The draft animal is commonly used in this system in Asia. Partial or high mechanization is more common in upland rice in Latin America, especially in Brazil. In addition to the biological and physical constraints, the socioeconomic situation contributes to low yields. Most farmers have low income and poor access to credit, inputs, and modern technologies. Production constraints Biological and physical constraints that limit upland rice yield are numerous.
Weeds are the number one biological constraint, followed by blast disease and brown spot.
Weeds reduce upland rice grain yield and quality. Small farmers cannot afford weed control. In shifting cultivation they abandon their fields after 2-3 yr of cropping. Stem borers and rice bugs are the predominant insect pests. Rodents are reported in many countries as a major problem and birds are sometimes serious pests.