20 Jun 2014
Production Pointers - Dr. Tom Jensen
June 20, 2014 – Don’t rely on just visual observations, or plant analysis from only a poor growth area, to accurately diagnose the cause of the poor growth. It is unwise to only rely on just a plant analysis from a poor growth patch to decide whether or not a nutrient deficiency is the cause of the poor growth. This is because there may be other soil nutrient or physical soil characteristics present that are causing the poor growth. For example on a field I was asked to visit one year, the farmer had been advised by neighbors that he might benefit from a micronutrient application on a field with quite extensive poor growth areas. However, when visiting the site I dug small soil pits in both a poor growth and a better growth area and it observed that the poor growth areas were where there were patches of high sodium level soils, resulting in formation of a shallow hardpan present at a 12 in depth. These poor growth areas were more easily observed in a low moisture year compared to a higher rainfall year. The shallow rooting of the crops was more of a problem in a dry year compared to a more moist crop year. Often use of a shovel to dig small soils pit from both poor growth and better growth areas is a useful activity.
June 10, 2014 – The type of nutrient deficiency observed and diagnosed will determine whether or not a corrective nutrient application will be beneficial. Some nutrient deficiencies can be effectively corrected by an early detection of deficiency and allow an effective top-dress or foliar application for correction of the deficiency. For example most corrective applications of macronutrients N and S, can be done by a top-dress granular or liquid fertilizer application, as long as the rate of application is adequate, but not excessive, and precipitation is received to move the N and S into the soil for crop root absorption. This can also work for a soil mobile micronutrient such as boron (B). Less soil mobile micronutrients, such as copper (Cu), manganese (Mn), or zinc (Zn) can be effectively applied at a low rate as a foliar spray application. It is beneficial to have your possible nutrient deficiency accurately diagnosed by a qualified crop adviser or consulting agronomist before going ahead with an in-crop application.
June 1, 2014 – Observing emerging crops. Much information can be obtained by observing how well your planted crops are doing, soon after crop emergence. For example if there are insect pests present at an economically serious threshold level, you may be able to apply a control measure in a timely manner. If fungal spores are present in a great enough level, the weather is conducive to disease development, and your crop variety is highly susceptible to the fungal strain, you might observe leaf fungal spots present at levels that will spread and a fungicide could be applied at a later growth stage to achieve an economically effective control. Lastly, you may observe patches of nutrient deficiency that could be corrected by a top-dress application of the deficient nutrient.
May 20, 2014 – Accurate seeding rates, depth of planting, soil seed contact and packing pressure, are important for desired crop stands and faster emergence. Don’t compromise effective planting for the sake of faster and sometimes excessive planting speeds. Yes, you can cover more acres in a day at a faster speed, but you may end up with the average seed depth being too shallow due to seed and soil movement out of the seed furrow, poor seed-soil contact because of poor soil cover and inadequate packing by the on-row packing wheel.
May 10, 2014 – Inadequate sleep by equipment operators can result in mistakes in seed depth. Planting can be a very demanding time for persons operating planting equipment. Long hours of field operations may mean persons are getting less than ideal hours of sleep. Sleep deprived equipment operators tend to make more mistakes such as forgetting to change planting depth from a deeper depth (e.g. 2 in) for large seeded pulse and small grain cereal crops, when switching to small seeded oil seed crops (e.g. canola and flax) ideally planted at a ¾ in depth.
May 1, 2014 – Balance farm logistics with efficiency of fertilizer placement. As average farm size continues to increase there is a challenge to plant all the cropped acres within the ideal planting window. For this reason there is a growing trend to broadcast apply fertilizer needs as a pre-plant application. This is usually done using a large fertilizer spreader or pneumatic floater. This type of application is in contrast to side banding all the fertilizer in a one-pass planting operation. This one-pass planting requires more stops to fill with fertilizer and seed, as well requiring more farm labor during the planting operation. However, even though the N and S fertilizer can be successfully applied as a broadcast operation, there is usually a benefit to seed-row, or side-banding (e.g. 1.5 in to the side and 1.5 in. deeper than the seed furrow) the P and K fertilizer. Don’t miss out on the benefit of starter P and K fertilizer, near the seed furrow, even if planting logistics are the emphasis.
