipment, damage it, and present danger to the operator.
Because of the protection provided by mulch, crusting problems are avoided. No-till also saves moisture, which can help improve success with late summer seedings of alfalfa. The stubble provides protection for the young, tender alfalfa seedlings from direct intense sunlight and possible damage from blowing sand or soil particles.
On rocky soils, use of no-till helps eliminate the need to pick rocks. Additional benefits include reduced fuel, labor and time requirements for no-till alfalfa establishment compared with alfalfa establishment in tilled soil.
Finally, lower seeding rates can be used because with a well-adjusted no-till drill seeding depth and metering is much better controlled than in conventional seed drills. However, if you just start thinking about no-till alfalfa now you are way behind the eight-ball. It would be better to start preparing for future no-till planting if you have not taken the necessary precautions or you could be disappointed and fighting the aftermath for the entire duration of the alfalfa stand. Preparation means addressing soil unevenness, weed control, soil fertility, soil pH, herbicide residues, etc. This is more than we can cover here where we assume you have done all the necessary homework so you are ready to plant alfalfa.
Make sure all weeds are killed. Use gramoxone or glyphosate to kill established and emerging weeds. However, it may not be necessary to apply herbicide if your field is clean, so check before you spray.
Any no-till drill can work as long as the seed can be placed within ¼ to ½ inch deep. The greatest threat is to place the seed too deep! Seeding depth is more critical than seeding rate. So the equipment needs to be able to place the seed at the right depth and uniform spacing across all units, and press the seed into the soil gently so it is covered and has good seed-to-soil contact.
Make sure the drill is well-maintained. Drill units should be tight and not wobbly-check bearings and parallel linkages. Make sure all units are in the same plane. Coulters, if present, need to cut through residue. It is best to have narrow coulters that do minimal soil disturbance-wide coulters may leave a lot of bare soil showing, and they also bring up moist soil which can stick to the coulters and depth wheels. By using narrow coulters such as rippled coulters or even bubble coulters you can work in a wider range of soil conditions. This is very important for spring establishment of alfalfa which often happened when the soil is on the wet side. The coulters should not run deeper than the planting depth to avoid dropping seeds too deep.
Double disk or single disk openers are the most common for no-till alfalfa seeding. Shoe types can also be used but tend to not handle residue as well, do more soil disturbance and can easily place the seed too deep. Make sure the double disk openers are not worn too much and have the right point of contact (check by placing two business cards between the disks to the point of contact-there should be something like an inch between them depending on the drill type).
The depth gauge wheel is often also the press wheel. It is very critical to set it to the right depth. There are also often ‘dough-nut’ shaped washers controlling seeding depth on the hydraulic cylinders. Play with the number of doughnuts and the settings on the press wheel to come to the right depth. Two inch wide closing wheels seem to work best-they cover the seed firmly while still controlling depth well. Narrower wheels lose to ability to control depth well, while wider wheels do a poor job closing the seed slot.
To determine seeding rate, use the seed charts on the drill as a first approximation. However, it is best to check calibration of the drillusing our fact sheet. You should also keep track on the acres planted and quantity of seed used. It is easy to use too much seed and then you are just wasting money!
After planting, continue to monitor the stand and address any issues. Guidance is available in the Penn State Agronomy Guide for weed and pest control. After about 5 weeks the alfalfa should be 3-5 inches tall.
Nebraska researchers lead project identifying causes of yield gaps in US soybean production
A new paper published in Agricultural and Forest Meteorology details the University of Nebraska–Lincoln’s efforts to identify causes for yield gaps in soybean production systems in the north central region of the United States.
Average soybean yield in the north central region from 2010-2014 was 43 bushels per acre, yet some producers reached soybean yields over 80 bushels per acre.
The three-year study, led by Patricio Grassini, assistant professor in the Department of Agronomy and Horticulture, and Shawn Conley, associate professor in the Department of Agronomy at the University of Wisconsin, sought to identify causes of yield gaps over large agricultural areas and diverse climates and soils. Faculty from 10 land-grant universities looked at rainfed and irrigated soybean in the north central U.S., which accounts for roughly one-third of worldwide soybean production.
