Effect of soil moisture stress on growth light azimuth and yield of dryland sorghum

Based on weekly data for 4 years (1986-1989) at Bellary, soil moisture balance for rabi sorghum has been worked out for both irrigated and non-irrigated conditions. These soil moisture values have been used to identify periods of water stress which the crop experienced. during the growth cycle. The extent of yield reduction due to the stress was then evaluated from the actual soil water content and total available water extent and discussed. The ratio of evapotranspiration to potential evapotranspiration and water requirement of the crop has also been worked out to assess the stress situation of the crop during its growing period. This ratio has been found to be related to moisture availability at the root zone.

Soil moisture balance and its application to yield monitoring of rainfed paddy at Raipur

The study presents a technique for computing soil moisture balance of paddy crop based on 10 years data from 1977-1988 except 1984 and 1987, from agro-meteorological observatory, Raipur Values of different components of the moisture balance have been determined and discussed. The stress values have been used to estimate possible yield reduction by devising an yield index. The study revealed that water demand of the plant is largest between tillering and reproductive stages. Dry matter production appears directly related to the consumptive water use. A significant association is observed between the yield index and the actual rice yield.

Evapotranspiration and soil moisture balance in relation to yield of pearl millet (Pennisetum gIaucum)

In this study. the agrometeorological data of Hisar and Bellary have been utilized to examine evapotranspirative demand of the pearl millet at different phases during the crop growing period.Water use efficiency of the crop has also been worked out and discussted. Cumulative soil moisture balance was computed to assess the crop stress situation, Attempt has also been made to assess the moisture availability to the crop during the growing period and to estimate the yield, The study revealed that the pearl millet used maximum amount of water during the flowering stage at both locations. The same variety of pearl millet was found to use water more efficiently at Hisar than at Bellary. The yield index based on soil moisture balance technique was found to give a good indication of the yield.

Natural Groundwater Recharge Response to Climate Variability and Land Cover Change Perturbations in Basins with Contrasting Climate and Geology in Tanzania

The response of aquifers with contrasting climate and geology to climate and land cover change perturbations through natural groundwater recharge remains inadequately understood. In Tanzania and elsewhere in the world, studies have been conducted to assess the impact of climate change and variability, and land use/cover changes on stream flow using different models, but similar studies on groundwater dynamics are inadequate. This study, therefore, examined the influence of land use/cover and climate dynamics on natural groundwater recharge in basins with contrasting climate and geology in Tanzania, applying the modified soil moisture balance method, coupled with the curve number (CN). The method hinges on the balance between the incoming water from precipitation and the outflow of water by evapotranspiration. The different parameters in the soil moisture balance method were computed using the Thornthwaite Water Balance software. The potential evapotranspiration (PET) was calculated using the daily maximum and minimum temperatures, utilizing two-temperature-based PET methods, Penman–Monteith (PM) and Hargreaves–Samani (HS). The rainfall data were obtained from the gauging stations under the Tanzania Meteorological Agency and some additional data were acquired from climate observatories management by water basins. The results show that there has been a quasi-stable CN in the Singida semi-arid, fractured crystalline basement aquifer (74.2 in 1997, 73.64 in 2005, and 73.87 in 2018). In the Kimbiji, humid, Neogene sedimentary aquifer, the CN has been steadily increasing (66.69 in 1997, 69.08 in 2008, and 71.42 in 2016), indicating the rapid land cover changes in the Kimbiji aquifer as compared to the Singida aquifer. For the Kimbiji humid aquifer, the PET calculated using the Penman–Monteith (PM) method for the 1996/1997, 2007/2008, and 2015/2016 hydrological years were 1156.5, 1079.5, and 1143.9 mm/year, respectively, while for the Hargreaves–Samani (HS) method, the PET was found to be 1046.1, 1138.3, and 1204.4 mm/year for the 1996/1997, 2007/2008, and 2015/2016 hydrological years, respectively. For the Singida semi-arid aquifer, the PM PET method resulted in 2083.3, 2053.6, and 1875.4 mm/year for the 1996/1997, 2004/2005, and 2017/2018 hydrological years, respectively. The HS method produced relatively lower PET values for the semi-arid area (1839.4, 1814.7, and 1710.2 mm/year) for the 1996/1997, 2004/2005, and 2017/2018 hydrological years, respectively. It was equally revealed that the recharge and aridity indices correspond with the PET calculated using two temperature-dependent methods. The decline of certain land covers (forests) and increase in others (built-up areas) have contributed to the increase in surface runoff in each study area, possibly resulting in the decreasing trend of groundwater recharge. An overestimation of the PET using the HS method in the Kimbiji humid aquifer was observed, which was relatively smaller than the overestimation of the PET using the PM method in the Singida semi-arid aquifer. Despite the difference in climate and geology, the response of the two aquifers to rainfall is similar. The combined influence of climate and land cover changes on natural groundwater recharge was observed to be prominent in the Kimbiji aquifer, while only climate variability appreciably influences natural groundwater recharge in the Singida semi-arid aquifer. El Nino and the Southern Oscillation as part of the climate variability phenomenon dwarfed the time lags between rainfall and recharge in the two basins, regardless of their difference in climate and geology.

