Effect of cropping systems on soil fertility and enzymatic activities in Calcareous soils of Bihar
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Date
2019
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Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur
Abstract
The present investigation was undertaken to study the “EFFECT OF CROPPING SYSTEMS ON SOIL FERTILITY AND ENZYMATIC ACTIVITIES IN CALCAREOUS SOILS OF BIHAR” during 2017-18 at the research farm of Tirhut College of Agriculture, Dholi, Muzaffarpur, a campus of Dr. Rajendra Prasad Central Agricultural University, Pusa, Bihar. In the farm, the different kinds of cropping patterns have been practiced at the same piece of land for the last five years or more. Each crop was grown with normal irrigation practice and recommended doses of fertilizer application, i.e, without any stress condition. A number of soil quality parameters were measured during the course of investigation to evaluate the effect of nine cropping systems on soil quality under similar, calcareous nature of the soil. Soil samples from surface (0-15cm) and sub-surface (15-30cm) were collected from each treatment (cropping systems) at the end of Rabi season (Mid April to Mid-May, 2018), i.e. completion of one cropping cycle. Each cropping system was represented by three plots with an area of 5 m x 5 m and a total of 27 (9 cropping systems x 3 plots) samples were collected for laboratory analysis.
The soil pH variability at surface layer of the soil recorded from 7.79 to 8.79, whereas in lower soil depth (15-30cm) recorded from 7.85 to 8.81. The lowest soil pH exhibited in rice-wheat cropping system followed by pigeon pea cropping system might be attributed to submergence of soil during rice cultivation and greater amount of leaf litters fall throughout the field during crop life of the later cycle. The variability in electrical conductivity was found from 2.54 to1.16 dSm-1. The low salt concentration noticed in pigeon pea cropping system at both the soil depths exhibiting more variability with respect to rice-potato cropping system at surface soil. The highest organic carbon content (0.63%) was associated with pigeon pea cropping system followed by that with mustard-moongbean (0.62%), pigeon pea (0.61%) and rice-wheat (0.55%), respectively at surface soil layer.
The lowest organic carbon (0.33%) was observed in fallow land. The variation in organic carbon under different cropping systems, particularly legume-based, contributed more organic matter thus scoring good quality of soil. The carbon was found to be higher in the surface and sub-surface soil layers in pigeon pea cropping system followed by that in maize-maize. The quantity of organic matter was directly related to the degree of organic carbon present in soil. Cation exchange capacity ranged from 16.66 to 28.62 (cmol (P+) kg-1) among the cropping systems which might be attributed to organic carbon content. The difference in CEC was statistically significant under different cropping systems. The lower bulk density (1.21Mgm-3) and (1.24 Mg m-3) was recorded under mustard-moongbean and pigeon pea cropping systems followed by tuber-moongbean (1.31 Mgm-3), rice-potato and maize-maize cropping systems over non-cultivated land. The bulk density in sub-surface soil depth increased under all cropping systems. Maximum water holding capacity (WHC) was recorded under pigeon pea cropping system in the surface layer (42.20%) and 40.36% in sub-surface layer.
The minimum WHC (36.46%) and (35.61%) was noticed in fallow land at both the soil depths. Mean weight diameter in different treatments varied from 2.51mm to 4.49mm. The highest MWD was recorded under pigeon pea cropping system, whereas the lowest was under fallow lands. The MWD generally promotes the soil aggregation and its stability. The marked variations in soil available nitrogen was observed in this study under different cropping systems due to the factors viz. addition of organic carbon and the application of different doses of inorganic
fertilizers. Available nitrogen varied from 120.13 to 300.11kg ha-1. The highest amount of available nitrogen (300.11 kg ha-1) recorded under pigeon pea cropping system might be due to deposition of plant biomass and biological nitrogen fixation.
The maximum soil available potassium (272.83 kg ha-1) was also reported in pigeon pea cropping system, whereas minimum in rice-wheat cropping (95.82 kg ha-1) and maize-maize cropping systems at the surface soil layer. Variations in Olsen‟s available phosphorus status in soil ranged from 12.59 to 18.77 kg ha-1 and it followed the order:pigeon pea> rice-wheat> onion-garlic> mustard–moongbean> maize-maize> turmeric-moongbean> rice-potato> tuber-moongbean> fallow land. Available sulphur ranged from 10.36 and 8.49 ppm and was recorded highest in both the soil depth under pigeon pea cropping system. However, minimum content of available sulphur (3.90 and 3.22 ppm) was recorded with fallow land in both surface and sub-surface layers.
The values of boron under cropping systems ranged from 0.07 to 0.17ppm. Rice-wheat cropping system contained maximum iron concentration (7.91ppm) followed by mustard-moongbean (7.65 ppm), maize-maize (7.48ppm) and pigeon pea (6.13ppm) cropping system respectively. Mn concentration was minimum in fallow lands than in other systems where cultivation was not performed. The available Cu concentration varied from 0.71 to 2.28ppm and 0.60 to 1.97ppm under different cropping systems in both soil depths. Wide variability in zinc concentration under surface soil (0-15cm) was recorded under different cropping systems. The build-up of DTPA-extractable zinc was recorded to be the highest in turmeric-moongbean followed by onion-garlic systems. Other cropping systems contained below 1ppm. Dehydrogenase and alkaline phosphatase enzymes showed variation from 6.87 to 19.91 (μg TPF g-124 h-1) and 6.77 to 33.55 (μg PNP g-1 soil h- 1) at the upper surface layer. Among the cropping systems, pigeon pea maintained higher amount of dehydrogenase and alkaline phosphatase enzymes in the soils than the other systems and fallow land showed the lowest value.