Grassini and his colleagues explored the use of producer survey data as an alternative approach to traditional field research to identify management practices that explain highest soybean yields for different combinations of climates and soils. In Nebraska the team relied on Nebraska’s Natural Resources Districts and 20 Nebraska Extension educators to obtain real-world producer data. In total, 3,568 soybean fields across 10 states were surveyed for this study, covering approximately 300,000 acres.
“Regional soybean yield was on average 22% and 13% below the yield potential estimated for rainfed and irrigated soybean,” said Grassini. “Sowing date, tillage and in-season foiliar fungicide and/or insecticide were identified as explanatory causes for yield variation.”
To reach these conclusions, researchers combined producer survey data with a spatial framework to measure yield gaps, identify management factors explaining the gaps and understand the biophysical drivers influencing yield responses to field management. According to Grassini, earlier sowing dates was the most consistent management factor leading to yield increases.
Juan Ignacio Rattalino, research assistant professor at Nebraska who authored the paper, sees this study as a proof of concept about the power of using producer data to identify opportunities for improving farm management and profit.
“There are a lot of studies about yield response to planting date but this is the first one to explain why such response varies across years and regions. We found that the yield benefit derived from earlier planting depends on the degree of water limitation during the period of pod setting in soybean,” Rattalino said.
The study was supported by $1.4 million from the North Central Soybean Research Program, with complementary funding from the Nebraska Soybean Board and Wisconsin Soybean Marketing Board. Other institutions involved include Iowa State University, Kansas State University, Michigan State University, North Dakota State University, Ohio State University, Purdue University, University of Illinois-Champaign, University of Minnesota and University of Wisconsin.
This time of year, local garlic is starting to appear at farmers markets, farm stands, and grocery stores. A staple in many types of cuisines, garlic is as fun to grow as it is to cook.
Types of Garlic
Garlic falls into two broad categories: softneck and hardneck. Softneck varieties have a flexible stalk that is an extension of the papers that wrap the cloves. This flexible neck dries down quickly and can be braided or cut for sale. Hardneck varieties are characterized by their stiff stalk that extends from the bottom plate of the garlic bulb to the top of the plant. This stalk produces a scape in early summer, which is similar to a flowering head, though instead of forming a flower, it forms a bulbil with small, genetically identical cloves that can self-sow to produce the next generation. However, most growers will remove these scapes to redirect energy downward, allowing for larger bulb formation. These scapes can be snapped off or cut above the top leave and eaten or sold as a garlic substitute.
Softneck and hardneck garlic can be further divided into different families, each of which is identified by its clove formation and flavor profile. There are numerous families of garlic, but below is a list of the most common:
Productive and easy to grow, artichoke varieties are very common. They typically consist of an outer row of large cloves with several inner cloves of a smaller size. The flavor of artichoke garlic can range from spicy to mild.
Silverskin garlic is some of the longest lasting in storage. Because of this, they are typically the most common to find in the supermarket. Similar to artichoke varieties, silverskin garlic has 12-20 cloves arranged in multiple layers. Also like artichokes, the flavor is wide ranging among varieties.
Porcelain garlic is identified by its four large, symmetrical cloves around the central stalk. The cloves can reach impressive sizes, which are a joy to cook with, but lead to fewer plants per pound of seed. Porcelain garlics have great flavor, balancing earthiness with strong heat.
Known for their excellent, full-bodied flavor, rocamboles are sought out by chefs and processors. They have 6-11 large, easy to peel cloves, though they have a shorter shelf life than other varieties. They can be identified by their scapes, which form a double loop as they form.
Purple stripe garlics earn their name by their beautifully colored papers that feature purple stripes and splotches that can vary with variety and weather. They feature 8-12 cloves per bulb, with slightly smaller cloves than rocambole varieties. They have a moderate storage life of six months.
Garlic benefits from rich, well-drained, near neutral soil, but can survive in a wide range of soil types. Softneck varieties tend to be more forgiving, but all garlic can succumb to rot when drainage is inadequate. A chisel plow or Yeoman’s plow can be used to ensure adequate drainage, especially when set up to break up the soil at each row position. Alternatively, a cover crop rotation including tillage radishes and a high-yielding legume improve drainage and provide nitrogen credits. Garlic benefits from heavy fertilization – 125 pounds of nitrogen, 150 pounds of phosphorous and 150 pounds of potassium per acre for maximum yields. Nitrogen should be applied at planting (75 pounds), at 6-inches of growth (25 pounds) and right before scape emergence (25 pounds). Compost can be applied to add fertility and organic matter, though it should be analyzed to better understand what is fertility it provides. Remember, before applying any fertility to a crop, soil testing should be done to ensure proper fertility application.
