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Thursday, 30 March 2017

Evaluating performance of macroscopic water uptake models at productive growth stages of durum wheat under saline conditions

Author
Vahidreza Jalali, Safoora Asadi Kapourchal and Mehdi Homaee
Agricultural Water Management, 2017, vol. 180, issue PA, pages 13-21

Abstract: Water management in agricultural lands largely depends on quantity and quality of available soil and water resources. In arid and semi arid regions, scarcity of fresh water and soil salinity are two main important limiting factors for crop production. Under such limiting conditions, one practical alternative for crop production is the use of unconventional or brackish water. If used, the quantitative response of plants to salinity must be carefully analyzed by means of modeling. On the other hand, plant response to salinity varies under different growth stages. Durum wheat (Triticum turgidum L.) is an important crop cultivated in some arid and semi-arid areas across the world such as Middle East and North Africa. This study was aimed to quantitatively characterize the Durum wheat response to salinity under different productive growth stages. Consequently, a large experiment in natural saline sandy loam soil (Typic Toriorthent) with five natural saline water treatments including 2, 4, 6, 8 and 10 dS/m each with three replicates was conducted. Furthermore, four predictive linear and nonlinear models of Maas and Hoffman, van Genuchten and Hoffman, Dirksen et al. and Homaee et al. were evaluated to predict relative transpiration and relative yield of durum wheat under heading and ripening growth stages. Three statistics including modified coefficient efficiency (E'), modified index of agreement (d') and coefficient of residual mass (CRM) were used to compare the used models and to assess their performances. Results indicated that among the examined models, the macroscopic model of Homaee et al. can provide more reasonable predictions at heading stage, while the piece-wise linear model of Maas and Hoffman provided slightly better prediction at ripening growth stage. The obtained threshold value and slope of reduction yield were quite different from those previously reported in the literature. These findings reveal that the widely cited tables describing the relationship between relative yield and electrical conductivity of saturated extract, averaged over the root zone as well as the entire growing season, are quite approximate and carry significant uncertainty. More experimental studies are still needed to obtain reliable data under different growth stages.
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Impact of irrigation, surface residue cover and plant population on sugarbeet growth and yield, irrigation water use efficiency and soil water dynamics

Author 
Amir Haghverdi, C. Dean Yonts, David L. Reichert and Suat Irmak
Agricultural Water Management, 2017, vol. 180, issue PA, pages 1-12

Abstract: Currently, sugarbeet producers in western Nebraska are facing the challenge of reducing their irrigation water usage due to ground water pumping restrictions and the unpredictable amount of rainfall that is available from year to year. Therefore, there is an increasing interest in developing season long deficit irrigation strategies for sugarbeet, the main objective of this study. The other objectives were to determine the impact of surface residue and plant population on sugarbeet production. Three field trials were conducted in eight consecutive cropping seasons (2008–2015). The average root and sugar yield for the full irrigation treatment were equal to 71.11 and 11.08Mgha−1, respectively during the 6 years of the two irrigation studies (2008–2013) while applying 75% and 50% ETc on average caused 9% and 11% yield reduction, respectively (2008–2011). Plots under full irrigation treatment and rainfed showed highest and lowest water depletion, respectively. Overall based on six years of data (2008–2013), stressing moderate and severe late in growing season produced 1.03 and 1.87Mgha−1 more sugar while consuming about 13mm less water than imposing same level of stress early in season. The residue covered plots produced 0.29Mgha−1 more sugar yield than bare soil plots on average across treatments and years. Overall, higher population rates resulted in higher sugarbeet yield. Findings of this research will deliver insight for sugarbeet irrigation management.
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Effects of treated wastewater irrigation on soil properties and lettuce yield

Author
Vanessa Ribeiro Urbano, Thaís Grandizoli Mendonça, Reinaldo Gaspar Bastos and Claudinei Fonseca Souza
Agricultural Water Management, 2017, vol. 181, issue C, pages 108-115

