Damodhara R. Mailapalli

Physically Based Model for Simulating Flow in Furrow Irrigation. I: Model Development

Researchers developed several mathematical models for simulating furrow irrigation using the Saint-Venant equations. Most of these irrigation models use numerical techniques to solve these equations, which in general, require extensive programming and computational skills. Moreover, several of these models consider uniform soil and use empirical equations for modeling infiltration. In this article, a physically based furrow irrigation model was presented for simulating flow in irrigated furrows under both uniform and layered soils. The model consisted of an overland flow and an infiltration module that are modeled using analytical solution of the zero-inertia and the Green and Ampt [one-dimensional and two-dimensional infiltration equations) equations, respectively. Furthermore, the infiltration was also modeled using the Kostiakov-Lewis infiltration equation. The model considered all possible furrow shapes and included graphical user interface. The developed model was evaluated using the field data and the model performance was discussed in the second part of the article.

Infiltration, Runoff, and Export of Dissolved Organic Carbon from Furrow-Irrigated Forage Fields under Cover Crop and No-Till Management in the Arid Climate of California

Development of best management practices (BMPs) such as conservation tillage and winter cover crop to mitigate runoff and reduce dissolved chemicals in irrigation runoff is an important objective for controlling surface water pollution attributable to agricultural activities. In this study, the effect of standard tillage (ST), STwith winter cover cropping (STCC), and no-till (NT) management practices on infiltration, runoff, and dissolved organic carbon (DOC) export from furrow-irrigated fields of 244-m length was investigated for summer 2007 and 2008 irrigations. The practices were implemented for 2 years. The average surface residue cover was 11, 44, and 32% for ST, STCC, and NT, respectively, for 2007 and 11, 59, and 61%, respectively, in the following year of the study. Two irrigations in each year were considered for the analysis. The runoff samples were collected from each tillage treatment using ISCO autosamplers at regular time intervals. The infiltration and runoff were estimated using a volume balance model (VBM) by considering a 0.2-m irrigation requirement. Converting from ST to STCC increased the infiltration by 14 and 43% and reduced the runoff by 48 and 43% in 2007 and 2008 irrigations, respectively; whereas, converting ST to NT enhanced the infiltration by 4% in both years and decreased the runoff by 19 and 23% in 2007 and 2008 irrigations, respectively. The authors observed only slightly higher DOC concentrations in STCC, but there was a 24% increase for NT in 2007 irrigations, and both compared to with ST ranged from 3.98 to 5:46 mg=L. The DOC concentration was not significantly different among the treatments in 2008 irrigations (3.48 to 4: 6m g=L). Combining the runoff and DOC concentration effects, the DOC export for STCC was decreased by 55% in both years; whereas, it was decreased by 4 and 27% for NT in 2007 and 2008 irrigations, respectively, compared with ST. Although STCC and NT have higher concentrations, the reduction in export in these treatments is attributable to lower runoff. These results suggest that DOC export can be controlled with STCC practice. No-till showed the same trend, although these results must be confirmed after extended implementation of this practice. DOI: 10.1061/(ASCE)IR.1943-4774.0000385.

Crop Residue Biomass Effects on Agricultural Runoff

High residue loads associated with conservation tillage and cover cropping may impede water flow in furrow irrigation and thus decrease the efficiency of water delivery and runoff water quality. In this study, the biomass residue effects on infiltration, runoff, and export of total suspended solids (TSS), dissolved organic carbon (DOC), sediment-associated carbon (TSS-C), and other undesirable constituents such as phosphate (soluble P), nitrate (), and ammonium () in runoff water from a furrow-irrigated field were studied. Furrow irrigation experiments were conducted in 91 and 274 m long fields, in which the amount of residue in the furrows varied among four treatments. The biomass residue in the furrows increased infiltration, and this affected total load of DOC, TSS, and TSS-C. Net storage of DOC took place in the long but not in the short field because most of the applied water ran off in the short field. Increasing field length decreased TSS and TSS-C losses. Total load of , , and soluble P decreased with increasing distance from the inflow due to infiltration. The concentration and load of P increased with increasing residue biomass in furrows, but no particular trend was observed for and . Overall, the constituents in the runoff decreased with increasing surface cover and field length.

Performance evaluation of hydrocyclone filter for microirrigation

In this study a hydrocyclone filter of 20 cm was selected and its performance was evaluated by studying the variation of discharge, pressure drop, influent concentration, and filtration efficiency with elapsed time of operation. The filter was tested with clean water to determine clean pressure drop and later it was tested with four concentrations of solid suspension, viz. 300; 600; 900 and 1,200 mg L-1. In the concentration of 300 mg L-1, the variation of pressure drop was low. But for the other concentrations of solid suspension, the variation was significant. The maximum pressure drops obtained were 41.19, 45.11, 50.01 and 52.95 kPa at 350, 390, 280 and 190 minutes of elapsed time, respectively. The maximum efficiency of solid suspension was 30.3, 32.96, 43.89 and 52.5% where as the minimum efficiencies were 9.91, 9.93, 9.62 and 9.9%, respectively. The hydrociclone tested presented inefficiency to filter small particles as clay. The initial removal efficiency of higher concentration was bigger than for lower concentration but, the final efficiency are almost the same irrespective of the concentration of solid suspension. The present tested hydrocyclone could be used as a pre-filter microirrigation to prevent emitter clogging.