Garlic can be planted on bare soil or into plastic mulch in far northern climates. Black and green plastic mulches can help retain moisture and boost soil temperatures in the spring. In warm climates, bare soil production systems are recommended to ensure proper soil temperatures for emerging garlic.
Average Plants per pound of seed
Garlic heads must be broken apart into individual cloves a few days prior to planting. Cloves should be graded and selected to achieve optimum head size. Large cloves tend to produce larger heads. The number of plants per pound of seed is variety dependent, but a rough guide is provided below:
Garlic is typically planted in rows six to 12 inches apart, with individual cloves set four to eight inches apart in-row. Larger bulbs result from greater spacing, but this will result in fewer plants per acre. Cloves are planted one to two inches deep with the clove oriented with the growth plate down.
Planting should be done two to four weeks before a hard freeze settles in. In Michigan, this is in October-November. Garlic needs to be planted early enough to allow for adequate root growth, but aboveground growth is not ideal. In areas with limited snowfall, two to four inches of straw mulch should be applied post-planting. Growers in high snowfall areas can sometimes utilize the snowpack as effective mulch, though most growers continue to mulch to minimize risk of freezing planted cloves.
Garlic is a poor competitor against weeds, so proper steps must be taken prior to planting to minimize weed pressure. Stale bedding for two to four weeks prior to planting and using clean, weed-free straw mulch can greatly reduce weed pressure. Mulch can be removed in the spring to allow for mechanical cultivation, though irrigation needs may increase as a result.
In order to achieve maximum bulb size, scapes should be removed as soon as possible on hardneck varieties, and soil should be consistently moist throughout the production cycle. An inch of water per week throughout dry spells will allow for maximum growth.
Garlic is ready for harvest when five to seven leaves have yellowed. Each of these leaves correlates with a wrapper on the bulb. Late harvests, in which leaves have senesced, yield fewer wrappers and poor storage life. Harvest usually occurs in mid-June to mid-July in Michigan.
Garlic can be lifted with an undercutter bar or dug by hand. Care should be taken to avoid damage to the bulbs during harvest.
If storage is required, garlic must be cured properly. Curing garlic can be done by hanging garlic in bunches, or by laying out on racks or on the floor. Some growers will power wash garlic post-harvest to reduce the amount of dirt on the wrappers before curing. This can result in cleaner wrappers and less handling post-curing. Most growers leave the tops intact while curing, though trimming the tops can speed curing and reduce handling post-curing. In areas with high humidity, circulating fans can be used to speed the curing process, while lower-humidity areas can have adequate curing in two to three weeks. After the leaves have dried and papers have shrunk to the bulb, the garlic can be trimmed and stored in clean boxes or mesh bags at 32-35°F and 65-75 percent relative humidity.
Heads can be graded for sale and seed selection. U.S. No. 1 garlic requires that bulbs be no less than 1.5” in diameter, but depending on your market, you can grade to further specifications. A simple grading tool can allow a grower to select bulbs for varying price points and seed selection.
Garlic can be a very rewarding and profitable crop for the commercial grower and home gardener. Through the use of proper production practices, growers can reach improved yields, year after year.
Utilizing sound research results to help make decisions on the farm is a wise business practice. It can be confusing, however, when you see two numbers that are clearly not the same labeled as “not significantly different.” One can quickly calculate the value of a few bushels per acre over hundreds of corn or soybean acres. It is key to look at just what this terminology means and its practical importance when using this information to make decisions.
First, consider why research is conducted in the first place. Research is typically conducted so that we can use the results to help make the best decisions possible in the future. We want to use practices that have a high likelihood or probability of paying off. Statistically sound research trials help us determine the likelihood that a practice really did influence yield versus any differences being due to some other factor(s) or random variability.
A term commonly used in research is the Least Significant Difference or LSD. In a hybrid variety trial, for example, this is the minimum bushels per acre that two hybrids must differ by before we could consider them to be “significantly different”. Note there is no way to calculate the LSD if a person simply splits a field in half and puts one treatment on one side of the field and a different treatment on the other. In this scenario, you have no way to sort out if a difference in observed yields was due to underlying factors such as soil type, planting population, drainage, compaction, disease, insect pressure, harvest issues, topography, etc., or the treatment.
