Abstract
The effects of four upland crops and fallow on the performance of rice (Oryza sativa L.) the main crop during the wet season, in the Philippines were assessed. After fallow or harvest of four upland crops on Typic Haplaquoll soil during the dry season, rice was dry-seeded, fertilized with 0, 40, 80, or 120 kg ha-1 N as ammonium sulphate, and grown to maturity under rainfed conditions during the wet season. Growth and grain yields of rice were highest after fallow, intermediate after soyabeans (Glycine max (L.) Merr.), cowpea (Vigna unguiculata (L.) Walp.) and mungbean (Phaseolus aureus (L.) Roxb.) and lowest after sorghum (Sorghum bicolor (L.) Moench) at most N levels. N fertilization increased most rice growth parameters and grain yield. Upland crops appeared to affect rice by influencing the soil N status or C:N ratio, although residual toxicity might have been involved. It is concluded that upland crops might decrease rice performance, but that higher combined economic yields of the upland crops and rice favoured an upland crop-rice sequence over the usual fallow-rice system.
