All posts by Angela McClure, Extension Corn and Soybean Specialist

About Angela McClure, Extension Corn and Soybean Specialist

Extension Corn and Soybean Specialist

UT Fertilizer Recommendations for Optimal Corn Productivity- Focus on K

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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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UT Fertilizer Recommendations for Optimal Corn Productivity

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


UT Fertilizer Recommendations for Optimal Corn Productivity

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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