​Rate and Timing of N-P-K Applications on Cotton in the Southeast​

February 2021 | 24 min., 22 sec.
by Glen Harris
University of Georgia


​Rate and timing are two of the four R's of fertilization (which also include source and place), and soil testing is another key element in making decisions about fertilization. Recommended rates for applying nitrogen (N), phosphorus (P), and potassium (K) fertilization are all discussed in the context of soil testing and yield goals, and the discussion of timing for each nutrient considers the efficacy of preplant, sidedress, and foliar applications. Research conducted during 2017–2018 at five Georgia locations and with six yield goals showed that despite a wide range in overall yields by location, small increases in N, P, and K produced good responses by yield goal. Also, on average, even when the higher yield goal was not reached, the increase in yield was big enough to cover the cost of more fertilizer.​​

About the Presenter

Glen Harris ​Glen Harris was born and raised in southern New Jersey, where he worked on vegetable and cut flower farms on Coastal Plain soils. After receiving a BS in Horticulture from Penn State University and MS and PhD degrees from Michigan State University in Crop and Soil Sciences, he was hired by The University of Georgia in March of 1994 as an Agronomist for Soils and Fertilizers. Located in Tifton, Georgia, on the UGA Tifton Campus, his responsibilities include Extension, applied research, and teaching in the area of soil fertility for all agronomic crops. The focus of his programs is fertilizer management for cotton, peanut, and corn. This also includes the management of animal manure such as poultry litter and numerous by-products such as fertilizers, liming materials, and soil amendments. The emphasis of Dr. Harris's applied research program in recent years has been the evaluation of enhanced efficiency fertilizers such as urease and nitrification inhibitors, potassium fertilization of cotton, and calcium nutrition for peanut.

Contact Information:
Email: gharris@uga.edu


In 2020, Grow webcasts had more than 110,000 views. Help support our mission to provide comprehensive high-quality, science-based resources to and for plant health researchers and practitioners at no cost.

PDMR submission guidelines and schedule information are available online.


Plant Health Progress is a peer-reviewed multidiciplinary, online journal of applied plant health.