Optimization of irrigation management and environmental assessment using the water cycle algorithm

Obtaining high crop yields with limited water consumption requires optimal irrigation strategies based on comprehensive studies of the parameters of plant–environment interactions. Here, we used a structural equation modelling (SEM) to assess the relationships among input irrigation factors and moderate factors to find an optimum water use efficiency (WUE) response factor, for outdoor and greenhouse cultivation of eggplant (Solanum melongena). The input irrigation factors (including irrigation interval, water salinity and environment) and the moderate factors (evapotranspiration, soil salinity, plant parameters, fruit parameters and crop yield) were used in water cycle algorithm (WCA) and genetic algorithm (GA) methods to optimize the water use efficiency. The optimization process included finding the best combination of irrigation factors and optimized eggplant cultivation. The structural equation modelling results indicate that irrigation interval negatively affected water use efficiency with a more dominant effect on plant parameters. Water salinity negatively affected the water use efficiency with a more dominant effect on soil salinity, crop yield and fruit parameters. Low salinity water was more effective than full irrigation to optimize the water use efficiency. The water cycle algorithm revealed that for outdoor cultivation, the optimal range of irrigation interval was 2–5 days and water salinity in the range of 0.8–2.2 ds/m. These factors optimized evapotranspiration (346.23–738.19 mm), soil salinity (4.16–9.45 ds/m), fruit parameters (33.81–35.12 cm) and crop yield (1715.7–2190.8 g/plant), as well as increasing the water use efficiency (3.08–4.89 g/(plant-mm)). Both the water cycle algorithm and genetic algorithm yielded very close to optimal values. Two years of repeated experiments and the closeness of the optimal values using the algorithms confirmed that the optimal amounts are reliable.     

Influence of soil physicochemical properties, particle size fractions and mineralogy on the leaching potentials of arsenic and antimony in abandoned mine soils

At abandoned mine sites, arsenic (As)- and antimony (Sb)-enriched soils are often disposed of through onsite burial or capping. In highly weathered mine sites, the mobility of As and Sb is typically controlled by iron (Fe)(Ⅲ)/Fe(Ⅱ) phases; thus, the suitability of such disposal methods and appropriate testing techniques are questionable. In the present study, leaching potentials of As and Sb were examined using the toxicity characteristic leaching procedure (TCLP), waste extraction test (WET), and WET-extended procedure (WET-EXT) at three abandoned mine site soils in Australia. The leached concentration of As regularly exceeded USEPA criteria (5 mg L^-1). The highest leached concentrations of As and Sb were observed in the finest particle size fraction (< 0.053 mm) by WET-EXT (1 040 mg L^-1 for As and 21.10 mg L^-1 for Sb) followed by WET (800 mg L^-1 for As and 20.90 mg L^-1 for Sb). The TCLP method resulted in the lowest concentrations of leached As (0.000 9 mg L^-1) and Sb (0.000 3 mg L^-1). Crystalline and amorphous As-bearing Fe oxides were the main phases in the soils studied. However, the best correlations of leached As determined by TCLP (0.832), WET (0.944), and WET-EXT (0.961) were found with the non-specifically sorbed (NS1) As fraction. The mineralogical and sequential extraction data clearly indicate the dominant role of Fe geochemistry in controlling leachability of As and Sb. The TCLP method was unlikely to be suitable for assessing leachability, as it exhibited no relationship with leachable Fe and substantially lower leached As and Sb than the other two methods. Given the high to extremely high leachable As and Sb concentrations, most of the soil samples would not be recommended for placement in capping works, old shafts, or reduction systems (e.g., collection in drainage basins).     

Evaluation of bermuda and paspalum grass types for urban landscapes under saline water irrigation

