Study On Methods For Determination Of Available Phosphorus In Soil Testing And Fertilizer Recommendation

Methods of available nutrient testing are the most basic and important question in soil testing and fertilizer recommendation. Content of the soil available nutrient is the basis of soil nutrient supplies level and soil testing. In all the necessary nutrients of crops, nitrogen, phosphorus and potassium affected the most on the growth and yield of crops; this is why they are called the three nutrient elements, In conventional measurement of soil nutrient, nitrogen, phosphorus, potassium is measured using chemical reagents in the extraction, extraction of soil P is complex. The purpose of soil testing is to design a suitable application of phosphate fertilizer.Conventional method of available phosphorus is chemical extraction. There re many different types of extraction agent, at present, three methods are applied in soil testing and fertilizer recommendation: Olsen, Mehlich and ASI. The correlation between measurement of which method and crop is better need further inspect and verify.In this study, using biological detection method to research the method of soil available phosphorus, it means that use field trials to carry out correlation research. In this study, it takes the crop reaction as standard reflect the crop as a benchmark. Strike a different method for determines the value and crop yield, relative yield, the yield rate, uptake of the correlation coefficient. As to Olsen method, it will be carried out under different temperature conditions and continuous extraction of P values is compared with the reference standard for conducting relevant studies. Fitting then combined to evaluate the extentThe object of this study is main agricultural soils in Sichuan Basin. The purpose of this research is to find the interrelation among measurement of different methods between the reactions of crop by field trials. So as to enhancing and improving the reflect extent on soil nutrient availability, selected suitable methods for the regional soil available phosphorus testing, offer scientific basis for available phosphorus test in soil testing and fertilizer recommendation. The main results are as follows:1. The available phosphorus measurement of Otsen, Mehlich and ASI method differs greatly, the mean value of these 3 methods are 12.8mg/kg, 22.1mg/kg, 5.33mg/kg. The measurement results showed that M3 method＞Olsen method＞ASI method. Among measurements of three methods, there was a significant or great significant interactive effects, correlation coefficient is 0.384^*, 0.721^**, 0.810^**, the measurement of different method can be interconvert to another. The appearance at different soil pH, using different methods and different utilization of arable land is solidly.2. The analysis of correlation of wheat yield, relative yield, production rate, the wheat phosphorus uptake, stem phosphorus uptake, total phosphorus uptake and soil available phosphorus value by the methods of M3, ASI and Olsen showed that:soil available phosphorus value determined by M3 method has significant correlation with relative yield, production rate, value is max, r=-0.688^*,-0.676^*,-0.823^**,-0.843^**,0.737,0.803^**,0.925^**,0.922^**. The correlation is better than soil phosphorus value determined by other two methods. From the analysis, we can draw the conclusion that M3 method is the most suitable method to determine soil available phosphorus in soil testing and fertilizer recommendation in the area of this study.3. The result of Continuous extraction of soil available phosphorus by Olsen method showed that the extraction time has great influence on the determined available phosphorus value. The cumulative value of different extraction time is increase duo to the increase of time the increase number is 3.32mg/kg. The increase is different because the content of available phosphorus is different. There was significant correlation among the cumulative value of different extraction time, r=0.980^**,0.950^**,0.890^**. From the correlation analysis we can conclude that the determined value of first extraction can reflect available phosphorus requirement of crops.4. Result of soil available phosphorus value determined by Olsen method in different temperature condition showed that: temperature has an important influence on the determined value of available phosphorus. In the rage of 10 Celsius degree to 30 Celsius degree, the available phosphorus value increases with the increment of temperature, and the increase value is different soils of different content available phosphorus. There was significant correlation among the determined value of different temperature, r=0.971^**,0.972^**,0.976^**,0.993^**. The result is also applicable when determined different soils of different pH, using different methods, and different levels of soil fertility. The correlation of the value determined under 20 Celsius degree, production rate 1 and 2, relative yield 1 and 2, uptake phosphate of grain, uptake phosphate of straw, total uptake phosphate is better than other temperature, r-=0.719^*,0.428,-0.714^*,-0.351. We can conclude that determined value of 20 Celsius degree in plough horizon correspond with the actual needs of wheat. The result of subsoil showed that the correlation of determined value of 30 Celsius degree, reference standard is better than other temperature.