Jurong City, Jiangsu Province, Dai Zhuang Cun of organic agriculture after nearly 10 years of development, now organic planting area reached 660h square meters with the, only organic rice has been developed to 200H square meters, since organic farming has had a certain scale, but its own machine rice production, production of organic rice always hovering lower yield in 3000 ~ 4125kg/ h square meters, except for a variety of reasons, mainly is the soil fertility. In order to improve the yield of organic rice, fertility, improve organic paddy soil quality, improve the quality of organic rice, from the beginning of 2009, in Dai Zhuang development a part of organic rice clover rotation. In order to fully understand the Dai Zhuang organic paddy soil quality, to find out the soil fertility status, reasonable arrangements for production of organic rice, organic rice production potential of mining, after the end of 2012 organic rice harvest, plots in different area, different ways of planting sampling test analysis.
1, materials and methods
1.1, Dai Zhuang soil profile
Dai village is located in the beautiful scenery of the Kowloon mountain, almost no industry, a good ecological environment. The ecological area belongs to north subtropical monsoon climate, the average annual rainfall is 1012mm. Average annual temperature of 15.2 DEG C, crop growth season accumulated temperature 5461.7 DEG and soil for the Quaternary loess, development of horse liver soil (yellow brown).
1.2, test design
By field experiment, namely in every village to select the adjacent plots, the whole field were used organic rice - clover, organic rice - wheat (Brassica napus L.) rotation mode.
1.3, soil collection
Sampling unit: per kilometer (about square meters for 15h) organic rice - clover rotation, organic rice - wheat rotation two planting patterns from each of the three samples, with four points from each test sample 1kg mixed; organic rice - clover rotation, organic rice rapeseed (Triticum aestivum L.) rotation land adjacent soil, ensure that the soil samples can represent the soil properties of the area. Sampling time: the end of the harvest of organic rice, natural dried rice straw sampling. Sampling depth: 0 ~ 20cm soil of the cultivated layer. Sampling method: according to the specific circumstances of the plots sampling (X shape distribution sampling, S-shaped sampling), so that the sample represents Honda block status.
1.4, test methods
Organic matter content was determined by potassium dichromate sulfuric acid digestion method; total nitrogen determination of selenium, copper sulfate, sulfuric acid digestion distillation method; total phosphorus and total potassium were measured with hydrofluoric acid, perchloric acid soluble - molybdenum antimony anti colorimetry; pH potentiometric method was used for the determination.
2, results and analysis
2.1, the status of soil fertility
2.1.1, soil organic matter content and organic matter content is one of the important indicators to evaluate the quality of soil. Dai Zhuang organic paddy soil chemical analysis results show that, rice field soil improve the overall content of organic matter, the average content of organic matter of 23.75g/kg, and in 2008 the implementation of organic rice clover rotation before) compared to an increase of 5.84%; organic rice clover rotation mode organic matter average content of 24.58g/kg, and 2008 compared growth reached 9.55%, and increase the content of organic matter are far higher than organic rice - wheat (Brassica napus L.) rotation mode; at the same time, soil pH value also changes, soil pH value reached neutral, which is beneficial to the growth of plants [1]. Increase may be due to the organic cultivation to reduce the input of chemical fertilizer, but from two different rotation patterns of soil pH value change of soil pH value, organic rice - clover rotation soil pH value increased by more than the organic rice - wheat (Brassica napus L.) rotation mode, so organic rice production in Rice - clover rotation mode is effectively improve soil organic matter content, improve soil structure, increasing soil fertility and the important method [2-6].
2.1.2, soil nitrogen, phosphorus and potassium content in the low rice field soil nitrogen, phosphorus, potassium nutrient content directly affect the production of organic rice. Soil sample analysis results show that Dai Zhuang organic rice field soil total nitrogen, available phosphorus content decreased and organic rice - clover rotation patterns of soil available potassium content increased, and organic rice - wheat (Brassica napus L.) rotation mode available K content decreased slightly. This is mainly because of the introduction of organic production, put an end to the use of chemical fertilizers, crop nitrogen, phosphorus and potassium mainly from soil slow release and crop root stubble and straw rot, rice and wheat in the whole growth period need to consume large amounts of nitrogen, phosphorus, potassium, and rice consumption of potassium mainly concentrated in the straw, also test the planting of rice varieties yield is low, less potassium consumption; organic rice clover rotation, a large number of Chinese milk vetch returning undoubtedly to the soil complements the large amounts of potassium, and organic rice - wheat (Brassica napus L.) rotation mode only consumption, resulting in potassium in different planting pattern changes are not the same. According to Zhejiang Province farmland quality investigation of soil nutrient classification standard [7], Dai Zhuang organic rice field soil nitrogen, phosphorus and potassium nutrient overall low: four soil accounted for 70% of the secondary soil, soil and five levels of soil, accounting for 10%; available K lower than the total nitrogen, accounted for 30% of the soil, accounted for 60% of the five levels of soil, soil accounted for 10%; available phosphorus was the lowest, four soil accounted for only 10%, five level soil accounted for 70%, six soil accounted for 20%. From the sample analysis results, Dai Zhuang organic paddy field nitrogen, phosphorus and potassium nutrient is inferior in quality [8-9], this should is the key factor of restricting the development of rice yield.
