Alley cropping as a soil nitrogen management practice for maize production

Abstract

Tropical maize yields are low, averaging 1.24 t/ha, compared to a 3.2 t/ha world average and a 6.3 t/ha average in the United States and Europe. Alley cropping is an attempt to increase yields and prevent the decline in soil fertility often found in traditional farming systems. A maize alley cropping experiment was established on a Typic Gibbsihumox to measure 1) maize yield response to alley cropping, 2) apparent nitrogen recovery, 3) changes in soil organic nitrogen and carbon, and 4) to construct a partial nitrogen soil-crop system budget. Maize yield, maize nitrogen uptake, and dry matter and nitrogen yields of tree prunings were monitored for six consecutive maize crops in alley cropping systems with Cassia siamea, Calliandra calothyrsus, Gliricidia sepium, Sesbania sesban, Cassia reticulata, Inga edulis, and Leucaena leucocephala, and in a monocropped control treatment. Maize yield response to alley cropping varied with tree species and cropping period. Total maize yield for the six crops in the alley cropped plots was greater than or similar to the control plot. In the alley cropped plots, maize yields declined initially and remained relatively constant thereafter. In the control plot, maize yields were relatively constant for two cropping periods and declined steadily thereafter, due to increasing nitrogen deficiency. Nitrogen applied via tree prunings ranged from an average of 42 to 115 kg/ha per maize crop. Apparent nitrogen recovery among the tree species ranged from 0 to 68 percent during the six cropping periods, increasing with time. Percent apparent nitrogen recovery was greatest for G. sepium and C. siamea; followed by 1. edulis, C. reticulata, and C. calothyrsus. After six maize crops, surface soil organic carbon increased in all treatments, ranging from 2.7 to 7.1 g/kg. Surface soil organic nitrogen increased in the C. calothyrsus plot by 0.32 g/kg, with no change found in the other treatments. Subsoil organic nitrogen decreased in all treatments. A net loss of nitrogen in the soil-crop system (0 to 0.50 m soil depth) occurred in all treatments.