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ThesisItem Open Access COMPARATIVE ASSESSMENT OF INSECT PEST- DISEASE DYNAMICS AND THE PERFORMANCE OF GREEN GRAM UNDER DIFFERENT MICROCLIMATES(2023) Yadav, Roshani; Medhi, KuldipField experiments were conducted in the Instructional-Cum-Research (ICR) Farm of Assam Agricultural University, Jorhat during kharif, 2022 and summer, 2023 with an objective to study the seasonal variation in incidence of insect pests and disease dynamics of green gram, and also to assess the performance of four cultivars of green gram viz., SGC 16, SGC 20, IPM 02-3 and MH 421 under three different microclimates created by manipulating sowing dates. The crop was sown on 11 September (D1), 28 September (D2) and 13 October (D3) during kharif, 2022, whereas it was sown on 13 February (D1), 28 February (D2) and 14 March (D3) during summer, 2023. The results revealed that aphid (Aphis craccivora) and jassid (Empoascakerri) population on green gram reached its peak in 50th and 42nd SMW, respectively in kharif season and 18th SMW in summer season. Pod borer (Helicoverpaarmigera) population recorded highest in 44th SMW during kharif and 20th SMW in summer seasons. Likewise, whitefly population (Bemisiatabaci) was recorded maximum in 46th and 16th SMW during kharif and summer seasons, respectively. In addition, Cercospora leaf spot (Cercospora canescens) and Moongbean Yellow Mosaic Virus (MYMV) disease infection reached its peak during 45thSMW in kharif and, 20th and 18th SMW, respectively during summer season. The Percent Disease Index (PDI) of Powdery mildew (Erysiphe polygoni) and Anthracnose (Colletotrichum sp.) was recorded highest in 51st SMW during kharif and 23rd SMW in summer season. In summer green gram, aphid population was significantly and positively correlated with maximum (0.55*) and minimum (0.45*) temperature; while it had a significant negative correlation with minimum temperature (-0.65**) duirng kharif season. Jassid and whitefly had positive and significant correlation with maximum and minimum temperatures. None of the weather variable had a significant impact on pod borer population during both of the season.Likewise, Cercospora leaf spot exhibited significant and positive correlation with temperature atripening phase in kharif green gram. The reliability of regression model (R2) developed based on insect pest and disease weather relationship were found to be varied within 0.04 to 0.77 and 0.24 to 0.85, respectively. The results revealed that among the varieties, MH 421 (539.1 kgha-1) performed better during kharif, whereas least yield (410.9 kgha-1) was observed when sown as summer crop. Poor performance of MH 421, can be indirectly referred from a depletion of 26.9% of intercepted PAR (iPAR) in summer crop relative to kharif crop due to low canopy growth. In contrary, SGC 16 maintained its performance in both kharif (491.2 kgha-1) and summer (512.5kgha-1) seasons. Mainly, substantial difference in plant height, LAI, above ground biomass and number of pods per plant corresponding to early and late sowings during kharif and summer, respectively defines the yield of the crop. In case of early (D1) sowing date, sufficient moisture is available during kharif season, whereas less moisture is available in summer season for supporting initial crop establishment. The mean percentage of iPAR was found 3.4% (SGC 16), 8.4% (SGC 20) and 9.6% (IPM 02-3) higher under late (D3) sown summer season crop relative to kharif season. Overall, protein content in seeds of green gram varied from 22.07 to 24.50%, irrespective of sowing dates and found maximum in SGC 20 (>24.0%); and minimum in SGC 16 (22.0%) in kharif and MH 421 (21.6%) in summer. Maximum protein content was recorded in D2 (23.8%) and D3 (23.9%) corresponding to kharif and summer season, respectively. Moreover, negative association was observed among seed yield and protein content of seedsof green gram.ThesisItem Open Access AGRO-CLIMATIC CHARACTERIZATION FOR PLANNING SMART AGRICULTURAL PRACTICES IN ASSAM(2023) Kakoti, Mriganko; Deka, Rajib LochanThe present study was undertaken with the objective to characterize the agroclimatic environment for improved planning of agricultural practices in Assam by calculating assured weekly rainfall at different probability levels along with occurrence of dry and wet spell and estimation of moisture availability index which will help in accessing