Excessive Nitrogen Fertilization Is a Limitation to Herbage Yield and Nitrogen Use Efficiency of Dairy Pastures in South Africa

Motsedisi P. Phohlo, Pieter A. Swanepoel and Stefan Hinck
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Motsedisi P. Phohlo: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa
Pieter A. Swanepoel: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa
Stefan Hinck: FARMsystem Hinck, Nelson-Mandela Strasse 1, 49076 Osnabrueck, Germany

Sustainability, 2022, vol. 14, issue 7, 1-11

Abstract: The response of crop yields to fertilizers is a long-standing topic of agricultural production. Currently, in dairy-pasture systems, nitrogen (N) fertilizer is used as a management tool that is said to be directly proportional to pasture yield. We evaluated a large dataset consisting of data from 153 fields over five years to examine the effects of N fertilization on pasture yield and nitrogen use efficiency in the Eastern Cape province of South Africa. Fertilizer application rates were grouped into three treatments viz., <200, 200–350, and >350 kg N ha −1 , and herbage yield response over the years was analyzed with mixed models. There were no differences found between treatments for total annual herbage yield over the years. High N fertilizer rates did not translate to a higher herbage yield of pastures. The N rate had a weak but significant negative correlation with the total annual yield and only accounted for 6% of the yield variation. The N use efficiency of pastures improved with reduced N application rates. Pasture yield varies through different seasons. Spring and summer account for the highest yield, coinciding with warm and moist conditions favorable for N mineralization in the soil. Farmers need to consider the time of the year and plan their monthly or seasonal fertilizer application accordingly to account for peak N mineralization rates.

Keywords: pasture yield optimization; nitrogen use efficiency; nitrogen fertilization (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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