April 20, 2014 – Be careful of too many years of seed furrow applied boron (B) and copper (Cu) fertilizers. I have observed and heard of situations where crop yields were declining and it was determined that a micronutrient was lacking. For example in west-central Manitoba on a farm there was concern about declining yields of barley, especially when N, P, K and S rates were thought to be applied at previously adequate rates, and growing season precipitation was not limiting yield. After soil testing was done on these sandy loam soils, it was determined that copper (Cu) deficiency was a possible cause. Application of a low rate of a low analysis (7% actual Cu), high solubility granular Cu fertilizer, e.g. 1.5 lb. actual Cu to the barley crop, it was seen to markedly restore crop yields to anticipated levels. However, the farm manager decided to apply 1.5 lb. of actual Cu every year in each crop of a four-year crop rotation (i.e. barley-field pea-wheat-canola). This was not necessary because only the barley and wheat tended to respond to the copper, and after no more than two applications of Cu in the barley and wheat years of the crop rotation there was sufficient Cu present to adequately supply Cu needs for a few cycles of the crop rotation. Adding excess Cu was an unnecessary crop input cost, plus excess levels could begin to become toxic to crops.
April 10, 2014 – Too much of a good thing can mean poor crop stands. More often than not excess levels of nutrients are unnecessarily applied in a starter fertilizer. For example the majority of N, S, and even eventual required P, K and micronutrients are more appropriately applied in a side band application, or under tilled cropping, possibly a pre-plant broadcast and incorporation application. Excessive seed-row rates of nutrients adversely affect the germinating seed and emerging plant, resulting in lower than desired plant stands. The appropriate, and tolerated seed furrow rates of starter fertilizer depend on the crop and soil conditions. It is useful to speak with your local crop adviser, or retail crop agronomist for advice on safe and useful rates of starter fertilizer.
April 1, 2014 – What nutrients are best placed as a starter fertilizer in a seed furrow? For most planted crops, the emerging plants live off the nutrient supply coming from the seed for the first week after planting. This is because plant seeds contain all the nutrients necessary for germination and early emergence. However, once the roots and true crop leaves begin to develop, plants need to begin sourcing needed nutrients from the soil. On most soils, even quite fertile soils, there can be a benefit from addition of a starter fertilizer, applied at low rates. This is because small plants do not need large amounts of supplemental nutrients. These starter fertilizers should contain dominantly P, and K, with lesser amounts of N, S, and a possible micronutrient such as zinc (Zn).
March 20, 2014 – What type of sample pattern should you use on a field?
The samples should be somewhat random, avoiding less representative minor portions of the field, e.g. a low lying saline area, or an eroded knoll, and also avoiding headlands and field access points because of possible overlap applications in previous years. There is no set pattern, but for convenience in moving about a field, some agronomists recommend a W or M shaped pattern of movement within a field for sampling and scouting purposes.
March 10, 2014 – How many sample sites should you take on a field, or sub-field, to get a representative soil sample?
It is recommended that if field size is greater than 80 acres (32 ha), there should be separate composite samples taken for at least each 80 acre field. Some agronomists recommend separate samples for each 40 acre (16 ha) size field. Regardless of field size whether 80 acres or less, it is recommended to take between 15 to 20 sample cores, mix them together, and take a subsample for analysis.
March 1, 2014 – How often should you consider taking soil samples?
It depends on the nutrient or nutrients in question. For high value crops where accurate levels of available N are needed, it is common to have annual soil sampling and analysis done. For P and K, and most micronutrients, soil testing every three years is considered adequate. The level of availability of P and K doesn’t change drastically from one year to another and these nutrients can be managed well in the longer term, three to five years, where N availability can swing considerably from one year to another.
February 20, 2014 – How deep should you take soil samples?
It depends on the nutrient or nutrients of interest. For nutrients that are very mobile in soil, e.g. N, S, and Cl it is recommended to sample down to 24 inches (0.6m), but for a deep-rooted crop such as sugar beet, sampling down to 48 inches or even down to 60 inches (1.2 or even 1.5 m) is often done. For less mobile nutrients, e.g. P, K and most micronutrients the top 6 inches (0.15m) is adequate, and quite representative of nutrient availability.
February 10, 2014 – When is the best time to take soil samples?
Generally the best time is close to when a crop is planted, so early spring for a spring planted crop. However, in the drier portions of the Northern Great Plains, it has been shown that mid to late fall soil sampling is logistically a useful time to take soil samples. This is because it gives the farmer time to get back soil test results, decide on fertilizer rates and get the fertilizer arranged for early spring application.
