CARBON SEQUESTRATION AND SOIL HEALTH UNDER LONG TERM SOIL FERTILITY MANAGEMENT IN RICE- RICE CROPPING SYSTEM
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Date
2018
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Acharya N.G. Ranga Agricultural University
Abstract
A field experiment entitled “Carbon sequestration and soil health under long term soil fertility management in rice-rice cropping system" was carried out under field conditions during kharif and rabi seasons of 2016-2017 and 2017- 2018 at Andhra Pradesh Rice Research Institute and Regional Agricultural Research Station, Maruteru, West Godavari district in the ongoing All India Coordinated Research Project on Long Term Fertilizer Experiment Project. The results of the initial (1989) soil analysis indicated that the experimental soil is clay loam in texture, neutral in reaction, medium in organic carbon and medium in available nitrogen, low in available phosphorus and high in potassium, while micro-nutrients were all above critical levels. This experiment is a part of the ongoing experiments of All India Coordinated Research Project on Long Term Fertilizer Experiment initiated at APRRI and RARS, Maruteru during kharif 1989. The treatments consisted of control (T1), 100 per cent recommended dose of fertilizers (T2), 100 per cent recommended dose of NK (T3), 100 per cent recommended dose of PK (T4), 100 per cent recommended dose of NP (T5), 100 per cent recommended dose of fertilizer+ZnSO4 @ 40 kg ha-1 (T6), 100 per cent recommended dose of fertilizer+ZnSO4 @ 40 kg ha-1 + FYM @ 5 t ha-1(T7), 50 per cent recommended dose of NPK (T8), 50 % NPK + 50 % N through green manures (T9), 50 % NPK + 50 % N through FYM (T10), 50 % NPK + 25 % N through green manures + 25 % N through FYM (T11) and FYM only @ 10 t/ha (T12). All together there were twelve treatments laid out in randomized block design (RBD) with three replications for kharif and rabi seasons in two years of study. Popular cultivars of rice (kharif and rabi), MTU-1061and MTU-1010, respectively, were used for the study.
The carbon pools were estimated at initial and harvest stage of crop during both the years of study and total carbon stock, carbon buildup/depletion and carbon sequestration rate were calculated after 29 years (1989-2018) of rice cultivation at the end of rabi season, 2018. The influence of long term use of fertilizers, manure application and their combination was evaluated for soil biological health by assaying soil urease, dehydrogenase activities at different growth stages. The soil quality parameters were assessed by analyzing the soil for physico-chemical, chemical and biological properties with special reference to the changes in soil enzyme activity. Plant samples at different growth stages were analysed for their nutrient concentration with respect to N, P and K and micronutrients and nutrient uptake was computed.
Highest active pools (MBC, MBN, MBP, WSC, KMnO4-C and K2Cr2O7-C) and slow pools (POC) were observed with the application of 100% RDF in combination with ZnSO4 and FYM @5t ha-1. However, it was on par with that of application of 50 % NPK + 50 % N through FYM except for MBC. The higher MBC was observed with the application of 100% RDF in combination with ZnSO4 and FYM @ 5t ha-1 and however it was on par with the only organic treated plot i.e. FYM @ 10 t ha-1 and with that application of 50 % NPK + 50 % N through FYM. The higher passive pools (HAC and FAC) were observed in only organic plot i.e. application of FYM @ 10 t ha-1 and it was significantly superior over other treatments. Application of 100 % RDF along with ZnSO4 @ 40 kg ha-1 and application of 100 % RDF were not significant. Among different fertilized plots, SOC stocks and carbon sequestration rate in the 15 cm plough layer were significantly higher under 100% RDF + FYM + ZnSO4 (T7) followed by 50 % NPK + 50% N through FYM (T10). At the starting of the experiment in kharif, 1989, the soil organic carbon stock was 11.14 Mg ha-1 and after 29 years of continuous application of organic and inorganic fertilizers, SOC stocks ranged from 11.06 to 24.39 Mg ha-1 at harvest of rabi rice in 2018.
In all the treatments, the urease and dehydrogenase enzyme activities showed an increasing trend with the age of the crop and exhibited highest activities at panicle initiation stage and thereafter the activity decreased towards harvest. The highest enzyme activity was observed with application of 100 % RDF + ZnSO4 +FYM @ 5t ha-1 (T7) (kharif and rabi) during both the years of study and it was significantly superior over other treatments. However it was on par with treatment T10. The application of zinc did not show any significant effect on enzyme activities. No significant difference was observed for enzyme activity between treatments 100% NPK (T2), 100% NK (T3), 100% NP (T5) and 100 % RDF+ ZnSO4 (T6). However the treatment T6 was significantly superior over T4 (100% PK) and T8 (50% NPK).
Long-term application of inorganic fertilizers, organic manures and their combination didn’t show marked difference on physico-chemical properties of soil (pH and EC) except at panicle initiation and harvest stage. At initial, tillering, panicle initiation and at harvesting stage, the highest available nitrogen, phosphorus, potassium and micronutrients in soil was recorded with application of 100 % RDF + ZnSO4 + FYM @ 5t ha-1 (T7). The treatments T9 (50 % NPK + 50 % N through green manures), T10 (50 % NPK + 50 % N through FYM) and T11 (50 % NPK + 25 % N through FYM + 25 % N through green manures) were on par with each other in all four seasons of study.
The highest dry matter production was observed with the application of 100% RDF in combination with ZnSO4 and FYM @ 5 t ha-1. However, it was on par with that of application of 100% RDF along with ZnSO4 @ 40 kg ha-1 during both the years of the study in kharif and rabi. The significantly highest grain and straw yield was observed with the application of 100% RDF in combination with ZnSO4 and FYM @ 5t ha-1 and it was significantly superior over other treatments.
The data regarding influence of long-term use of inorganics, organics and their combination on nutrient content and uptake at different growth stages in kharif and rabi during both the years of the study indicated that there was significantly increase with application of 100% RDF in combination with ZnSO4 and FYM @ 5t ha-1. However, it was on par with that of application of 100 % RDF along with ZnSO4 @ 40 kg ha-1 and significantly superior over other treatments. The application of 50 % NPK + 50 % N through FYM was on par with 100 % RDF. Application of 100 % RDF along with ZnSO4 @ 40 kg ha-1 and application of 100 % NPK though not differ significantly and on par with each other during four seasons of study.
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D5661
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