Nitrate leaching in field lysimeters at an agricultural site in Zimbabwe

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Abstract
Nitrate leaching in lysimeters containing a tropical sandy agricultural soil was studied over two summers with maize (Zea maysL.) and one winter season with wheat (Triticum aestivumL.). The treatments included two moisture regimes and two nitrogen sources, cattle manure and inorganic fertilizer‐N (either ammonium nitrate or ammonium sulphate) applied at 100 kg N/ha in the summers. Neither manure nor fertilizer‐N was applied in the intervening winter. Leachate volume from the manured lysimeters was mostly larger than from fertilized ones because of poor growth and less evapotranspiration. The largest seasonal nitrate loads (17–39 kg N/ha) were obtained in the wet summer immediately after installation of the lysimeters. Nitrate loads in winter (3.7–18.6 kg N/ha) were larger than those obtained in fertilized (0.6 and 9.3 kg N/ha) and manured (0.3 and 3.0 kg N/ha) lysimeters for the two moisture regimes in the second summer. The drier conditions in the second summer decreased N‐mineralization and leaching of manure.