Effects of soil water on crop growth and yield are performed on the changes of crop growing conditions and
biomass growth. In this paper, long-term field experiment data at Zhengzhou Experiment Station were used to
statistically analyze the relationships between crop growing conditions and biomass growth at current stage and soil
water at previous stage. And the relationships between soil water and yield were also set up. Subsequently, optimum soil
water and drought indexes were determined for different growth stages of winter wheat. All these results lay the
foundation for dynamic evaluation of drought in winter wheat.
In line with the equation of soil moisture balance and the results from field experiments for years, the source and
consumption of soil water components and their calculating models were scientifically analyzed. And based on the wheat
condition in its whole growth and development period, as well as water consumption pattern and soil water stress index,
a computer-based comprehensive study was made for discussing spatial distribution of non-stress soil water content,
field moisture utilization and irrigation mode for winter wheat in different climate years to provide useful suggestion as
to directing irrigation and management. The analysis showed that: no matter under what type of climatic conditions,
winter wheat fields need irrigation at least once in northern part of Henan Province, however, in southern part, especially
the southern area of Huai River, irrigation is needless; cornfields in the middle of the province should be irrigated once in
the years short of precipitation, while not be irrigated in the years with abundant rainfall.
Using experimental data on winter wheat from Bushland, Texas and Zhengzhou, Henan, analysis is performed of the distribution of its root system in 0~50 (50~100) cm soil depth, with the density of root length and its weight making up 57.7% (23.4%) and 66.7% (18.7%), respectively, thereby constructing the model of the roots growth and also by the distribution of the root system and its water absorption, study is undertaken of the appropriate depth of background field
moisture for growing winter wheat.
Shortage of water supply in the growing season is the key condition to form a drought in the winter wheat
production. Knowledge of risks brought about by the drought in winter wheat production is helpful in agricultural
management. In this work, we investigated the intensities of droughts and probability of their occurrence as well as their
impacts on the wheat yield based on water requirement by the crop and the nature of precipitation. Various techniques to
comprehensively assess the risks of droughts in winter wheat production are exploited to develop the model of risk
assessment of climatic droughts, the model of risk assessment of crop droughts, and the model of comprehensive risk
assessment of crop-climatic droughts. The models are used in regional comprehensive risk assessment of droughts in
winter wheat production in Northern China. A regionalization of risk levels is performed for this area. The results are
helpful in adjusting the cropping arrangement and in carrying out agricultural managements to minimize or prevent the
risk of droughts.
The characteristic of climate in North China is short of precipitation in winter and spring. Insufficient supply of water is a major factor affecting yield of winter wheat. The variation of yield caused by irrigation or drought at different stages is not alike. The relationship between them can be represented with water-yield reaction coefficient. Based on the experiment conducted in 2001 through 2004, yield of winter wheat has a marked positive correlation with precipitation at different stages after winter. The water-yield reaction coefficients increase with crop development, especially in turning green stage. The maximum occurs at head sprouting stage. Then it decreases slightly at milking stage. In order to raise water use efficiency of winter wheat, it is necessary to practice irrigation at elongating and head sprouting stages first and milking stage next.
From the dependence of winter wheat on water for growth a study is conducted of drought intensity and probability as well as their impacts upon the yield, whereupon are developed models for venture evaluation of drought damage to the crop grown in Henan province, with which to make the venture evaluation and regionalization of drought effects to provide scientific basis for modifying crop structure and preparing countermeasures for preventing and alleviating drought loss.
KEYWORDS: Meteorology, Climatology, Atmospheric modeling, Data processing, Sun, Lithium, Statistical analysis, Information science, Information technology, Information security
As a major agrometeorological disaster of winter wheat in Henan, drought is a big contributing factor to the steady rise of the yield. To make risk assessment of the drought-caused yield decline is of much significance to rational choice of culvars and putting forth measures against drought loss. Based on interannual meteorological and yield records, analysis is undertaken of yearly drought probability, percentage yield decline and yield coefficient of variation, whereupon is constructed a model for comprehensive risk assessment of wheat yield and regionalized is the risk happening. Evidence suggests that the indices of the risk assessment range over 1.23 ~ 4.88, with the high-value zones making up 12.5%, distributed mainly in eastern, and northeastern Henan, the middle-value zones accounting for 36.5% in southwest, southeast, eastern, northeast and northwest Henan and the low-value zones (51.0%) in the extensive region, with Lushi - Xiangcheng (Beijing to Guangzhou railway in Henan) as the axis line in the east - west (south - north) Henan province.
Drought is one of the major meteorological disasters to agriculture in north China so that the development of methods for effectively monitoring droughts is of great significance to dry land crops. This paper makes analysis of products of energy and water balances retrieved from LAS (Large Aperture Scintillometer) measurements, indicating that the structural parameter of LAS refractive index shows regular difference in daily variation between different weather backgrounds and remarkable difference in sensible heat flux on a seasonal basis, with higher negative correlation between such flux and soil humidity at 0 ~ 50 cm depth.
Drought is a principal agrometeorological disaster to winter wheat zones in North China. From the correlation of wheat yield to rainfall the drought indices are determined that correspond to varying levels of severities on an agricultural basis. In wheat growing season, when rainfall displays its negative anomalies of <15, 15-35, 36-55 and <55%, there occurs a slight, moderate, heavy and extreme drought, leading to yield drop by <10, 10-20, 21-30 and <30%, respectively. The economic loss consists of yield reduction and drought-fighting input like irrigation. A drought-caused loss model is presented from historical meteorological and wheat yield datasets, with which to make the distribution of economic losses in the last 30 years over the province of Henan. Evidence suggests that in years of heavy droughts the loss was between 450 to 675 (<250) RMB yuans per hectare in the NE (west − SW) segment of the province.
Based on the relationship between water balance and crop-water, water-saving irrigation model was integrated with monitoring and prediction of soil moisture, forming a system of decision-making of irrigation. It is demonstrated that straw mulching for winter wheat is an effective way to reduce soil evaporation at early stages and increase yield and improve water utilization efficiency. Combination of water-saving irrigation and straw mulching plays an important role in China water-saving agriculture.
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