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

• Published in: Sustainability 2022-04, Vol.14 (7), p.4322
• Main Authors: Phohlo, Motsedisi P., Swanepoel, Pieter A., Hinck, Stefan
• Format: Article
• Language: English
• Subjects: Agricultural production; Agrochemicals; Crop yield; Efficiency; Emission standards; Farmers; Farms; Fertilization; Fertilizer application; Fertilizers; Irrigation; Loam soils; Mineralization; Nitrogen; Pasture; Pastures; Soil moisture; Sustainability
• ISSN: 2071-1050; 2071-1050
• DOI: 10.3390/su14074322

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., 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.