GB/T 34818-2017 in English

The amount of water surplus and deficit in farmland is an important basis for evaluating the balance of soil water in farmland and for rationally managing farmland water. This standard is based on the drafting rules of GB/T1.1-2009, proposed by the China Meteorological Administration, and managed by the National Technical Committee for Agricultural Meteorological Standardization. This standard solves the long-standing problem of lack of a unified calculation method in farmland water management, and provides a scientific basis for agricultural water-saving irrigation and precision agriculture.

Soil effective water content (W): refers to the soil water content above the wilting humidity within the range of crop root activity. Calculation formula: W = (wt - wd) × ρ × h × 0.1.

Crop water requirement (E): Considering the crop coefficient Kc and potential evapotranspiration ET0 at different growth stages, the Penman-Monteith formula recommended by FAO is used for calculation. For example, in the middle growth period of corn, the Kc value is 1.05~1.2, corresponding to a daily water requirement of about 8 mm.

Effective precipitation (Pe): Determined by combining daily precipitation Pi and utilization coefficient σi. In the seedling stage of crops, when Pi<5mm, σi is 1; when Pi>50mm, σi is 0.7~0.8.

1. Data collection and preparation:

- Soil moisture (wt, wd) and bulk density (ρ) need to be obtained through field measurements;

- Daily precipitation Pi data can be obtained through meteorological stations or farmer records;

- Irrigation volume I should be based on records of irrigation system metering devices.

2. Calculation process optimization:

- Use automated calculation tools to process large-scale data; - Combine GIS technology for spatial analysis to generate regional water surplus and deficit distribution maps;

- Regularly update the calculation model of crop coefficient Kc and potential evapotranspiration ET0.

3. Application scenario expansion:

- Support precision agricultural decision-making: guide irrigation time and water volume;

- Optimize water resource allocation: evaluate regional water conditions and formulate water-saving measures;

- Support insurance claims: provide scientific basis for drought or flood disasters.