February 1, 2014 – Do you know the difference between the various nutrient levels in a soil; total amount, not available, slowly plant available, and immediately available.
This is an important concept to understand, because even though a soil may contain quite high levels of total nutrients they are often present in forms not available, or slowly available to crops. Most soil test extraction methods attempt to measure what is immediately available, plus a portion of the slowly available, that may become available and will be used by a crop during the early part of a growing season and contributes to crop yield. For example in the case of N, well over 90% of the N in soil is contained in organic compounds, the majority of which are not immediately available, or are even extremely slowly available to crop plants. One general estimate of the amount of N being mineralized from the soil organic matter during a growing season is a one half of one percent of the organic matter N present. So, if a soil had an organic matter content of 6% in the topsoil, and 4% of this organic material is actual total N, and the topsoil had an estimated acre furrow (6 2/3 inches deep) weight of 2,000,000 lb, there could be about 24 lb of N/A mineralized or released from the soil organic matter in a growing season. However, the amount of total N in the organic matter is actually 4800 lb N/A.
January 20, 2014 – Have you ever heard of root simulator soil probes?
This is a technology that uses ion exchange membranes packaged in plastic probes that you place in your field soil for a limited time, e.g. three days. There is both a negative ion exchange probe and a positive ion exchange probe. The membranes in the probes simulate the absorption of both nutrient anions and cations into crop roots. At a lab set up to measure the adsorbed ions on the membranes, there can be estimates made of nutrient availability. This technology is useful to help explain why on some soils even though standard soil test methods may indicate sufficient levels of specific nutrients, the actual availability may be restricted by interaction with other nutrient ions or certain site specific soil properties.
January 10, 2014 – Soil test reports have useful information on how to manage your soil.
Quite often we only look at the nutrient rate recommendations on a soil test report, but there is much more information available that can help you manage your soil. For example on regular soil test results there is also information about the soil pH, soil salinity levels, and a description of the availability of all plant nutrients tested. Often, some of this other information may not affect the coming years specific nutrient rate recommendations, but it is a way of monitoring how your soil is doing, and may help you to consider future management decisions. For example if the soil pH levels are decreasing to a level where the soils are becoming too acidic for your crops, you may plan to have ag-lime applied within a couple of years. Another example is if a nutrient or nutrients may be marginal and not yet yield limiting. You may consider applying moderate rates of these marginally available nutrients to prevent the nutrients from becoming deficient and yield limiting.
January 1, 2014 – Keep your crop quality goals in mind when developing your nutrient rates?
When developing nutrient management plans, and deciding on what nutrients to supplement, and what forms of fertilizers to use at needed rates, timing and placement, it is important to not only consider the target yield of the crop but also the quality of the harvested portion of the crop. For example, in some crops you may be able to add additional N to increase yield but this might reduce the quality of the harvested crops. Two examples are sugar beets and malt barley. Both of these crops achieve wanted crop quality at a N rate that is suboptimal for yield, but yet gives a reasonable yield at a somewhat lower level of protein. When the level of protein is excessive, processing costs are higher, and there is less extractable sugar per acre for sugar beet, and less quality malt per bushel of barley. However for the macronutrients P and K, adequatel supplies can lead to observable increases in crop quality even though the actual crop yield may not measurably increase. This can be for two reasons: 1) having additional P and K can help the crop grow faster and stronger in the cool spring weather so the crop matures earlier in the fall and allows earlier harvest; 2) especially for K and somewhat less so for P, the crop is more naturally resistant to crop diseases, and harvested grain grades higher and gives a better net return to the farmer.
December 20, 2013 – Why Do We Apply Much More Nitrogen than Potassium in Cereals even though these Crops Use Similar Amounts of Each Nutrient?
The real answer for this question is large differences in partitioning within crops, between these two nutrients. For example about 80% of N used by a grain crop ends up in the harvested grain mostly as protein, while only 20% of the N remains in the crop residue including straw, chaff and roots. For K the partitioning is almost opposite, with only 20% remaining in the grain and 80% in the crop residue. So, we recycle the majority of K back onto fields when we return crop residues to the soil, but we harvest and export the majority of N. Even so, we still need to consider replacing K harvested and removed from fields.
Another couple of factors affecting these two nutrients in soil is first that the main form of available K in soil is a positively charged K+ cation. It is attracted strongly to the negatively charged clay particles in soils greatly reducing the potential for leaching losses. Nitrogen however dominantly gets changed over to a negatively charged nitrate (NO3-) ion that is repelled by the negatively charged clay particles, flows along with soil water, and can be leached down and out of the rooting depth of crops. A second factor is that NO3- is very biologically reactive in the soil environment and can be susceptible to losses as N2 and N2O gases to the air under wet soil conditions.
