Category Archives: Fertility

In-season Plant Testing Interpretation During Dry Soil Conditions

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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

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Cotton Specialists’ Corner Podcast: PGR use on dry acres, farms with mixed maturity

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We are quickly approaching the period of time in which we typically apply PGRs.  Unfortunately, May was not kind and June has been dry.  Many are struggling with figuring out when to start PGR applications and how aggressive we should be with that first application.  In this blog, I link to our most recent Cotton Specialists’ Corner podcast on this very issue.  This episode highlights several things to keep in mind before we run a stiff rate of PGR to an already stressed plant and potentially hurt yields.

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2022 UT Soybean Scout Schools

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UT’s Soybean Scout Schools will be held in July (see details below). These field-side programs cover the basics of soybean growth, scouting, pest identification, and general management. Pesticide recertification and CCA CEU points will be available. Scout Schools are offered free of charge with sponsorship from the Tennessee Soybean Promotion Board. Registration is not required. Participants will receive a scouting notebook and a sweep net while supplies last.

West TN – Madison County, July 11th, 9:00 AM – 11:30 AM. This school will be at the West TN Research and Education Center, 605 Airways Blvd. Jackson TN, 38301. Signs will be up at the station to direct you to the field.

West TN – Henry County, July 12th, 9:00 AM – 11:30 AM. This school will be at Norwood Farms, 645 Norwood Rd, Mansfield, TN.

Middle TN –  Lincoln County, July 13th, 9:30 AM – Noon. This school will be at H&R Agri-Power, 11 Highland Rim Road, Fayetteville, TN 37334.  Lunch will be provided courtesy of H&R Agri-Power. A head count is required for the meal,  please contact Bruce Steelman of the UT Lincoln County Extension Office at (office) 931-433-1582 or (cell) 615-542-1364 if you plan to attend.

 

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Ascochyta, herbicide burn, poor stand. . . do I replant it?

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Large rainfall events and cool weather in late May strained Tennessee’s cotton crop.  In some areas, individuals are considering replanting cotton that failed to emerge or cotton that appears to be just sitting.  In other areas, reports of damaged or desiccated cotyledons have been reported and healthy, large cotyledons are hard to find most anywhere. In this blog, I cover a few rules of thumb to consider when determining whether or not to keep the stand and give a few words of advice to those that are considering May 30-something cotton. Continue reading

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UT Cotton Scout School

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The UT Cotton Scout School is scheduled for the last Friday of the month, May 27th, at the West Tennessee Research and Education Center (605 Airways Blvd, Jackson). There is no fee, and preregistration is not required. Registration begins at 8:00 AM with the program starting at 8:30. Content will include classroom and hands-on training with an optional go-to-the-field session after lunch. Topics covered will include cotton development and identification and symptoms of insect pests, plant diseases, and weeds.

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UT Cotton Scout School (Friday, May 27, 2022)

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The UT Cotton Scout School is scheduled for the last Friday of the month, May 27th, at the West Tennessee Research and Education Center (605 Airways Blvd, Jackson). There is no fee, and preregistration is not required. Registration begins at 8:00 AM with the program starting at 8:30. Content will include classroom and hands-on training with an optional go-to-the-field session after lunch. Topics covered will include cotton development and identification and symptoms of insect pests, plant diseases, and weeds.

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Management Practices to Optimize Nitrogen Fertilizer Use with High Fertilizer Prices

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Nitrogen (N) fertilizers may be a limiting factor for corn production based on rising N fertilizer prices and other production input. There are a few things to consider with high N fertilizer prices: (a) apply N fertilizer at the right time, (2) add or treat urea-based fertilizers with a proven N stabilizer, and (3) apply the N fertilizer at the appropriate N rate.

Apply N fertilizer at the right time

Preplant N application in corn is not recommended in Tennessee because of the length of time from application to when the corn plant will begin significant N uptake. One exception is the application of anhydrous ammonia with properly calibrated equipment. Corn plants take up little N (<12% of N uptake during the growing season) until V6 growth stage, with the most active period of N uptake occurring between V8 to V14. Hence, there is a greater risk for N loss via ammonia volatilization or nitrate leaching from preplant N. Split application is recommended when N rates are greater than 120 lb N/A. A typical split management practice is to apply a third of the total intended N per acre at planting and sidedress the remaining N fertilizer between V4 to V6. Split application also provides flexibility to adjusting N rate during growing season as compared to just a single application at planting. Split-application of a third of the recommended N at planting and sidedress the remaining N fertilizer provides greater yield than single application at planting (Figure Below-average across six trials). Continue reading

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Integrating Cover Crops in Nitrogen Management

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.

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