the crop growing duration as well as planning suitable agricultural practices in the region. Long- term rainfall data for a span of 31 years (1991-2021) across 33 designated stations located at six agro-climatic zones of Assam were gathered from IMD, Pune. However, the daily temperature data (maximum and minimum) for the same period were not available in the IMD dataset for all the selected stations. To compensate for this missing information, daily temperature data was obtained from the NASA POWER (Prediction of Worldwide Energy Resources) data portal. The amount of weekly rainfall at different probability levels (90%, 75% and 50%) were calculated using incomplete gamma distribution model and Markov chain model was used to find out the probabilities of occurrences of 2 and 3 consecutive wet weeks or dry weeks by taking threshold limit of 20 mm of rainfall per week. Characterization of rainfall revealed that annual mean rainfall was highest at Karimganj (3397 mm) followed by Lilabari (3182 mm), Kokrajhar (3170 mm), Silchar (3104 mm), Gharmura (3095 mm) and lowest was observed at Lumding (1305 mm) followed by Bokajan (1341 mm). The coefficient of variation (CV %) of annual rainfall varied from 12.4 % to 24.9 % in Lower Brahmaputra valley zone (LBVZ), 13.1 % to 18.1 % in North Bank plains zone (NBPZ), 15.1 % to 18.9 % in Central Brahmaputra valley zone (CBVZ),11.4 % to 18.3 % in Upper Brahmaputra valley zone (UBVZ), 13.2 % to 26.8 % in Hills zone (HZ) and 17.3 % to 27.4 % in Barak valley zone (BVZ) during 1991-2021 indicating rainfall was highly dependable and less erratic in LBVZ, NBPZ, CBVZ and UBVZ as compared to HZ and BVZ which showed high CV. Seasonal rainfall analysis revealed that contribution of monsoon season rainfall to the total annual rainfall was highest (66 %) followed by premonsoon season rainfall (26%), post-monsoon (7%) and winter (2%). Rainfall during postmonsoon and winter were highly variable as CV (%) was more than 45% and 50%. The weekly rainfall data indicated that rainfall was mainly concentrated between 16th to 38th SMW and more than 20 mm of assured rainfall was received during this period at 75% probability level. However, in some stations under Kamrup (R), Kamrup (M) and Sonitpur district this period was between 16th to 35th SMW while the stations under rain shadow belt like Lumding, Golaghat and stations of eastern Karbi Anglong district the period was between 19th to 36th SMW. From 42nd SMW onwards less than 10 mm of weekly rainfall was received at 75% probability level across all the designated stations. The probable occurrence of two consecutive wet weeks increased from 15th, 16th to 38th SMW across all the stations except this period was less for stations under Kamrup (R), Kamrup (M) and Sonitpur district (NBPZ) and for stations located under the rain shadow belt (18th to 38th SMW). Occurrence of dry weeks probability was more than 50% from 43rd SMW across all the stations which corresponds with the growing season of rabi crops in the region. The weekly Moisture Adequacy Index (MAI) values were determined by computing the ratio of AET to PET. PET values were estimated using Thornthwaite's (1948) method, while AET values were derived from Thornthwaite and Mather's (1955) water balance model. This calculation allowed us to assess the availability of moisture in the study area on a weekly basis. Assam comprises of a mixture of different types of soil types. For crop planning and suggesting suitable practices, major two types viz., sandy loam soil having 100 mm water holding capacity and silt clay loam soil with 200 water holding capacity were considered and accordingly MAI was calculated. MAI value increased from 0.4 in rabi season and reaches maximum value of 1 during kharif season indicating enough moisture to support water demanding crops. Almost in most of the stations there was greater chance for water surplus during monsoon season thus offer opportunity for water harvesting and supplemented irrigation to mitigate moisture stress conditions. It can prove beneficial for successive rabi crops also. Soil with high water holding capacity i.e., 200 mm WHC had higher MAI value in all the seasons as compared to soils with l00 mm WHC. The weekly MAI suggests the possibility of sowing kharif crops without affecting the later rabi crops. The length of growing period (LGP) calculated over the period 1991-2021 revealed that the lowest average LGP