Effects of Tobacco-rice Continuous Cropping Years on Soil Physicochemical Properties and Tobacco Yield and Quality

To investigate the effects of long term tobacco-rice continuous cropping on soil nutrients and flue-cured tobacco leaf yield and quality, the soils of different con- tinuous cropping years were selected in tobacco-rice multiple system of Hengyang. Some important indexes, including pH, contents of organic matter and available nu- trients of N P K, contents of medium trace elements of soil samples, and contents of main chemical components of flue-cured tobacco samples were detected for fur- ther analyzing. The results showed that pH value of moderate continuous cropping soil（≤7 years） was more coordinated, in addition, leaf yield and quality of flue-cured tobacco were contained, and the sugar-nicotine ratio and potassium-chlorine ratio were proper. However, under long-term continuous cropping （≥10 years） condition, the soil became acidification, and yield and output value of flue-cured tobacco de- clined. It was suggested that improving soil quality by planting green manure or keeping fallow after continuous cropping 7 years in tobacco-rice system.

Selection of Grape Varieties Suitable for Double Cropping a Year in Northern Greenhouse

With the development of the greenhouse grape cultivation area,the supporting greenhouse grape varieties appear to be single.At present,there are few researches on the selection of grape varieties suitable for two-harvest-a-year cultivation in greenhouses.In order to meet the needs of fruit growers for the diversity of greenhouse grape varieties,experimental studies had been carried out.Through three consecutive years of two-harvest-a-year production of six grape varieties of‘Jingxiangyu’,‘Ruidukemei’,‘Xiangfei’,‘Jingyan’,‘Zaomanao’and‘Hanxiangmi’,the first crop of greenhouse grapes matured from May to July,and the second crop matured during the New Year s Day and Spring Festival.Through the investigation and analysis of their phenological periods,fruit economic characteristics and economic benefits,it was found that the four varieties of‘Jingxiangyu’,‘Ruidukemei’,‘Xiangfei’and‘Jingyan’performed well under greenhouse cultivation conditions,and thus can be used as supporting fine varieties for large-scale promotion.

Study on the Yield Reduction Mechanism of Soybean Planted under Continuous and every Second Year Cropping Conditions

Three-year investigation was conducted to demonstrate the mechanism of reduction of soybean yield aroused by continuous and every second year cropping. Compared to normal cropping, there are many unfavorable changes in some major elements of soybean plant and soil environment. Chloropyll content was lower. Phosphorous content of soybean plant was decreased seriously. Potassium content was lower while calcium content was higher. Magnesium content was wot affected and decreased in susceptive varieties. Some deseases and insects of soybean under continuous and wery second year cropping conditions became serious as continuous years prolonged. Organic matter content tended to go down from normal rotation to continuous cropping. Amount of bacteria and antinomyces decreased while amount of fungi increased. The development of symbiotic nitrogen fixation system wsa deteriorated.

High-efficiency Planting Techniques of Five Crops a Year for Fresh Edible "Faba Bean/Spring Mazie+Soybean-Autumn Maize/Autumn Soybean"

The high-efficiency planting mode for five crops a year of fresh edible ＂faba bean/spring maize＋soybean-autumn maize/autumn soybean＂ was introduced, and its yield and economic benefits were compared with the planting mode of three crops a year of ＂faba bean-spring maize/red bean＂. The results showed that the planting method for fresh edible ＂faba bean/spring maize＋soybean-autumn maize/autumn soybean＂ was much easier to operate with the input-output ratio of about185.6%, and its yield and economic benefits were 2.09 and 1.83 times of that of the planting mode for three crops a year, significantly improving the agricultural yield and income of farmers. In addition, the cropping index of the planting mode for fresh edible fresh edible ＂faba bean/spring maize ＋soybean-autumn maize/autumn soybean＂ reached up to 350%, and planting faba bean once a year and soybean twice a year could make the biological fixation amount of nitrogen increase 350-450kg/m^2, which equaled to up to 700 kg/m^2 of urea, showing significant ecological and social benefits. Based on the comparison results, the high-yield culture techniques of the planting mode of fresh edible ＂faba bean/spring maize＋soybean-autumn maize/autumn soybean＂ were summarized.