Key Laboratory for Crop Water Use and Regulation

Xinxiang, China

Key Laboratory for Crop Water Use and Regulation

Xinxiang, China
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Qiang X.,Chinese Academy of Agricultural Sciences | Qiang X.,Key Laboratory for Crop Water Use and Regulation | Cai H.,Northwest Agriculture and Forestry University | Sun J.,Chinese Academy of Agricultural Sciences | And 7 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

To investigate the adaptability of ET 0 in in Guanzhong Region of Shaanxi, four ET 0 equations including FAO-17 Modified Penman (FAO-MP), China scholar Modified Penman (PBX-MP), Penman-Monteith (PM) and Standard ASCE Penman-Monteith equation (ASCE-PM), were assessed. on the basis of measured data by weighting Lysimeters. The results showed that ASCE-PM was the best equation for estimating ET 0 in semi-humid area with a linear regression coefficient of 1.03 (R 2=0.87) and mean absolute error (MAE) of 0.31 mm, compared to the measured values. The next was PM equation, followed by the PBX-MP and FAO-MP equations. The deviation between calculated and measured values was mainly caused by radiation and aerodynamic terms. Air temperature, sunshine and relative humidity had a significant effect on radiation term, while wind speed had a significant effect on aerodynamic term. The ASCE Penman-Monteith equation was proved tocompute the local ET 0 properly in Guanzhong region of Shaanxi province.


Song N.,Chinese Academy of Agricultural Sciences | Song N.,Key Laboratory for Crop Water Use and Regulation | Sun J.,Chinese Academy of Agricultural Sciences | Sun J.,Key Laboratory for Crop Water Use and Regulation | And 8 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Aiming at the main problem that existed in estimating the crop water requirement through multiplying the crop coefficients of main crops determined in the early 1990s by ET0 calculated using the Penman-Monteith equation, the reasons for crop coefficients which need to be revised were analyzed. There is a significant difference in ET0 calculated by using the modified Penman equation and by Penman-Monteith equation, which affects overwintering crops with a longer growth period of greater than summer crops with a shorter growth period. The result showed that the monthly ET0 and ETrad calculated by using Penman-Monteith equation were higher than that by modified Penman equation, and the difference between radiation terms was the main reason that caused the difference between the calculation results by using two equations based on the meteorological data of 18 stations in Henan province. The difference of monthly ET0 and ETrad calculated by two equations in autumn and winter was higher than in spring and summer. The effect of aerodynamic term on ET0 was related to wind speed, and the reason that the effect of aerodynamic term on ET0 is higher than the radiation term maybe caused by high wind speed. Except for the relative humidity, average temperature and sunshine hours, radiation term was affected by the elevation of stations, as for the stations with a higher elevation, the impact of elevation on Penman-Monteith equation was greater than that on modified Penman equation. Using the sensitivity analysis method to evaluate the effect of average air temperature, relative humidity and sunshine hours on ETrad showed that Penman-Monteith equation was better than modified Penman model in calculating ETrad. The ETrad calculated through Penman-Monteith equation was little influenced by seasons and stations, and had a high stability. The results from 18 stations showed that the effect of average temperature on ETrad was the minimal, the impact of relative humidity in January, November and December on ETrad was larger, and the influence of sunshine hours from February to October on ETrad was also greater. Therefore, ET0 in Henan Province was calculated by Penman-Monteith equation instead of modified Penman equation, crop coefficients must be corrected, otherwise it caused the estimated values of crop water requirement to be higher, and its impact on overwintering crops with a longer growing period was greater than that on summer crops with a shorter growth period. Finally, according to the relationship between two difference methods of estimating ET0, the correction method of crop coefficient based on Penman-Monteith equation was proposed. This study has an important significance in improving the estimation precision of crop water requirement.

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