of 239 days was found in stations of Hills zone and the highest average LGP of 303 days was found in stations of BV zone. When averaged over 31 years, it was observed that the mean LGP accounts for 277 ± 31 days with RF/PET ratio greater than 0.5 and MAI value ranging more than 0.75. The weeks in which the RF/PET ratio was greater than 0.25 with MAI value ranging from 0.4 to 0.75 indicated the presence of residual soil profile moisture. Based on these approaches, pre sowing cultivation, seed bed preparation, sowing and transplanting window was suggested for different agroclimatic zones of Assam.ThesisItem Open Access EVALUATION OF FINGER MILLET GENOTYPES AS CLIMATE SMART CROP UNDER THE AGROCLIMATE OF JORHAT(2023) Boruah, Angita; Deka,Rajib LochanA field experiment was conducted during kharif, 2022-23 at Instructional cum Research (ICR) Farm of Assam Agricultural University, Jorhat to study crop weather relationship and genetic diversity among five finger millet genotypes viz. Gossaigaon Maruadhan (V1), FMAVT 4001 (V2), FMAVT 4006 (V3), FMAVT 4007 (V4) and FMAVT 4012 (V5) grown under three microclimatic regimes: 6th August (D1), 22nd August (D2) and 6th September (D3), following split plot design with three replications. The weekly mean maximum (Tmax) and minimum temperature (Tmin), rainfall (RF), morning (RH-I) and evening relative humidity (RH-II), bright sunshine hours (BSSH), pan evaporation (EVP) and wind speed (WS) ranged from 22.1ºC to 34.9ºC, 7.9ºC to 25.6ºC, 0 to 104.4 mm, 91 to 100%, 51 to 85%, 1.9 to 9 hours, 1.1 to 3.8 mm and 0.8 to 3.1 kmph respectively during the period of experimentation. Biometric observations, viz. plant height, leaf area index (LAI), biomass, number of effective tillers/m2, number of earheads/m2, number of fingers per earhead, finger length, test weight, grain and straw yield were recorded periodically during entire growing season and at the time of harvest. Soil temperature at 10 cm depth was recorded daily, soil moisture at 15 days interval and incident, reflected and transmitted photosynthetically active radiation (PAR) at 7 days interval were also recorded during the experimental period. Results revealed that LAI, plant height and biomass at all the growth stages differed significantly under different microclimatic regimes with highest values recorded in the early sown (D1) crop. Accumulated agroclimatic indices such as GDD (growing degree days), HTU (heliothermal units) and PTU (photothermal units) decreased gradually with successive delay in sowing time with highest value being recorded under D1. Yield attributes and grain yield were found highest in early sown crop (D1) as compared to late sown crops. The vegetative phase of the first sown (D1) crop was exposed to comparatively higher soil temperature regime as compared to late sown crops (D2 and D3). The crop sown on 6th August (D3) had the highest PAR interception rate (72.6%). Among the genotypes, Gossaigaon Maruadhan (V1) was found to be superior with respect to growth parameters and yield (17.94 q/ha). Correlation analysis revealed that yield attributes and yield were significantly positively correlated with Tmax, Tmin, and WS whereas the correlation was negative and significant with RHI during all growth phases. EVP and BSSH had significant positive association with yield and yield attributes in all the phases of the crop growth except during reproductive phase. Yield predictive models were developed by utilizing step-wise multiple regression method using mean and accumulated agroclimatic indices during different pheno phases and entire period of crop growth. The most efficient yield predictive model among mean phasic meteorological parameters was found with Tmin during vegetative phase with highest coefficient of determination (R2=0.932) irrespective of varieties. While, among the accumulated meteorological indices, the best models were found for PTU (R2=0.932) and RF (R2=0.932) during vegetative phase and entire growing period respectively. For genetic diversity analysis, 20 RAPD primers were used out of which 7 were found to be polymorphic. These markers amplified 46 alleles with an average of 4.6 alleles per marker. Genetic relationship among finger millet genotypes were found out on the basis of pairwise Jaccard’s similarity coefficient whose value ranged from 0 to 0.6 with an average of 0.295. Cluster analysis by UPGMA method grouped 20 samples into two major