December 10, 2013 – Considering Growing Soybeans? Check Your Soil pH
Soybean is a crop that can display iron (Fe) deficiency on high pH (> 8.2) soils more than many other crops. Extensive research on this topic has been done in the Red River Valley of eastern North Dakota. Fe deficiencies are usually indicated by chlorosis (yellowing) of younger growth. Research by Dr. R. Jay Goos at North Dakota State University has shown that growing varieties more tolerant of the high pH soil conditions is the most effective way to manage Fe deficiency of soybean on these high pH soils. His research also showed some benefits from using applications of Fe containing foliar fertilizers, and or Fe containing seed treatments, but these methods were less effective compared to planting soybean varieties more tolerant of Fe deficiency (Goos and Johnson, 2000). You may not farm in the Red River valley of eastern North Dakota or southern Manitoba, but on many farms in the Northern Great Plains you might have portions of your fields with high soil pH, for examples on eroded hilltops. If these eroded, high pH areas are a significant part of your overall fields you might consider finding out which soybean varieties are more Fe deficiency tolerant, or consider adding in some foliar Fe fertilizer into the spray tank, at the time of in-crop herbicide applications.
December 1, 2013 – It is Important to Know the Previous Crop when Deciding on Nitrogen Fertilizer Rates.
If you grew a pulse crop (e.g., soybean, lentils or field pea) the previous year, chances are you should have slightly more available N for the following crop, compared to if you had grown a cereal crop. This is because the C:N ratio of pulse crop residues (e.g., 20:1) is lower compared to a cereal crop (e.g., wheat straw 80:1, and corn stover 60:1). In many states and provinces in the Northern Great Plains, an N credit is considered after growing a pulse crop. For example about 1 lb N/A for each bu of pulse crop yield. So if a 40 bu pulse crop was grown, there could be 40 lb of available N to be mineralized out of the pulse residues, for the following cereal crop. This can result in slightly lower N rates compared to planting a cereal crop into cereal crop residue (e.g., corn into corn residue).
November 20, 2013 – Relying on Nutrient Deficiency Symptoms before Taking Corrective Action May lead to Yield Loss
It is better to have an indication of a potential nutrient deficiency from fall or early spring sampling soil test results, than to wait until a deficiency is observed in a growing crop. This is especially so for less mobile macronutrients such as P and K, where in-crop applications rarely result in yield increases. There is a better chance to correct N and S deficiencies with an early in-crop application. But even for N and S the additional fertilizer should be applied before stem elongation stage of crop growth.
November 10, 2013 – How does the Multiple Freeze Thaw Cycles Experienced During the Winter and Spring Period in the Northern Great Plains Affect Nitrogen Release from Crop Residues?
Generally, plant-available soil N will be higher in the spring than in the previous fall. This is because the freeze thaw action in fields tends to help break apart crop residue particles, and soil organic matter, plus kill off some of the soil microbe population. All of this results in a flurry of renewed microbial growth and decomposition of organic materials resulting in a release of available N. It is important to understand this when comparing soil test N level results from a fall soil sampling to a spring soil sampling. Often the spring sampling may have 10 to 20 more lb of available N/A. Keep this in mind when deciding on your N fertilizer rates for a field next year. The field sampled in the fall will probably have slightly more available N come springtime.
November 1, 2013 – Your Neighbor Asks if You Want Manure from His or Her Cattle Feedlot, Applied to Your Fields.
Before accepting manure onto your fields it is important to know the properties of the manure. This can be best determined by analyzing a representative sample from the manure. One of the properties vitally important is the average carbon to nitrogen ratio (C:N) of the manure. This can be greatly affected by what type and how much bedding has been used. For example, I was asked in the summer of 2002 to visit a few poor growth fields of barley in central British Columbia, while I was visiting with a fertilizer dealer agronomist there. The farmer said he was disappointed in the growth of the barley crop on the fields. The fields displayed N deficiency. We asked what rate of N was applied. The farmer said around 80 lb N/A, reasonable for the area, but then also mentioned he had applied 20 tons/A of feedlot manure. He thought that with the applied N as urea fertilizer, plus the feedlot manure the crop should have had plenty of N. We asked what type of bedding was used in the feedlot. Because of the local lumber mills, they used sawdust for bedding. This was great for cattle health as sawdust is an excellent a bedding material to absorb moisture, but the C:N ratio of spruce wood sawdust is about 1000:1, compared to a wheat straw having a C:N ratio of 80:1. The sawdust bedding would tie up about 12.5 times as much N compared to wheat straw if it composed the same proportion of the manure applied to fields. We recommended he top-dress additional N onto the barley fields to correct the N deficiency.
