半干旱地区地膜覆盖、底墒和氮肥对春小麦根系生长的集成效应

The integrated effect of plastic film mulching,soil water storage amount before sowing and nitrogen fertilizer on spring wheat root growth

在年降水量 4 1 5 m m的黄土高原中部黄绵土上 ,以春小麦 (Triticum aestivum)为供试作物进行大田试验 ,研究地膜覆盖 (设不覆膜、播种后覆膜 30 d、覆膜 6 0 d和全程覆膜 )、底墒 (设低、高 2种底墒 )和施氮 (设不施氮和施氮 75 kg/hm2 )对春小麦根系生长的影响。结果表明 ,覆膜后作物根系生长加快 ,中下层根系比例增加 ,有利于吸收土壤深层水分。相对发达的根系保证了作物吸收器官 (根 )和失水器官 (叶 )间的平衡 ,协调根冠间的干物质分配关系 ,能在不影响根系吸收能力的前提下 ,提高光合产物的繁殖分配比例。适时揭膜能够改善光合产物分配 ,促进根系生长下扎 ,维持生长后期活性。全程覆膜处理的表层和中层 (30～ 6 0 cm)土壤中 ,根系生物量显著低于其他处理 ,原因在于后期覆膜使土壤温度急剧升高 ,造成根系大量死亡和活性下降。因此及时揭膜 ,有利于作物生长后期的根冠比保持在较高水平 。

A field experiment was carried out on cultivated loessial soil in semiarid area with 415 mm precipitation and spring wheat ( Triticum aestivum ) was used as an indicating crop to study the effects of plastic film mulching period(including no mulching,mulching for 30 days,mulching for 60 days,after sowing and mulching for whole growing period), soil water storage amount in profile before sowing (including low and high treatments) and nitrogen fertilizer application (including no nitrogen application and nitrogen application 75 kg/hm 2) on the spring wheat growth.After being covered with plastic film,the root of crop grew quickly,and the ratio of the root that distributed in middle and low soil layer increased,it was useful to absorb the water in deep soil.The flourishing root assured the balance between the absorb organ and the dehydrate organ of crop,coordinated the relation of dry matter distribution between the root and the shoot ,and with the premise of not affecting the absorption ability of root,it could also enhance the ratio of the breed distribution of the photosynthate.The results showed that uncovering the plastic film at right moment could improve the distribution of photosynthate,stimulate the root to plunge into the deep soil and keep the activation during later growth period.The root biomass of the top layer and the middle layer (30-60 cm) in the treatment of the plastic film mulching for the whole growth period was lower than other treatments apparently,the reason was that plastic film mulching during later growth period made soil temperature rise rapidly and led to large numbers of root mortality,and root activity decreased.As a result,uncovering plastic film in time could ensure that the ratio between the root and the shoot keeps at high level during later growth period,and plastic film mulching for the whole growth period was unfavorable to keep the ratio between the root and the shoot at high level during later growth period.