B. Panigrahi

Field test of a soil water balance simulation model

A simple soil water balance model is used to simulate the soil water content in the active root zone of mustard crop (Brassica juncea) as well as is tested with field experimental data of 2 years (1998 and 1999) under rain-fed (no irrigation) and irrigated conditions. The model used includes physical process like infiltration from rainfall or irrigation, redistribution in soil water zone, plant water uptake in the form of actual evapotranspiration and percolation out of the soil reservoir. In addition, the model considers dynamics of crop root growth model that affect the plant water uptake and hence the soil water in the unsaturated zone. The model satisfactorily simulates the soil water content in the active root zone of the crop on daily basis. Values of the mean absolute relative error (MARE) index between the observed and simulated soil water content of the rain-fed mustard in 1998 and 1999 are found to be 0.046 and 0.058, respectively, whereas for irrigated mustard, it is 0.051 in 1999. Prediction efficiency (PE) index is found to be 0.98, 0.97 and 0.97 for rain-fed mustard of 1998 and 1999 and irrigated mustard of 1999, respectively. Since the MARE index is low and PE index is high for both rain-fed and irrigated mustard, the model can be used to simulate the soil water content in the active root zone of the crop.

Modeling Evaporative Water Loss from the On-Farm Reservoir with Biological Shading

An attempt has been made on modeling evaporative water loss from the on-farm reservoir (OFR) with biological shading in rainfed upland areas. Biological shading over the water surface of a lined OFR has been developed by growing a creeper, namely, bottle gourd (Lagenaria siceraria) on an erected bamboo platform. Based on normalized reference crop evapotranspiration, a canopy growth model was developed for predicting the percentage of ground cover of the creeper ( Gi ) with respect to time. The predicted and observed Gi values were in close agreement with each other having root-mean-square error (RMSE) of 11.43 and 5.86% during 2006 and 2007, respectively. The same model, when applied for simulating the growth rate of canopy cover on the embankment as well as on the bamboo platform of the OFR, maintained a very close agreement with the observed canopy cover on the embankment ( RMSE=0.79% ) , whereas in case of bamboo platform the RMSE was 17.32 and 7.16% of observed canopy cover during 2006 and 2007, respe...

Prediction of hydrological events for planning rainfed rice

Abstract Daily rainfall and evaporation data of 30 years (1969–1998) are analysed for prediction of hydrological events, such as occurrence of effective monsoon (EM) and withdrawal of monsoon (WM), for planning rainfed rice in Eastern India. Those hydrological events are treated with normal (ND), lognormal (LND), Pearson type III (PTD), and log-Pearson type III (LPTD) distributions. The historical data of hydrological events are also transformed by power and modified SMEMAX transformations and ND is fitted. Normal distribution fitted to power transformed data is found to be the best for both the events. Accordingly, these events are predicted at various probabilities of exceedence (PE). At 50% PE level, the monsoon is effective in the region for 110 days. The study reveals that short-duration rice will face less drought stress than long-duration rice during the critical growth stage and will produce higher yield under rainfed conditions. At 50 and 70% PE levels, the simulated yield of short-duration rainfed rice is observed to be 2265 and 1890 kg ha−1, respectively, that is 6.7 and 7.6% more, respectively, than the yield of long-duration rainfed rice.