| China is an agricultural country, which agricultural water consumption accounted for 70% of the total water consumption. Irrigation is the main water consumer, of which the water use efficiency is fairly low at present. Water resources shortages have become a heavy constraint on agriculture development in our country and it is imperative to adopt water-saving agriculture. Research on diagnostic method of crop water deficit, management control indicators could enhance timely and adequate irrigation. It is one of the fundamentality approaches to reduce water wastage, develop sustainable agriculture and optimize water resources management.In the study, using the foreign advanced instruments to monitor the physiological indexes of different crops automatically, these indexes are canopy temperature, soil moisture, photosynthetic rate, transpiration rate and stomatal conductance. Sensitivity and ability of water deficient criteria which could reflect the crop water deficient is analyzed. Established relationship of different crops between indicators of soil moisture&crop eco-physiology and water deficient level. Ascertained index of irrigation and threshold of main crop is decided according to the monitoring of soil moisture, collection methods, and sensitivity and stability of water deficient criteria. The main findings were as follows:1. The appearance of winter wheat and summer corn were obviously effected by water conditions. Plant height and leaf area could increase along with the increase of irrigation frequency. Compared the treatments of one-time and two-time irrigation, it showed that T3 was the most productive in plant height, dry matter and grain number, then T1, and T2 was the worst, which indicate that proper deficient irrigation can increase crop yield and WUE. As for summer corn, compared two-time irrigation (T1) and one time irrigation (T2, T3), the former is 9~11cm higher than the latter in plant height, increased 40~60g /plant in dry matter, and the yield is increased 100~200 kg/hm2 than the latter.2. Study on the test result of winter wheat that proper deficient irrigation can increase crop yield and WUE. And large amount of irrigation water can not always lead to better crop yield. According to the relationship between water condition and crop growth, for wheat, irrigation in critical growing stages (jointing, heading and flowering stages), grain yield could increase and water resources would be saved, while ensuring proper soil moisture before sowing. As for corn, in the period of jointing and heading stage, more irrigation lead to higher crop yield.3. The evapotranspiration rate (Tr) in different irrigation amounts don't vary obviously, the daily biggest difference of which occurs at 14:00 pm, and there is marked trend that evapotranspiration rate decrease with the decreasing of soil water content in different irrigation amounts. The net photosynthesis rate (Pn) in the same irrigation amount has similar daily changing characteristic to the evapotranspiration rate, the daily biggest value occurs at 9:00-11:00 am, the crop will have a"rest"in noon, and afterwards, net photosynthesis rate decreases gradually within one day. The stomatal conductance varies drastically within one day, and which doesn't change in step with Tr and Pn sometimes. Generally, the daily peak value of stomatal conductance usually precedes the peak value of Tr and Pn, and the stomatal conductance also decreases with the decreasing of soil water content.4. The ratio of stomatal conductance and evapotranspiration rate could be regarded as water use efficiency in leaf scale. For wheat, the biggest leaf water use efficiency occurs in jointing-filling period, because wheat has sharp metabolism in this period.5. Evapotranspiration rate, net photosynthesis rate and stomatal conductance change (increase or decrease) synchronously in usual conditions, and the stomatal conductance directly impacts on evapotranspiration rate and net photosynthesis rate, there are extremely significant correlation among the three indexes. And soil water index also has significant correlation with evapotranspiration rate, net photosynthesis rate and stomatal conductance.6. Crop Water Stress Index and Canopy-air Temperature Difference are important methods to evaluate crop water demand according to canopy temperature. And, there is obvious changing trend within one day for canopy temperature and canopy temperature difference, and the peak value of canopy temperature occurs between 12:00-14:00. The canopy temperature in 14:00 has excellent representativeness to indicate crop water demand. The average values of CWSI in vigorously growing stages for winter wheat and summer maize have nonlinear correlation with total yield of grain. The result shows that, the optimum water supply for winter wheat is keeping average CWSI between 0.1-0.23, but, the performance is not satisfactory using CWSI to evaluate summer maize water demand and total yield. |
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