Meteorological Grading Indexes of Water–saving Irrigation for Corn

Abstract

To optimize irrigation and provide a technical guide on agricultural production, the water-saving irrigation meteorological grading indexes of different development stages of maize were built in this paper, based on the principle of farmland water balance, the theories of insufficient irrigation and regulated deficit irrigation, and by using multidimensional information including day-by-day meteorological data in 1961 － 2008 from 500 meteorological stations, soil moisture data in ten-day periods in 1993－2008 from 239 agro-meteorological stations (of which, the data in 1980－2008 came from 68 agro-meteorological stations)，irrigation amount and yield data were collected to analyze the relationship between the moisture deficiency rates, the quantity of water deficit and yield reduction rates at sowing-jointing stage, jointing-heading stage, heading-mature stage and the whole growth stage of maize referring to the product-water function(FAO-1979). Results indicated that water-saving irrigation meteorological grading indexes from Ⅰ－ Ⅲ levels of moisture deficiency rate and the quantity of water deficit (secondary indicators) were [10%, 25%), [25%, 40%) and ≥40%, corresponding to 1 － 2 irrigations (600m3∙hm–2 each time), 2－3 irrigations and >3 irrigations for the whole growth stage of maize, respectively. For sowing-jointing stage, the indicators were [15%, 30%), [30%, 45%) and ≥45%, corresponding to 0.5 irrigation, 1 irrigations and ＞1 irrigation, respectively. For jointing-heading stage, the indicators were [15%,30%), [30%, 45%) and ≥45%, corresponding to 0.5 irrigation, 1 irrigation and ＞1 irrigation, respectively. For heading-mature stage, the indicators were [15%, 30%), [30%, 50%) and ≥50%, corresponding to 1 irrigation, 1 － 2 irrigations and ＞2 irrigations, respectively. These indices could supply scientific support for the optimization of irrigation，and give guidance to agricultural production.