When you see the LSD calculated at the .05 significance level, this means we can be 95 percent certain that the treatments (or hybrids, etc.) really did differ in yield if the difference between them was equal to or greater than the LSD. A significance level of .05 or .10 are most commonly used in agricultural research.
How do we end up with “no significant difference?” This can occur when there is so much variability in the results due to other factors that we can’t make a conclusion with confidence, or when the treatments or hybrids in the study simply don’t differ in yield.
Results from a U of MN tillage trial demonstrates the importance of statistical analysis in helping determine if a yield difference is likely “real.” Three long-term tillage systems were evaluated at multiple locations over three years across southern MN. Tillage treatments were randomized and replicated four times at each location. At one site in 2011, average corn yield for strip tillage (ST) was 10 bu/ac greater than in moldboard plow (MP). Yield was not statistically significant, however, so we couldn’t say one tillage system resulted in a higher yield than another (Table 1).
Table 1. Corn grain yield for each plot by replication (rep) and average yield by tillage system at one on-farm, long-term tillage trial site in MN in 2011. Although average yields were numerically different, statistical analysis determined we could not say with any confidence that the tillage systems resulted in different yields.
Corn grain yield
bushels per acre
*NS = Not significant
Closer examination of data shows that while ST out-yielded MP in the first replication (rep) by 13 bu/ac, MP out-yielded ST by 14 bu/ac in the fourth rep. Also, chisel plow (CP) was the lowest yielding treatment in rep 2, while it was the top yielding treatment in rep 3. Due to this variability, statistical analysis revealed we couldn’t say with confidence that any of the tillage systems resulted in a higher yield than another. Other factors we couldn’t account for appeared to have impacted results at this site, highlighting the value of conducting research over a number of locations and years.
Lastly, if yields are not statistically different, don’t treat them differently. Resist the temptation to put economics to average yields if they are not significantly different. Doing so could lead to poor and costly decisions in the future.
Crop rotations with small grains in the sequence allow for an adequate seasonal window to establish variety of cover crop blends following grain harvest. However, producers with strict corn-soybean rotations are limited in their options for cover crop species, since there is not enough growing degree days left for cover crops to grow after primary grain crop has been harvested. One cover crop that has caught attention and has consistently worked in South Dakota environments where pre-dominant rotation is corn-soybean is winter rye.
About Winter Rye
Winter rye is known for its winter hardiness allowing late fall planting and puts on a rapid growth the following spring. Furthermore, adding a cool season small grain component into a corn-soybean rotation would not only add diversity the cropping system but also help break pest pressures in the field. Winter rye is also known for its inherent ability to suppress weeds because of its allelopathic characteristics, i.e. its ability to produce biochemical compounds that inhibits germination, growth, and reproduction of other plants. On a long term basis incorporating cover crops would also help improve soil health and provide supplemental forage.
Fitting Into Rotation
Considering growing habits of all three crops is essential when determining the order of winter rye within the cropping sequence. Planting rye after corn, and ahead soybeans, seems to be a better fit than to grow rye before corn. This way corn residue provides protection to rye seedlings. In addition, soybeans can tolerate later planting in the spring better than corn which allows rye to accumulate more spring growth. Rye biomass in the spring can be terminated as cover or utilized as forage depending on the farm need. Research conducted in various locations of Southeast SD for the last few years has shown no negative impact on soybean yields when grown on rye cover crop residue. On the other hand corn yield tends to suffer following a rye cover crop which could be due to allelopathic effects of growing rye cover crop or the micro climate created by the rye residue on the soil surface at the time of corn seeding. It is suggested to terminate rye 2-3 weeks prior to corn planting to avoid any negative impact on corn plant health and grain yield.
Seeding rate is about 40 lbs/ac as a cover crop, however, it can be increased to 75 lbs/ac if weed suppression is the primary objective.
Aerial seeding can be done during mid to late corn seed-filling stage (early Sept). Research results show that aerial seeded (or broadcast method) rye produces about 80% of the spring biomass of drill-seeded following grain harvest.
Producers of small grains such as wheat, oat, barley, etc. are suggested not to use winter rye as a cover crop because it may act as significant contaminant or weed in small grain crops.