In the arid regions, turfgrass cover is an integral part of landscape to protect the soil from erosion, enhance the aesthetic value, and improve the microclimate. The salinity and the scarcity of fresh water of the arid region are the major challenging factors in turfgrass production. Therefore, the need for salt tolerant turfgrass with functional quality is necessary to improve the turf performance. The detrimental effects of salinity include growth suppression, and lowered osmotic potential ultimately leading to firing of the leaf blades. In this context, the study was undertaken to determine the relative salt tolerance and growth response of turfgrass genotypes in order to recommend turfgrass cultivars that can tolerate high salinity irrigation and maintain excellent visual and functional qualities under United Arab Emirates (UAE) condition. The paspalum cultivars maintained the highest succulence percentage compared to the bermudagrass cultivars under enhanced salinity levels. The shoots count, fresh weight (FW), and dry weight (DW) were found highest in paspalum types. The chlorophyll a, chlorophyll b and the total chlorophyll content was found higher in bermuda grass types under high salinity levels. The bermudagrass cultivars showed significantly higher carotenoids, anthocyanins and proline compared to the paspalum types under salt stress condition. In the case of princess 77 and Yukon, an inherently high amount of proline was recorded which confirmed an increase up to 10,000 ppm and drastically declined beyond this concentration. Sea Dwarf paspalum and Sea Isle 2000 maintained uniformity in the proline level at all levels of salinity without significant variation. These findings point to the fact that both paspalum and bermuda types exhibited varied responses to different physiological and biochemical parameters under the saline conditions. Paspalum types have an edge over the bermudagrass in terms of shoot density, which is a potential factor in determining the high-quality turfs. Bermudagrass types can be applied in lower salinity conditions based on the responses as evidenced from the present results.     

Evaluation of growth indices and quantitative traits of safflower under organic farming and conventional agriculture

Application of organic fertilizers in sustainable agriculture systems improves yield sustainability of field crop production. The current research has been formed to investigate the effects of various levels of vermicompost (zero, 3, 6 and 9 t ha^?1) in combination with foliar spraying of potassium humate (0, 1, 2 and 3 mL L^?1) on spring safflower, in Iran during 2012–2013. In addition, inorganic fertilization has been considered as conventional agriculture (CA). In the current experiment, growth indices, seed yield, yield components and flower yield were evaluated. The results showed that the maximum leaf area index, total dry weight and crop growth rate have been determined at 9 t ha^?1 vermicompost and 3 mL L^?1 K-humate while the maximum netto assimilation rate has existed in CA at the emergence of flower buds. Likewise, the results indicated that vermicompost leads to a significant increase in seed yield, flower yield and yield components except 1000 seed weight. Flower yield, head number per plant and seed number per head were affected by K-humate concentrations and increased significantly from 1 to 3 mL L^?1. It should be mentioned that 9 t ha^?1 vermicompost and 3 mL L^?1 K-humate produced the highest seed and flower yield.     

Silicon application positively alters pollen grain area,osmoregulation and antioxidant enzyme activities in wheat plants under water deficit conditions

Role of exogenously-applied silicon (Si) on antioxidant enzyme activities was investigated in wheat under drought stress using a completely randomized factorial design with four replications. Drought stress significantly enhanced activities of ascorbate peroxidase, peroxidase, superoxide dismutase and catalase, and elevated accumulation of osmotically active molecules, soluble sugars and proline. Si application further enhanced activities of enzymes involved in oxidative defense system and accumulation of osmotically active molecules in drought-stressed plants. Under drought stress conditions, water shortage decreased protein content in all cultivars; however, application of Si increased it. Pollen area ratio was lower than 1 for cvs. Shiraz and Marvdasht under drought, but greater than 1 for cvs. Chamran and Sirvan. Water-limited regimes resulted in decreased leaf Ψ_w in all cultivars, but Si supply was effective in improving Ψ_w under water-limited regimes. Water shortage increased leaf K, Mg, and Ca concentrations. Under drought stress, Si-treated plants had higher K concentration than the none-treated plants.     

Evaluation of pan coefficient equations for estimating reference crop evapotranspiration in the arid region

Reference evapotranspiration (ET₀) can be estimated on basis of pan evaporation data (E_pan), whose measurements have the advantage of low cost, simplicity of the measuring equipment, simple data interpretation and application as well as suitability for locations with limited availability of meteorological data. E_pan values were converted to ET₀ using the pan evaporation coefficient (K_pan). In this study, seven common K_pan equations were evaluated for prediction of ET₀ in the growing season (April to October) in arid region of Iran. The Cuenca approach was best suited compared to the standard FAO Penman–Monteith method (FAO-56 PM).     