clusters, each further sub-divided into two sub-clusters. Cluster A comprised of 15 samples while cluster B had only 5 samples. All the treatment combinations of varieties V2, V3, V4 and V5 were grouped in cluster A, while treatment combinations of V1 were grouped in cluster B which indicates their genetic dissimilarity. These results indicated that different plant characters exhibiting strong positive genotypic and phenotypic correlation with grain yield can be used for development of high yielding genotypes of finger millet crop.ThesisItem Open Access Rainfall Probability Analysis for Crop Planning of Unakoti and West Tripura(2021) Ganchaudhuri, Somnath; Sarmah, KushalThe rainfall data of two districts of Tripura namely Unakoti and West Tripura for 20 years (2001-2020) were collected from Weather Stations under Airport Authority of India through Regional Meteorological Centre, Guwahati and were used to analyze annual, seasonal, monthly and weekly rainfall using statistical methods. It was also used to find and analyze weekly rainfall probability by using incomplete gamma probability module of WEATHER COCK software. The analyzed data revealed that the average rainfall for the last 20 years of Unakoti and West Tripura district were 2597.5 mm and 2138.4 mm respectively. The rainfall data also revealed that the districts of Unakoti and West Tripura district received about 1510.7 mm and 1272.5 mm during monsoon contributing about 58.2% and 59.5%, respectively to the total rainfall which is highest as compared to any other season. Also rainfall amount along with contribution total rainfall received in other seasons are 206.3 mm (7.9%) and 199.8 mm (9.3%) in post monsoon, 854.3 mm (32.9%) and 566.8 mm (26.5%) during pre monsoon followed by winter. The two districts of Unakoti and West Tripura district received highest rainfall of 500.2 mm and 450.3 mm in May and June respectively. Least rainfall of 5.5 mm and 2.7 mm was received during January in Unakoti and West Tripura respectively. Rainfall probability analysis is one of the most important tools to predict the rainfall of an area. The total annual rainfall of Unakoti at 90%, 75% and 50% probability is predicted to be 1640 mm, 1686 mm and 1722 mm respectively. The total annual rainfall of the West Tripura at 90%, 75% and 50% probability is likely to be 1631 mm, 1847 mm and 2108.4 mm respectively. The SWM 23 for Unakoti and SMW 24 for West Tripura is probably to receive highest rainfall in all the three level of rainfall probabilities (90%, 75% and 50%). Agro-climatic conditions of both the districts are quite similar, hence crops and cropping patterns in both the districts are same and do not vary much. The Risk proof crop which can be best suitable for kharif season are blackgram, greengram in medium and upland, aman rice in medium land and late aman can be grown in lowland condition. The crops which can be grown in rabi season are vegetables like cole crops, tomato, chilli etc along with potato, pea, toria etc. The crops grown in summer include short duration greengram, aush rice, sesame, jute in all land situations while early aush can be grown in lowland.ThesisItem Open Access Impact of modified microclimate on the performance of green gram under different planting systems in Upper Brahmaputra Valley Zone of Assam(AAU, Jorhat, 2021) Pathak, Karabi; Neog, PrasantaA field experiment was conducted during the summer, 2021 in the Instructional-Cum-Research (ICR) Farm of AAU, Jorhat to study the Impact of modified microclimate on the performance of green gram under different planting systems in UBVZ Assam. The variety SGC-16 was grown in a split-plot design with 3 dates of sowing (D1-20th February, D2-6th March, and D3-20th March) in main plots and three planting systems (P1 – ridge and furrow, P2 – raised bed with two rows in bed and P3 –flat bed ) in sub-plots, with three replications following recommended agronomic practices. Microclimatic parameters such as soil temperature (10 cm depth) and soil moisture content at two depths (0 - 15 cm and 15 - 30 cm) were recorded at regular intervals. The different components of photo-synthetically active radiation (PAR), viz., incident (IPAR), and transmitted (TPAR) were recorded at 7 days intervals using line quantum sensor (Model LQM-70-10) at local noon time (11:30 AM). Crop growth parameters viz., plant height, leaf area index and dry matter accumulation, phenological observations