Crop Diversity Enhances Soil Fertility in Newly-Reclaimed Soils of North-Western China.

There are large amount of reclaimable lands if irrigation is available in the arid areas of north-western China. However, it is important how to enhance the fertility of the reclaimed soils. Two field experiments were conducted initially in 2009 at the soils which were reclaimed for 3 years at Hongsipu in Ningxia (Exp. 1) and for 20 years at Jinyuan in Gansu (Exp. 2), China. The Exp. 1 was split-split-plot design, where main plot treatments included inoculation with rhizobium or not, and the sub-plot treatments included five N-application rates (0, 75, 150, 225 and 300 kg N ha⁻¹), and the sub-sub-plot treatments were sole faba bean, maize, and faba bean/maize intercropping. The Exp. 2 was two-factorial design, where main factor was P application rates (0, 40, 80 kg ha^-1) and the second factor was cropping systems, including canola/maize, chickpea/maize, faba bean/maize, and soybean/maize intercropping, and their corresponding monocropping. Each treatment has three replicates in both field experiments. Productivity, soil physical and chemical properties (bulk density, water-stable aggregates, infiltraction, compactivity, soil organic matter, total N, Olsen-P, Exchangable K, CEC, and pH), and some enzyme activities were measured in 2012 and 2013 in both experiments. Results showed that percentage of water-stable macro-aggregate (> 2.0 mm) was increased by intercropping compared to monocropped faba bean (67.9% vs 56.0%). Soil organic matter and total N were increased significantly by intercropping compared to monocropped maize (6.86 g/kg and 0.27 g/kg vs 6.03 g/kg and 0.22 g/kg) in the Exp. 1. In the Exp. 2, similarly, percentages of soil water-stable macro-aggregate were significantly increased by faba bean/maize, chickpea/maize, canola/maize intercropping, but not by soybean/maize intercropping. Soil organic and total N presented similar trends to Exp. 1. In summary, soil fertility was significantly improved after 4-5 years of intercropping compared with monocropping, especially in rewly-reclaimed desert soil.