As winter rye accumulate rapid growth in the spring, it is a good practice to look out for short or medium term spring weather so that rye can be terminated early when conditions are drier than usual.
While no one knows exactly which mix of factors and to what extent those factors are causing algal blooms on Lake Erie, it’s clear among the scientific community that, in the western basin, farmers are at the very least playing a significant role.
Along with sunlight, the release of soil nutrients like phosphorus and nitrogen through farm field runoff helps create environments in waterways where harmful algal blooms can form, threatening health outcomes in the area and putting a major damper on the region’s tourism and fishing industry dollars.
That’s why former Kentucky farmer, Dr. Kevin King, research leader and supervisory research agricultural engineer with the U.S. Department of Agriculture’s Agricultural Research Service-Soil Drainage Research Unit was on hand at the Williams Soil and Water Conservation District’s Field Technology Day to discuss possible solutions and to enlist farmers’ help in further understanding the problem.
According to King, testing at 80 fields across 40 sites has revealed that drainage from tiles contains a phosphorus concentration of about .05-.06 parts per million (ppm), right at the level accepted through an agreement between the U.S. and Canada.
“Our tile is just about there,” King said, noting that some individual sites rich in phosphorous do contain much higher concentrations.
However, surface flow drainage contains concentrations of about 0.2 ppm on average.
While tile drainage accounts for anywhere from 40 to 95 percent of annual discharge, surface drainage’s higher concentration remains a bigger issue, according to King.
“Concentration is what really feeds the algal bloom,” he said.
King noted that the region has had 4,500 rainfall events since 2010 and that individual rainfall events totaling 1.5 to 2 inches or more cause the loss of 60 to 70 percent of all nutrients leaving test sites.
“If we can store 1.5 to 2 inches of rain in our landscape or at the edge of the field, then we can go a long way to reduce the amount of nutrients going downstream and eventually in the lake,” King said, listing possible solutions like elevating tiles at certain times of the year and planting cover crops, though he noted those ideas may not work for everyone.
King said for every 1 percent of organic matter in soil, 3 quarters of an inch of water can be stored. Organic matter can be restored through no-till practices and manure application.
When informally polled by King about who had water management plans, of the dozens of farmers in attendance only several raised their hands. A group of farmers estimated less than 50 percent of farmers practice water management.
However, King said 93 percent of farmers in the region test their soil at least once per crop rotation. Over-application of phosphorous-containing manure over many years is believed to be a contributor to the issue. Some 5 percent of farmed acreage in the western Lake Erie basin contains phosphorous levels of 150-200 ppm.
King mentioned a farmer who hasn’t applied phosphorous in five years who haven’t seen a drop in yield.
“It’s not a large percentage of the land, but we definitely don’t (need) to be putting fertilizers on those areas,” King said. “We can’t just look at our soil tests and say, “That’s what my level is.’ We’ve got to look at what the historical crop rotation is and start taking a more holistic approach, looking at the microbial biomass as well.”
He talked about the level of nutrient loss per acre the scientific community is asking farmers to achieve.
“It’s about a quarter-pound per acre, that’s what we’re striving to get to,” King said. “That ought to scare you. If we think about what you’re applying right now, you’re applying 15, 20 pounds an acre and we’re asking you to get down to a quarter of a pound loss.
“Right now, your losses are somewhere in the 1 to 1.50 pounds (range) an acre of loss.
“We’re already doing 90 percent recovery efficiency, so what do we do now to get us down 0.25 of a pound?” he said. “That’s the margin we’re working with … It’s that quarter of a pound an acre that’s causing the lake to be green.”
He recommended putting fertilizer on just before planting, if possible.
“What I would encourage you to do is turn off the hoppers when you fertilize for 100 yards in two or three spots,” King said. “Don’t wait on the science, it’ll be four, five, six years before we figure out and get those recommendations. Convince yourself that you don’t need that much phosphorous. There’s a lot in the soil.”
Joe Nester, owner of Bryan-based Nester Ag, as well as the test field where Thursday’s Tech Day was held, encouraged independent research among farmers and stressed the importance of organic matter and the use of gypsum which has been proven to effectively create bonded phosphates which don’t leave the field as easily in drainage.
“Gypsum’s not the silver bullet — There are no silver bullets and there are no smoking guns,” King said. “We don’t know what’s causing this problem. We know that in this watershed we see dissolved phosphorus going up. We don’t know why. It’s not just an Ohio issue, it’s a world issue.”