and yield attributing characters, and seed yield were recorded. Agro-climatic indices viz., growing degree day (GDD), heliothermal unit (HTU), phenothermal index (PTI), and heat use efficiency (HUE) for biomass and seed yield were computed following standard procedures. The daily maximum temperature never exceeded 37.6°C, but the daily minimum temperature went below 20°C (up to 12.4°), which was detrimental to the crop. The average soil moisture content in the upper 30 cm soil profile was the highest in the D3 (80.39 mm), followed by D2 (75 mm) and D1 (66.4 mm). As compared to P3, the decrease in weekly evening soil temperatures under P1 and P2 was up to 2.1 and 1.4°C, respectively. Incident PAR (IPAR) during the crop growth season varied from 712 to 1721 μ mol s-1 m-2. In all dates of sowing and planting systems, the lowest transmitted PAR was recorded in the case of D3 date of sowing and in P1, when the crop was with full canopy coverage. The crop took 4 to 11 days, 28 to 35 days, 34 to 43 days, 39 to 50 days, and 62 to 75 days to attain the different phenological events, such as emergence, bud formation, flowering, pod initiation, and physiological maturity, respectively under different sowing dates and planting systems. Irrespective of sowing dates mean maximum leaf area index was recorded in P1 (2.06), followed by P2 (1.91) and P3 (1.77). The biomass production at maturity was highest in D3 (15.6 g plant-1), which decreased in earlier dates of sowing, while it was highest under P1 (14.6 g plant-1), followed by P2 (13.4 g plant-1) and P3 (11.6 g plant-1), irrespective of sowing dates. The seed yield of green gram cultivar SGC-16 sown under different sowing dates and planting systems ranged from 286.3 to 681 kg ha-1 with an overall mean of 509.8 kg ha-1. Irrespective of sowing dates, the highest GDD accumulation in the entire growth period was recorded under the P1 (1010°C day) system, followed by P2 (973°C day) and P3 (930°C day). The accumulation pattern of PTU by the crops under different treatments was similar to that of GDD. HUE for total biomass production and seed yield ranged from 2.61 to 4.01 kg ha-1°C-1 and 0.38 to 0.65 kg ha-1°C-1, respectively. Regression studies showed that there were linear significant relationships between total biomass, seed yield, and max LAI with iPAR .Correlation studies between seed yield, and thermal indices confirmed the existence of a significant and positive correlation between them.ThesisItem Open Access ASSESSMENT OF CLIMATE CHANGE IMPACT ON RICE PRODUCTIVITY IN THE LOWER BRAHMAPUTRA VALLEY (LBV) ZONE OF ASSAM(AAU, Jorhat, 2021) Hussain, Jemima; Deka, R. L.The present study investigates the trend in area, production and productivity of winter rice along with meteorological parameters, namely, temperature and rainfall during 1990-2019 and impact assessment of temperatures and rainfall on observed rice yield in the lower Brahmaputra valley (LBV) zone of Assam. In the zone, winter rice covers an area of 5.18 lakh ha with a production of 1.128 million tonnes and productivity of 2169 kg/ha. The rate of change of productivity with respect to linear time trend was found to be 35.82 kg/ha/year in the LBV zone. The decadal compound annual growth rates (CAGR) for winter rice area during 1990-2019 were negative with statistically significant negative growth observed during the decades 1990-1999 and 2010-2019. However, the growth rates for production and productivity were positive in the zone. Maximum growth rate (2.51%) for productivity was observed during the recent decade (2010-2019). Theil Sen’s slope method was used to detect the trends of temperature and rainfall during the growing season of winter rice and Mann-Kendall rank test was applied to understand the statistical significance of the trends. Results revealed that there was a significant increasing trend in maximum temperatures for the months of August, October (Reproductive phase) and November (Maturity phase). Minimum temperature showed increasing trends in August, October and November and decreasing trends in July and September. A significant increase in average temperature during maturity phase was also observed. Rainfall in different months of the growing season of winter rice exhibited no significant trend except for the month of September where it increased significantly by 4.38 mm/year. A strongly balanced district-wise panel data (yield and climatic variables