Economically Optimal N Fertilizer Rates for Maize Produced on Vertisol and Inceptisol Soils under No-Till Management: A Case Study in Maphutseng, Lesotho
Ivan B. Cuvaca
Department of Biosystems Engineering and Soil Science, University of Tennessee Institute of Agriculture, 2506 E. J. Chapman Drive, Knoxville, TN 37996-4518, USA
Dayton M. Lambert *
Department of Agricultural and Resource Economics, University of Tennessee Institute of Agriculture, 321 Morgan Hall, 2621 Morgan Circle, Knoxville, TN 37996-4518, USA.
Forbes R. Walker
Department of Biosystems Engineering and Soil Science, University of Tennessee Institute of Agriculture, 2506 E. J. Chapman Drive, Knoxville, TN 37996-4518, USA.
Makoala Marake
Department of Soil Science and Resource Conservation, National University of Lesotho, P.O.Box 180 Roma, Maseru 100, Lesotho
Neal S. Eash
Department of Biosystems Engineering and Soil Science, University of Tennessee Institute of Agriculture, 2506 E. J. Chapman Drive, Knoxville, TN 37996-4518, USA.
*Author to whom correspondence should be addressed.
Abstract
Aims: To determine differences in maize yields, optimal nitrogen (N) rates, and profitability on contrasting soil types and no-till and till management.
Study Design: Randomized block design field trials involving no-tillage and tillage practices were conducted on contrasting soil types (vertisols and inceptisols) to investigate the effect of N fertilizer rates on maize (Zea mays) grain yield.
Place and Duration of Study: Mohale’s Hoek District, Maphutseng, Lesotho over the 2012/2013 agricultural year.
Methodology: Maize response to N was estimated with a linear response plateau function. Economically optimum N rates were estimated for both soil types and tillage practices assuming typical corn and N fertilizer prices for the 2012/2013 agricultural marketing year.
Results: The economically optimal N rates were estimated at 141 kg of N ha-1 with a predicted maize grain yield of 7.75 tons ha-1 for no-till vertisol maize system, 150 kg of N ha-1 with a predicted maize grain yield of 4.90 tons ha-1 for no-till inceptisol maize system, and 73 kg of N ha-1 with a predicted maize grain yield of 7.37 tons ha-1 for the till vertisol maize system. A Monte Carlo analysis suggests these findings are robust to N cost, maize prices, and sampling uncertainty.
Conclusion: Findings of this study suggest that if other production factors remained constant, farmers in Lesotho - a country where access to commercial fertilizer is limited and average fertilizer N use is less than 25 kg ha-1 - would need to increase significantly their N fertilizer rates to meet their food needs.
Keywords: Lesotho, inceptisols, vertisols, no till -, maize, nitrogen