FAUNAL ACTIVITY IN A CONTINUOUSLY MANURED RICE SOIL IN RELATION TO CHANGES IN SOIL PROPERTIES
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Date
2018
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Orissa University of Agriculture and Technology, Bhubaneswar
Abstract
Rice-rice is an important production system for eastern India. Over years of continuous cropping the system has lost its potential to sustain the productivity. For restoration of the degraded soil there is an urgent need to understand the changes occurring in soil. Soil organisms play important role in the functioning of rice field ecosystem. Fertilizers and manures which significantly contribute to rice production also directly or indirectly influence soil biota and their functioning. In the past many works have been done on effect of nutrient management practices on soil flora. But work on soil fauna is very limited. Faunal community is equally important in rice field ecology. The present investigation aimed at studying the long term effect of manurial practices on soil earthworm and nematode population and their diversity using an 11 year old Long Term Fertilizer Experiment conducted on an acidic sandy loam soil of Bhubaneswar with 12 numbers of manurial treatments. Nematode and earthworm population and diversity studies were made on soils of pre planting, tillering and flowering stages of both kharif and rabi seasons. After transplanting of rice in both kharif and rabi season, the earthworm population showed an increase at tillering and flowering stages. Among the treatments the FYM amended treatments had significantly higher population (24 -38 /m2) than rest of the treatments (1.83- 18.98 /m2) because supply of additional food source for them. Lime application significantly increased the earthworm population in both the seasons because of improvement of pH of the acid soil. Under nutritionally imbalanced situations the population was very low (4 – 14.65 /m2). The population at pre planting, tillering and flowering stage positively and strongly correlated with available P (r = 0.885** to 0.952** and DTPA extractable Fe (r = 0.659* to 0.818**), positively correlated with SOC (r = 0.574 to 0.835**) and negatively correlated with DTPA extractable Zn (r = -0.362 to 0.078). Between two classes of nematodes studied, the plant parasitic nematode population varied from 64 to 324 /200g soil. FYM 5t /ha per season significantly reduced the parasitic nematode population at pre planting and flowering stage. Lime 1 t /ha also caused 7.19% - 20.0% fall in parasitic nematode population. They were negatively and strongly correlated with P (r= -0.754**) at flowering stage in both the seasons which implies that P is antagonistic to plant parasitic nematode. In contrast, free living nematode population increased with application of organic manure and Lime. FYM caused an increase of 4.62 to 42.05 % and Lime 25.5 to 65.3% in kharif and rabi respectively. The relationship was strong mostly with P, K and Fe, particularly at pre planting stage of rabi season (r= 0.625* to 0.812**). Based on the morphological characteristics most of the earthworms found in 0-15 cm soil belonged to 2 families, Monligastridae and Megascolecidae. Drawida willsi and Lampito mauritii were the two dominant species observed to be present throught out the year. Similarly three parasitic nematode species, Hirschmanniella oryzae, Helicotylenchus abunaamai, Tylenchorhynchus mashhoodi, and one saprophytic, Dorylaimidae were identified to be present in the rice field irrespective of seasons. Some unidentified saprophyties were also dominant in rice field irrespective of stages and seasons.
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