viz. Tmax, Tmin and rainfall during different pheno-phases) was used to assess the impact of climatic variables on the observed yield of winter rice during 1990-2019. Fixed effect regression model based on Hausman test was used to determine the relationship between yield and climatic variables. The coefficient of determination (R2) value revealed that variables included in the model explained variation in observed rice yield up to 71 per cent. Regression results indicated that the maximum temperature during vegetative phase was negatively associated while it was positively associated with yield during reproductive and maturity phases. The minimum temperature during vegetative and reproductive phases was positively correlated with rice yield whereas during maturity phase, it was negatively correlated. Results also revealed the maximum and minimum temperature during vegetative and maturity phases and rainfall during vegetative phase were statistically significant. The maximum and minimum temperature during vegetative and maturity phases played significant role in determining the yield of winter rice during the study period. Rainfall in all the three phases had a negative impact on yield but the extent of impact on yield was negligible compared to that of temperature. Time trend (T) on the observed yield was positive and statistically significant, implying positive effects of technological advancement on the observed yield of winter rice in the study area. The present study is only an indicative of the extent of loss which could be occurring in yield due to changes in the climatic variables. Given the severity of winter rice yields to climatic factors, specific adaptation strategies like adjustment of transplanting time, growing of heat tolerant varieties must be adopted to mute the adverse effects of climatic variables. Availability of timely weather information and the development of climate-resilient varieties are two key options that the researchers and policy makers should urgently address.ThesisItem Open Access IMPACT OF THERMAL AND RADIATION REGIMES ON GROWTH AND YIELD OF POTATO (Solanum tuberosum) UNDER VARYING MICROENVIRONMENTS(AAU, Jorhat, 2019-07) Saikia, Raktim Jyoti; Neog, PrasantaA field experiment was conducted during rabi, 2018-19 in the Instructional-Cum-Research (ICR) Farm of Assam Agricultural University, Jorhat to study the impact of thermal and radiation regimes on growth and yield of Potato under varying microenvironments. The cultivar Kufri Jyoti was grown in split plot design with four dates of planting (P1 - 10th Nov, P2 - 20th Nov, P3 - 30th Nov and P4 - 10th Dec) in main plots and mulches (M0 - non mulch, M1 - water hyacinth and M2 - black polythene) in sub-plots, following recommended agronomic practices. Microclimatic parameters like soil temperature (daily), soil moisture and photosynthetically active radiation (PAR) were recorded periodically. Occurrences of different phenological events along with periodic LAI, plant biomass, yield attributing characters and tuber yield were recorded. Phenophase-wise agroclimatic indices viz., growing degree days (GDD), heliothermal unit (HTU), day temperature, phenothermal index (PTI) and heat use efficiency (HUE) were computed following established procedure. The weekly maximum and minimum temperature throughout the crop growth period ranged from 21.3 to 27.2℃ and 8.1 to 16.1℃, respectively. A total of 110.7 mm rainfall from 16 rainy days was received during the growing period and weekly average BSSH ranged from 1.5 to 7.7 hr. The maximum soil moisture depth (mm) was recorded under water hyacinth (85.7 mm) followed by non-mulched (81.2 mm) and lowest under black polythene mulch (79.7 mm). Among different dates of plantings P1 recorded highest (83.3mm) soil moisture depth, followed by P4 (82.0 mm), P2 (81.8 mm) and P3 (81.5 mm). The weekly mean morning and evening soil temperature ranged from 13.6 to 19.3°C and 19.6 to 28.6°C, respectively under different planting dates and mulching treatments. Irrespective of planting dates, soil temperatures under black polythene was higher in morning and evening by 0.8 to 1.9°C and 1.5 to 2.8°C, respectively, while soil temperatures under water hyacinth were 0.3°C to 0.9°C higher in the morning and 0.5 to 2.2°C lower in the evening as compared to non mulched treatment. No considerable difference in incident PAR was observed among mulching treatments. However, it varied