【作者】 闫映宇；

【导师】 赵成义；

【作者基本信息】 新疆农业大学 ， 土壤学， 2009， 硕士

【摘要】 滴灌一般不产生深层渗透,难以利用灌溉水淋洗盐分,盐分仅在土体中转移而无法消除。基于绿洲灌区农业的可持续发展考虑,长期采用膜下滴灌可能会存在潜在的生态风险。因此膜下滴灌水盐平衡关系与淋盐水量定量化研究已成为绿洲区农业可持续发展的研究重点与热点问题。本文首先从农田水盐运移特性、水盐模型及水盐平衡、淋盐水量等方面分析了膜下滴灌水盐动态及平衡的研究现状。发现膜下滴灌条件下,土壤盐分呈逐渐积累的趋势;缺乏对滴灌条件下淋盐方式、淋盐水量及膜下滴灌技术的适宜性评价研究。为此,通过三年膜下滴灌田间试验,从水盐动态及平衡,棉花根系、地上部生物量累积对水分的响应入手,分析了膜下滴灌节水效果、淋盐效果、棉花耐盐指标及膜下滴灌技术的适宜性。对膜下滴灌棉田水分动态及平衡的研究表明:土壤水分的水平分布表现为宽行>窄行>膜间。垂直方向,滴灌只能影响0-100 cm的土壤含水量,而100 cm以下基本相同。在3926-4265 m³/hm²滴灌量下,湿润峰可达100 cm,2947-3600 m³/hm²滴灌量下,湿润峰可达60 cm,而2618 m³/hm²滴灌量下,湿润峰只能达到40 cm深度。南疆膜下滴灌棉花生育期需水量543.2 mm。苗期最小,占生育期总需水量的10.0 %;花铃期最大,占53.0 %;蕾期占15.4 %;吐絮期占21.6 %。休闲期耗水量238.1 mm。计算得出最佳耗水区间为506.0-536.7 mm。滴溉量达3464 m³/hm²时,棉花产量最高为6361 kg/ hm2。膜下滴灌棉花根系、地上部生物量及产量对水分响应的研究发现:各水分处理棉花根系主要分布在膜下,占根系总生物量的60.7 %-73.5 %,而膜间仅占39.4 %-26.6 %。水分亏缺可以增加根系下扎深度及根系水平分布范围。膜下距离棉株24.1 cm,12.9 cm深度处,棉花根长密度最大为26.5 mm/cm3。水分过量处理(4265 m³·hm^-2)的棉花株高、倒四叶宽、果枝数、蕾数均增加,干物质积累速率加快,根冠比及干物质在营养器官中的分配比例增大,生物产量提高。但同时蕾铃脱落率也增加,经济产量降低。3600 m³/hm²滴灌量下,棉花干物质在不同器官及生育期的累积与分配最合理,可以获得高产。对膜下滴灌棉田土壤盐分分布特征及平衡的研究表明:土壤盐分呈“Y”状的空间分布特征。膜下土壤盐分含量小于膜间,呈“两头小、中间大”的分布,而膜间从下层到表层呈逐渐增大的趋势。随滴灌量增加,膜下土壤盐分峰值位置下移。滴灌结束后,膜下0-60及0-100 cm土壤平均含盐量均减小,脱盐率随滴灌量增大而增加。0-60 cm土层脱盐率在6.0 %到34.8 %;而膜间土壤积盐,积盐程度随滴灌量减小而增大。随滴灌年限增加,0-60 cm土壤含盐量逐年增加。在综合分析膜下滴灌的土壤盐分分布特征、淋盐效果及棉花耐盐性的基础上,建立了基于水盐平衡的“测盐配方”淋盐水量估算模型。并通过该模型估算了淋盐水量。初步确立了膜下滴灌的适宜性评价指标。更多还原

