Benefits Are Limited with High Nitrogen Fertiliser Rates in Kikuyu-Ryegrass Pasture Systems

Charné Viljoen, Janke van der Colf and Pieter Andreas Swanepoel
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Charné Viljoen: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa
Janke van der Colf: Western Cape Department of Agriculture, Outeniqua Research Farm, George 6529, South Africa
Pieter Andreas Swanepoel: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa

Land, 2020, vol. 9, issue 6, 1-20

Abstract: Nitrogen (N) fertiliser is applied to pastures in dairy farming systems to ensure productivity, but it is an expensive input that could be damaging to the environment if used excessively. In the southern Cape region of South Africa, N fertilisation guidelines for pastures were developed under conditions different to current management practices, yet dairy producers still base fertiliser programmes on these outdated guidelines. This study aimed to determine the efficiencies of N fertilisation. Various N fertiliser rates (0, 20, 40, 60 and 80 kg ha −1 applied after grazing), as well as a variable rate according to the nitrate concentration in the soil water solution, were assessed on a grazed pasture. Dairy cows returned to a pasture approximately 11 times per year. Pasture production showed a minimal response to fertilisation within each season. The most responsive parameters to fertilisation were the herbage crude protein content, soil mineral N content and urease activity. Reduced microbial activity was observed when more than 40 kg N ha −1 was applied. When considering the soil total mineral N content, N is used inefficiently at rates above 40 kg N ha −1 . The results are indicative of an N saturated system that provides a rationale for reducing N fertiliser rates.

Keywords: dry matter production; crude protein; nitrogen use efficiency; soil mineral nitrogen; urease activity (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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