October 20, 2013 – A Soil Property that Indicates How Much Nutrient a Soil Can Store is Called Cation Exchange Capacity (CEC).
CEC is a measure of what volume of positively charged cations such as calcium (Ca2+), magnesium (Mg2+), potassium (K+), sodium (Na+), and hydrogen (H+) a soil can retain. It is described in units of milliequivalents per 100 g of soil (meq/100g). It is greatly affected by the content of clay particles in a soil, the type of clay, and also the level of organic matter in the soil. The following table gives general CEC ranges for various soil textural classes.
Table 1. Typical CEC (meq/100 g) of Some Soil Textural Classes
Soil Texture | Typical CEC Range |
| Sand and Loamy Sand | 2-6 |
| Sandy Loam | 3-8 |
| Loam | 7-15 |
| Silt Loam | 10-18 |
| Clay and Clay Loam | 15-30 |
A generally accepted formula for calculating CEC if you know the percent clay content and soil organic matter content is as follows:
CEC = 0.5 x % clay + 2 x % O.M.
For example if a soil had a clay content of 10%, and a soil organic matter content of 5%, the CEC could be estimated as = (0.5 x 10) + 2 x 5. The calculated value for CEC is 15. Generally speaking a soil with a higher CEC has greater inherent fertility and will require less additional fertilizer than a soil with a lower CEC. Usually CEC can’t be altered significantly but it is useful to know the CEC of a soil to help you know the natural soil fertility of a soil.
October 10, 2013 – When was the Last Time You Checked the pH of Your Soils?
Most crops grow best at a so-called neutral pH, generally between pH 6.5 to pH 7.2. If your soil pH has gradually acidified to below pH 5.5 or lower you can apply agricultural lime, mix it into the topsoil, and raise the soil topsoil pH into the neutral pH range. This generally improves nutrient availability and crop growth. The best way to check soil pH is to have soil samples taken from your selected fields and analyzed at a soil test laboratory. Most laboratories can also do a test to determine how much lime to apply to raise the soil pH up to a more neutral level. This is called a lime requirement test.
If your soil has an inherently high pH, for example 8.2 or even up to 9.0, it is possible to apply fine particle size elemental S and mix it into the topsoil to lower the pH. As soil microbes oxidize the elemental S, sulfuric acid is produced and the release of hydrogen ions (H+) lowers soil pH. This process can be done in much the same way as using agricultural lime to raise the pH, however this acidification of soil using elemental S tends to be excessively costly on a field basis and is used more in horticultural applications on smaller fields for high value crops, or for container grown plants that require low pH or acidic soil conditions. For most field crops it is more economic to grow crops more tolerant of high pH, and or apply required nutrients to a crop that are more available under high pH soil conditions.
October 1, 2013 – Taking Care of Soil Microbes Helps Crops Grow Better.
Many soil microbes help crops obtain necessary nutrients, so management practices that encourage microbial growth usually improve crop growth. For example, Rhizobium species bacteria form nodules on legume crops and fix N for the legumes from N gas in the air. Mycorrhizal fungi grow into many crop species roots, while extending their branches (hyphae) out into portions of the soil where roots don’t reach. This effectively increases the rooting exposure to more of the soil mass, and helps supply P and other plant nutrients to crops. Most soil microbes do better in soils where crop rotations, along with residue conserving management, return higher quantities of crop residues to the soil. In the longer term this helps to gradually increase soil organic matter content to an improved level. Higher soil organic matter content is beneficial to soil microbes and subsequently to the crops grown in the soil.
September 20, 2013 – How long has it been since you had soil sampling done on some of your fields?
Having soil samples taken and analyzed from your fields is one of the best methods to monitor plant nutrient availability for next years crop, and help determine the optimum rates of fertilizer you will apply. It is advised to have samples done at least once every three years, especially to monitor P and K availability. It can be useful to sample more often if you are concerned about N levels. If it has been more than five years since soil samples have been taken, or you are growing different crops in rotation, or recently you are growing higher yielding crop varieties, it may be time to have soil sampling done.