considerably when measured at different days in all planting dates. Irrespective of planting dates the reflected PAR increased in later growth period of the crop with the onset of senescence. The lowest (65 μ mol s-1 m-2) RPAR values under black polythene treatment were attributed to greater absorption by black surface. The transmitted PAR was lowest, when measured on 55 DAP with full coverage of canopy, after that it increased again with maturity of the crop. PAR interception was highest on 55 DAP (74.8 %) in all the planting dates and mulching treatments. Among the mulching treatments, crops under water hyacinth recorded highest (80.6%) interception of PAR. The duration of the crop was highest under first date of planting (100.33 days) followed by second (96.7 days), third (90 days) and fourth (87.6 days) date of planting. The maximum leaf area index (LAI) was observed under water hyacinth (2.77) followed by black polythene (2.44) and non-mulched (2.14) treatment. Maximum partitioning of photosynthates towards tuber was found in case of water hyacinth (386.77 g m-2) and lowest in non-mulched (241.63 g m-2). Highest average total dry matter accumulation was obtained in P1 (465.2 g m-2) followed by P2 (431.6 g m-2), P3 (309.6 g m-2) and P4 (284.8 g m-2). The tuber yield was found to be highest on P1 (135.6 q ha-1) followed by P2 (118.3 q ha-1), P3 (86.3 q ha-1) and P4 (60.0 q ha-1). The RUE for tuber yield was highest under water hyacinth (2.35 g MJ-1) followed by black polythene (2.03 g MJ-1) and non-mulched (1.67 g MJ-1) condition. From correlation study it was observed that tuber yield, biomass accumulation and LAI were found significant and positively correlated with PAR interception and RUE as well as with AGDD, AHTU, HUE and PTI. The predictive model have been developed by using stepwise regression to predict tuber yield from radiation and thermal indices with higher R2 value of 0.96 and 0.99, respectively.ThesisItem Open Access DRY AND WET SPELL ANAYSIS FOR CROP PLANNING IN UPPER BRAHMAPUTRA VALLEY ZONE (UBVZ) OF ASSAM(AAU, Jorhat, 2019-07) Hazarika, SangeetaThe present research work was carried out for five districts under Upper Brahmaputra Valley Zone of Assam (UBVZ) to find out the probabilities of occurrence of dry and wet spells and onset and withdrawal of rainy season to suggest suitable crop planning in the region. Long term rainfall data were collected from Department of Agrometeorology, AAU, Jorhat and IMD, Pune for all the districts. The probability analysis was carried out by using Markov chain model which calculates the initial, conditional and consecutive probability of occurrence of dry and wet spell and onset and withdrawal of rainy season were determined by using forward and backward accumulation method, result pertaining to which was used for crop planning in different growing season over the region. The highest annual rainfall was recorded in Dibrugarh district (2590.2mm) followed by Tinsukia (2475.7mm), Sivasagar (2022.0 mm), Jorhat (1923.5mm) and lowest in Golaghat (1648.2mm). Seasonal rainfall analysis indicated that, monsoon season receives the highest amount of rainfall with least CV and the winter records the lowest rainfall with a higher CV in all the districts. From the result of initial probability, it was found that there was higher chances of occurrence of wet spell of minimum 10mm of threshold limit from 12th SMW (19th – 25th March) to 41st (8th – 14th Oct) and 42nd SMW( 15th – 21st Oct) in all the districts. The consecutive probability of occurrence of wet spell of two weeks is more than 50% from 13th (26th march – 1st April) and 15th SMW (9th – 15th April) onwards in Sivasagar and Golaghat, respectively whereas the such condition occurs from 12th SMW in rest of the three districts. There was higher chances of getting wet spell of three consecutive weeks of more than 40mm rainfall at different periods in Jorhat (26th – 28th SMW), Sivasagar (25th – 28th ), Dibrugarh (23rd – 31st ) and Tinsukia(22nd – 29th , 31st , 32nd SMW), which may lead to flood like condition in the districts. So, water harvesting of the excess moisture as well as provision of drainage in the crop field is suggested during the aforesaid period. The probabilities of occurrence of dry spell were higher before 12th SMW and after 42nd SMW, but during monsoon season it was found to be very less which indicates that Kharif crops can be grown without any supplemental