基于稳定碳同位素的牧草水分利用效率研究

The North China Plain (NCP) is the most important grain production area as well as a major area for animal husbandry in China, stock raising developed rapidly in these areas in the last decade. But the high quality forage cultivars are not adequate in this area which became a limited factor to develop stock raising. However, water shortage is the primary limiting factor for crop production and long-term agricultural sustainability of the NCP and it is also a threaten factor for food security in China. Water management at farm level consists of the determination of water requirement and irrigation schedule, which are crucial steps to solve water shortage problem in this area. As forage cultivation emerged recently in this region, there will be increasing demands for water supply, and planting programs for water use efficiency improvement in forage cultivation will play an important and vital role in the future. There is insufficient research in measuring water use patterns of forage cultivars compared to crop water usage research, which may have impeded farm level decision making. To provide policy makers with information on suitable forage cultivars and on the optimal irrigation management options in NCP, we need to measure water use efficiency during the growing season specific for each forage cultivars. The objectives of this study will be to evaluate water use efficiency (WUE) in Wiatergrazer-70 and Triticate-830 under water deficit and water sufficient supply conditions. The growing season of these two forage cultivars are from the middle of September or early October to the following April or May in the NCP, that can greatly improve the utilization of time, energy and fields recourses while the idle after cotton harvest and also can offer green feed in winter and early spring in the NCP. So the key issues of these two forage cultivars planting are to improve WUE and developing reasonable irrigation systems. The research of the mechanism of water use efficiency is the basis and prerequisite for all those problems. Stable carbon isotope ratio (δ13C) can provide the information on water use efficiency in C3 plants and this method is widely used international wide. So a field experiment and series of pot control tests under different water deficit conditions also in Yucheng Integrated Experiment Station, Shandong province. In this study, water usage, the δ13C values for the stem, leaf, and grain, as well as main ecological characteristics will be measured. The relationship of the carbon isotope discrimination (Δ) and water use efficiency will be analyzed. The variation of carbon isotope ratio (δ13C) under different circumstances, especially soil water content change will be determined too. The results will reveal the mechanism of forage cultivars on the response of the different water supply. And also it can provide policy makers with the necessary information for optimizing water resource management.

华北平原是我国重要的粮食生产基地，也是我国肉蛋奶的主产区，是粮食生产和畜牧业发展的重点区域，优质牧草特别是青绿牧草的短缺是华北平原畜牧业发展的主要制约因素，需要大力发展人工牧草的种植。然而，水资源短缺是华北平原农牧业可持续发展的瓶颈，也是制约粮食安全的严峻问题。开展人工牧草种植首要解决的是水资源高效利用的问题，其中植物水分利用效率研究是基础和前提。本项目选取冬牧70黑麦和中新830小黑麦两种冬闲地主要牧草，通过大田和盆栽试验相结合的方法，应用稳定同位素分析技术，研究不同水分条件和不同生育时期牧草不同器官的δ13C的变化规律，建立碳同位素分辨率与水分利用效率的相关关系，揭示不同水分条件下牧草水分利用效率的变化机理，探索牧草生长过程对不同水分亏缺情景的响应，提出人工牧草种植的水资源高效利用模式。项目研究对华北平原水资源合理配置和畜牧业发展具有重要的科学意义。

农黑麦和中新830小黑麦能充分利用华北平原广阔的冬闲地资源，填补该区优质牧草特别是冬春季青绿饲草的短缺，对稳定该区的粮食生产和畜牧业发展的具有重要意义。然而，水资源短缺是该区农牧业可持续发展的瓶颈，因此，亟需开展对这两种牧草水分利用的试验研究。同时，鄱阳湖作为我国第一大淡水湖和国际重要湿地，研究湖区植物的水分利用对湿地的保护具有重要意义。本研究采用水文学、生态学等多学科交叉的研究手段，利用稳定同位素测定的新技术，通过大田试验、野外采样和室内处理分析，得出以下结果：.（1）农黑麦与中新830小黑麦叶面积指数随着生长进程逐渐增大，达峰值后呈下降趋势。农黑麦在拔节前后出现峰值，中新830小黑麦在孕穗期前后。（2）株高返青后即进入快速增长期，且同期株高农黑麦一直高于中新830小黑麦。单株干重自返青后也不断增加，除孕穗期外，农黑麦单株干重均高于中新830小黑麦。（3）叶片的光合速率日变化上午升高，升高趋势比较平缓，农黑麦峰值出现在12时，而中新830小黑麦峰值出现在14时，随后又骤然下降，二者的净光合速率平均值接近。二者拔节期的蒸腾作用具有相同的日变化规律。（4）农黑麦各个生育期的干、鲜草产量均比中新830小黑麦的高，二者干草产差在0.91-5.82 t•hm-2之间。仅从产草量的角度来说，孕穗期是两种牧草刈割的最佳时期。（5）各器官不同生育期的δ13C值变化范围在-26.281‰～-29.928‰之间。农黑麦与中新830小黑麦叶片水平的水分利用效率十分接近，只有早上10时中新830小黑麦略高一些。研究结果也表明，绿叶δ13C值与水分利用效率有很好的正相关关系，是这两种牧草水分利用同位素测定的最佳器官。（6）鄱阳湖湿地不同采样点的植物叶片δ13C值变化范围是-14.302‰～-33.134‰，比北方干旱地区人工牧草农黑麦与中新830小黑麦变化范围宽。在本实验中，断面田间持水量平均值的大小与断面植物的δ13C值平均值的大小有很好的对应关系。狗牙根和南荻具有较高的水分利用效率，因此在鄱阳湖湿地高程较高的相对干旱区域分布广泛。