September 10, 2013 – When is the best time to take soil samples?
Usually in the Northern Great Plains region it is advised that soil sampling be done after harvest from mid fall to early winter, or when freeze-up occurs. By this time soil temperatures have cooled sufficiently so there will be little change in mineralized N levels. For most of the other nutrients, P, K, and S, etc. you could soil sample almost any time of the year, but for convenience the fall after crops are all harvested field access is best. Also most falls tend to be a time of the year when we receive lower amounts of precipitation and travelling over field with trucks equipped with hydraulic soils samplers is possible. Early spring is also an excellent time to take soil samples, but spring time tends to be more hectic, fields can be to wet to drive on. Also if you have soil sampling results available in late fall you have all winter to look over the analysis results and decide about next years fertilizer rates. Having made fertilizer rate decisions in the late fall or early winter you can arrange your fertilizer purchases and deliveries from your local fertilizer dealer.
September 1, 2013 – Does weed growth in the fall remove nutrients from next years crop?
It all depends on how much weed growth there is. For example if you harvested a winter wheat crop in late July, and you had warm and moist weather from after harvest until well into the fall, there could be lots of weed growth. This weed growth could take up and immobilize considerable amounts of nutrients. These nutrients are not lost, but could be tied up and less available for next years crop, until the weed residues are decomposed. To reduce weed use of nutrients you may choose to either cultivate a field, or spray weeds with a non-selective herbicide in the early fall, e.g. the first week of September.
August 20, 2013 – Mycorrhizal fungi an important friend to most crops
Many of our crop plants rely on a symbiotic relationship with soil fungi called mycorrhiza to grow well. Mycorrhiza are soil-inhabiting fungi that colonize crop roots by growing into or on the outside of plant root cells. They have been shown to more effectively dissolve some insoluble plant nutrients in soils compared to plant roots themselves. The mycorrhiza use these nutrients for their own growth and also share the nutrients with the crop plants. The crop in turn shares photosynthetic sugars with the fungi and this helps the fungi grow better. An example is mycorrhiza that help crops such as wheat, soybean, corn, flax, and peas obtain additional phosphorus from soils. The fungal hyphae or strands go out from the crop roots into the soil where roots aren’t growing and this effectively increases access to more parts of the soil or increases rooting area. Some crops are not hosts for the mycorrhiza and are called non-mycorrhizal crops. Canola is a non-mycorrhizal crop, and sometimes after canola is grown the following mycorrhizal host crop may show early growing season P deficiencies until a healthy mycorrhizal hyphae network is re-established in the soil. There have been attempts to grow the mycorrhiza commercially and apply it as inoculants to crops. This has had limited success, but research continues.
August 10, 2013 – Plant growth promoting bacteria
Bacteria living near or on crop roots can benefit crop growth. Normally the first soil bacteria thought of as beneficial to crops are the Rhizobia species of bacteria that live in the root nodules of legume crops and supply nitrogen to those crops. However, there are other bacteria that can help crops. These are bacteria that live in the soil near roots (rhizosphere) and have been shown to help plants by enhancing root absorption of nutrients, produce plant growth enhancing hormones, or by controlling antagonistic root fungal organisms. There have been attempts to develop commercial inoculants of some rhizosphere bacteria that you could treat crop seed with and the bacteria will multiply and grow in the rhizosphere and improve crop growth. However, many attempts have worked well in greenhouse trials but not well in field trials. If you are approached to purchase and use one of these products ask for field research results, hopefully close to your cropping region, done by third party researchers at a university or government research station, that show significant benefits to the crops you grow.
August 1, 2013 – Crop roots help feed soil microbes
We usually think of crop roots as absorbing water and nutrients for plant use, but roots are also an important food source for soil microbes that live in the soil near the roots (rhizosphere). As a plant grows some of the photosynthetic products (e.g. sugars) are moved from leaves down into the roots to nourish the roots, but a portion of these sugars are leaked out of the roots and nourish soil microbes including bacteria, fungi and actinomycetes. In most cases these soil microbes live in a friendly co-existence with the plant. The sugars also act as an energy source to help the soil microbes decompose previous crop residues and soil humus. After crops reach maturity and are harvested the dead crop roots become an additional food source for the soil microbes.
July 20, 2013 – Have you considered planting winter wheat on a field where you planned to plant a spring crop, but couldn’t because of excess spring rains?
