Cover illustration
In the semi-arid loess plateau areas of Northwest China, water is the limiting factor for rain-fed wheat yields. Genetic advances in grain yields under rain-fed conditions have been achieved with the introduction of Rht genes. This picture, which was taken in a field of semi-arid loess plateau area in Northwest China, displays a promising autumn harvest scene resulting from introducing specific dwarf genes into current wheat cultivars. This study reviewed the mechani [Detail] ...
Climate change has increased the risk of drought, which significantly limits plant productivity. Various ways of increasing water availability and sustaining growth of crop plants in drought-prone environments are available. Genetic advances in grain yields under rainfed conditions have been achieved with the introduction of dwarfing genes. A thorough understanding of the effects of different dwarfing genes on root growth, coleoptile length, grain yields and water using efficiency (WUE) will provide opportunities to select appropriate Rht genes for breeding high WUE and grain yield cultivars. This review focuses on the mechanism involved in Rht genes that reduce plant height and affect root and coleoptile length, their consequent effects on grain yields and WUE, and suggests that for rainfed and irrigation-limited environments, combining GAR and GAI dwarfing genes in breeding may help boost WUE and yields, and more materials from different parental sources should be collected to assess opportunities for potential comprehensive application of specific Rht genes.
Knowledge of the spatial distribution of soil textural properties is important for determining soil moisture storage and soil hydraulic transport properties. Capturing field heterogeneity without exhaustive sampling and costly sample analysis is difficult. Our objective was to employ electromagnetic induction (EMI) mapping in low apparent electrical conductivity (ECa) soils at varying soil water contents to capture time invariant properties such as soil texture. Georeferenced ECa measurements were taken using a ground conductivity meter on six different days where volumetric water content (θv) varied from 0.11 to 0.23. The 50 m × 50 m field included a subsurface gravelly patch in an otherwise homogeneous silt-loam alluvial soil. Ordinary block kriging predicted ECa at unsampled areas to produce 1-m resolution maps. Temporal stability analysis was used to divide the field into three distinct ECa regions. Subsequent ground-truthing confirmed the lowest conductivity region correlated with coarse textured soil parent materials associated with a former high-energy alluvial depositional area. Combining maps using temporal stability analysis gives the clearest image of the textural difference. These maps could be informative for modeling, experimental design, sensor placement and targeted zone management strategies in soil science, ecology, hydrology, and agricultural applications.
The effect of mulching with straw, white plastic film and black plastic film for improving soil water storage and on the soil properties was examined in a wheat-maize rotation system on Loess soil in northwestern China. All the mulches improved the water storage to some extent and led to warmer soils. However, the organic C and total N contents of the soils declined significantly under the mulches, particularly the plastic film mulches, and this could have long-term detrimental effects on soil quality and the sustainability of the some mulching practices.
Antitranspirants are exogenous substances applied to leaves to reduce luxury transpiration by regulating stomatal conductance to increase water use efficiency (WUE). A cheap and environmentally-friendly antitranspirant, FZ, was newly developed, extracted mainly from Alhagi sparsifolia. Its effects on soybean water use were investigated in a field experiment using the locally-used irrigation rate and a low irrigation rate (The lower and upper limit of irrigation is 40%–70% of field capacity). Foliar application of FZ and measurement of leaf physiological characteristics, final biomass, seed yield and water use efficiency were carried out during the pod bearing and pod filling stages of drip-irrigated soybean with film-mulching. Under the low irrigation rate, leaf stomatal conductance (gs) and transpiration rate (Tr) decreased significantly by 7 d after spraying, but photosynthesis (Pn) and instantaneous water use efficiency (WUEin) were not significantly affec ted. The stomatal frequency, stomatal aperture, gs, Tr and Pn decreased by 1 d after spraying, without significantly increasing WUEin. However, applying FZ during the pod bearing and pod filling stages did not significantly affect the final biomass, water consumption, seed yield and WUE of soybean. Under the locally-used irrigation rate, applying FZ increased the activities of superoxide dismutase and peroxidase in the leaves by 38% and 33%, respectively, but did not significantly affect gs, Tr, Pn, stomatal aperture and stomatal frequency. Applying FZ three times during pod bearing and pod filling stages enhanced seed yield and WUE by 24% and 21%, respectively, but did not significantly affect the final biomass and water consumption. Therefore, seed yield and WUE of soybean were significantly increased by foliar application of FZ during the pod bearing and pod filling stages under the locally-used irrigation rate in arid region, but applying FZ did not have a positive effect on water use efficiency of soybean under a low irrigation rate.
