Soil tests for phosphorus and soya bean response | |
| Author | Ranjith, Subasinghe Arachchige |
| Call Number | AIT Thesis no. AE-82-12 |
| Subject(s) | Soils--Testing Soils--Phosphorus content |
| Note | A thesis submitted in partial fulfilment of the requirement for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Many P extractants that are in use today have been adopted without sufficient investigations. A field experiment which consisted of twenty plots, each planted with soya bean was conducted at the Asian Institute of Technology experimental field to determine the correlation of three P tests namely, Bray, Olsen and Anion Exchange Resin method with crop response. In addition, a simple modified Neubauer test was conducted with mungbean for the same purpose. Linear correlations are presented for the relations between values for 3 chemical soil P tests and dry matter yield of soybean seeds, P content of young plants and of seeds, clay content, pH, CEC, extractable Al, Mn, Fe, Zn, of the soil and the net uptake of P in the modified Neubauer test. P content determined by three chemical methods was positively correlated with yield, P content of seeds and plants and pH of the soil while negatively correlated with clay content, CEC, and extractable Al content of the soil. The correlation coefficients for Bray and Olsen test with crop response data were equally high while Anion 2 Exchange Resin gave somewhat lower results. Correlation coefficients (r ) between plant P contents at 2 months stage and Bray, Olsen, and Resin methods were 0. 87, O. 81, and O. 65 respectively, Correlation coefficients between seed P contents and Bray, Olsen, and Resin methods were 0.84, 0.89, and 0.72 respectively, Correlation coefficients between the yield and Bray, Olsen and Resin methods were 0.66, 0,87, and 0.61 respectively. It was concluded that both the Bray and Olsen methods are equally satisfactory for extracting available P in acid sulfate soils, However, due to the limitations such as larger volume of extractant required and longer shaking period, the Olsen method was considered uneconomical and time consuming, thus leading to the preference of BRAY method. In contrast to the chemical methods, short term extraction of P by mung bean plants in the modified Neubauer test showed very poor correlation with P contents of young plants and of seeds, and with seed yield. No explanation can be offered for this anomaly. The correlation coefficient of pH with the dry seed yield (r2 = 0.69) was somewhat higher than that of P determined by Bray and Resin methods. However, it was clearly shown for a number of plots that the seed yields responded greatly to varying soil-P levels independent of soil pH. |
| Year | 1982 |
| Type | Thesis |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Eppendorfer, W.H. |
| Examination Committee(s) | Apichart Anukularmphai ; Jensen, Jens Raunso |
| Scholarship Donor(s) | KEIDANREN, Japan |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1982 |