Effect Of Intercropping On Nitrogen And Water Use

Intercropping, due to the more effective use of resources and high productivity, is practiced widely in northwestern China.In recent years, nitrogen application rate is increasing continually, and irrigated water input is also relatively great. However, the research on nitrogen and water use efficiency are very few. Our work reported here are aiming at improving nitrogen and water use efficiency in wheat/maize, faba bean/maize, pea/maize and soybean/maize intercropping through field experiment.The main results obtained were as the following:(1) Land equivalent ratio (LER) was greater than 1.0 for faba bean (Viciafaba L.)/maize (Zea mays L.) intercropping regardless of nitrogen fertilizer application or not. Based on grain yields production, LER of pea (Pisum sativum L.)/maize intercropping was over 1.0 in spite of nitrogen fertilizer application, while LER was higher than 1.0 only when nitrogen fertilizer was applied based on biomass production. However, LER in soybean (Glycine max L.)/maize intercropping was smaller than 1.0 both nitrogen applicationa and no nitrogen application. In wheat (Triticum aestivum L.)/maize intercropping, LER was greater than 1.0 when nitrogen fertilizer was applied, and LER was varied with wheat varieties and experiment conditions without nitrogen fertilizer application.(2) Nitrogen uptake by intercropped faba bean and maize was greater than those in sole cropping, semilar trends were observed in pea/maize intercropping.Nitrogen uptake of intercropped wheat was higher in wheat/maize intercropping than that in sole cropped wheat, and nitrogen uptake of intercropped maize was lower or close to that in sole cropped one. In contrast, intercroped soybean was less than that by sole soybean,whereas nitrogen uptake by intercropprd maize was greater that that by sole maize in soybean/maize intercroping. Nitrogen utilization efficiency in intercropped faba bean, pea, soybean and wheat was greater than that in corresponding sole cropps, however, intercropped maize was lower than that in sole cropped maize.(3) Nitrogen surplus and nitrogen loss were less, and apparent nitrogen recovery by plants, nitrogen production rate were generally greater in intercropped faba bean, pea, soybean and wheat than those in sole cropped faba bean, pea, soybean and wheat respectively.(4) Soil NO3"-N concentration and accumulation were increased with increased nitrogen application. NO3"-N accumulation in soil of intercropped faba bean and pea were grater than that in sole faba bean and pea, but varied with different nitrogen application and time in intercropped soybean, wheat and maize.(5) Soil water contents in intercropped faba bean, pea, soybean and wheat were higher than those in corresponding sole crops, and the content in intercropped maize was decreased compared with sole maize when determined after faba bean harvesting. After maize harvest, soil water contents in intercropped maize were grater than that in sole cropped. Water use efficiency (WUE) of faba bean/maize intercropping relative to sole cropping was increased with or without nitrogen application, pea/maize intercropping and wheat/maize intercropping were increased after nitrogen fertilizerapplication, yet soybean/maize intercropping were reduced regardless of nitrogen fertilizer application or not.(6) Different irrigation level hardly affected yields of wheat/maize intercropping. Grain yields improved with increased nitrogen rate, however, there was little difference between application of 225 kg.hm-2 and 450 kg.hm-2 nitrogen rate. NO3--N concentration and accumulation in soil of maize strip increased obviously, and moved below 140 cm soil depth with the raise of irrigation rate. Apparent nitrogen recovery by plants and nitrogen production rate were the highest at 225 kg.hm-2 nitrogen application rate. WUE improved with the reduction of water level and the increase of nitrogen rate, however, no big difference existed between 225 kg.hm-2 and 450 kg.hm-2 nitrogen application.