水氮调控对冬小麦根冠比和水分利用效率的影响研究

通过田间和桶栽试验研究了水、氮调控对冬小麦根冠比和水分利用效率的影响。田间试验结果显示,土壤水分条件对冬小麦根冠生长影响显著。当冬小麦生育期60 cm土层土壤水分维持在田间持水量的60%以上时,根冠比维持稳定状态,不随灌溉次数的增加而变化;当冬小T麦生育期60 cm土层土壤水分低于田间持水量的60%时,土壤越干旱,根冠比越大。桶栽试验结果显示,氮素水平对冬小麦根冠比影响显著,而水氮互作效应对根冠比影响不显著。在所有水分处理条件下,随着施氮量增加,冬小麦根量减少。施氮对冬小麦地上部分和地下部分的影响不同。在水分亏缺条件下,随着氮用量增加,冬小麦经济产量呈增加趋势,水分利用效率与施氮量存在明显正相关关系;而在充分灌溉条件下,产量随着施氮量的增加表现出先增加后降低的趋势,存在一个氮肥用量阈值。因此,水氮通过调控地上地下干物质分配而影响作物产量和水分利用效率,在水分供应受限制条件下,增施氮肥会降低根冠比,更利于地上干物质的积累和经济产量形成。田间试验和桶栽试验均表明,冬小麦根冠比与水分利用效率呈负相关,根冠比大不利于地上部分干物质的积累和作物产量的形成,导致水分利用效率降低。

Effects of water and nitrogen on root/shoot ratio and water use efficiency of winter wheat

Water and nitrogen (N) fertilizer have been identified as the two key factors that influence wheat root and shoot development. Root/shoot ratio and water use efficiency (WUE) of winter wheat were studied in the field and tub experiments at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences in the North China Plain. The field experiment involved with 5 irrigation treatments (with zero to 4 irrigations) during winter wheat growth period. The tub experiment involved 15 treatments of five levels of N (0 g·tub^-1, 2 g·tub^-1, 4 g·tub^-1, 6 g·tub^-1, 8 g·tub^-1) and three levels of irrigation (with 140 mm, 210 mm, 280 mm irrigation), with 6 replicas of each treatment. The PVC tub used in this experiment was 1 m in depth and 20 cm in diameter. The bottom of each tub was sealed with plastic film and buried in the field. Field data showed that soil water content significantly influenced root and shoot biomass accumulation. The root/shoot ratio was not affected by irrigation when water content of the top 60 cm soil layer was above 60% of field capacity. Below this soil water level, root/shoot ratio increased with decreasing soil water content. The tub experiment showed that the root/shoot ratio was significantly driven by N dose and not by the combined effect of water and N. Root dry weight decreased and grain yield increased with increasing N dose under deficit water supply. Concurrently, WUE increased with increasing N dose. Under sufficient water supply, winter wheat yield initially increased with increasing N dose to a certain level, after which it no longer changed with increasing N dose. A threshold value for N dose was noted under sufficient water supply. While under deficit water supply, more N meant higher WUE by reduced root/shoot ratio. This study suggested that N and water regulated biomass allocation to the parts of the above-ground and below-ground systems of the plant that influenced grain production and WUE. Both experiments showed a negative correlation between root/shoot ratio and WUE. That implied that higher root/shoot ratio increased biomass allocation to root but at the same time reduced above-ground biomass and WUE.