| Spatial variability of soil nutrient and crop yield in Shanghai Chongming Island large-scale management farm was studied by modern geo-statistical and geographic information technology. Additionally, integrating field computer, DGPS and variable mechanical control system to a tractor produced by China, initial practice of variable rate fertilization (VRF) was conducted under the guidance of VRF machine. And the effects of nitrogen VRF on rice were studied. The main results are summarized as following:1 The study to evaluate soil nutrient status of the experimented-farm by ASI method showed that the soil acidity was neutral. The soil was rich in available calcium, sulfur, boron, copper, iron, and medium in available phosphorus and potassium. Available nitrogen was very low and nitrogen fertilizers were need most. Available zinc in soil was lower than the critical level.2 Conventional statistics of soil nutrients and pH value of 477 sampling sites showed the distribution of soil nutrient was not always normal. Available P and Ca had logarithmic normal distribution. The variability of soil pH was smallest and the coefficients of variance of available B, S and Zn were higher than 50%. The variability of available N was medium. The coefficients of variance of other nutrients were from 16% to 30%.3 Geo-statistics analysis on soil nutrient indicated that the variance of soil nutrients in one field was smaller than that between fields but it depended on field's location. It indicated there was a good relation of the spatial variability of soil nutrient with the field management such as cultivations, fertilization etc.in the large-scale management farm.4 Semi-variance analysis showed that the variability of soil pH was not only small but also there was a weak spatial structure which indicated soil pH was only slightly affected by the field management such as cultivations, fertilization. Other available nutrients still remained spatial self-correlation to certain degree in spite of a strong effect by field management such as cultivations, fertilization and so on.5 The results of partial correlation analysis on the relation between crop yield and soil available nutrient showed that there was a significant negative correlation of available Fe with the crop yield but a significant positive correlation of available P, Ca, S with crop yield.6 Variable rate fertilization (VRF)is the key part in soil nutrient precision management and this study made the China's tie-niu tractor conformed with GPS AgGPS132 of America's corp. Trimble, field computer AgGPS170, variable controller TASC6100 of America's corp. Mid -Tech and rotary tiller with variable rate fertilizing, which formed the variable-controlled applying fertilizer mechanism system.7 Directed by DGPS, soil samples were collected by certain grid in two fields and the content of soil available N and organic matter were tested by ASI soil nutrient system. Using GIS technique and themethod of kriging interpolating to predict spatial distribution of the content of soil available N and organic matter and combined with ASI recommended fertilization model the entire map of operation of N fertilizer applying variably, which could be offered to machine and manual variable rate fertilization , or the routine fertilization.8 The variable rate controlling system and the map of variable rate fertilization are both in good work condition checked by field practice, which really make the variable rate fertilization come true that have been pushed in to force by developed countries.9 The result prove that rotary tiller with variable rate fertilizing can reach the high-qualified precision in fertilization by given older, and it can meet the request of variable rate fertilization in precision agriculture. The experiment just testifies the urea, and it need more tests about applicability of other kinds of fertilizers diameter of granule and state.10 The results of partial correlation analysis on the relation between crop yield and soil available nutrient showed that there was a significant negative correlation of available Fe with the crop yield but a significant positive correlation of available P, Ca, S with crop yield.11 The result of VRF experiment showed that VRF made the distribution of soil organic matter and available N uniform. Sampling scale affected on crop yield of VRF and small-scale sampling could make higher crop yield. But the small-scale sampling could result in a dramatic increase of the cost so that 40m or 50m grid sampling could be accepted.12 There was no significant difference between VRF by machine and by hand. It showed the VRF machine was successful in application of VRF. The spatial distribution map of crop yield showed VRF resulted in more uniform distribution of crop yield.
|
PDF Full Text Request