Nanofertilisers, Nanopesticides, Nanosensors of Pest and Nanotoxicity in Agriculture

Food security in the world is challenging due to the limited available resources for the rising population. Various efforts are being practiced by governments, organisations and researchers to mitigate the demand and supply gap in human food chain. Agriculture took the roots of growth prior to industrial revolution, in around 90 countries. Though nanotechnology has already found industrial applications, the use of nanotechnology in agriculture is much more recent.

Physically Based Model for Simulating Flow in Furrow Irrigation. II: Model Evaluation

In this study, the physically based furrow irrigation model presented in Part 1 was evaluated using the experimental data collected from a field plot consisting of three 40-m-long free-drained furrows of parabolic shape and having a top width of 0.30 m, a depth of 0.15 m, and a slope of 0.5%. The irrigation experiments were carried out with a constant inflow of 0.2–0.5l s−1 and 0.3–0.7l s−1 on bare and cropped fields, respectively. The field data pertaining to furrow cross section, advance and recession times, water depth and velocity, and runoff rate and volume were collected from the irrigation experiments. The model performance was studied for simulating advance, recession, infiltration, and runoff using two–dimensional (2D) Fok, one–dimensional (1D) Green-Ampt, and KL infiltration functions (Part 1) by estimating the root mean square error and index of agreement ( Ia ) . For all the irrigations performed under bare and cropped furrow conditions, the model slightly overpredicted the advance time and ru...

Sediment Transport Model for a Surface Irrigation System

Controlling irrigation-induced soil erosion is one of the important issues of irrigation management and surface water impairment. Irrigation models are useful in managing the irrigation and the associated ill effects on agricultural environment. In this paper, a physically based surface irrigation model was developed to predict sediment transport in irrigated furrows by integrating an irrigation hydraulic model with a quasi-steady state sediment transport model to predict sediment load in furrow irrigation. The irrigation hydraulic model simulates flow in a furrow irrigation system using the analytically solved zero-inertial overland flow equations and 1D-Green-Ampt, 2D-Fok, and Kostiakov-Lewis infiltration equations. Performance of the sediment transport model was evaluated for bare and cropped furrow fields. The results indicated that the sediment transport model can predict the initial sediment rate adequately, but the simulated sediment rate was less accurate for the later part of the irrigation event. Sensitivity analysis of the parameters of the sediment module showed that the soil erodibility coefficient was the most influential parameter for determining sediment load in furrow irrigation. The developed modeling tool can be used as a water management tool for mitigating sediment loss from the surface irrigated fields.

Infiltration Evaluation Strategy for Border Irrigation Management

Water infiltration into soil plays a vital role in the performance of surface irrigation. Real-time information on infiltration characteristics is necessary to use surface irrigation models to manage irrigation systems. The present field study deals with the evaluation of the Kostiakov infiltration parameters using water front advance information at three different locations (50, 75, and 100% of the field length) along the alfalfa irrigated borders. Two irrigations were conducted on four border checks. The parameters of the Kostiakov infiltration model were determined using the one-point and two-point methods for these locations. The infiltration parameters for each border were used in a surface irrigation model to evaluate their impact on irrigation performance measures. The mean irrigation performance measures, such as inflow volume, application efficiency, tailwater ratio, deep percolation ratio, and low quarter distribution uniformity, were significantly different for one-point and two-point methods. ...

Quantifying yield gap for rice cropping systems in Lower Gangetic Plains

Rice crop production needs to be increased to meet the food demand of the growing global population by utilizing the limited available resources. Reducing yield gap between potential and actual farmers’ yields could be one of the promising options for increasing rice production. In order to quantify the yield gap of rice, field experiments were conducted at two different locations in the Lower Gangetic Plains. Decision Support System for Agro-technology Transfer model was used to quantify potential yield for analyzing the attainable yield gaps with respect to water limitation, agronomic managements, difference in transplanting dates and soil variability. The results showed that an attainable average yield gap of 0.33 t/ha in rainfed condition existed in farmers’ fields due to rice transplantation after 30th July, whereas the use of supplementary irrigations produced an average attainable yield gap of 0.86 t/ha in irrigated condition. Poor agronomic practices adopted by farmers may be causing the reduction in average yield of 0.29 t/ha. The yield gap due to different transplanting dates and agronomic managements suggested to identify yield optimum transplanting date of a cultivar and appropriate agronomic management strategy to reduce the yield gap. The soil variability contributed very less attainable yield gap (0.02–0.16 and 0.02–0.19 t/ha for rainfed and rainfed with subsequent irrigation, respectively), than other factors because of similar type of soil at the study sites. Results also suggested that farmers should emphasize more on management strategies such as quantity of N-fertilizers, timing of fertilizer applications, supplementary irrigation and transplanting date that might reduce the yield gap.

Evaluation of Nitrogen Fertilization Patterns Using DSSAT for Enhancing Grain Yield and Nitrogen Use Efficiency in Rice

ABSTRACT Temporal variation of rice growth and nitrogen (N) uptake generally follow a sigmoid curve and may respond positively to the N-fertilizer application at critical growth stages. In this study, it was hypothesized that the amount of N-fertilizer applied at critical growth stages possibly follows a geometric pattern such as line, parabola, and sinusoidal to attain maximum yield and nitrogen use efficiency. To test and identify the best pattern, short-term modeling-field testing-long-term modeling strategy was followed. The patterns with the highest simulated yield and nitrogen use efficiency from short-term modeling were tested in the field. Finally, long-term evaluation of N-fertilization patterns was performed using 25 years of historical weather data, resulting in the line pattern with 14% more yield and 25% less NO3− leaching in comparison to the conventional N-Fertilization pattern. Therefore, line pattern may be adopted to enhance the yield and nitrogen use efficiency in rice.