Daily Crop Evapotranspiration, Crop Coefficient and Energy Balance Components of a Surface-Irrigated Maize Field
Daily Crop Evapotranspiration, Crop Coefficient and Energy Balance Components of a Surface-Irrigated Maize Field
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DOI：
10.5772/18352
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发表时间：
2011-11
期刊：
影响因子：
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通讯作者：
J. Payero;S. Irmak
中科院分区：
文献类型：
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作者：
J. Payero;S. Irmak
灌溉用水短缺正在影响世界许多地区。这是内布拉斯加州和美国高原其他地区的情况。在内布拉斯加州，大田玉米（Zea mays L.）是主要的灌溉行作物，是该州经济最重要的驱动力之一。内布拉斯加州最典型的轮作是连续种植玉米和大豆后种植玉米。随着乙醇和生物燃料工业的发展，玉米连续种植的做法正在增加。过度抽取地下水用于灌溉，加上最近的干旱情况，以及玉米产量持续增加，使人们对水资源的未来供应和可持续性感到严重关切。燃料价格上涨，增加了抽水成本，这应该为农民提供经济激励，使灌溉应用与作物用水需求相匹配。准确测定实际作物蒸散量（ETc）可以通过精心设计的灌溉管理方案提高水资源的利用率。对ETc的可靠估计对于制定以下标准也至关重要：季节灌溉管理、水分配、水供应的长期估计、水需求和使用、水管理基础设施的设计和管理，以及土地使用和管理变化对水平衡的影响（Irmak和Irmak，2008年）。水资源短缺导致种植者需要用更少的水来生产作物。一种选择是使用更有效的灌溉系统，在过去的四十年里，美国中西部各州已经很大程度上从地面灌溉转换为高架洒水系统。例如，水和劳动力短缺已经迫使内布拉斯加州的种植者从地面灌溉转向更有效的高架喷灌系统（主要是中心喷灌机）。目前，在350万公顷的灌溉土地中，75%使用中心喷灌机灌溉，25%仍然使用地面灌溉，主要是沟灌。然而，采用更有效的滴灌系统（如地下滴灌）来灌溉玉米受到限制，主要原因是其初始成本和维护费用较高
Irrigation water shortage is affecting many areas of the world. This is the case in Nebraska and in other areas of the USA High Plains. In Nebraska, field maize (Zea mays L.) is the primary irrigated row crop and is one of the most important drivers of the state’s economy. The most typical cropping rotations in Nebraska are continuous maize and maize following soybeans. With the development of ethanol and bio-fuel industries, continuous maize farming practices are increasing. Over-pumping of groundwater for irrigation, coupled with recent drought conditions, and increasing continuous maize production are causing serious concerns about the future availability and sustainability of water resources. Increasing fuel prices, which increases pumping costs should provide an economic incentive for farmers to match irrigation applications to crop water requirements. Accurate determination of actual crop evapotranspiration (ETc) can improve utilization of water resources through welldesigned irrigation management programs. Reliable estimates of ETc are also vital for developing criteria for in-season irrigation management, water allocations, long-term estimates of water supply, water demand and use, design and management of water management infrastructures, and the effect of changes in land use and management on water balances (Irmak and Irmak, 2008). Water shortage is creating a need for growers to produce crops using less water. An option is to use more efficient irrigation systems, which has already occurred to a large extend over the last four decades in the USA Midwestern states by converting from surface irrigation to overhead sprinkler systems. For example, water and labour shortages have already driven growers in Nebraska to switch from surface irrigation to more efficient overhead sprinkler irrigation systems (mainly center pivots). Currently, of the 3.5 million ha of irrigated land, 75% is irrigated using center pivots and 25% still uses surface irrigation, mainly furrow irrigation. Adoption of more efficient drip systems, like subsurface drip irrigation, to irrigate maize, however, has been limited due mainly to their high initial cost and maintenance