Impact of variable-rate application of nitrogen on yield and profit: a case study from South Africa |
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| Authors: | Ntsikane Maine James Lowenberg-DeBoer Wilhelem Thomas Nell Zerihun Gudeta Alemu |
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| Institution: | (1) Agricultural Development Programmes, City of Tshwane Metropolitan Municipality, P.O. Box 440, Pretoria, 0001, South Africa;(2) International Programs in Agriculture, Purdue University, West Lafayette, IN, USA;(3) Department of Agricultural Economics, Faculty of Natural and Agricultural Sciences, Centre for Agricultural Management, University of the Free State, Bloemfontein, South Africa;(4) Development Bank of Southern Africa, Johannesburg, South Africa |
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| Abstract: | The response of maize (Zea mays) to banded variable-rate nitrogen (N) application over a period of 3 years (2002/3–2004/5) is analyzed. The experimental
design alternated variable-rate (VR) and single-rate (SR) applications of N. The yield monitor data were spatially autocorrelated
and therefore were analyzed with spatial regression methods. The baseline spatial regression model defined in this study showed
that the VR treatment, treatment by year and treatment by management zone were statistically significant. Sensitivity tests
were applied; the first showed that VR treatment had a yield advantage when soil depth was greater than the field average
of 174 cm. The second test showed that the VR N rates applied were close to those that would maximize profit. Partial budgeting
indicates that benefits from VR vary from year to year, but in this test VR was slightly more profitable than uniform rate
application. Economic sensitivity testing indicates that farm size and the price of maize are the key factors in the profitability
of VR N. |
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