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Long-term effects of intensive cultivation and imbalanced fertilization were studied on nutrient concentration of soil and in wheat grown on loamy sand alluvial soils belonging to Lukhi soil series located in semiarid-subtropical region of North-Western India. The same 86 farmers' fields were sampled during 2009 and 2010 which had earlier been studied during 1983 and 1984. Electrical conductivity of soil decreased, pH did not change, and organic carbon improved. In soil, K extractable in 1N NH4OAc and boiling 1N HNO3 depleted to a deficient levels in 2009 from medium levels of 1983. Similarly, DTPA extractable Cu depleted to deficient level from earlier sufficient level in 2009 from medium K and sufficient Cu levels in 1983. Consequently, K and Cu in the top two leaves of wheat decreased to a deficient level in 2010 from a sufficient level in 1984. Sulfur in soils and leaves decreased significantly. Olsen P and DTPA-extractable Zn increased, increasing their contents in leaves. DTPA-extractable manganese (Mn) and iron (Fe) improved. [ABSTRACT FROM AUTHOR]

Different forms of manganese (Mn) were investigated, including total, diethylenetriamine penta-acetic acid (DTPA) extractable, soil solution plus exchangeable (Mn), Mn adsorbed onto inorganic sites, Mn bound by organic sites, and Mn adsorbed onto oxide surfaces, from four soil taxonomic orders in northwestern India. The total Mn content was 200–950 mg kg−1, DTPA-extractable Mn content was 0.60–5.80 mg kg−1, soil solution plus exchangeable Mn content was 0.02–0.80 mg kg−1, Mn adsorbed onto inorganic sites was 2.46–90 mg kg−1, and Mc adsorbed onto oxide surfaces was 6.0–225.0 mg kg−1. Irrespective of the different fractions of Mn their content was generally greater in the fine-textured Alfisols and Inceptisols than in coarse-textured Entisols and Aridisols. The proportion of the Mn fractions extracted from the soil was in the order as follows: Adsorbed onto oxide surfaces > adsorbed onto inorganic site > organically bound > DTPA > soil solution + exchangeable. Based on coefficient of correlation, the soil solution plus exchangeable Mn, held onto organic site and oxide surface (amorphous) and DTPA-extractable Mn, increased with increase in organic carbon of the soil. The two forms, adsorbed onto inorganic site (crystalline) and DTPA extractable, along with organic carbon, increased with increase in clay content of the soil. DTPA-Mn and Mn adsorbed onto oxide surfaces and held on organic site decreased with increased with an increase in calcium carbonate and pH. Total Mn was strongly correlated with organic carbon and clay content of soil. Among the forms, Mn held on the organic site, water soluble + exchangeable and adsorbed onto oxide surface were positively correlated with DTPA-extractable Mn. DTPA-extractable Mn seems to be a good index of Mn availability in soils and this form is helpful for correction of Mn deficiency in the soils of the region. The uptake of Mn was greater in fine-textured Inceptisols and Alfisols than in coarse-textured Entisols and Aridisols. Among the different forms only DTPA-extractable Mn was positively correlated with total uptake of Mn. Among soil properties Mn uptake was only significantly affected by pH of the soil. [ABSTRACT FROM AUTHOR]