Effect of phosphorus on corn grown on skeleti - hyperiystry-rhodic acrisols in Hoa Binh Province, Vietnam

摘要

Corn is an important food crop in North Vietnam. In 2000, it was sown on an area of 730.2 thousand ha in the whole country and 21.6 thousand ha in Hoa Binh Province, northern Vietnam. In that year, corn grain yield was 2005.9 thousand tons in the whole country and 48.8 thousand tons in Hoa Binh province. Com is grown on upland soils where there are many constraints for corn cultivation. The field trial was carried out from 1998-2000 to determine the effect of different P sources and rates of P on corn growth. The growth and yields of com showed positive responses to rate of P application. Continuous application of 0-72.8 kg P/ha in 5 crops as single superphosphate (SSP) increased grain and stover yields. The highest relative grain yield was obtained at the rate of 43.6 kg P/ha while the highest stover yield was obtained at the higher rate of 57.6 kg P/ha. Application of inorganic phosphorus sources increased grain yield by 108%-117%. Application of farmyard manure increased grain yields by 83%. A combination of 43.6 kg P/ha as SSF with FYM could increase grain yield by 141.3%-144.7%. There were significant differences in corn yields between rainy and dry seasons. Application of different P sources always resulted in higher grain yields in the rainy season than in the dry season, except for the application of FYM. The P application to corn had high P use efficiencies of 33-111 kg grain kg~(-1) P. The most economic returns were given at the rates of 28.8-43.6 kg P ha~(-1). Application of FYM or in combination with inorganic fertilizer resulted in higher profits. A rate of 43.6 kg P ha~(-1) as FYM was recommended to farmers at the study site.