近59年保定市谷子生育期需水变化特征和影响因素分析

Variation of water requirement and its effect on the developmental stage of foxtail millet in Baoding city during past 59 years

[目的]利用保定市气象站1955—2013年逐日气象数据,分析谷子各生育时期需水量、有效降水量和水分亏缺指数变化特征,以期为保定市谷子生产制定合理的灌溉制度。[方法]利用FAO推荐的Penman-Monteith公式对谷子生育期需水量进行计算,分析谷子需水规律及影响因素。[结果](1)保定市谷子生育期需水量、有效降水量和水分亏缺指数多年平均值为372.44mm、301.49mm和0.45,年际发生干旱的概率为33.90%。谷子生育期需水量整体上呈减少趋势,气候倾向率为-1.93mm·10a^-1,主要是由于6月下旬(播种-拔节)和7月中旬(拔节-抽穗)需水量显著减少造成的。丰水年、平水年和干旱年谷子生育期需水量分别为355.01mm、364.12mm和390.36mm,有效降水量分别为463.75mm、296.10mm和186.79mm。(2)谷子生育期季节性干旱明显,8月上旬、9月上旬和中旬均出现轻旱,8月上旬(抽穗-灌浆期)水分亏缺指数显著升高,干旱风险增加。丰水年未形成干旱;平水年在8月上旬和9月中旬达到轻度干旱;干旱年8月上旬处于中旱,8月下旬~9月中旬均处于轻旱。(3)谷子需水量与平均气温、最高气温、日照时数和风速均呈极显著正相关关系(P<0.01),与相对湿度呈极显著负相关关系。造成谷子生育期需水量减少的原因是日照时数减少和风速降低,气候倾向率分别为-38.1h·10a^-1、-0.04m·s^-1·10a^-1。需水量与气象因子建立的回归方程为ETc=13.89Tmean-2.20Tmax-1.53RH+0.22n+30.43U2-1.15。[结论]保定市谷子抽穗-灌浆期干旱风险较大,因此在农业生产中,应当注意完善该时期灌溉制度,加强保水抗旱措施。

[Objectives] In order to establish a reasonable irrigation system for foxtail millet production in Baoding City, the various characteristics of water requirement, effective precipitation, and water deficit index of millet in different growth stages were analyzed using daily meteorological data collected by Baoding Meteorological Station between 1955 and 2013.[Methods] The water requirement of millet during growth season was calculated by using the Penman-Monteith formula as recommended by FAO, and the water requirement regularity and influencing factors were analyzed.[Results](1) The average annual water requirement, effective precipitation, and water deficit index of foxtail millet in Baoding City were determined as 372.44 mm, 301.49 mm, and 0.45, respectively. The probability of drought occurrence was 33.90%. The water requirement displayed a decreasing trend during entire growth stage. The climatic tendency rate was measured as -1.93 mm ·10a^-1 , which was mainly induced by the significant decrease of water requirement in late June (sowing to jointing stage) and mid-July (jointing to heading stage). The water requirements were calculated as 355.01 mm , 364.12 mm, and 390.36 mm for flood year, plain year, and drought year, respectively, while the effective precipitation was 463.75 mm, 296.10 mm, and 186.79 mm in that order.(2)The seasonal drought was commonly occurred during the growth season of foxtail millet. Light drought was usually occurred in the first ten days of August as well as the first and second ten days of September. Water deficit index was increased significantly in the first ten days of August ( P <0.05) which induced an increased risk of drought. No drought was observed in high water year, while slight drought was detected in early August and mid- September in plain water year. There were moderate shortage of water happened during early August and light drought occurred during late August to mid-September in drought year.(3)The water requirement of foxtail millet was positively correlated with mean temperature, maximum temperature, sunshine hours, and wind speed ( P <0.01), and negatively correlated with relative humidity. The decrease of water requirement was responding to the decrease of sunshine hours and wind speed. The climatic tendency rates were -38.1 h ·10a^-1 and -0.04 m ·s^-1 ·10a^-1 for sunshine hours and wind speed, respectively. The regression equation between water demand and meteorological factors was determined as Y=13.89 T mean -2.20 T max -1.53 RH+0.22 n+30.43 U2-1.15.[Conclusion] A higher drought risk facing by foxtail millet during heading to grain-filling period was observed in Baoding City. Therefore, the attention should be paid to improving the irrigation system and strengthening measures of water conservation and drought resistance in this period in agricultural production.