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2014 - 20192
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Subject: Soil Science × Author: Harpreet Kaur × Start date: 1980 × Type: Thesis ×
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    ThesisItemOpen Access
    Contribution of different chemical pools of potassium towards wheat nutrition
    (Punjab Agricultural University, Ludhiana, 2019) Harpreet Kaur; Gill, Roopinder Singh
    The field and pot experiments were conducted to study the effect of potassium (K) application on availability of K to wheat and contribution of exchangeable and non exchangeable K towards wheat nutrition. In pot experiment, twenty bulk soil samples having a range in available K were used and K was applied @ 0, 15, 20, 25 and 30 kg K ha-1soil. Wheat (cv PBW 725) was grown as a test crop. The different potassium fractions i.e. water soluble, exchangeable, available and non exchangeable K were determined. The amount of corresponding forms ranged between 8.86 to 23.7, 66.1 to 379.8, 75.1 to 403.1 and 898.4 to 1861.3 mg kg-1 soil in these soils. The mean grain yield varied from 8.43 to 20.58 g pot-1. All the forms of K showed positive and significant correlation with grain & straw yield, K content and K uptake. The highest positive and significant correlation of wheat grain yield was found to be with water soluble K (r = 0.905*) followed by available K (r = 0.836*), exchangeable K (r = 0.831*) and non exchangeable K (0.815*). In K deficient oils, grain yield of wheat increased significantly with graded levels of applied K. However, in K sufficient soils, grain yield increased significantly up to application of 25 kg K ha-1. In both K deficient and sufficient soils, K concentration and uptake by grain and straw of wheat increased significantly with incremental levels of applied K. About 83.6 per cent variation in grain yield of wheat was due to the combined influence of water soluble and exchangeable potassium while available and non exchangeable form of potassium explained only 2.3 per cent variation in grain yield of wheat. However, in K deficient soils, contribution of non exchangeable K towards grain yield was higher as compared to K sufficient soils. The critical limit of available and non exchangeable potassium for wheat as determined by graphical method was 168 and 1338 kg K ha-1, respectively. The field experiment was conducted at two sites, at the Research Farm of Department of Soil Science, Punjab Agricultural University (PAU), Ludhiana (medium in available potassium i.e. 228.9 kg ha-1) and at Regional Research Station, Gurdaspur (low in available potassium i.e. 125.6 kg ha-1). The K was applied @ 0, 10, 15, 20, 25, 30, 35 and 40 kg K ha-1 soil and wheat (cv PBW 725) was grown as test crop. The mean grain yield in PAU, Ludhiana and RRS, Gurdaspur soil was found 47.5 and 42.5 q ha-1, respectively. In PAU, Ludhiana soil, the significant response of wheat to applied potassium was recorded up to 25 kg K ha-1 soil, however, in RRS, Gurdaspur soil response was recorded up to 40 kg K ha-1. The water soluble, exchangeable, available and non exchangeable K were found to be 13.8, 75.9, 84.5 and 1053.6 mg kg-1 soil, respectively in PAU, Ludhiana soil and 10.1, 61.1, 70.5 and 969.7 mg kg-1 soil, respectively, in RRS, Gurdaspur soil. The kinetics of non-exchangeable K release from ten bulk soil samples having a range in available K was investigated using 0.01 M oxalic acid. The cumulative amount of K released in 200 h ranged between 86 and 253 cmol kg-1 x 10-2. The highest amount of non exchangeable K release (253 cmol kg-1 x 10-2) was found in Mansa soil (sufficient in K) and lowest amount (86 cmol kg-1 x 10-2) was recorded in Gurdaspur soil (deficient in K). Kinetics of non exchangeable K release from soils were adequately described by Elovich, first order, power function and parabolic diffusion models while zero order model was not suitable to describe K release.
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    ThesisItemOpen Access
    Transformation and availability of copper to wheat (Triticum aestivum L) as influenced by phosphorus fertilization
    (Punjab Agricultural University, Ludhiana, 2014) Harpreet Kaur; Manchanda, J. S.
    A pot experiment was conducted to study the effect of P and Cu application on transformation and availability of Cu to wheat. The soils used were i) calcareous loamy sand (ls) Typic Ustipssament (pH 8.1, EC 0.375 dS m-1, OC 0.15%, available P 8.5, CaCO3 0.13%, DTPA-Cu 0.18 and DTPA-Fe 3.20 mg kg-1 soil) and ii) non calcareous sandy loam (sl) Typic Haplustept (pH 6.5, EC 0.295 dS m-1, OC 0.38%, available P 12.65, DTPA-Cu 1.05 and DTPA-Fe 51.6 mg kg-1 soil). Six levels of P (0, 25, 50, 100, 200 and 400 mg P kg-1 soil) as monocalcium phosphate monohydrate and four levels of Cu (0, 5, 10 and 20 mg Cu kg-1 soil) as Cu-EDTA were applied in all possible combinations to eight kg of each soil per pot with three replications. Wheat (cv HD 2967) was grown and soil, root, grain and straw samples were collected at maturity. Soil (pH, available P, DTPA-Cu, DTPA-Fe and chemical pools of Cu) and plant samples (Total P, Cu and Fe) were processed and analysed. Soil pH decreased with Cu application while EC and Olsen P increased with P application in both soils. DTPA-Cu and Fe decreased up to a level of about 75 mg P kg-1 soil and thereafter followed an upward trend. In ls soil P application decreased exchangeable and specifically adsorbed Cu but increased carbonate bound-Cu. However in sl soil, applied P decreased the content of Cu in exchangeable, amorphous and crystalline oxides but increased in organically bound Cu. Growth and yield of wheat improved significantly with graded levels of applied P. However, when any level of P was combined with 20 mg Cu kg-1 soil, severe Fe chlorosis of leaves, a drastic reduction in growth, chlorophyll content and increase in activity of super oxide dismutase was observed in calcareous ls only. The results indicated that it was Cu and not P that induced Fe deficiency in wheat grown in alkaline calcareous soil and the Cu requirement of the crop seemed to be much lower in the light textured soils. Root dry matter, grain and straw yield decreased with increasing levels of applied Cu in ls but in sl a maximum increase of 62.5, 74.3 and 63.7 per cent in root, grain and straw yield was observed with a combination of P400Cu5 over P0Cu0. Path coefficient analysis revealed the importance of DTPA-Cu, exchangeable, specifically adsorbed and amorphous oxides bound Cu in effecting the grain yield of wheat in ls soil and that of oxides and organically bound Cu in sl. Phosphorus uptake by each plant part decreased with increase in DTPA-Cu while Fe uptake increased with increase in Olsen P but decreased with increase in DTPA-Cu. Accumulation of Cu in root decreased the Fe absorption by roots. The root Cu: Fe concentration ratio at which severe Fe chlorosis of leaves was observed varied between 0.304 to 0.429. About 6.56, 5.39 and 5.37 mg DTPA-Cu kg-1 in soil and 436, 11.04 and 19.33µg Cu g-1 in root, grain and straw produced 50 per cent reduction from the maximum yield of root, grain and straw, respectively which may be considered as the upper critical values for wheat.