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Open AccessArticle

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

1
Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa
2
Western Cape Department of Agriculture, Outeniqua Research Farm, George 6529, South Africa
*
Author to whom correspondence should be addressed.
Land 2020, 9(6), 173; https://doi.org/10.3390/land9060173
Received: 26 March 2020 / Revised: 9 May 2020 / Accepted: 11 May 2020 / Published: 29 May 2020
(This article belongs to the Section Soil-Sediment-Water Systems)
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conditions different to current management practices, yet dairy producers still base fertiliser programmes on these outdated guidelines.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. View Full-Text
Keywords: dry matter production; crude protein; nitrogen use efficiency; soil mineral nitrogen; urease activity dry matter production; crude protein; nitrogen use efficiency; soil mineral nitrogen; urease activity
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MDPI and ACS Style

Viljoen, C.; van der Colf, J.; Swanepoel, P.A. Benefits Are Limited with High Nitrogen Fertiliser Rates in Kikuyu-Ryegrass Pasture Systems. Land 2020, 9, 173.

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