Browsing by Author "Rajalekshmi, K"

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Assessment of soil quality in the post flood scenario of AEU 6 in Thrissur and Malappuram districts of Kerala and mapping using GIS techniques
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2020) Safnathmol, P; Rajalekshmi, K
Kerala State experienced a devastating flood in 2018, causing significant damage to agricultural sector and human life. Major crop systems in the State have been negatively impacted, with more than 80 per cent of paddy fields including in kole lands. Kole land (AEU 6) is a low lying area situated 0.5m to 1m below mean sea level, which spread over an area of 13,632 ha in coastal parts of Thrissur and Malappuram districts of Kerala. Considering the damage caused by the flooding to the kole lands, the present study was carried out in the flood affected areas of kole lands in order to put forward post flood management strategies. A survey was carried out to identify the flood affected locations in kole lands. Hundred georeferenced composite soil samples were collected from seven block panchayats viz., Mullassery, Anthikkad, Cherpu, Irinjalakkuda, Puzhakkal, Perumpadappu and Ponnani of Thrissur and Malappuram districts and analysed for different physical, chemical and biological soil quality indicators. The results showed that the soils of kole lands were low in bulk density and high in porosity while particle density varied from 2.05 to 2.67 Mg m-3. Maximum water holding capacity and soil moisture content of the soil samples ranged from 18.11 to 73.49 per cent and from 12.00 to 41.60 per cent respectively. High mean weight diameter of soil was also noticed in the study. The soils were acidic in reaction and the exchangeable acidity varied from 0.05 to 2.2 cmol (+) kg-1. Electrical conductivity was below toxic level. The organic carbon was shifted towards medium to high level from low to medium after the flood. Available nitrogen content was high with a mean of 704.59 kg ha-1. Availability of phosphorus and potassium were in the medium status within 55 and 44 per cent of samples respectively. Among the secondary nutrients, available calcium was sufficient in 64 per cent of soil sample while available magnesium was deficient in 72 per cent of soil samples and available sulphur was sufficient in 89 per cent of soil samples. The micro nutrients like available Fe, Mn and Zn were high in AEU 6. Available copper was sufficient in 83 per cent of soil samples, whereas available boron was deficient in all the soil samples. Effective cation exchange capacity of soil in AEU 6 varied from 0.62 to 9.00 cmol (+) kg-1. Among the biological attributes, kole lands showed high dehydrogenase activity while microbial biomass carbon was found medium in 58 per cent of soil samples. Available Ca, S, N, porosity, exchangeable acidity, available Fe, Zn, particle density and available B formed the minimum data set for soil quality index. The highest mean soil quality index was recorded in Mullassery block panchayat and the lowest mean was in Cherpu block panchayat. Relative soil quality index varied from 25.93 to 72.22 per cent with 63 per cent of soils showing poor soil quality and 3 per cent showing high soil quality. Nutrient index was high for nitrogen and medium for phosphorus, potassium and organic carbon in kole lands. Significant positive correlations were observed between organic carbon and available nitrogen, organic carbon and soil moisture content. Negative correlation existed between bulk density and porosity, organic carbon and bulk density. The post flood study in kole lands revealed that drastic changes in soil environment had occurred with more than 50 per cent of soil samples falling in low soil quality range. Hence, proper adoptions of site specific soil management practices are essential to improve the soil fertility in kole lands.
Bioplastics-an alternative with a future
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2020) Safnathmol, P; Rajalekshmi, K
Carbon sequestration and soil health under different organic sources in wetland rice
(Department of Soil Science and Agricultural Chemistry, Vellanikkara, 2018) Rajalekshmi, K; Betty Bastin
Soil test crop response studies in cluster bean (Cyamopsis tetragonoloba L.) in lateritic soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellanikkara, 2021) Ayisha, V V; Rajalekshmi, K
Cluster bean, commonly known as guar, is a legume crop cultivated as a vegetable, green manure and forage crop. India is the leading producer of cluster bean in the world and accounts for around 80 per cent of global production. The generalised application of fertilizers by farmers result in under or over fertilization, lowering production and profitability while also polluting the environment. So the emphasis on soil test based balanced fertilizer recommendation has become more pertinent in the current scenario of high fertilizer costs and yield maximisation programmes. Hence, the investigation entitled “Soil test crop response studies in cluster bean (Cyamopsis tetragonoloba L.) in lateritic soils of Kerala” was undertaken. The study was conducted at College of Agriculture, Vellanikkara in lateritic soils (Ultisol) in the STCR field during 2020-2021 with the objective of developing soil test based fertilizer prescription equation for cluster bean using inorganic fertilizers alone and with the combined use of organic manures. A fertility gradient experiment was conducted to create soil fertility gradient in the field by applying graded doses of N, P and K fertilizers and raising fodder maize var. CO1. After the development of fertility gradient, the main STCR experiment was conducted in the same field with the test crop, cluster bean var. Pusa naubahar. The treatment structure consisted of four levels of nitrogen (0, 10, 20 and 40 kg ha-1 ), four levels of phosphorous (0, 30, 60 and 120 kg ha-1 ) and four levels of potassium (0, 40, 80 and 120 kg ha-1 ) along with three levels of FYM (0, 15 and 25 t ha-1 ). The basic parameters such as nutrient requirement (NR) and contributions of nutrients from soil (CS), fertilizer (CF) and FYM (COM) were computed from the field experimental data. The nutrient requirements (NR) for cluster bean were worked out as 0.68, 0.05 and 0.22 kg N, P2O5 and K2O to produce one quintal yield. The contributions from soil (CS) were estimated as 9.84, 2.29 and 1.99 per cent of N, P2O5 and K2O respectively. The contributions from fertilizer (CF) were calculated as 90.90, 3.29 and 10.82 per cent and that from FYM (COM) were 7.17, 1.92 and 2.96 per cent for N, P2O5 and K2O respectively. From the above basic data, fertilizer prescription equation for specific yield targets of cluster bean in the lateritic soils were derived as follows, NPK alone: FN = 0.74*T - 0.11*SN FP2O5 = 1.47*T – 1.59*SP FK2O = 2.05*T- 0.22*SK NPK + FYM (IPNS) FN = 0.74*T - 0.11*SN – 0.08*ON FP2O5 = 1.47*T – 1.59*SP – 1.34*OP FK2O = 2.05*T - 0.22*SK – 0.33*OK Where, FN, FP2O5 and FK2O = Fertilizer N, P2O5 and K2O in kg ha-1 T = Yield target in q ha-1 SN, SP and SK = STV for available N, P and K in kg ha-1 . ON, OP and OK = Amount of N, P and K supplied through FYM in kg ha-1 . The multiple regression model calibrated with yield as dependent variable and soil test results and inorganic fertilizer doses as independent variables had 62.5 per cent predictability. The yield of cluster bean increased with the application of NPK alone and IPNS viz. NPK plus FYM treatment and the magnitude of increase was higher under IPNS over NPK alone. The study is useful to adjust fertilizer doses based on yield target and available resources of organic manure with the farmers. The equations developed for cluster bean should be tested in places with similar agro climate and soil situations for validation.