Tree and Crop Growth and Soil Resource Availability in Hardwickia binata Roxb Agroforestry Systems in the Indian Desert

Abstract

Integrating trees in agricultural fields may be beneficial in controlling land degradation and improving productivity in dryland areas. Two-year-old Hardwickia binata Roxb trees were intercropped for 7 years to examine tree-crop interactions and the effect of tree integration and the cropping pattern on land productivity. The tree integrated treatments comprised a Vigna radiata (L.) R. Wilcz crop with H. binata in all years (fixed crop) (FC) and a rotation crop with H. binata in alternate years (RC). Sole crop treatments provided controls for the V. radiata crop (CFC) and rotational crop (CRC) treatments. Pennisetum glaucum (L.) R.Br., V. radiata, Sesamum indicum (L.) and Cymopsis tetragonoloba (L.) Taub were harvested in the RC/CRC plots in 1996, 1997, 1998, 1999, 2000, 2001, and 2003. Tree growth and growth increments did not differ between the FC and RC treatments (p > 0.05). Crop yield (grain + dry matter) was highest (p < 0.01) in the FC treatment in 1996, 1997, 1998, 1999, and 2000, indicating that the presence of trees was beneficial. The observation that yield was highest in the CFC/CRC treatments in 2001 and 2003 indicates a competitive effect of trees for soil resources in these years. Soil water content (SWC) in September was lowest in 2002 and highest in 2003. The effect of cropping pattern on SWC was significant (p < 0.05) only in 2000, 2001, 2002, and 2003, whereas SWC differed (p < 0.01) between 0–25-, 25–50-, and 50–75-cm soil layers. Soil water content to 75-cm soil layer was lower by 0.4 (1996) to 18.9 mm (2003) in tree-integrated treatments than in the control treatments, affecting crop yield. Soil organic matter, NH4-N, NO3-N, and PO4-P in the 0–25-cm soil layer were increased by tree inputs (p < 0.05). H. binata was apparently beneficial in increasing productivity even during droughts, and the benefits may be further improved by root trenching to reduce competition for soil resources in relatively low rainfall years.