All posts by Dr. Frank Yin, Systems Agronomist

26 May 2021

UT Fertilizer Recommendations for Optimal Corn Productivity- Focus on K

26 May 2021
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This is the third article in a series of blog articles that will focus on some fundamental information on UT fertilizer recommendations for corn, with a different nutrient featured in each article. Commonly recommended nutrients for use in corn production in TN include nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and zinc (Zn). Each nutrient will be discussed in terms of the relevant soil test that may be used or used in recommendation; recommended preplant, starter, sidedress, and foliar fertilizer applications; and plant/tissue analysis. Today’s blog will focus on UT potassium recommendations for optimal corn productivity under conditions in TN. Potassium is a macronutrient that plays important functions in the plant including protein and starch formation in the grain, movement of water, nutrients, and carbohydrate within the plant, stomata closure, cell wall and stalk strength. Thus, corn plants with inadequate K are susceptible to drought stress, diseases and insects, and greater risk of lodging after maturity. Additionally, K-deficient corn plants may have shorter ear length and narrower ear diameter.

 

Soil test for potassium

Potassium fertilizer application rate should be based on soil test. In TN, K fertilizer recommendations are based on Mehlich I extraction procedure because it correlates well with the soils in Tennessee. Detailed information on how UT recommendations were developed is addressed in UT Publication W795, University of Tennessee Fertilizer Recommendation Development. Recently, a calibration for Mehlich III was established for west TN soils and ranges of sufficiency for soil K using Mehlich III testing are described in the UT Publication, UT Fertility Recommendations for Tennessee Row Crops.

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19 May 2021

UT Fertilizer Recommendations for Optimal Corn Productivity

19 May 2021
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This is the second article in a series of blog articles that will focus on some fundamental information on UT fertilizer recommendations for corn, with a different nutrient featured in each article. Commonly recommended nutrients for use in corn production in TN include nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and zinc (Zn). Each nutrient will be discussed in terms of the relevant soil test that maybe used or used in recommendation; recommended preplant, starter, sidedress, and foliar fertilizer applications; and plant/tissue analysis. Today’s focus will be on phosphorus (P).

UT phosphorus (P) fertilizer recommendations for optimal corn productivity

Today’s blog will focus on UT phosphorus recommendations for optimal corn productivity under conditions in TN. Phosphorus plays an important role in plant reproduction especially pollination and kernel setting. In adequate P can reduce stalk strength, delay crop maturity,  poor kernel set and lead to yield loss.

Soil test for phosphorus

UT Publication PB 1645, Best Management Practices for Phosphorus in the Environment provides an excellent review on phosphorus. Phosphorus fertilizer application rate should be based on soil test. In TN, P fertilizer recommendations are based on Mehlich I extraction procedure because it correlates well with the soils in Tennessee. However, a calibration for Mehlich III has been established for west TN soils is described in the UT Publication SP763, UT fertility recommendations for Tennessee row crops. Detailed information on how UT recommendation was developed is addressed in UT Publication W795, University of Tennessee Fertilizer Recommendation Development. Row crop sustainability. Extension Publication, SP763. Continue reading →


17 May 2021

UT Fertilizer Recommendations for Optimal Corn Productivity

17 May 2021
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This is part one of a series of blog articles that will focus on some fundamental information on UT fertilizer recommendations for corn. Commonly recommended nutrients for use in corn production in TN include nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and zinc (Zn). Each nutrient will be discussed in terms of the relevant soil test that maybe used or used in recommendation; recommended preplant, starter, sidedress, and foliar fertilizer applications; and plant/tissue analysis. To ensure simplicity and better assimilation of the voluminous information, each nutrient will be featured on a different day of this week. Today’s focus will be on nitrogen (N).

UT nitrogen (N) fertilizer recommendations for optimal corn productivity

Today’s blog will focus on UT nitrogen recommendations for optimal corn productivity under conditions in TN. Nitrogen is a major component of chlorophyll (the green pigment), that is essential for photosynthesis. Hence, its deficiency tends to cause chlorosis. In addition, inadequate supply of N at critical growth stage can reduce ear size and lead to yield loss.

Soil test for nitrogen

Plants use N in the nitrate (NO3–) and ammonium (NH4+) forms. However, ammonium levels are generally very low in upland soils so soil nitrate tests are used to measure plant available N and adjust N fertilizer applications for corn. There are two commonly used soil nitrate tests used in the US, the Pre-Plant Nitrate Test (PPNT) and Pre-Sidedress Nitrate Test (PSNT). Soil samples for PPNT is collected prior to preplant N application while PSNT are collected prior to pre-sidedress application.

In TN, only the Pre-sidedress Soil Nitrate Test (PSNT) is recommended for corn production, particularly for producers using animal manure such as poultry litter. Detailed information on sample collection and processing procedure are described in the UT Publication, The Pre-Sidedress Nitrate-N Soil Test (PSNT) For Nitrogen Management in Corn Production Systems of Tennessee. Interpretation of the PSNT in Tennessee is made based on yield potential of the field, soil test level, and field history.

In TN, current N application rate for corn production is based on yield goal. However, adjustment can be made based on past production records and PSNT if applicable. Another tool available for estimating corn N rate is the Nitrogen Rate Calculator at www.utcrops.com.

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22 Apr 2020

Does boron fertilizer use increase corn and soybean yields?

22 Apr 2020
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Boron is associated with cell wall biosynthesis, cell wall structure, membrane function, pollen germination, pollen tube growth, and carbohydrate metabolism; hence, insufficient supply can severely impair crop performance, and ultimately result in sub-optimal yields.
Boron deficiency symptoms vary among crops, but, are often noticed on the youngest leaves or terminal buds since boron is not very mobile within the plant. In some crops, deficiency symptoms appear as misshaped leaf blades (Fig. 1). Failure of seed and fruit set has been observed on boron deficient soils (Fig. 2). Deficiency in boron during flowering and fruit may reduce the retention of bud flowers and developing fruits. Some boron deficient crops tend to have short internodes and swollen nodes giving the crops a bush appearance.

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03 Apr 2020

Minimizing Nitrogen Loss in Row Crop Production Using Nitrogen Stabilizers

03 Apr 2020
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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 →