Maize nitrogen uptake and productivity under reduced and conventional tillage

NUTRIENT CYCLING IN AGROECOSYSTEMS(2020)

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摘要
Reduced tillage (RT) systems have been promoted for crop production intensification in low potential areas through enhancement of fertiliser response of degraded soils and drought mitigation. A 3 year study was conducted from 2015/2016 to 2017/2018 growing seasons in sub-humid (650–1000 mm rainfall year −1 ) Zimbabwe to determine nitrogen (N) uptake and maize yield response to nitrogen fertilisation rate (0, 30, 60, 90 120 150, 180 k gha −1 ) under RT and conventional tillage (CT). The experimental design was a split plot, with the two tillage systems as main plot and seven N rates as the sub-plot treatments. Four sites were established in smallholder farmer fields with clayey soils (160–400 g clay kg −1 ; Chromic Luvisols and Rhodic Ferralsols) and sandy soils (40–100 g clay kg −1 ; Eutric Regosols). Results show that the study sites had rainfall deficits of 4–47% in the first and third growing seasons. Nitrogen uptake rates of 8–60 kg ha −1 resulted in fertiliser N recovery efficiencies of 5–40% which were two fold higher under RT than under CT system. Maize grain yields (0.3–11 t ha −1 ) were 33% higher under RT than CT and increased 1.88–2.72 fold under N fertilisation compared to the control. The mismatch between top dressed N and peak crop demand require precision fertilisation in the dry seasons. Agroecology based quadratic modelling revealed that maximum maize yields of 2–13 t ha −1 were obtainable at optimum N fertilisation rates that were lower under RT than CT. The study provided a robust starting point in the improvement of nitrogen fertiliser management for maize under reduced tillage and climate variability.
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关键词
Agroecology, Apparent fertiliser nitrogen recovery efficiency, Nitrogen footprint, Nitrogen uptake, Optimum yield, Quadratic model
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