Soil productivity of peanut-cassava sequential cropping system for sustainable agricultural production in the Northeast of Thailand

Peanut-cassava sequential cropping system was studied for three successive years (1987-1990). The aims of the study were to evaluate effect of this cropping system to the change of soil fertility, to severity of root damage as well as to test for suitable chemical fertilizer application. The experiment was conducted at Muang district, Khon Kaen in two soil series, Korat (Kt; Oxic Paleustults) and Nam Phong (Ng; Ustoxic Quartzipsamments) in 1987-1990. Peanut was sown at the end of May using cv. Tainan 9 in Nam Phong soil series and cv. (MGS9xChico)-12-16-5 in Korat soil series. Peanut residue was incorporated into the soil after harvest. Cassava cv. Rayong 1 for Nam Phong soil series and Rayong 3 for Korat soil series were planted the same time as peanut in the treatments number 1 and 2 and in October, after harvesting peanut, in the treatment number 3-7. Cassava was applied with 15-15-15 of N-P2O5-K2O 50 kg/rai(F1) in the treatment number 2 and 5 and 30 kg/rai (F3) in the treatment number 6. Peanut was also applied with the same chemical fertilizer at the rate of 50 kg/rai in the treatment number 4 and 20 kg/rai(F2) in the treatment number 6. Peanut seeds were inoculated with rhizobium prior to sowing in the treatment 2-6. The potential of Korat soil on peanut and cassava production average over 3 years were higher than Nam Phong soil which obtaining yield from former soil was 132 kg/rai of peanut seed and 4,402 kg/rai of cassava root yield. The response of peanut and cassava to chemical fertilizer was markedly higher in Korat soil than in Nam Phong soil especially in early rainy season (treatment 2) was higher than in dry season (treatment 5). In Korat soil, satisfactory yield was increased with 20-50 kg/rai of 15-15-15 application whereas in Nam Phong soil must be applied with 50 kg/rai of 15-15-15 to obtain similar yield. The incidence of root rot was decreased 20 percent in peanut-cassava sequential cropping system in both soil series than cassava sole cropping. However in Nam Phong soil the incidence of root rot was higher than in Korat soil. This always occurred in the year that well precipitation and distribution of rainfall. In addition this cropping system was able to maintain soil fertility better than cassava sole cropping particularly for organic matter and potassium contents in these two soil series.