If a field was left unplanted to your regular spring planted crop because of excess spring rains, consider planting winter wheat on that field in the early fall as an option. You can prepare for planting the wheat by controlling weed growth on the field during the summer after the field dries up sufficiently. Check with your local agriculture retail dealer or seed grower for winter wheat varieties well suited and available for your area. There has been good progress made developing high yielding and winter hardy winter wheat varieties for much of the southern portions of the Northern Great Plains.
July 10, 2013 – What happens to the nutrients on land fertilized but not planted because of excess moisture?
It is unfortunate to have applied fertilizer to part of a field and then be prevented from planting a crop because of excess spring rains. There is often concern that the nutrients applied may be lost. It depends on whether or not wet conditions persist and the nutrient in question. For the less mobile nutrients P and K there is little chance of losing these nutrients. Although if P and K was surface broadcast and not incorporated some losses may occur from granules being dissolved and some soluble P and K being lost in surface runoff water. If incorporated or subsurface banded both P and K will react with soil and losses are very minimal. P reacts with soil cations such as calcium and magnesium forming low solubility compounds, or with soil organic humus again becoming less mobile. Potassium is strongly attracted to clay particles and is retained on or between clay and clay particle layers in the soil.
Both N and S do have more potential to remain dissolved in soil water and be lost due to leaching down through the soil, or become lost as gaseous forms if wet conditions persist. Under wet conditions soil microbes become oxygen starved due to the soil pores being filled with water and having little air. Under these low oxygen conditions they will source oxygen first off nitrate ions and then sulfate ions. The nitrate can be lost as N2 or N2O gases, while sulfate can be lost as H2S gas. Normally N losses are much more prevalent than S losses. It is difficult to know exactly how much of the N and S is lost from a soil. You can take soil samples in the fall or following spring, after the wet affected areas dry up, and have a soil test laboratory analyze for nitrate and sulfate levels in the soil. This will give you an indication how much of the applied N and S fertilizer remains.
July 1, 2013 – Management options for land too wet, too long to be planted
In springs with excess rainfall there are low lying portions of fields that are too wet, for too long to allow planting of regular crops. But after the areas dry up later in the spring and summer, there are a couple of options for what can be done so they don’t turn into weedy patches. Weed control is advised to prevent build up of weed seeds in the soil. One is to fallow the area using either tillage, or a non-selective herbicide, or a combination of tillage and non-selective herbicide. Another is to plant a later seeded cover crop once the areas are dry enough to allow access with equipment. This cover crop, e.g. oats, can be used as a green feed crop for hay, or terminated in the early fall using tillage or a non-selective herbicide.
June 20, 2013 – Which major plant nutrients should be considered for a top-dressing application?
If significant portions of a field are diagnosed with a nutrient deficiency at an early stage of crop growth, for example before stem elongation, a decision will be made whether or not to consider an in-crop application to try to correct the deficiency. Of the major plant nutrients, namely N, P, K and S, it is possible to correct N and S deficiencies but much less possible to correct P and K deficiencies. Both N and S are mobile in the soil, and as long as sufficient moisture is received after applying the fertilizer, it should move to plant roots and the crop’s N or S status should improve. Both P and K are so slowly mobile in the soil that an in-crop rescue application for a P or K deficiency is usually not effective. Usually the better strategy is to make plans to supply sufficient P and K for future crops.
June 10, 2013 – Don’t forget rate when applying a micronutrient.
There are many ways to apply a needed micronutrient for a crop. You can apply a granular or liquid product as part of a pre-plant broadcast and incorporate or banded blend, or a powder seed-dressing, or a granular product included in a dry seed-row or side-banded blend at planting, or a liquid product in a liquid seed-row or side-banded blend at planting, or lastly a post-emergent foliar liquid application. Some people claim one method is more effective than another. However it is important to make sure the rate of micronutrient applied is sufficient to supply the amount of micronutrient needed by the crop. One of the methods described above may be a bit more effective than another, but if the actual rate applied is too low it doesn’t matter how effective the method of application is, the crop needs to absorb sufficient amount of the nutrient to improve crop growth.
June 1, 2013 – Many field tours occur in late June or July, so check dates and locations
I like taking the opportunity to attend summer field days at research centers, or field tours organized by grower commodity organizations. There is useful information presented about new crop varieties and new cropping technologies. It is worth the time to check the websites or newsletters of local ag-extension centers, or grower organizations, to find out the scheduled dates of field days or tours in your area. You usually cannot attend all of the events you would like, but it is disappointing to hear about a tour you would of liked to attend but didn’t know about it until after it happened.
