Gogoi, BhabeshBora, Bhaswati2024-09-232024-09-232023https://krishikosh.egranth.ac.in/handle/1/5810214795The research reports on the effect of intensive cropping systems on soil properties in the acid Inceptisol of north-east India are not adequately available. Therefore, a study was carried out during 2021-22 at Instructional-cum-Research Farm, Assam Agricultural University (AAU), Jorhat to investigate the impact of different cropping sequences on the physico-chemical and biological properties of soil. The present study forms a part of the experimental trial on “Identification of cropping systems module for different farming systems” that has been going on since 2018-19 under the All India Coordinated Research Project on Integrated Farming Systems at AAU, Jorhat. The experiment was laid out in a Randomized Block Design replicating 3 times with 10 treatment combinations viz.,T1: Winter rice-Autumn rice, T2: Winter rice-Toria, T3: Winter rice-Pea-Cowpea, T4: Green manure- Toria-Blackgram, T5: Winter rice-Rajmah-Cowpea, T6: Winter rice-Toria-Blackgram, T7: Teosinte-Oat-Cowpea, T8: Maize-Oat-Rice bean, T9: Ridge gourd-Broccoli-Lady’s finger and T10:Bittergourd-Tomato-French bean sequence. Results revealed that the effect of intensive cropping system on soil bulk density and water holding capacity were nonsignificant. However, aggregate size and infiltration rate were significantly affected by the various cropping sequences. The highest mean weight diameter and infiltration rate were recorded under T10 and T4 respectively. Significant variations were also observed in soil pH, cation exchange capacity (CEC) and electrical conductivity (EC) after the end of the cropping sequences. The highest soil pH and CEC were recorded in T4, whereas EC was found to be the highest in case of T3. Significantly highest organic carbon content in soil was recorded in T4 followed by T9. Ammoniacal and nitrate N content in soil varied from 28.33 to 38.30 and 15.90 to 22.53 kg ha-1, respectively. Significant variations in available N, P2O5 and K2O status in soil were recorded at the end of the cropping sequences due to long-term cultivation of various cropping sequences. The highest soil available N and P2O5 were recorded in T4, whereas the lowest was in T1. Available K in soil was found to be the highest in T9 followed by T4 . Exchangeable calcium and magnesium content in soil ranged from 0.91 to 1.20 and 0.47 to 0.65 c mol (p+) kg-1, respectively. The available sulphur ranged from 11.70 to 17.13 kg ha-1 and the highest was recorded in T9 (Ridge gourd-Broccoli-Lady’s finger) followed by T4. DTPA micronutrients (Fe, Mn, Zn and Cu) in soil were significantly affected by the various cropping sequences and treatment T4 and T5 recorded highest values. Data on dehydrogenase, phosphomonesterase and urease activities varied from 95.5 to 141.1μg TTF g-1soil 24 h-1, 117.3 to 145.5 μg p-nitrophenol g-1 soil h-1 and 1.50 to 2.70 μg NH4-N g-1 soil h-1, respectively. Microbial biomass C, water soluble C, very labile and labile C fractions v were recorded highest in T4 with Green manure-Toria-Black gram sequence. The treatment under Ridge gourd-Broccoli-Ladys finger sequence (T9) showed the highest content of less labile and non-labile C fractions in soil. The total organic C and total C content in soil were found to be the highest in T4, whereas the highest total inorganic C was recorded in case of T5. Data on soil organic C stock under intensive cropping systems varied significantly from the lowest 45.27 Mg ha-1 under T7 to the highest 56.84 Mg ha-1 under T4. The effect of various cropping sequences on NPK uptake by the cropping sequences showed significant variations, and the data on rice equivalent yield was also varied significantly from the lowest 24.89 to the highest 656.45 q ha-1. The highest benefit: cost ratios (4.33 and 3.70) were recorded in case of the cropping sequences meant for income enhancement i.e. in T9 and T10, respectively. Correlation studies showed positive correlations of physico- chemical properties (except bulk density) with available nutrient status and C fractions in soil. Overall, the present study revealed that the inclusion of green manure and legume crops in the cropping sequences sustains soil productivity and hence triple cropping is possible without having negative impact in the soil system under long-term.EnglishThesis