Irrigation and crop water requirement estimation for oil palms using soil moisture balance model in Peninsular Malaysia

This study presents the irrigation and crop water estimation in a Malaysian oil palm plantation for effective irrigation water management during water years 2013 and 2014. The study area was divided into four plots: 2000, 2002, 2006 and 2010, indicating years of peat swamp forest conversion to oil palm plantation. Hydrologic Engineering Centre-Hydrologic Modeling System (HEC-HMS) and Soil moisture balance hydrologic models were used to model the rainfall-runoff in the basin. Statistical analysis using coefficient of determination (R2) and Nash–Sutcliffe efficiency coefficient (NSE) were used to evaluate the performance and correlation of the two hydrologic models. The result showed that R2 and NSE were 0.94 and 0.90 respectively for calibration and 0.92 and 0.54 respectively, for monthly validation. This showed that the models performed well for simulation of the peatland hydrology. With the modelling of rainfall-runoff satisfied, the irrigation demand of the study plots was determined using the same soil moisture balance model. The irrigation demand ranged from 0.893 to 1.6 million cubic meters (MCM) in 2010 and 2000 study plots respectively. Irrigation demand is observed to be site specific which depends on the soil moisture deficit, readily available water in the oil palm root zone and oil palm rooting depth. Estimation of a future oil palm water requirement using the soil moisture balance model would be recommended for further studies for use as an advisory manual for the oil palm managers to enhance adequate water resources planning for oil palm productivity.

Climatic variability on groundwater recharge of Mymensingh district in Bangladesh

A study was carried out in Mymensingh sadar upazila of Bangladesh in order to evaluate the effects of climatic variability on groundwater (GW) recharge and evapotranspiration (ET) over the period of 2006 - 2015. The annual GW recharge was computed by using soil moisture balance method, while CROPWAT-8.0 model was used to determine potential evapotranspiration (PET) and Grindley method was also used to estimate actual evapotranspiration (AET). In the case study area, the average temperature and rainfall showed no trend (almost constant), whereas humidity showed a declining trend over the study period. Analysis of rainfall trend revealed that there was considerable increase in annual rainfall with a mean of 2125 mm found over the study period. Groundwater recharge showed an increasing trend over the whole period, and the maximum recharge of 247.86 mm found in 2013, while maximum GW depletion of 136.8 mm found in 2014. In case of annual PET, the maximum of 1403.76 mm found in 2006, whereas the minimum of 1115.76 mm found in 2013. The AET showed a slightly declining trend over the 10 years of study, and the highest average AET of 1014.24 mm observed in 2007, whereas the lowest of 772.92 mm was in 2013. There was no significant relationship among groundwater recharge and annual variability of average temperature, and average rainfall found while only the annual variability of average humidity was found to be inversely related with groundwater recharge. Progressive Agriculture 30 (1): 104-112, 2019