Browsing by Author "Usha, P B"

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Carbon - nitrogen relationship in laterite soils of Kerala
(Kerala Agricultural University, 1983) Usha, P B; Jose, A I
Surface soil samples from 490 sites representing upland laterite areas of the different districts of Kerala were analysed in order to establish precise relationships between organic carbon and total as well as available nitrogen in these soils. As the acidity increased, the content of organic carbon, total nitrogen and available nitrogen (aN) in soils also increased. The content of organic carbon in soil was found to be significantly and positively correlated with the clay content (r=0.i282*). Organic carbon content had positive and significant correlation with total nitrogen (r=0.4008*) of soil. The C N ratio for low, medium and high organic carbon soils were 8.1 9. 9.63 and 1 1 .26 respectively. Simple linear equation for calculating total nitrogen based on organic carbon content of soil was worked out as N %=0.0803 C% + 0.03 8- C/aN ratio had positive and significant correlation with organic carbon (r —0,6128**) and total nitrogen (r=0.32Q9**). On an average, 10.82 percent ^ftotal nitrogen in soil was retained in available form. The N/aN ratio increased with increase in organic carbon, but not in linear proportion.
Characterisation of soil organic matter in different soil types of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1982) Usha, P B; Jose, A I
Large number of surface soils representing the different districts of the state were analysed in order to work out precise relationships between organic carbon, total nitrogen and available nitrogen in these soils. The soils were categorized into different groups based on soil texture and content of organic matter. Relationships between different soil properties applicable to the different categories of soil were then examined. Fractionation of soil organic matter was carried out in a limited number of soils. Also the distribution of elemental components of soil organic matter was studied in soils selected for the fractionation of organic matter. Observations on the general characteristics of soil revealed that the content of organic carbon, total nitrogen and available nitrogen showed an increasing trend with increase in acidity of soil. In general more organic carbon was seen in fine textured soils. The total and available nitrogen content of soil increased with increase in content of organic matter. The content of available nitrogen showed significant and positive correlation with total nitrogen. Since the C/N ratio increased with increase in content of organic carbon it was necessary to predict the total and available nitrogen content of soil based on precise regression equations rather than depending on a conversion factor. On an average 10.82 per cent of the nitrogen in soil was extracted as available nitrogen. The C/aN ratio was positively and significantly correlated with organic carbon and total nitrogen while it was negatively correlated with available nitrogen. On an average the percentage of humic acid, fulvic acid and humin in soil organic matter were 28.28, 36.51 and 35.21 respectively. Of the 28.28 per cent humic acid, 9.60 per cent (of organic matter) was represented by hymatomelanic acid and the remaining 18.68 per cent by the insoluble fraction of humic acid. Humic acid was found to be significantly and positively correlated with total organic carbon, total nitrogen, clay and fulvic acid. Of the total fulvic acid 12.35 per cent (of organic matter) was represented by beta humus and the remaining by the soluble fraction of fulvic acid. Fulvic acid was positively and significantly correlated with organic carbon, total nitrogen, humic acid and clay. Humic acid and fulvic acid maintained a constant proportion irrespective of the variation in content of total organic matter. Humin was also positively and significantly correlated with organic carbon and total nitrogen. The mean phosphorus, sulphur and potassium content of organic matter were 0.051, 6.96 and 0.32 per cent respectively. The C/org.P, C/org.K, C/org.S, N/org.P, N/org.K, N/org.S, Org.P/org.K, Org.P/org.S and Org.K/org.S ratios were 1672.8, 94.1, 19.23, 205.81, 9.77, 2.91, 0.07, 0.008 and 0.0073 respectively.
Effect of sulphur on yield, quality and uptake of nutrients by cowpea (Vigna unguiculata L. Walp) in a rhodig haplustox
(Department Of Soil Science And Agricultural Chemistry,College Of Agriculture, Vellayani, 2000) Beena, V I; Usha, P B
Evaluation of acidity parameters in wetland soils of Kerala in relation to nutrient availability
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1995) Usha, P B; Thomas Varghese
Fractionation of soil organic matter in laterite soils of Kerala
(Kerala Agricultural University, 1984) Usha, P B; Jose, A I
Soil samples collected from faten'te zones of Kerala were examined for fractions and elemental components of organic matter. The humic acid accounted for 28.28 percent of organic matter. Humic acid was found to be significantly and positively correlated with organic C (r=0.8520**), total nitrogen (r = 0.7397**), clay (r= 0.7799**) and fulvic acid (r = 0-90S2**). Humic acid and fuivic acid maintained a constant proportion irrespective of the variation in content of organic matter. Fulvic acid accounted for 36.51 per cent of total organic matter. Significant and positive correlations were observed for fulvic acid with organic carbon (r=0.9618**), total N ;r = 0.891 3**) and humic acid (r= 0.8552**), The HA/FA ratio of soil organic matter ranged from 0.23 to 1.06 with a mean value of 0.78. Humin fraction accounted for 35.21 per cent of soil organic matter. Hunnin content was found to be positively and significantly correlated with total nitrogen (r —0.7374**) and organic carbon (r —0.6455**}. The mean contents of nitrogen, phosphorus, sulphur and potassium in soil organic matter were 7.34, 0.051, 6.96 and 0.32 per cent respectively.