Abstract: Domestic effluents may contain important nutrients for agricultural crop development, and reusing this effluent on irrigation can reduce the potable water demand, recycle nutrients, and decrease effluent discharges on water bodies. This study evaluated the changes on physical, chemical and microbiological characteristics of a Dusky Red Latosol, the yield and the quality of lettuce after cultivation with treated wastewater on irrigation. In a greenhouse, lettuces were irrigated using drinking water with conventional fertilization (T1) and treated wastewater with partial conventional fertilization (T2). After the lettuce harvest, the physical, chemical and microbiological properties of soil, the nutrients, and the microbiological quality of lettuce leaves were evaluated. Sodium adsorption ratio, magnesium, calcium, sodium, potassium, nitrate, chlorate, pH, electrical conductivity, total coliforms, Escherichia coli, chemical and biochemical oxygen demand were analyzed in irrigation water. The concentration of some soil nutrients (K, Ca, H, Al, and S) increased after irrigation with T2, and the presence of E. coli bacteria was not observed on lettuce leaves or in the soil. The T2 did not damage the physical properties of soil and increased its nutrients. Lettuce production (in terms of fresh weight) was higher in lettuce cultivated on T2 than that cultivated on T1. The treated wastewater quality was appropriate for lettuce drip irrigation.
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Estimation of transpiration fluxes from rainfed and irrigated sugarcane in South Africa using a canopy resistance and crop coefficient model

Author
E. Bastidas-Obando, W.G.M. Bastiaanssen and C. Jarmain
Agricultural Water Management, 2017, vol. 181, issue C, pages 94-107

Abstract: The area under sugarcane is rapidly growing worldwide. The consequences of such growth on basin scale water consumption and competing water resources need to be understood. Conventional models for sugarcane evapotranspiration have shown limitations for different environmental conditions. To improve current estimations of sugarcane water consumption, hourly and daily transpiration of rainfed sugarcane in Kwazulu-Natal (South Africa) and daily transpiration for irrigated sugarcane in Mpumalanga (South Africa) were calculated by using the Penman-Monteith equation (TPM) with a variable canopy resistance. Canopy resistance was calculated with the Jarvis-Stewart model from calibrated environmental stress functions. The classic FAO56 crop coefficient approach (TFAO56) was also investigated and crop coefficient values, crop basal coefficient and water stress coefficient were derived. There were differences between derived crop coefficient values and FAO56 weather-adjusted values. Derived crop basal coefficient (Kcb) was 0.9 for rainfed and irrigated sugarcane, which was lower than FAO56 weather-adjusted values of 1.19 for rainfed and 1.15 for irrigated at mid-stage. The reduction of the crop basal coefficient with the water stress coefficient resulted in an underestimation of transpiration for rainfed sugarcane. This indicates that water uptake under stress conditions is a complex process, not easy to model as water can be extracted from considerable depths. Daily estimates obtained from TPM outperformed those obtained from TFAO56 when compared to Bowen ratio and Surface Renewal system field measurements. For rainfed sugarcane with water-stressed conditions the TFAO56 RMSE was 1.55mmday−1 compared to 0.3mmday−1 for TPM. For rainfed sugarcane with water-unstressed conditions the TFAO56 RMSE was 0.5mmday−1 and the TPM RMSE was 0.22mmday−1 for TPM. For irrigated sugarcane the TPM RMSE of 0.47mmday−1 was slightly lower than the TPM RMSE of 0.49mmday−1, and TPM showed better correlation with an R2 of 0.85 compared to an R2 of 0.64 for TFAO56. This suggests that calibrated variables of the Jarvis-Stewart model for sugarcane proved to be suitable for both rainfed and irrigated sugarcane in South Africa. More research is needed to verify the validity of the calibrated stressed functions in other regions with high intensity of sugarcane plantations.
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Effects of zeolite and water stress on growth, yield and chemical compositions of Aloe vera L

Author
Saeid Hazrati, Zeinolabedin Tahmasebi-Sarvestani, Ali Mokhtassi-Bidgoli, Seyed Ali Mohammad Modarres-Sanavy, Hamid Mohammadi and Silvana Nicola
Agricultural Water Management, 2017, vol. 181, issue C, pages 66-72

Abstract: A. vera is one of the most economically important medicinal plants in many countries which is widely used in food, cosmetics and pharmaceutical industries. Water stress is the primary environmental factor that limits crop production. Therefore, in order to study the effects of water stress (20, 40, 60 and 80%) of the field capacity (FC) and zeolite (0, 4 and 8gkg−1 soil) on growth, yield and chemical compositions of A. vera an experiment was conducted in 2013 and 2014. The plants were harvested 90, 180 and 270days after imposing the treatments. The greatest number of new leaves and pup were produced by the plants irrigated 20 and 40% FC with 8g zeolite, respectively. Generally, the highest leaf fresh weight and gel fresh weight were observed 270days after imposing the treatments when plants were irrigated after depleting 40% of the FC and treated with 8g zeolite. Water use efficiency of A. vera increased with less water and more zeolite availability. In addition, the results indicated that the maximum aloin and proline accumulation were obtained 90days after imposing the treatments when the plants were irrigated after depleting 80% and 60% of the FC where no zeolite was applied, respectively. Irrigation after 80% depletion of the FC without zeolite application resulted in highest fructose and glucose content. In general, zeolite application could alleviate water stress adverse effects, and improved plant growth and yield. Severe water stress decreased leaf yield and plant growth while caused an increase in phytochemical and biochemical compounds.
Keywords: Aloe vera; Aloin; Growth; Water deficit; Yield (search for similar items in EconPapers)
Date: 2017
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Modification of the CERES grain sorghum model to simulate optimum sweet sorghum rooting depth for rainfed production on coarse textured soils in a sub-tropical environment

