连续免耕对不同质地稻田土壤理化性质的影响

以我国南方地区典型的单季水稻生产大田为研究对象,按土壤质地分为壤质和粘质两个系列,探讨不同质地稻田土壤理化性质变化对连续免耕的响应规律。结果表明,在无秸秆覆盖条件下,随着免耕年限的增加,壤质和粘质稻田土壤的耕层均有紧实度提高的趋势,特别是粘质土壤,导致耕层变浅。与常年翻耕土壤相比,免耕6a后壤质水稻土0—20 cm土层的紧实度值平均增加了32%,而粘质的平均增加了90%。在相同免耕年限条件下粘质稻田土壤容重的增加也比壤质土壤的明显。壤质土壤0—10 cm土层有机质和碱解氮含量随免耕年限延长而提高,而在粘质土壤则显著降低。无论是壤质还是粘质土壤,连续免耕多年后土壤速效磷均在耕层(0—20 cm)富集,而速效钾则相反。总体而言,壤质水稻土对免耕的适宜性要优于粘质土壤;应根据土壤质地的不同选择性地实施免耕技术,并结合秸秆覆盖,以实现免耕稻田土壤的可持续利用。

Effects of soil texture on variations of paddy soil physical and chemical properties under continuous no tillage

As one of soil conservation tillage methods, no tillage (NT) has been widely applied in farmlands worldwide. Due to the combined effect of soil type, cropland ecological condition and cropping system type, there is still ongoing debate concerning the positive versus negative effect of NT on paddy soil properties. Although soil texture has been recognized as one of important factors in characterizing soil property variation in response to different management practices, few attempts have been performed to address effects of tillage method on soil property considering the difference in soil textures. Such effort will be beneficial to explain the ongoing debate and improve our knowledge on the effect of NT on soil property.In this study, effects of soil texture (i.e., loam and clay) on the variations of soil physical and chemical properties in response to continuous NT were addressed for the single cropping paddy field in Shaoxing area in southern China. Studied paddy fields were commonly and continuously used for rice cultivation by local farmers, which would be significant to reveal effects of NT on soil property under practical production. To avoid the disturbances from other factors, all soil samples were collected in the paddy fields with same field management measures in rice seeding, fertilization, and irrigation. Soil sampling efforts were finished during 5-10 days after rice harvesting at November, 2008. According to local practices, rice straws were all removed from paddy fields.Results indicated that although soil compactions at 0-20 cm layers were increased with increasing NT applied years in both the loam and clay paddy soil, its increased intensity was higher in the clay soil than that in the loam soil, resulting in shallower plough layer occurring in the NT clay soil. Compare to the conventional tillage soil, the penetration resistance was increased by 32% and 90% in the loam and clay soil after 6 years of continuous NT, respectively. The clay soil also presented greater soil bulk densities than the loam soil after same years of continuous NT. Furthermore, soil organic matter and available nitrogen contents were both increased with NT applied years in the loam soil, while they were both significantly decreased in the clay soil. Although soil available phosphorus contents at the plough layer (0-20 cm) in both the loam and clay soils were increased after 6 years of continuous NT, their soil available potassium contents were both decreased. After 1-6 years of continuous NT, the loam paddy soil presented more positive consequences than the clay ones in terms of soil physical and chemical properties. When assessing the feasibility of applying NT method in paddy fields, the role of soil texture should be further considered in study, as it is an important factor in regulating variation of soil property under continuous NT. Rice straw mulching is an economic and effective way to mitigate soil degradation under continuous NT in practice. Considering the tillage cost and soil quality maintenance, overall ploughing is suggested to be performed once after every 3-4 years of continuous NT for clay paddy soils but for loam paddy soils it can be applied after a bit longer years of continuous NT in southern China.