水稻覆膜旱作对根叶性状、土壤养分和土壤微生物活性的影响

Effects of film mulching of upland rice on root and leaf traits,soil nutrient content and soil microbial activity

研究了水稻覆膜旱作、裸地旱作、常规水作处理对根系形态、叶片水势、土壤养分、土壤微生物数量和土壤酶活性的影响。结果表明，覆膜旱作能改善水稻田间的生态环境，提高早季土壤温度1～3℃。与裸地旱作相比，覆膜旱作能增加抽穗期水稻根系的总根长、比根长，而这些指标与常规水作差别不大。在水稻抽穗期，无论是剑叶还是倒2叶的水势，均有如下趋势：水作〉覆膜旱作〉裸地旱作，但均未达到显著水平。不同处理对叶片叶绿素含量的影响在分蘖期差异不大，中后期覆膜旱作明显高于裸地旱作和常规水作，抽穗期分别增加29．44％和15．15％，成熟期则为74．4％、38．9％。覆膜旱作能显著增加水稻的有效穗数，早季和晚季产量比裸地旱作增产10．6％和12．5％，而与常规水作差别不大。与裸地旱作和常规水作相比，覆膜旱作土壤养分含量在分蘖期除了全磷、速效氮显著增加外，其他指标差异不大。而抽穗期则由于覆膜后作物对养分的消耗加大从而使土壤养分含量下降，特别是总磷、速效磷、速效钾与常规水作相比显著下降，分别降低25．9％，31．9％，16．2％。而成熟期则大多指标与常规水作相比有所下降，但未达到显著水平。与常规水作栽培相比，覆膜旱作能增加土壤微生物细菌、真菌、放线菌2．5倍，显著增加土壤过氧化氢酶和蔗糖酶的活性，而土壤脲酶活性则差异不大。土壤过氧化氢酶活性在分蘖期、抽穗期、成熟期分别增加13．8％，81．3％，17．4％，蔗糖酶活性则分别增加42．8％，28．8％和69．9％。

Rice is a heavy consumer of fresh water and Traditional lowland rice with continuous flooding requires increase of water shortage. In recent years, water-saving water-limited environments, including alternating wetting approximately 60% of the fresh water is used for rice production. relatively high water inputs and its sustainability is threatened by the rice production techniques have been developed in China and in other and drying （AWD）, aerobic rice, and ground-cover rice production systems （GCRPS）, also called ＂plastic film mulched dryland rice＂. GCRPS is a promising new production technology to grow rice using less water, it has been reported to save up to 60% of the water usually needed growing paddy rice without causing any significant reduction in grain yields. Field experiments with three treatments, upland rice cultivation without mulching （UC）, upland cultivation with film mulching （FM）, traditional paddy rice cultivation （CK） in two seasons were carried out to study the effects of rice mulching cultivation on root and leaf traits, soil nutrient content and microbial activities. All plots were enclosed by isolating dams of 50 cm width and 15 cm height to assure independent hydrological conditions. Except traditional paddy rice production （ CK）, the rice field were irrigated only at the time when the rice was sensitive to water stress i.e. one week after transplanting, panicle illumination and heading. Dynamic changes of soil chemical properties and soil enzyme activities were monitored at tillering, heading and ripening stage by collecting soil samples from rhizosphere. The results indicated that film mulching （FM） could increase soil temperature by 1-3℃ than UC and CK treatments, total root length and specific root length at heading stage were also increased compared to UC treatment. Water potential of flag leaf and the second lower leaf of the rice plant was in the decreasing order： CK 〉 FM 〉 UC. There was no significant difference in chlorophyll content of leaf at tillering stage among the three treatments. However, film mulching treatment （FM） significantly increased chlorophyll contents of leaf by 29.4% and 15.2% at heading stage and 74.4% and 38.9% at ripening stage compared to UC and CK treatment respectively. In comparison with UC treatment, FM treatment led to an increase in grain yield by 10.6% and 12.5% respectively at early and late season, there was no significant yield difference between FM treatment and CK treatment. Film mulching did not cause changes in soil nutrient content except that total P, available N occasionally increased at tillering stage. However, soil fertility index especially total P, available P and available K were decreased by 25.9%, 31.9%,16.2% respectively than CK treatment at heading stage, there was no obvious difference of soil fertility among UC, FM and CK treatments except for effective N content at ripening. Compared to CK treatment,, FM treatment could increase the amount of soil bacteria, fungi and actinomycetes by 2 to 5 folds, increase soil enzyme activity at tillering, heading and ripening stage, especially sucrase activity by 42.8%, 28.8% and 69.9% ,catalase activity by 13.8% ,81.3%, 17.4% respectively. The above results suggest that film mulching could improve the water utilization efficiency in rice production. It could also enhance the release of soil nutrient and increase decomposition of soil organic matter through increasing the amount of soil microbes and soil enzyme activity, which increased the availability of nutrient elements for rice plants. However, soil nutrient deficiency in the late stage of rice growth may be a problem for upland rice cultivation under film mulching treatment（ FM）.