Author
Jose R. Lopez, John E. Erickson, Senthold Asseng and Edmundo Lopez Bobeda
Agricultural Water Management, 2017, vol. 181, issue C, pages 47-55

Abstract: There is potential to reduce irrigation water requirements in bioenergy feedstock cropping systems by breeding for deep rooted sweet sorghum cultivars that intercept more rainfall water. Such cultivars would require little or no irrigation in some environments. Consequently, the objective of this study was to quantify the potential benefit of deeper rooted sweet sorghum cultivars by simulating a range of root depth and planting date scenarios in the subtropical climate of the southeastern USA by modifying the CERES grain sorghum cropping system model for sweet sorghum. A two year field study was conducted to collect data for model development. The new sweet sorghum model was validated against independent studies from six different locations around the world. The root mean squared error of prediction of the model was 4.7% for days to maturity (6 days), 21% for total biomass weight, and 22.6% for stem dry weight. We then simulated sweet sorghum growth and yield for nineteen hypothetical rooting depths between 30 and 210cm. Based on model simulations, including uncertainty analysis associated with model parameters, the optimal root depth for our environment in the southeastern USA under rainfed conditions, was between 110 and 140cm to maximize final biomass yield. The simulated hypothetical 120cm root depth sweet sorghum had final biomass yields up to 48.2% higher than the simulated widely grown cultivar ‘M81 E’ in rainfed systems and would require up to 32% less irrigation to meet actual evapotranspiration demand. These results highlight the importance of breeding for deeper rooted sweet sorghum cultivars along with optimized sowing dates for higher biomass yields. However, model simulations also indicated that, even with optimal rooting depth and density, irrigation would be needed to maximize final biomass yields.
Keywords: Water; CERES; Modeling; Root length density; Irrigation; Rainfed (search for similar items in EconPapers)
Date: 2017
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Valuing farm access to irrigation in Nepal: A hedonic pricing model

Author
Janak Joshi, Mohammad Ali and Robert Berrens
Agricultural Water Management, 2017, vol. 181, issue C, pages 35-46

Abstract: The objective of this research is to quantify the economic value of access to irrigation for agricultural lands in rural Nepal, while controlling for the effects of social institutions that can either enhance or detract from agricultural production and land values. The analysis employs the hedonic pricing method (HPM) and uses self-assessed land value data from the Nepal Living Standards Survey, 2011. For the econometric modeling, a Box-Cox transformation supports the selection of the double log HPM model. Results show that the value of land with access to irrigation water is approximately 46 percent higher than the value of non-irrigated lands with a marginal implicit price of approximately NRs. 150,840 in 2011, (representing about seven times the median rural annual per capita income). Results also show the importance of built irrigation infrastructure, such as canals and tube wells, as well as access to multiple sources of irrigation water. We find that land-owner membership in community-managed irrigation systems and forestry user groups has positive impacts on land values. In consideration of extensive 2015 earthquake damages across large areas of Nepal, the findings support the critical importance of repairing irrigation access, especially to built irrigation infrastructures, and supporting community-managed irrigation and forestry user groups, which often lack the initial capital to initiate projects, for restoring rural well-being.
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Comparison of ET partitioning and crop coefficients between partial plastic mulched and non-mulched maize fields

Author
Daozhi Gong, Xurong Mei, Weiping Hao, Hanbo Wang and Kelly K. Caylor
Agricultural Water Management, 2017, vol. 181, issue C, pages 23-34

