In season plant tissue testing helps producers monitor plant nutrition and can be useful in diagnosing nutrient deficiency. Detecting deficiencies early can allow the corrective or preventive action that will minimize yield effects from deficiency during the growing season. Nutrient concentrations vary greatly with plant growth stages and the part of the plant that is sampled so specific sampling guidelines and interpretation have been instituted to prevent false diagnosis. Continue reading
Cover crops can supply nitrogen (N) to the soil for the subsequent cash crops and this nitrogen credit may be successfully integrated into N management. The challenging question is how much of the N supplied by cover crops is available for the next cash crop. Unfortunately, there is not a simple answer to this question since several factors influence the N availability from cover crops. There are two primary considerations if the goal of planting cover crops is to contribute N to the soil: the proportion of species in cover stand and the timing of cover crop termination.
The proportion of species in the established cover stand is important because different species have different effects on N. Depending on the species of cover crop planted, soil N may be removed or supplied to the soil. Grass cover crops (e.g. cereal rye, annual rye, wheat, oats), which are referred to as “scavengers” take up nitrates from either residual N fertilizers or organic matter decomposition. So, grasses do not contribute a whole lot to the soil N since not all of the scavenged N is available for the next growing season. An established cover stand comprised of all or mostly grasses will not provide any significant N benefit. Hence, the recommended N rate for the cash crop should not be reduced. In contrast, legumes (e.g. clover, winter pea, hairy vetch) supply additional soil N through biological N fixation. A well-established legume cover crop stand would supply sufficient N to warrant reducing the recommended N rate. UT currently recommends a 60 to 80 lb N credit for a well established legume cover crop that has reached early bloom.
Generally, most growers plant multispecies of cover crops with less than 50% of biomass being a legume. Since legumes supply N, a good percentage of legume in cover stands is required to maximize plant available N for the next cash crop. A study in TN has shown that 30% legume biomass in cover stands can supply up to 43 pounds of N per acre when terminated late. It is critical to evaluate a stand of mixed species cover crops to determine actual legume proportion if some N credit is desired.
The second consideration is the timing of cover crop termination. There is a thin line between growing cover for extended periods to maximize plant available nitrogen (PAN) and yield loss of the cash crop. Generally, if the goal is to maximize PAN from a well-established legume stand, late termination may be a preferred choice. It is worth pointing out that late termination would result in delayed planting and increase the potential for yield loss of cash crops such as corn. If the legume is terminated early, those plants are smaller and have less time to fix N which can be released back into the soil. In contrast, well-established grass stands must be terminated early, especially if growing a cash crop with high N demand (e.g. corn). This strategy will not necessarily supply N but, rather prevent N from being tied up in the soil.
In summary, unique challenges presented by rising N fertilizer costs may present opportunities to rely on cover crops to meet some N need for the next cash crop. However, to integrate cover crops in N management, the cover crop should consist of at least 30% of established legume in the cover crop stand and should be terminated at early bloom. Currently, UT only recommends a N credit of 60-80 pounds per acre of plant available N following a single species well-established legume cover crop that has reached early bloom.
If you haven’t noticed, our UTcrops.com website has gotten a facelift. You may not recognize it when you first visit us at https://utcrops.com/. However, it’s organized similarly to the old version. I’m sure there are a few bugs that need to be fixed, but take a look! This site gives you ready access to essentially all UT resources related to row crop production.
Generally, a nutrient deficiency occurs as a result of low soil nutrient levels. However, prevailing environmental conditions, soil properties, and growth conditions may restrict nutrient uptake and induce deficiencies in crops even if soil nutrient levels are deemed sufficient for optimum yield. For example, low or high soil pH, soil compaction, and excessively wet or dry soil may prevent nutrient uptake. A handy diagnostic tool to identify nutrient deficiency in crops is via visual symptoms. In some instances, this tool may not provide a definite diagnosis of the nutrient status of the plant. Keep in mind that there are other conditions that are cable of inducing symptoms that closely resemble those of nutrient deficiencies. Visual symptoms should be corroborated with tissue and/or soil testing. Adequate knowledge of visual symptoms and tissue testing may help guide corrective actions in-season or preventive action in the following season to avoid yield loss.
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I am Nutifafa Adotey, University of Tennessee’s Soil and Nutrient Management Extension Specialist. A thriving and productive land for subsequent generation is of uttermost importance to every farmer, rancher, or grower. This survey is designed to gather brief but valuable information on some basic production practices in Tennessee. This information will help with the accurate delivery of innovations or interventions on soil fertility that caters to the needs of producers in Tennessee.
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Nitrogen (N) fertilization is a costly operation for most row crop producers. Consequently, it is important to implement best management practices (BMP) available for N fertilizer application in order to be profitable. The problem with N fertilizers is their potential to be lost through different N loss pathways: ammonia volatilization, denitrification, and leaching. Spring of 2020 has been generally wet and if this weather pattern continues, farmers should have no problem receiving incorporating rain, minimizing risk for ammonia volatilization from surface-applied at planting N. In TN, most row crop producers split-apply N, with the majority of N fertilizer applied as a sidedress which is closer to the period of high N demand. Since a large portion of N is applied as sidedress, there is the greatest risk for N loss depending on management practice as well as soil and environmental conditions. Continued wet weather might support the use of nitrification inhibitor type products in wetter soils. This blog addresses N stabilizers as a tool to minimize the risk of N loss and ensure that N is available for crops during the period of high demand. Continue reading