【作者】 王金凤；

【导师】 康绍忠； 张富仓；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2009， 博士

【摘要】 目前我国西北部农田灌溉大都采用传统的地面灌溉,水资源浪费十分严重,农业水资源的利用系数仅为0.46左右。如此低的水分利用效率使节水灌溉技术的改进有了很大的发展空间,通过改进灌溉技术来提高水利用效率是发展农业优先考虑的问题。控制性根系分区交替灌溉是人为使作物根系始终有一部分生长在干燥或较为干燥的土壤区域中,限制该部分的根系吸水,同时通过人工控制使根系的干燥区域交替出现,使干燥区的根系尤其是根尖产生水分胁迫信号(ABA),有效地调节气孔关闭。而处于湿润区的根系从土壤中吸收水分以满足作物的最小生命之需,使对作物的伤害保持在临界限度以内。本文以控制性根系分区交替灌溉为研究主线,设计了玉米盆栽和大田试验,涉及不同灌水方式(常规灌溉、交替灌溉和固定灌溉)、不同灌水水平(充分灌水、轻度水分亏缺和重度水分亏缺)、不同施肥水平(无肥、120kgNhm-2和240kgNhm-2)以及局部施肥等试验处理。主要对玉米根区土壤微生物数量和分布以及玉米生长和产量进行研究。同时,以油菜为供试作物,设计了一个与外界环境非常接近的,具有较大种植容器(50×50×70cm)的遮雨棚下试验和一个补充盆栽试验,涉及不同灌水方式和地下水处理。主要对油菜的根系生长和分布、形态变化和最终产量进行研究。主要取得以下研究成果:(1)交替灌溉条件下玉米根系在两侧根区分布均匀,长势良好;固定灌溉因为一侧根系受到严重水分胁迫而使根系分布不均,直接影响地上部分生长和干物质积累;常规灌溉条件下玉米生长旺盛,产量最高,但是水分利用效率却低于交替灌溉。盆栽试验中轻度水分亏缺的干物质总量虽不如充分灌溉,但在大田试验中前者却明显高于后者。而且在中度施肥下的玉米作物产量最高。水肥异区施肥方式能有效地避免环境污染,利于作物养分吸收和提高作物产量。(2)控制性根系分区交替灌溉对油菜的生长形态及最终产量影响很小,不适用于油菜作物的灌溉,指出控制性根系分区交替灌溉并不适用于所有作物。尤其对具有不确定生长特性植物的影响还有待进一步的研究。(3)在盆栽试验中,交替灌溉根区两侧菌落数均衡,而在固定灌溉条件下,干燥区的土壤细菌和放线菌显著小于湿润区,土壤真菌却在干燥区生长较好。在大田试验中,由于各种试验处理的交互作用使土壤微生物在根区分布更加复杂。总的来说,交替灌溉特殊的干湿交替土壤环境促进了土壤微生物,尤其是细菌和真菌的生长。(4)土壤微生物总数与土壤含水量呈现出二次抛物线关系,在土壤中度水分亏缺条件下达到峰值,这归结于土壤良好的通气条件。细菌适于在氮素含量相对较高的土壤环境下生存,而真菌和放线菌则更倾向于氮素含量较低的根区。土壤微生物在玉米整个生育期的数量随着生育期的推进逐渐增加,到蜡熟期达到峰值,后又在收获期降低。研究结果表明,控制性根系分区交替灌溉能够促进玉米根系土壤微生物的健康发展,有利于促进玉米的生长发育和提高产量。但是控制性根系分区交替灌溉并不适用于所有农作物,具有不确定生长特性的油菜就是其中的特例。控制性根系分区交替灌溉必然有其适用的范围,受作物品种、气候条件、地理条件等的约束。除此之外,农业生产除了考虑最大经济利益外,还要节水节肥,杜绝浪费水资源,避免氮素流失,维护农业生态环境。更多还原

【Abstract】 The conventional surface irrigation is very popular in northwest of China for field irrigation, a large amount of water is wasted and the agricultural water use efficiency is only about 0.46. Such low water use efficiency created enormous room for improving of water-saving irrigation technique. Agriculture developing should give priority to enhancing water use efficiency through improving irrigation technique. Controlled alternate partial rootzone drying irrigation (APRI) is a new irrigation technique which requires that approximately half of the root system is always exposed to drying soil and prevent from water consumption. Moreover, the dried and wetted sides may be shifted periodically. Part of the root system in drying soil can produce large amount of abscisic acid (ABA) and regulate stomatal opening while the rest of the root system in wet soil may function normally to keep the plant hydrated.Thus, APRI is the main line of this thesis. Pot experiment and field experiments of maize were designed, including distinct water patterns (conventional irrigation, alternate irrigation and fixed irrigation), distinct watering levels (sufficient, moderate water deficit and severe water deficit), distinct fertilizer levels (no fertilizer, 120 kgNhm-2 and 240 kgNhm-2) and fertilizer placement treatments. The number, distribution of soil microorganism in rootzone of maize, the growth and yield of maize were investigated. Other two experiments about oilseed rape were carried out under near-field rain shelter, one of them was conducted in big size of container (50×50×70cm), water patterns and groundwater condition were involved. The growth and distribution of oilseed rape roots were monitored and the data of morphological parameter and yield were recorded. The main results of this thesis are as follows:(1)Maize roots distributed evenly in both sides of rootzone and plants grew well under alternate irrigation. Meanwhile, roots were asymmetry under fixed irrigation because of extremely severe water deficit on one side of root system, resulting in restraining growth of aboveground and dry biomass accumulation. Although vigorous maize plants and preponderance yield were gained under conventional irrigation, water use efficiency was lower than that of alternate irrigation. The dry biomass of plant under full irrigation outperformed other water levels in pot experiment, but the highest yield was gained under moderate water deficit treatment, especially with low nitrogen application in field experiments. Moreover, water and nitrogen were provided in distinct furrows, which could avoid environment pollution and enhanced nutrition absorption and yield of plants.(2)Water patterns had little effect on oilseed rape growth and yield components (number of branches, branch lengths, number of pods, etc.). The results suggest that partial root-zone drying doesn’t work well with oilseed rape. More researches on indeterminate growth habit plants under APRI should be conducted to determine the limits of this irrigation technique.(3)In pot experiment of maize, soil microorganism distributed evenly in both sides of rootzone under APRI. But under fixed irrigation, the bacteria and actinomyces were less in dry rootzone than that of wet rootzone. However, the fungi preferred drying soil to wet part. In field experiments, the distribution of soil microorganism was more complex because of the treatment factors and their interaction. In general, special wet-dry cycling condition under alternate irrigation created an appropriate micro environment for soil microorganism, especially for bacteria and fungi.(4)A quadratic parabola relationship between the number of soil microorganisms and soil water content was found, indicating the number of soil microorganisms reached a peak at the moderate soil water deficit condition, possibly due to better soil aeration. In terms of nitrogen condition in soil, bacteria multiplied very well in high nitrogen level rootzone; on the contrary, lower nitrogen level in soil provide an appropriate soil environment for fungi and actinomyces. Moreover, the total number of soil microorganism grows with the growth period of maize going on and reached the peak during dough stage and decreased in harvesting period.Our results suggest that APRI could enhance soil microorganism reproduction, resulting flourishing plants and high yield. But APRI is not the most ideal water pattern for all of plants. APRI has its limit in agriculture, restricted by plant species, climate, geographic condition and so on. Moreover, the main goal of agricultural production is not only the greatest economic interest, but also water-nitrogen-saving and sustainable development of agricultural environment.更多还原