2.2, the reason of the change of soil fertility
2.2.1, organic matter content of the soil increased wear Zhuang organic paddy soil organic matter content increased, mainly because of the introduction of organic farming, reducing the use of chemical fertilizers, organic rice - clover rotation, organic rice - wheat (Brassica napus L.) rotation makes a lot of green manure, crop straw and root of returning decay, increase the content of soil organic matter. Although Dai Zhuang organic paddy soil organic matter content in the past few years has increased, however, with reference to the classification standard of soil nutrient [7], Dai Zhuang organic paddy soil organic matter content is still in low level, the four soils accounted for 90%, and 10% of soil organic matter content in the fifth level. To improve wear Zhuang organic paddy soil fertility status, also need to vigorously develop the green manure, the implementation of organic rice and green manure (clover) rotation mode.
The reason for the lower 2.2.2, soil nitrogen phosphorus and potassium content in Dai Zhuang Development of organic agriculture, change of soil fertility in the paddy field, the traditional organic rice wheat rotation mode (rapeseed), soil nitrogen, phosphorus and potassium content decreased; while organic rice - clover rotation mode, the content of nitrogen and phosphorus the soil potassium decreased, but increased, this is mainly because of the use of chemical fertilizers and eliminate the Dai Zhuang organic rice varieties selected in Japan is more light, the varieties of short growth period, yield is low, even very good soil fertility yield is only 5250 ~ 6750kg/h square meters, and Dai Zhuang organic rice straw returning most. So the organic rice consumption of nitrogen and phosphorus more, take less potassium; wheat take relatively more potassium, but no clover green manure added, resulting in different potassium changes.
3, discussion
According to the sampling analysis results, Dai Zhuang organic paddy soil and improve the overall content of organic matter, soil nitrogen, phosphorus and potassium content is generally low, the content of nitrogen and phosphorus in the organic rice clover rotation soil decreased, potassium content increased slightly; organic rice wheat rotation soil nitrogen, phosphorus and potassium were decreased, so organic rice clover rotation system on soil fertility improvement is far superior to the organic rice - wheat rotation mode. Therefore, vigorously popularize development of organic rice clover rotation to improve the organic paddy soil structure, improve soil fertility is important, and to improve the yield of organic rice, improve organic rice quality has a positive effect.
Soil fertility is one of the bottlenecks that restrict the production of organic. Because a small number of producers only see the immediate benefits, do not want to abandon the winter wheat, or follow the rice wheat rotation model, wheat yield is very little, soil fertility is not improved, affect the production of organic rice. From the point of view of Dai village in recent years of production experience, the implementation of organic rice clover rotation, a large number of high-quality green manure, soil fertility improved, the production of organic rice also tended to be normal. From the sample analysis results, winter green manure planting pattern of organic matter increased by a big margin, slow speed of consumption of nitrogen and phosphorus, so the development of organic agriculture to vigorously develop the green manure crop rotation, such as planting Chinese milk vetch, Medicago falcata, light leaf vetch, broad bean, Medicago sativum and Vicia villosa and [2, 10]. In recent years, Dai, Zhuang and open up a rotation of rice and Chinese milk vetch, winter by the use of green manure, goose, goose feces returning, forming a virtuous cycle, soil fertility is expected to increase dramatically, while increasing the farmers' income.
There are a large number of livestock and poultry manure in rural areas, usually collected, concentrated in the fermentation, when plowing spread into farmland. The manure contains various nutrients of crop, which in the sheep manure fertility best, the contents of nitrogen, phosphorus and potassium amounted to 0.83%, 0.23%, 0.67%. Manure fertilizer effect lasting, in crop growth process in a continuous supply of nutrition; manure on decomposition will produce large amounts of carbon dioxide, carbon nutrition for plant; manure containing large numbers of microorganisms, applied into soil, in microbial activity, soil nutrient in some crops difficult to use slowly released, and it also has positive effect on improving soil aeration and water permeability.
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