He provided the example of algal blooms in once-pristine Colorado streams.
“In this watershed, agriculture absolutely has a role in what’s happening, but it’s not explanatory for what’s happening around the globe,” King said.
“We have to keep taking a chance of failing and put yourself out there,” Nester said. “Find that breaking point on phosphorous on you operation under your management. Find that breaking point on nitrogen so we’re not contributing.
“The answer will come from farmers, not the legislature. We have to bring the answers,” Nester said.
A few farmers present at the discussion voiced their belief that factors like animal waste, human waste from cities and the changing chemistry of (acid) rain play roles that are not commonly acknowledged by the scientific community.
Currently, there are no tangible incentives from state or federal governments for farmers to implement best practices determined by research to limit algal blooms.
When asked, several other farmers indicated by-acre incentives for best practices would help more quickly increase implementation.
Rep. Lamar Smith said climate change “alarmists” ignore the “positive impacts” of more carbon dioxide in the atmosphere, such as increased food production and quality. But the impact of increased CO2 levels on agriculture is more complicated than that — and, on balance, likely negative, particularly in the future.
Other factors aside, an atmosphere with more CO2 does boost crop yield in the short term via increased rates of photosynthesis. In the long term, multiple experts told us the positive effect of increased CO2 on crops will diminish and the negative impacts of climate change, such as higher temperatures and extreme rainfall, will grow.
Smith, the chairman of the House Committee on Science, Space & Technology, made his claim in a July 24 op-ed published in the Daily Signal, a news website created by the conservativeHeritage Foundation.
Smith, July 24: A higher concentration of carbon dioxide in our atmosphere would aid photosynthesis, which in turn contributes to increased plant growth. This correlates to a greater volume of food production and better quality food. Studies indicate that crops would utilize water more efficiently, requiring less water. And colder areas along the farm belt will experience longer growing seasons.
In making his claim, Smith also argued, “The American people should be made aware of both the negative and positive impacts of carbon dioxide in the atmosphere,” adding, “Without the whole story, how can we expect an objective evaluation of the issues involving climate change?”
We agree. Below, we take a look at both the pros and cons of increased CO2 on agriculture.
Carbon Dioxide’s Diminishing Return
Let’s take a look at Smith’s claims one by one. First, does a “higher concentration of carbon dioxide in our atmosphere … aid photosynthesis, which in turn contributes to increased plant growth,” as Smith said?
Yes, but to a point.
During photosynthesis, plants use energy from sunlight to convert CO2 and water into oxygen and glucose, a sugar molecule. Plants then release oxygen from their leaves, but they also combine oxygen with glucose to produce energy for growth through a different process called respiration.
The United Nations Intergovernmental Panel on Climate Change’s 2014 report does say that increased atmospheric CO2 has “virtually certainly enhanced [crop] water use efficiency and yields.” So, Smith is right that more CO2 leads to more photosynthesis, which correlates to increased crop yields. And he’s also right that “[s]tudies indicate that crops would utilize water more efficiently” in an atmosphere with more CO2.
But the IPCC adds that the CO2 effect has a greater impact on wheat and rice, than on corn and sugarcane.
Photosynthesis in wheat and rice relies more on CO2 in the atmosphere, while corn and sugarcane rely more on “internal cycling” during photosynthesis, Jerry Hatfield, the director of the U.S. Department of Agriculture’s National Laboratory for Agriculture and The Environment, explained to us over the phone.
In other words, increased CO2 doesn’t boost crop yield equally across the board.
Hatfield, who was also part of the IPCC process that received the 2007 Nobel Peace Prize and who currently serves on an IPCC special committee, also explained to us that the positive impacts of CO2 may “reach a point of diminishing return,” or “saturation,” in the future. What does that mean?
Right now, the concentration of CO2 in the atmosphere is just over 400 parts per million, according to NASA. (For comparison, before 1950, the level of CO2 hadn’t surpassed 300 ppm for hundreds of thousands of years.)
Hatfield told us that plants would reach CO2 saturation at around 550 to 600 ppm, at which point the more gas “won’t be as beneficial.”
In an email, Frances Moore, an assistant professor studying climate change’s impact on agriculture at the University of California, Davis, put it this way: “My research does show that higher CO2 concentrations are beneficial to crops, but this effect quickly declines at higher and higher concentrations because plant growth becomes limited by other nutrients.”
