Research On Variation Characteristics Of Soil Temparature In Crop Field And Fallow Field On Loess Tableland

The change of soil temperature has very important influence on crop growth, crop yieldand quality. A study on spatiotemporal variation characteristics of soil temperature canprovide guidance and reference for artificial regulation of crop growth environment andperfecting the theory of regional agriculture. In this study, the soil temperature distributionand variation characteristics of soil temperature were analyzed based on the soil temperaturedata on fallow field and crop field measured at the soil moisture-heat monitoring field at theChangwu agro-ecological experimental station on the loess plateau of China. Results are asfollows:1. A daily variability of soil temperature can be observed in superficial layers of fallowfield, which can be expressed as a sine curve. The soil temperature amplitude decreasedgradually and the phase variation of soil temperature displayed a gradual lag with theincrease of soil depth. However, the soil depth that displayed daily variation was different indifferent season, the soil temperature displayed an obvious daily variation at the depth higherthan5cm in January,20cm in April, July and October; there was no daily variation at thedepth lower than20cm in January,70cm in April and40cm in July and October. The soiltemperature amplitude was different in different season, the April’s soil temperatureamplitude was the largest and the January’s amplitude was the smallest in four months, andthe July’s amplitude was larger than the October’s.2. An obvious seasonal variation of soil temperature was observed between0and110cm soil layers. However, the seasonal variation between250and650cm was very weak andwas almost no annual variation at1000cm. The relationship between annual range of soiltemperature and soil depths can be expressed as an exponential function. The lowest monthmean of soil temperature between0and40cm appeared in January, and the highest monthmean of soil temperature between5and40cm appeared in July, but it appeared in June at0cm. Additional, the time of the highest and lowest month mean of soil temperature at thedepth lower than40cm was apparently lagged. Frozen layer may come to the depth of40cmin winter. 3. Soil temperature between0and20cm displayed an obvious daily variation in cropfield and fallow field while the depth between0and10cm in winter, which can be expressedas a sine curve. The soil temperature amplitude was the maximum in spring, the middle insummer and autumn, the minimum in winter. The daily variation of soil temperature incloudy day was more complex and the soil temperature amplitude was smaller than sunnyday.4. The time that the highest monthly mean of soil temperature occurred between0and70cm in spring corn field was lagged compared with fallow field. The highest monthly meanof soil temperature at the depth between0and110cm was0.6to1.5℃lower than thefallow field. The daily mean of soil temperature in spring corn field is obviously lower thanthat in fallow field, and the difference value decreased significantly when a rainfall occurred.The monthly mean soil temperature of winter wheat field and fallow field decreased beforeFebruary, then increased after March during the whole growth period. The temperaturedifference was the minimum in different soil layers in March. From April to June, the soiltemperature of winter wheat field rise slower and temperature difference in different soillayers was smaller than fallow field. During the whole growth of winter wheat, there was asignificant difference in soil temperature between wheat field and fallow field from April toJune.