Resumen de Forage production and soil water balance in oat and common vetch sole crops and intercrops cultivated in the summer-autumn fallow season on the Chinese Loess Plateau
Zikui Wang, Hailiang Jiang, Yuying Shen
Integrating forage crops into traditional wheat and maize cropping systems is a potential alternative for increasing fodder supply while maintaining sustainable grain production on the Loess Plateau of China. This study was conducted to evaluate the biomass and crude protein production as well as the soil water balance and water use efficiency of oat (Avena sativa L.) and common vetch (Vicia sativa L.) intercrops compared to sole crops. Field experiments were conducted during the fallow season after wheat harvesting (mid-July to late October) in 2011 and 2012. Five cropping patterns were tested: sole oat (SO), sole common vetch (SV), and three intercrops of oat to common vetch in rows of two to one (I21), one to one (I11), and one to two (I12). Rainfall in the middle and late growing season in 2011 was abundant, but the early season was very dry. Rainfall in 2012 was less than average but distributed similarly with the long-term pattern. When harvested in late September, I21 showed the greatest aerial biomass and crude protein yield of 3.20 and 0.36 t ha−1, respectively, in 2011, and SO showed the greatest biomass and crude protein yield of 5.70 and 0.51 t ha−1, respectively, in 2012. When harvested one month later, the crude protein content of common vetch maintained a large value, while that in oat was reduced by 21 %–29 %. I21 still showed the greatest biomass and crude protein yield in 2011, and in 2012, SO had the highest biomass yield of 7.74 t ha−1 while SV showed the highest crude protein production of 0.65 t ha−1. The land equivalent ratio was above unity in all intercropping systems in 2011 and below unity in all systems in 2012. The soil water in the 0−120 cm layer in all treatments was fully recharged in 2011, but depleted in 2012, and the depletions in SV and I12 were significantly less than that of the other treatments (P < 0.05) on both harvesting dates. In 2011, water use efficiencies based on biomass and crude protein on both harvesting dates were all greatest in I21, water use efficiencies at the early and late harvestings were greatest in SO and I12, respectively. Therefore, the intercrops with a greater oat proportion had the advantage of maintaining system production when early season water availability was unfavorable, while those with a greater common vetch proportion had the potential of improving forage quality and conserving soil water to maintain the production of the main crop under normal water conditions. Selection of a proper planting pattern should take initial soil water conditions and rainfall availability into consideration.