Higher levels of CO2 wouldn’t necessarily be harmful to crops, added Hatfield. Still, “we know so little about the effects of super high concentrations of CO2 on plant growth,” he said.
At an increase of 3 ppm per year, the rate in 2015 and 2016, according to the National Oceanic and Atmospheric Administration, the Earth would reach saturation well before the end of the century. Since 1960, the rate has fluctuated, so it could decrease, but the trend generally shows an increasing rate.
Better Quality Food?
In his op-ed, Smith also said increased CO2 correlates to “better quality food.” We reached out to his office to get some clarification on what the chairman meant by “better quality.”
Alicia Criscuolo, a press assistant for the House science committee, told us by email, “Chairman Smith uses ‘quality’ as a term to encompass a wide range of benefits,” such as a “rise in production and size of plants grown in a CO2 enhanced environment” and an “increased concentration of vitamin C that results from increased CO2 exposure.”
Specifically, his office pointed us to two papers, one about strawberries and another concerning sour oranges.
The paper about strawberries, published in Photosynthesis Research in 2001, didn’t exactly conclude that increased CO2 “leads to an increase in biomass and overall production of strawberries,” as Criscuolo said in an email to us.
Rather, the study, authored by USDA collaborator James A. Bunce, investigated how other factors, such as temperature and soil quality, affected a strawberry plant’s propensity to increase its photosynthesis rate in an environment with elevated CO2 levels. While the study did show that strawberries photosynthesize more with increased CO2 levels, it didn’t look at strawberry quantity or quality.
The paper about sour oranges, published in the journal Agriculture, Ecosystems & Environment in June 2002, found that when a 75 percent increase in CO2 levels — from 400 ppm to 700 ppm — doubles fruit production, it also increases the vitamin C concentration of the fruit’s juice by 7 percent.
It’s important to note two things about this study. First, its primary author, SherwoodB. Idso, is the president of the Center for the Study of Carbon Dioxide and Global Change, a nonprofit that denies that increased CO2 causes global warming. Second, sour oranges shouldn’t be confused with juicing oranges. Sour oranges are mostly used to make marmalade.
We also asked Samuel B. Myers, a senior research scientist at Harvard studying the human health impacts of climate change, what he thought of the idea that increased atmospheric CO2will lead to “better quality food,” as Smith said.
“Rep. Smith’s claim about better quality food is pure fabrication,” he told us by email. “All our research shows that rising concentrations of CO2 reduce the nutritional value of staple food crops,” such as wheat, barley and rice. “We have shown … that staple food crops lose significant amounts of iron, zinc, and protein (critical nutrients for human health) when grown in open-field conditions” at elevated CO2 levels, he said, though scientists aren’t sure why increased CO2 leads to decreased nutrients in staple crops.
In fact, earlier this month, Myers and colleagues published a paper in Environmental Health Perspectives that found that “an additional 1.6% or 148.4 million of the world’s population may be placed at risk of protein deficiency” because of elevated CO2 levels.
Longer Growing Seasons?
In his op-ed, Smith also claimed that, due to increased CO2, “colder areas along the farm belt will experience longer growing seasons.” This is true, but warmer regions, such as the southern states, will also experience negative effects because of climate change.
To support his claim, Smith’s office pointed us to a June 2014 paper in Nature by Melissa Reyes-Fox, a technician at the USDA, and others. The paper explains that scientists have previously found evidence to suggest that global warming has caused a lengthening of the growing season in temperate and polar regions of the Earth.
Reyes-Fox and her group found that a longer growing season, especially when water is a limiting factor, “is not due to warming alone, but also to higher atmospheric CO2concentrations.” However, the researchers didn’t look at food crops, but a grassland in Wyoming.
Still, the IPCC’s 2014 report does say with “high confidence that warming has benefitted crop production in some high-latitude regions, such as northeast China or the UK,” and that “high-latitude locations will, in general, become more suitable for crops.” This is due, in part, to the fact that “declines in frost occurrence will lead to longer growing seasons,” the report says.
However, this “latitudinal expansion of cold-climate cropping zones polewards … may be largely offset by reductions in cropping production in the mid-latitudes as a result of rainfall reduction and temperature increase,” the IPCC adds. “For tropical systems where moisture availability or extreme heat rather than frost limits the length of the growing season, there is a likelihood that the length of the growing season and overall suitability for crops will decline.”