【Abstract】 Drip irrigation is not able to generate deep permeability. The salt in soil can not be removed by leaching of irrigation water. Considering the sustainable development of irrigation agriculture in oasis, long-term drip irrigation under mulch may induce potential ecological risk. Therefore, the sustainable development of oasis agriculture is concentrated on the water and salt balance under the condition of drip irrigation below mulch and quantity of the salt-leaching water.Based on characteristics of water and salt transport of farmland, water and salt model, water and salt balance and leaching water quantity, the dynamics and balance of water and salt under the condition of drip irrigation under mulch were reviewed. Previous studies showed that soil salt accumulated gradually in drip irrigation under mulch, and the mode, salt-leaching water quantity and suitability assessment under such conditions were scarce. Therefore, through three-year field experiment on the water and salt dynamics and balance, the response of root system and aboveground biomass accumulation of cotton to soil moisture, the effects of water-saving and salt-leaching in drip irrigation under mulching and the salt-tolerant index of cotton were analyzed by which the water-saving mechanism of drip irrigation under mulching was revealed .Water dynamics and balance in cotton field under the condition of drip irrigation below mulch were studied. The results showed that the horizontal distribution of soil water content followed the order: width row land > narrow row land > bare land. The effects of drip irrigation on soil water content was limited within top 100 cm soils below which soil water content are similar. The wetting front was able to reach 100 cm in depth with the drip irrigation amount between 3926 and 4265 m3/hm2, and 60 cm between 2947 and 3600m3/hm2, 40 cm for 2618 m3/hm2. The growth period of cotton under the condition of drip irrigation below mulch in South Xinjiang.required 543.2 mm water. The water requirement in seedling, budding, flowering and bolling accounted for 10.0 %, 15.4 %, 53.0 % and 21.6 % of the total, respectively, minimum in seedling period and maximum in flowering and bolling period. The water consumption in fallow period was 238.1 mm. The optimal water consumption ranged between 506.0 and 536.7 mm. The cotton yield reached the highest, 6361 kg/hm2, when irrigation amount was 3464 m~3/hm~2.The root biomass under different irritation treatments was mainly distributed at mulched area, occuping 60.7 %-73.5 % of the total and correspondingly, 39.4 %-26.6 % at inter-mulch areas. Water stress increased the rooting depth, root biomass and the extent of lateral rooting. The maximum root length density is 26.5 mm/cm3, appearing at 24.1 cm away from the plants, 12.9 cm under the mulch. Over-irrigation increased the height, width of the inverse-fourth leaf, amounts of branch and square, thus accelerating the biomass accumulation rate. It also increased the root/shoot ratio and the proportion of biomass allocated to vegetative organs. However, over-irrigation increased the rate of fruit abscission and therefore reduced the economic yield. These results suggested that both excessive soil moisture and water stress could affect the biomass accumulation and allocation in different organs in various life stages. Under the conditions of the current experiments, 3600 m3·hm-2 seemed to be the optimal irrigation amount.Soil salt presented a Y-shaped distribution in space. The soil salt content under mulch was less than inter-mulch lands, presenting a characteristic of’low at two ends and high at the middle’within of the soil profiles. Differently, it increased gradually from the lower soil layers to soil surface at inter-mulch lands. The peak position of soil salt under mulch moved downward with the increases of drip irrigation amount. The average salt content in 0-60 cm and 0-100 cm soil layer decreased after drip irrigation. The desalinization rate increased with the increase of drip irrigation amount. In 0-60 cm soil layer, desalinization rate ranged between 6.0 % to 34.8 %. Soil salt of inter-mulch lands trended to accumulate, with the accumulation rate decreasing with the increase of drip irrigation amount. The average salt content in 0-60 cm soil layer increased with the time of drip irrigation. Based on water-salt balance, estimation method of salt content-dependent water requirement of salt-leaching was proposed, which was applied in current study. Furthermore, preliminary index system for suitability assessment of drip irrigation under mulch was established.更多还原