Rainfed Paddy Soil Fertility Evaluation in Upper Northern Region for Effective Fertilizer Application

Abstract

Soil fertility under the rainfed paddy field conditions was evaluated during 1992-1996. Data was obtained from 9 provinces in the upper north of Thailand : Chiang Mai, chiang Rai, Phayao, Mae Hong Son, Lamphun, Lampang, Phrae, Nan and Uttaradit. The Majority of 269 soil samples analysed was defined with moderate level of soil fertility having 1.5-3.5% organic matter. Available phosphorus was lower than 10 ppm while the moderate level of 60-90 ppm of extractable potassium was detected. The soil pH was moderately acidity with 5.1-6.0 and soil texture were sandy loam, clay loam and loam. response of chemical fertilizer, 16-20-0 at the rate of 0, 15, 15 and 35 kt/rai, was study in rice variety RD 6 in 4 type of soil series : Phan/hang Dong (Tropaqualfs), chiang Rai (Paleaqualfs), Mae Sai (Tropaqualfs) and Mae Rim (Paleaqualgs). The highest average yield of 596 kg/rai was obtained from 25 kg/rai in Phan/Hang Dong series. The average yield of 564, 508 and 416 kg/rai were observed in chiang Rai. Mae Sai and Mae Rim series with the application of 35, 25 and 35 kg/rai, respectively. Maximum fertilizer response in Phan/Hang dong Chiang Rai, Mae Sai and Mae Rim soil series was analysed using the Cate-nelson Mode. Results revealed maxima, 580 kg/rai with the application of 19 kg/rai of fertilizer to the Phan/Hang Dong soil series resulting in the return of income of 2,139 baht/rai. To a lesser extent, the yield of 516, 494 and 380 kg/rai were obtained 21, 17 and 30 kg/rai of fertilizer to chiang Rai, Mae Sai and Mae Rim soil series with the 1,736, 1,641 and 945 baht/rai return of income, respectively. The analysis on the effect of critical level of soil organic matter on fertilizer response using the 2 -means discontinuous model showed that highly response of fertilizer was obtained from the soil with organic matter lowe than 1.69%