水肥配合对太行山山前平原高产区土壤矿质氮分布及作物产量的影响

在中国科学院栾城农业生态系统试验站的潮褐土上,通过水、肥2因子3水平的完全方案,研究冬小麦-夏玉米轮作下,水、肥对土壤矿质氮分布及作物产量的影响。试验表明,NO3--N在土壤剖面中的分布除受水、肥作用外,还与土壤质地,作物及雨季降水有关;NO3--N在土壤剖面中的累积则受水肥二因素的共同制约。高水高肥处理,在收获2季作物后,土壤剖面中NO3--N明显积累;当水分或肥料不足,NO3--N的积累量减少;冬小麦全生育期旱作,不仅影响当季NO3--N的形成转化和冬小麦对N素吸收,而且直接影响后季夏玉米的产量以及土壤NO3--N的积累。土壤NO3--N的累积量与土壤水分含量存在明显的耦合作用。NH4+-N在土壤中所占比例很小,不同水、肥组合处理对其分布和累积无明显影响。肥料和水分都是冬小麦产量的限制因素,尤其水分不足,对当季和后季作物都有直接影响。针对该区地下水紧缺的矛盾,在有限水分供应时,应首先保证冬小麦季灌足底墒水和拔节水,每水至少灌60mm,施肥量不宜太高,否则会造成NO3--N在土壤中积累或淋失。本试验条件下该区适宜的水肥处理应为W2MF。

Effects of treatments with water and fertilization on nitrate leaching loss in the piedmont of Taihang mountain

The piedmont of Mt. Taihang, an important agricultural area in North China, is characterized by high crop production and large fertilizer input. Land rotated winter wheat with summer maize accounts for 85 %-95 % of the land used for agricultural purpose in this region. For maximizing grain yield, oversupplied irrigation and fertilization was a common practice here. According to our investigation on the farm field in 2001, the annual fertilizer N application was more than 450kg/hm2 per year (more than N 250kg/hm2 and N 200kg/hm2 for winter wheat and summer maize, respectively) . P2O5 input was 150-390 kg/hm2. Potassium and micronutrients was imbalanced applying. Excessive fertilization brought about crop lodging or slow-maturing and enriched Nitrate in deep soil profile. Moreover, according to the observations from Luancheng station, CAS, groundwater level was continually decreasing during the last decade and many "ground-funnels" were formed due to time after time irrigations; therefore, agriculture was facing with a serious water deficiency. To co-ordinate the relationship among resources saving, environment safety and sustainable agriculture development , a field experiment on the coupling of water with fertilize was conducted in Luancheng station, CAS. The results showed that the concentration of NH4 -N was less than 5 mg/kg and different treatments had no effect on its distribution and accumulation, whereas distribution and accumulation of NO3- -N in the soil profile, the major form of mineral nitrogen, were strongly affected not only by irrigation and fertilization, but also by the soil texture, crop uptake and climatecondition. The accumulation of NO3--N was restricted by water and fertilizer together. After the harvest of two seasonal crops, NO3--N accumulated markedly in the soil profile for treatments with high level water and fertilizer. When water or fertilizer was deficient, the amount of accumulated NO3--N reduced. Dryland crop of winter wheat throughout the period of duration affected not only the NO3--N transformation and formation and N absorption of winter wheat, but also the yield of ersuing maize and the accumulation of NO3--N. There was a coupled relationship between the amount of cumulated nitrate and soil moisture content. Both fertilizer and water are limited factor of winter wheat; especially water deficiency that had directly effect on current and ensuing crops. Therefore, aiming at the shortage of ground water of this region, supposing there is only insufficient water available, irrigation in the sowing and pre-jointing stage should have priority. For each irrigation, at least 60 mm should be applied. The dosage of fertilizer should not be very high; otherwise, it could bring about the accumulation and leaching of NO3--N, The optimal treatment for this region was W2MF.