May 20, 2013 – Plant analysis and soil testing
When scouting fields after crop emergence a farmer or crop adviser will notice patches of poorer growth compared to the rest of the field. One of the purposes of crop scouting is look at these poorer growth areas and determine what might be the cause of reduced growth. The cause may be an infestation of weeds, insects, a fungal disease, or a nutrient deficiency. If after initial investigation the adverse effects of weeds, insects or fungal disease are ruled out and a nutrient deficiency is suspected, it is important to further investigate effectively. It is suggested that notes and photographic images be taken of visual differences between poor growth and good growth areas. Also it is useful to take plant and soil samples from both the poor growth and good growth areas. These samples can be sent to a soil and plant test laboratory for analysis. Usually by having both soil and plant analyses it is easier to determine if a nutrient is lacking, compared to just having plant analysis results.
May 10, 2013 – The acres planted to canola in the Northern Great Plains region (NGP) increased to all time highs in 2012.
The acres planted to canola continue to increase in all provinces and states in the NGP. This has resulted in total acres in the NGP going from 13,205,000 acres in year 2000 up to the all time high of 22,491,000 acres in 2012. Canola consumes more S per bushel of harvested grain compared to cereal crops. Wheat for example uses 1 lb of S for every 10 lb of N. In contrast canola uses 1 lb of S for every 6 lb N applied. If an average N rate of 80 lb N/A is applied to both wheat or canola, a canola crop would require 13.3 lb S compared to 8 lb S for the wheat crop. If you are growing more canola on your farm you will need to apply more S fertilizer to satisfy the S needs of this crop.
May 1, 2013 – Potassium for soybean and pulse crops
If you haven’t ever grown soybeans or pulse crops (dry peas, dry beans, lentils or chickpeas) and you want to include them in your crop rotation, you may need to consider applying higher rates of K in your fertilizer blends. For example if you compare wheat to dry peas or soybean at the equivalent 50 bu/A yields, the amount of K removed with the harvested grain is respectively 17, 30 and 65 lb of K2O/A for wheat, dry peas and soybeans. More soybeans or pulse crops in your rotations means more removal of K. Applying potash (KCl, 0-0-60) is an excellent way to supply needed K.
April 20, 2013 – If you grow a new higher yielding variety or hybrid, you may need to increase your fertilizer rate.
If you treat a high yielding crop like a lower yielding crop you may just get a low yield. I’ve seen situations where a farmer has switched from a lower potential yielding hybrid to a higher yielding hybrid but didn’t increase the fertilizer rates applied and ended up with disappointing yields. If a new variety or hybrid has been recently introduced to your area, check with farmers or seed company representatives who have experience with the new variety or hybrid to know what fertilizer and management practices are used to exploit the greater yield potential.
April 10, 2013 – If droughty conditions were experienced last year and spring soil moisture is low at planting, what is a reasonable strategy for fertilizer rates?
Many farmers will have a tendency to reduce all fertilizer nutrient rates after dry conditions the previous year. However a contingency plan should be considered if moisture conditions improve significantly early in the growing season. For example it is advised that P and K rates remain close to regular rates just in case moisture conditions improve, as it is difficult to supply additional amounts of these two nutrients as an in-crop application. However, N and S can be successfully top-dressed if ample post-planting rainfall is received. Discussion should be done with your local retail fertilizer dealer to determine if you will be able to access N and S fertilizers for top-dressing if needed.
April 1, 2013 – Excess seed-row fertilizer can reduce plant stands, delay maturity, and sometimes reduce yields.
Seed-row fertilizer can be an effective way to apply required nutrients to a crop, however there should be caution that the rate of the fertilizer applied isn’t excessive. If too high a rate is applied there can be fertilizer salt injury. Also, if the N rate is too high using urea as an N source, or an ammonium containing N source under higher soil pH conditions (e.g. pH 7.5 or higher), the generation of free ammonia (NH3) can cause ammonia toxicity to germinating seeds and seedlings. Either way excess salt injury or excess ammonia concentrations can kill or delay germinating seeds and seedlings. Check with your local agronomist or crop adviser for advice so that adequate but safe rates of seed-row fertilizer can be applied considering your planter design, row spacing and local soil conditions.
