POPULATION DENSITY OF SOIL MITES AND CERTAIN SUCKING PESTS AND AVAILABILITY OF NPK IN SOYBEAN PLANT AND SOIL AS INFLUENCED BY ORGANIC MANURES AND MINERAL FERTILIZERS

Abstract

This experiment was carried out at Sakha Agricultural Research Station Farm in 2007 season to find out the effect of organic manures and mineral fertilizers on the population density of mites and some sucking insects. Also, the availability of NPK and organic matter was investigated. The spider mite, Tetranychus cucurbitacearum (Sayed) exhibited the highest population in plants treated with poultry manure > urea > sheep manure > ammonium nitrate > pigeon refuse. The whitefly populations was highest on plants treated with mineral fertilizers than on those treated with organic manures while the contrast was found in the insect predators population. Aphid population was highest in case of urea and sheep manure, but lowest in pigeon refuse. The thrips numbers were highest on plants treated with poultry manure > pigeon refuse > urea > ammonium nitrate > sheep manure. Both nitrogen and potassium were more available in soybean plants treated with organic manure than those treated with mineral fertilizers. Regarding soil mite groups, soil of poultry manure exhibited the highest population density of mites, followed by pigeon refuse and sheep manure, while the lowest mite populations were detected in plots treated with mineral fertilizers. Cryptostigmata usually exhibited the highest percentages among mite groups followed by Heterostigmata, Prostigmata, Mesostigmata and Astigmata. The highest available N and organic matter were detected in the soils treated with pigeon refuse, while the highest levels of P and K were found in soils treated with sheep manure.