Proton toxicity interferes with the screening of common bean (Phaseolus vulgaris L.) genotypes for aluminium resistance in nutrient solution

Common bean (Phaseolus vulgaris L.) proved to be very sensitive of low pH (4.3), with large genotypic differences in proton sensitivity. Therefore, proton toxicity did not allow the screening of common bean genotypes for aluminium (Al) resistance using the established protocol for maize (0.5 mM CaCl₂, 8 μM H₃BO₃, pH 4.3). Increasing the pH to 4.5, the Ca²⁺ concentration to 5 mM, and addition of 0.5 mM KCl fully prevented proton toxicity in 28 tested genotypes and allowed to identify differences in Al resistance using the inhibition of root elongation by 20 μM Al supply for 36 h as parameter of Al injury. As in maize, Al treatment induced callose formation in root apices of common bean. Aluminium‐induced callose formation well reflected the effect of Ca supply on Al sensitivity as revealed by root‐growth inhibition. Aluminum‐induced callose formation in root apices of 28 bean genotypes differing in Al resistance after 36 h Al treatment was positively correlated to Al‐induced inhibition of root elongation and Al contents in the root apices. However, the relationship was less close than previously reported for maize. Also, after 12 h Al treatment, callose formation and Al contents in root apices did not reflect differences in Al resistance between two contrasting genotypes, indicating a different mode of the expression of Al toxicity and regulation of Al resistance in common bean than in maize.     

Estimation of the rootzone depth above a gravel layer (in wild blueberry fields) using electromagnetic induction method

Wild blueberry (Vaccinium angustifolium Ait.) fields in the north east Canada are naturally grown in a course textured thin layer of soil and below this layer is a soilless layer of gravel. The root zone depth of this crop varies from 10 to 15 cm. Investigating the depth to the gravel layer below the course textured soil is advantageous, as it affects the water holding capacity of the root zone. Water and nutrient management are the two primary determinants of crop yield and the amount of leaching. The objective of this study was to estimate the depth to the gravel layer using DualEM-2 instrument. A C++ program written in Visual Studio 2010 was used to develop mathematical models for estimating the depth to the gravel layer from the outputs of DualEM-2 sensor. Two wild blueberry fields were selected in central Nova Scotia, Canada to evaluate the performance of DualEM-2 instrument in estimating the rootzone depth above the gravel layer. The mid points of squares created by grid lines were used as the sampling points at each experimental site. The actual depth to the interface was measured manually at selected grid points (n = 50). The apparent ground conductivity (EC_a) values of DualEM-2 were recorded and the depth to the interface was estimated for the same sampling points within the selected fields. The fruit yield samples were also collected from the same grid points to identify the impact of the depth to the gravel layer on crop yield. After calibrations, comprehensive surveys were conducted and the actual and estimated depths to the interface were established. The interpolated maps of fruit yield, and the actual (z_in) and estimated (\( {\text{z}}_{\text{in}}^{*} \)) depths to the interface were created in ArcGIS 10 software. Results indicated that the z_in was significantly correlated with \( {\text{z}}_{\text{in}}^{*} \) for the North River (R ² = 0.73; RMSE = 0.27 m) and the Carmel (R ² = 0.45; RMSE = 0.20 m) sites. Results revealed that the areas with shallow depth to the gravel layer were low yielding, indicating that the variation in the depth to the gravel layer can have an impact on crop productivity. Non-destructive estimations of the depth to the gravel layer can be used to develop erosion control strategies, which will result in an increased crop production.     

Physicochemical,including spectroscopic,and biological analyses during composting of green tea waste and rice bran

The aims of this study were to monitor the changes in physicochemical, including spectroscopic, and biological characteristics during composting of green tea waste–rice bran compost (GRC) and to define parameters suitable for evaluating the stability of GRC. Compost pile temperature reflected the initiation and stabilization of the composting process. The pH, electrical conductivity, NO₃ ⁻-N content, and carbon-to-nitrogen ratio were measured as chemical properties of the compost. The color (CIELAB variables), humification index (the absorption ratio Q _4/6 = A ₄₇₂ / A ₆₆₄ of 0.5 M NaOH extracts), absorption at 665 nm of acetone extracts, and Fourier-transform infrared (FT-IR) spectra were measured to evaluate the organic matter transformation; germination of komatsuna or tomato seeds was measured to assess the potential phytotoxicity of composting materials during composting. No single parameter was capable of giving substantial information on the composting process, the nutrient balance, phytotoxicity, and organic matter decomposition. The FT-IR spectra at 3,300, 2,930, 2,852, and 1,065 cm⁻¹ provided information on the molecular transformation of GRC during composting and they decreased over the composting. Most of the assayed parameters showed no further change after about 90 days of composting suggesting that GRC can be used for agricultural purposes after this period.