Red soils in southern China had poor physical and chemical properties and low fertility. The plants in red soil are often suffered from soil water stress due to seasonal drought. Poor soil properties and seasonal drought are the main limiting factors for agricultural production in red soil region. Fertilization systems and field managements are important in improving soil properties and stimulating plant growth. Thus, the soil and plant water relationship could be also regulated by the fertilization systems. However, it is still unknown how the soil-plant-water continuum is changed with fertilization systems different in red soil region of China. Applications of organic and mineral fertilizers to clayey red soil improved soil properties. Generally, the organic fertilizers yielded significant increase in soil water retention capacity at most potential and available water content. In particular, soil water content was increased at all soil depths with organic fertilizers under dry and wet periods. Therefore, decreased unsaturated hydraulic conductivity, soil bulk density and penetration resistance showed significant decrease with organic fertilizers than other treatments. The soil organic carbon content exhibited significant differences in the organic plots compared with mineral treatments.
The high negative correlation was observed between the soil organic carbon and the bulk density and the penetration resistance (P < 0.01). The results showed that the meteorological index, crop drought index and soil moisture index could reflect drought status at farmland. But they had not fully reflected the drought status in the red soil area at field scale at a variety of conditions. To monitoring crop water stress status effectively and timely, we advise that several different indices should be combined to reflect the agricultural drought in red soil area at farmland scale.
All correlations between CWSI, grain yield and soil water content related by fertilization systems because it increases soil water content and penetration resistance decreases, CWSI decreases as the corn yield increases. Therefore, crop water stress could regulate by fertilization systems. Variations in plant water potential could be accounted for by variations in soil water, temperature and relative humidity. Fertilization systems improved soil water potentials and plant water potential; may be affected due to changes in atmospheric water potential. Therefore, could evaluated fertilization systems in red soil in terms of soil - crop water relation.
Finally, the long-term applications of OM and NPK+S were helpful to improving red soil properties and above-and below-ground corn performance. As well as were improving soil water potential, plant water potential and CWSI. On the other hand, OM and NPK+S resulted in the reduced soil penetration resistance and increase soil water content, thus improved crop-water relations. Therefore, increased the crop growth and this helpful to reduce the seasonal drought in red soil of China.
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