Impact of organic farming practices on soil health,yield and quality of cowpea (Vigna unguiculata subsp. sesquipedalis (L.) Verdcort)
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2005) Devi Krishna; Usha, P B
Inter-relationship between organic carbon, nitrogen, organic phosphorus and organic sulphur in two red loam soil series of South Kerala
(Kerala Agricultural University, 1991) Korah, P A; Usha, P B; Sudharmai Devi, C R
Investigations on the efficacy of biochar from tender coconut husk for enhanced crop production
(Department of soil science and agricultural chemistry, College of agriculture, Vellayani, 2015) Mariya Dainy, M S; KAU; Usha, P B
An investigation was carried out at College of Agriculture, Vellayani to characterize biochar from tender coconut husk and to assess its effects on soil properties, growth and yield of yard long bean (Vigna unguiculata subsp. sesquipedalis). The experiment consisted of production and characterization of biochar, laboratory experiments on nutrient sorption- desorption studies, carbon dioxide emission studies and a field experiment. Biochar was produced from tender coconut husk by the process of pyrolysis and it was crushed, sieved and the 2 mm sieved samples were used for further studies. The produced biochar had an alkaline pH (9.13), high CEC (15.26 cmol kg-1) and C: N ratio (68.86). Electrical Conductivity, total C, N, P, K, Ca, Mg and S contents in the prepared biochar were 1.73 dS m-1, 72.3 per cent, 1.05 per cent, 0.38 per cent, 2.27 per cent, 0.40 per cent, 0.20 per cent and 0.27 per cent respectively. The produced biochar recorded very high water holding capacity (226 per cent), low bulk density (0.14 Mg m-3) and high Brunauer Emmett Teller surface area (157.93 m² g-1) A laboratory experiment was conducted to study the desorption and sorption of nutrients like N, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu using biochar. 32.35 per cent NH4+, 75.65 per cent PO42-, 45.14 per cent K+, 46.00 per cent Ca2+, 23.45 per cent Mg2+, 74.38 per cent SO42-, 36.80 per cent Fe2+, 30.20 per cent Mn2+, 26.75 per cent Zn2+ and 26.72 per cent Cu2+ were found to be desorbed from biochar after 7 rinses using de-ionized water in 1:100 ratio. The highest per cent of nutrient desorbed was P (75.65 per cent), followed by S (74.38 per cent) and the lowest per cent of nutrients desorbed were Zn (26.75 per cent) and Cu (26.72 per cent) within 72 hours. Sorption experiments were performed using rinsed biochar at different concentrations of nutrients and at different time intervals in 1:100 ratio. The results of the study indicated that biochar could sorb 100 per cent NH4+, 90.70 per cent PO42-, 92.00 per cent K+, 87.00 per cent Ca2+, 86.15 per cent Mg2+ and 91.82 per cent SO42- when it was equilibrated with 100ppm solutions within 24hours. For micronutrients, when 50 mg l-1 Fe2+, Mn2+, Zn2+ and Cu2+ solutions were given, biochar could sorb 99.67 per cent, 100 per cent, 99.12 per cent and 99.12 per cent respectively. Biochar from tender coconut husk is a good sorber and slow releaser of nutrients. An incubation study was carried out to estimate and study the pattern of carbon dioxide emission by the application of biochar into soil and it was compared with that of common organic amendments viz. FYM and vermicompost. The experiment consisted of 7 treatments with 3 replications and the study revealed that the cumulative amount of carbon dioxide emitted was highest for FYM @ 2 per cent (1014.05 mg CO2 100 g-1) and biochar @ 2 per cent registered an emission of 87.17 mg CO2 100 g-1 after 6months of incubation. There observed 91.40 per cent reduction in CO2 emission when soil was incubated with biochar @ 2 per cent compared to 2 per cent FYM. A field experiment was carried out with biochar and other commonly used organic manures at different doses using yard long bean variety Vellayani Jyothika as the test crop during January 2013 to April 2013, at the Instructional farm, College of Agriculture, Vellayani. Yield (1358 g plant-1) and yield attributes like pod length (54.50 cm), pod girth (3.90 cm), number of pods per plant (51), nutrient uptake and B: C ratio were significantly superior for the treatment T8 which received biochar @ 20 t ha-1 with 2 per cent PGPR and NPK as per POP. Physical properties chemical properties of the soil were significantly improved by the application of biochar @ 30 t ha-1. Biochar application reduced the bulk density, increased water holding capacity, water stable aggregates, pH, Cation Exchange Capacity, organic carbon status and nutrient availability. From the investigations, it can be concluded that application of biochar @ 20 t ha-1 along with 2 per cent PGPR and NPK as per POP which resulted in the yield of 1358 g plant-1 (20.12 t ha-1) can be considered as the economically viable and the best treatment. Biochar from tender coconut husk can be used as a good soil amendment which can improve soil health and enhance crop production.
Nitrogen and sulphur interaction on their release pattern and use efficiency in ferralitic soils.
(Department of Soil Science and Agricultural Chemistry,College of Agriculture, Vellayani, 2011) Mariya Dainy, M S; Usha, P B
Technology refinement for biochar production and evaluation of its effect on soil health and crop productivity
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2017) Sainath Nagula; Usha, P B