Fewer frost days may also negatively impact fruit and nut trees, Hatfield, at the USDA, told us. The IPCC and the U.S. Global Change Program make similar conclusions in their reports.
The Global Change report explains, for example, that fruit and nut trees “have a winter chilling requirement,” or a number of hours a year where temperatures are between 32 and 50 degrees F, ranging from 200 to 2,000 hours depending on the type of tree. These temperatures signal fruiting trees to develop flower buds in the spring.
But not all crops and not all regions will be affected in the same way.
“Projections show that chilling requirements for fruit and nut trees in California will not be met by the middle to the end of this century,” the Global Change report says. However, the report adds that scientists expect apples in the Northeast to have sufficient chilling hours for the rest of the century, though this might not be the case for plums and cherries in the region.
The IPCC report also points out, “Several studies have projected negative yield impacts of climate trends for perennial trees, including apples in eastern Washington … and cherries in California … although CO2 increases may offset some or all of these losses.”
The projections for wine and coffee are even less favorable. Increasing temperatures associated with rising CO2 emissions are likely to reduce the area suitable for grapes used to produce the highest-quality wines “by more than 50% by late this century,” the Global Change report says. And coffee production in Costa Rica, Nicaragua and El Salvador “will be reduced by more than 40%,” according to the IPCC report.
Smith didn’t address how changes in rainfall might affect agriculture in the future. But all the experts we spoke with emphasized the importance of reliable water availability, in addition to temperature and CO2, for crop production and quality. For this reason, it’s worth outlining how climate change will change precipitation patterns.
First, as we’ve written before, scientists are more confident when linking temperature-related weather to global warming than they are linking precipitation changes to global warming. But there is still plenty of evidence to suggest global warming will affect rainfall patterns across the globe.
Hatfield, at the USDA, explained to us that crops generally prefer steady rainfall during the summer, when the most growth occurs. But climate change, due to increased CO2, is causing the U.S. to see more precipitation in the form of spring storms.
The Global Change report also makes a note of this.
The Midwest, for example, is seeing “increasing intensity of storms and the shifting of rainfall patterns toward more spring precipitation,” the report says. In Iowa in particular, there hasn’t been an increase in total precipitation per year, but there has been a “large increase in the number of days with heavy rainfall,” the report adds.
Extreme rainfall is bad for crops for a number of reasons, one being that it leads to soil erosion. During these weather events, the nutrients from the soil are washed away into nearby lakes and rivers, polluting them. The extreme rainfall then leaves the soil less capable of supporting crop growth, the Global Change report adds.
Yet More Cons to CO2
Increased CO2 can also negatively impact crop production by disproportionately benefiting weeds, says Global Change report. Hatfield explained to us that weeds are genetically diverse and, as a result, can adapt to changing environments. Crops, on the other hand, are, by default, inbred and genetically uniform. For this reason, they aren’t as adaptable to changing environments.
There are also other negative effects of burning fossil fuels — such as an increase in ground-level ozone, which hinders photosynthesis and other important plant functions, as the IPCC explains in its report. “This results in stunted crop plants, inferior crop quality, and decreased yields … and poses a growing threat to global food security,” the report adds.
Overall, every expert we spoke with said the net impact of CO2 and climate change will leave crop production and quality worse off in the future, not better.
For example, Myers, at Harvard, told us, “While there may be a small fertilization effect of elevated CO2 on plant growth, this increase will be more than offset by climate change which is causing increased temperatures, changes in precipitation, and complex changes in agricultural pests, pathogens and pollinators.”
Moore, at the University of California, Davis, also told us: “Considering just CO2 fertilization and the effect of higher temperatures, we find that at very small amounts of warming (i.e. one degree C) the net effect might be a slight increase in crop yields.” (Since 1880, the Earth has warmed nearly 1 degrees C already, according to NASA.)
But Moore added that “at higher levels of warming, the negative effect of higher temperatures rapidly comes to dominate the positive effect of CO2 fertilization, causing crop yields to decline markedly, including in the United States.” And that doesn’t even take into account other negative effects, such as “disruptive rainfall patterns” and benefits to weeds, she said.
So Smith is right that there are some positive sides to increased CO2 in the atmosphere, but the net impact is likely negative, especially in the future.