| Effect of rice chaff and duckweeds on plant growth,yield and plant nutrient content of no-tillage cast transplanting rice,and ammonia volatilization,soil fertility,and duckweeds on N conversion of the suffer water in soil were investigated with pot trial and field experiments in present studies to provide basis for technique of rice chaff and duckweeds used on no-tillage cast transplanting rice in south red soils two-season farming rice area.The main results showed as follows:1.There was no significant negative influence on plants height by using duckweed in field.However the growth of rice was inhibited by using rice chaff alone or duckwee combined with rice chaff,as well as to significant improved the rice tillering capability,effective panicles,setting grains per panicle,setting grain percentage,103-grains weight and yield.Applying rice chaff 100 g/m2 and 150 g/m2 in no-tillage field,grain yield incerased by 6.12%and 8.49%respectively,and Yield increased with rice chaff rate increase.Moreover,using duckwee 100 g/m2 + rice chaff 100 g/m2 and duckwee 200 g/m2 + rice chaff 150 g/m2 in field,grain yield incerased by 7.1%and 11.1%respectively.The effect was the best by using duckwee 200 g/m2 + rice chaff 150 g/m2,the grain yield increased by 11.1%,the theory and harvested yield were increased 775.6 kg/hm2 and 747.2 kg/hm2 respectively,the income were increased 385.8 yuan/hm2,increased by 4.4%, the economic efficiency was the best.2.Rice chaff or duckwee combined with rice chaff improved the resisting fall capability of rice,also increased chlorophyll content and amino acid content of leaf in rice,darkened the leaf color promoted the leaf photosynthesis during the late growth periods.As the result of the enhancement of plant physiological activities,it is beneficial to cumulate the nutrient matter of rice grain.3.The nitrogen,phosphorous and potassium concent of plant stems and leaves in rice were improved gradually during the late growth periods by using rice chaff or duckwee combined with rice chaff.However,the effect wasn't obvious on the nutrient concent of rice plant stems and leaves by using duckwee.4.Using the highest number duckwee,rice chaff alone or duckwee combined with rice chaff increased available nutrients and organic matter in soils during the middle and late periods of rice.The available nutrients was reduced in soils during the early periods of rice by using duckwee alone, compared With contrast,but they were improved gradually in soil while duckwee died and nutrient was returned to soils.Moreover,available nutrients and organic matter were increased obviously by uSing rice chaff or duckwee combined with rice chaff in the harvested petiod of rice.5.Regardless of using duckwee,rice chaff alone or duckwee combined with rice chaff,the ammonia volatilization loss amount was reduced in paddy soil.During the growth period,the effect of restraining the ammonia volatilization loss amount showed as:duckwee 200 g/m2 + rice chaff 150 g/m2＞duckwee 200 g/m2＞duckwee 100 g/m2+rice chaff1 50g/m2＞uckwee 100 g/m2＞rice chaff 150 g/m2＞duckwee 50 g/m2＞ricec haff 100 g/m2. Among them,the ammonia volatilization loss amount was only 7.74 kg/hm2 by using duckwee 200 g/m2 + rice chaff 150 g/m2,reduced by 18.2% compared with contrast.6.The results of pot trial showed that duckweed would accelerate NH4+ -N thickness rising,high-number duckwee not only could achieve the peak in 1 day early,but also the peak was low than low-number duckwee and contrast.The changes of TN and NO3--N thickness approach to coincide basically in the experiment.duckweed could uptake and assimilate NH4+-N and then saved them during the early growth period of rice,but NH4+-N and NO3--N thickness had the trend of rising again by the tillering late period of rice,compared with low-number duckwee,high-number duckwee show obviously.It was indicated that duckweed could release N when duckweed save part of N to reach certain degree in water environment.
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