irrigation. Considering forward accumulation from 9th SMW there was accumulation of 75 mm and 200 mm of rainfall within 13th – 15th SMW and 16th – 19th SMW, respectively in all the districts which indicates that sowing of summer crops can be started within these weeks. Considering forward accumulation from 22nd SMW it was found that within 23rd – 24th SMW and 25th – 26th SMW, there was accumulation of 75mm and 200 mm rainfall, respectively in the districts. The mean week for end of rainy season was found to be within 34th – 37th SMW (20th Aug – 16th Sept) for 300mm rainfall and 31st to 35th SMW (30th Aug – 2nd Sept) for 500 mm rainfall for all the districts. It indicates that delayed sowing of rice crop may be done latest by the week on which rainy season ends after backward accumulation of 500 mm of rainfall. On the other hand sowing of short duration crops with low water requirements may be done latest by the week on which there will be backward accumulation of 300mm of rainfall. Sowing of summer crops such as greengrm, blackgram, ahu rice were suggested to complete within 12th SMW onwards for all the districts. Nursery bed preparation for Sali rice can be started as early as 18th SMW in the district of Jorhat, Dibrugarh and Tinsukia. Sowing of Kharif greengram blackgram could be started after 34th SMW and Rabi crops and sowing of vegetables could be started after 40th SMW.ThesisItem Open Access EFFECT OF WEATHER PARAMETERS ON GROWTH AND YIELD OF GREEN GRAM [VIGNA RADIATA (L.)] UNDER THE AGROCLIMATIC CONDITIONS AT JORHAT(AAU, Jorhat, 2019-07) Annie, Mangshatabam; Goswami, B.A field experiment was carried out during kharif, 2018 at the Instructional-Cum-Research (ICR) Farm of Assam Agricultural University, Jorhat to study crop-weather relationships of Kharif green gram grown under different micro-climatic environments: MR-I: 25thAug, MR-II: 10th Sep and MR-III: 25th Sep with three varieties: SG-16 , SG-20 and IPBM-02-3, following a split plot (in number) design with four replications.Weekly mean maximum and minimum temperatures,morning and evening relative humidities, duration of bright sunshine hours and pan evaporation ranged from 25.6 to 34.5°C , 11.1 to 25.8°C, 89 to 99%, 59 to 83%, 1.3 to 8.2 Hours and 1.3 to 3.4 mm respectively. Rainfall during the crop growth season was found to be nearly evenly distributed, barring few weeks when there was no rainfall. Biometric observations, viz. leaf area index, plant height, total biomass production, no of pod per plant , no of seeds per pod, Test weight and seed yield were recorded periodically. Meteorological variables showed a near normal distribution during the crop growth period. Total accumulated agro-climatic indices showed a gradual decrease in the three successive micro-climatic regimes irrespective of varieties. Early-sown (MR-I) crop took less number of days from sowing to maturity as compared to late sown crop (MR-II & MR-III). Total biomass differed significantly both in varieties and microclimatic regimes in all the crop growth stages. Highest biomass was found in MR-I and the lowest in MR-III. Similarly, leaf area index (LAI) also differed significantly under microclimatic regimes and varieties at 45 DAS and 60 DAS. Most of the agro-climatic indices and meteorological parameters yielded higher correlation coefficients with final yield irrespective of varieties and microclimatic regimes for all growth stages. Highest correlation coefficient of seed yield (0.965) was obtained against accumulated growing degree days (AGDD) corresponding to physiological maturity stage. Among the mean meteorological parameters, the highest correlation coefficients was found in rainfall, DTRF (0.957), corresponding to the Vegetative stages. A few predictive models involving both accumulated indices and mean parameters were also developed combined over both varieties and microclimatic regimes corresponding to some selected crop growth stages. From the stepwise regression analysis, the most efficient model was found for the accumulated bright sunshine hours (ABSH) and accumulated rainfall (ADRF) corresponding to Pod Initiation stage. Among the mean meteorological parameters, the best model was found for the maximum temperature (MAXT) corresponding to the physiological maturity stages. Lower per cent variations (PCV) were indicative of the fact that the predicted models are very effective under agro-climatic conditions of Jorhat.