Abstract: The ratio of evaporation to evapotranspiration (E/ET) and crop coefficients (Kc) are important parameters for evaluating the water-saving potentials of agronomic technologies and they may vary with different practices of dryland cultivation. This study synchronously investigated changes of E/ET and Kc for three years using two eddy covariance systems and multi-microlysimeters under two cultivation methods—conventional flat planting without mulching (CK) and a furrow-ridge system with plastic film partially mulching (MFR)—on the semiarid Loess Plateau of China. Due to an increase of vapor diffusion resistance at the soil-air interface partially mulched by plastic film, the average E and ET of MFR were lower than those of CK by 38.1% and 9.3%, respectively, for the three growing seasons. Thus, the average E/ET in MFR decreased by 11.2 percentage points compared with CK. E/ET showed a significant logistic function with the green leaf area index (GLAI) under both treatments during the three growing seasons. The seasonal Kc varied with GLAI following a step function curve for both treatments, and was linearly correlated to GLAI with significance levels when GLAI was below the thresholds of 3.0 and 3.2–3.4 for CK and MFR, respectively. Maximum Kc values were 1.01±0.05 and 0.91±0.09 for CK and MFR, respectively, at the middle crop growth stage. These results suggest that MFR can significantly reduce E/ET and maximum Kc, which help to improve yield and water use efficiency in rainfed spring maize fields. Consequently, MFR enhanced the average grain yield and crop water use efficiency by 12.5% and 24.6%, which amounted to 11527kg/ha and 3.36kg/m3, respectively. Therefore, MFR promoted crop water productivity and is an effective approach to solve water crises in dryland regions.
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AquaCrop-OS: An open source version of FAO's crop water productivity model

Author
T. Foster, N. Brozović, A.P. Butler, C.M.U. Neale, D. Raes, P. Steduto, E. Fereres and T.C. Hsiao
Agricultural Water Management, 2017, vol. 181, issue C, pages 18-22

Abstract: Crop simulation models are valuable tools for quantifying crop yield response to water, and for devising strategies to improve agricultural water management. However, applicability of the majority of crop models is limited greatly by a failure to provide open-access to model source code. In this study, we present an open-source version of the FAO AquaCrop model, which simulates efficiently water-limited crop production across diverse environmental and agronomic conditions. Our model, called AquaCrop-OpenSource (AquaCrop-OS), can be run in multiple programming languages and operating systems. Support for parallel execution reduces significantly simulation times when applying the model in large geospatial frameworks, for long-run policy analysis, or for uncertainty assessment. Furthermore, AquaCrop-OS is compliant with the Open Modelling Interface standard facilitating linkage to other disciplinary models, for example to guide integrated water resources planning.
Keywords: AquaCrop; Crop model; Agriculture; Water; Open source; Policy (search for similar items in EconPapers)
Date: 2017
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Root development and water uptake in winter wheat under different irrigation methods and scheduling for North China

Author
Shiva K. Jha, Yang Gao, Hao Liu, Zhongdong Huang, Guangshuai Wang, Yueping Liangand Aiwang Duan
Agricultural Water Management, 2017, vol. 182, issue C, pages 139-150

Abstract: A field experiment was conducted on winter wheat (Triticum aestivum L.) during 2013–2014 and 2014–2015 to study the root distribution profile and soil water dynamics under the main currently used irrigation methods in the North China Plain (NCP). The WinRHIZO system and the HYDRUS-1D model were used to identify a promising irrigation schedule. In this two-factor experiment, three irrigation methods, i.e., sprinkler irrigation (SI), surface drip irrigation (SDI) and surface flooding (SF), were scheduled to irrigate the crop as soon as the soil water content decreased to 70%, 60% and 50% of the field capacity. The results showed that both the irrigation method and irrigation schedule influenced root development, the profile root distribution pattern and the profile root water uptake (RWU). The soil surface temperature fluctuated very rapidly depending on the irrigation method and scheduling system used, whereas profile soil temperature fluctuations became more consistent with depth. The RWU was higher in the upper soil layer (0–60cm) for all irrigation methods for frequently irrigated treatments, and the maximum was observed in SDI compared to SI and SF due to the higher root length density (RLD) in the top soil under SDI. On the other hand, the RWU was higher in SF at a deep soil profile below 60cm, where it had a higher RLD compared to that of SI and SDI. SDI at 60% of FC not only improved water uptake but also resulted in better water productivity and produced the highest grain yield (9.53t/ha). The simulated RWU and soil water dynamics presented in this paper will be helpful to improve winter wheat production in the NCP and can be used as a reference for further research on water management practices.
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Advantages and Disadvantages of Fasting for Runners

Author BY   ANDREA CESPEDES  Food is fuel, especially for serious runners who need a lot of energy. It may seem counterintuiti...