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Subject: Soil Sciences × Author: Dahiya, Garima × End date: 2023 × Start date: 2023 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Nitrogen mineralization potential and soil organic carbon thresholds for sustaining wheat productivity in semi-arid soils
    (CCSHAU, Hisar, 2023-07-21) Dahiya, Garima; Dev Raj
    The present investigation entitled “Nitrogen mineralization potential and soil organic carbon thresholds for sustaining wheat productivity in semi-arid soils” was conducted in the screenhouse by collecting samples from on-going long-term fertilizer experiment initiated in the year 1967 and 1995 by adopting Complete randomized Design (CRD). It was planned with 7 different OC soils (0.36, 0.59, 0.88.00, 1.00-1.25, 1.380, 1.50-1.75 and 1.90%), 4 doses of FYM (0, 5, 10 and 15 t ha-1) along with N application 150 kg ha-1 and 3 levels of replication. Wheat was grown in the pots during 2021-22 and 2022-23. The soil samples were obtained after crop harvest in 2022-23 and were analyzed to evaluate soil chemical and biological properties. Yield, nutrient content and uptake by the crop was also worked out. Maximum ammonification, nitrification and nitrogen mineralization potential was obtained in the soils having OC 1.14% while minimum in the control with OC 0.36%. The NH4+-N significantly increased up to 42nd day of incubation period thereafter it start decreasing upto 120 day. While NO3--N continuously increased from 0 day and reached highest level at 120 day of incubation. The total N mineralized, percent N mineralization from the amount of added N as well as N mineralization rate also followed similar trend. As the incubation study proceeds, nitrifying bacteria increased at all days of incubation. Maximum threshold value for nitrifying and total bacterial population in the incubation study was soils with OC range of 1.14 and 1.38%, respectively. Soil pH decreased with the increase in OC in soil while EC, SOC, TOC and its fractions and available N, P and K in soil increased proportionally with the rise in OC content and FYM dose in soil. In 1.14% OC range, N and P content increased with increase in FYM dose to 10 t ha-1 thereafter decline in NP content was observed. Potassium content increased with increase in OC in soil as well as with the FYM doses. Grain yield increased with increase in dose of FYM upto OC level of 1%. In soils having OC 1.14%, grain yield increased with increase in FYM dose to 10 t ha-1. For 1.38% OC soil, grain yield increased with increasing dose of FYM upto 5 t ha-1 application. Increasing OC status beyond 1.5% decreased the grain yield at all doses of FYM application. Similar trend was observed in case of biological yield. It can be concluded that OC level should be maintained to the range of 1.14% for maximum nitrogen mineralization, nitrifying bacteria and grain yield. Beyond 1.25% OC, all these properties were observed to decrease. The relative yield was observed to increase upto the threshold value of 1.15% OC which was at par with the yield at 1.37% OC. This range should be maintained to obtain maximum relative yield. Beyond this range, yield was observed to decrease.