To determine the main parameters of droplet strike damage and avoid flower injury due to the unsuitable practices during sprinkler irrigation, an indoor experiment of irrigation droplet impact on cyclamen was conducted. The influences of different parameters such as droplet diameter, application intensity, specific power on flower strike damage was analyzed using Image Pro-Plus software to compute strike damage area and define damage level by sense-analysis. The results showed that a damage area of <1% represents a safe irrigation level, 1%–3% slight damage level, 3%–6% moderate damage level, and>6% heavy damage level. Equations of application intensity, specific power with sprinkler irrigation time and flower injury ratio were regressed against parameters which cause impact damages. The results indicated that specific power has a significant correlation with injury, and flower damage area increased as the increasing of the value of specific power for the same irrigation time. Application intensity was also correlated with injury when the droplet diameter was larger than 1 mm. When the duration of sprinkler irrigation was 1, 5 and 10 min, the threshold of impinging damage of application intensity was 25.30, 5.01 and 1.64 mm·h−1 and the specific power was 0.467×10−3, 9.340×10−3 and 3.110×10−3 W·m−2. These results provide a reference for determining the suitable values of sprinkler properties in operation design.
Due to varying crop responses to water stress at different growth stages, scheduling irrigation is a challenge for farmers, especially when water availability varies on a monthly, seasonal and yearly basis. The objective of this study was to optimize irrigation between the vegetative (V) and reproductive (R) phases of maize under different available water levels in Colorado. Long-term (1992–2013) scenarios simulated with the calibrated Root Zone Water Quality Model were designed to meet 40%–100% of crop evapotranspiration (ET) requirements at V and R phases, subject to seasonal water availabilities (300, 400, 500 mm, and no water limit), with and without monthly limits (total of 112 scenarios). The most suitable irrigation between V and R phases of maize was identified as 60/100, 80/100, and 100/100 of crop ET requirement for the 300, 400, 500 mm water available, respectively, based on the simulations from 1992 to 2013. When a monthly water limit was imposed, the corresponding suitable irrigation targets between V and R stages were 60/100, 100/100, and 100/100 of crop ET requirement for the above three seasonal water availabilities, respectively. Irrigation targets for producing higher crop yield with reduced risk of poor yield were discussed for projected five-year water availabilities.
This paper explores the effect of varying agricultural management practices on different water efficiency indicators: irrigation efficiency (IE), crop water use efficiency (WUE), and green and blue water footprint (WF). We take winter wheat in an experimental field in Northern China as a case study and consider a dry, average and wet year. We conducted 24 modeling experiments with the AquaCrop model, for all possible combinations of four irrigation techniques, two irrigation strategies and three mulching methods. Results show that deficit irrigation most effectively improved blue water use, by increasing IE (by 5%) and reducing blue WF (by 38%), however with an average 9% yield reduction. Organic or synthetic mulching practices improved WUE (by 4% and 10%, respectively) and reduced blue WF (by 8% and 17%, respectively), with the same yield level. Drip and subsurface drip irrigation improved IE and WUE, but drip irrigation had a relatively large blue WF. Improvements in one water efficiency indicator may cause a decline in another. In particular, WUE can be improved by more irrigation at the cost of the blue WF. Furthermore, increasing IE, for instance by installing drip irrigation, does not necessarily reduce the blue WF.
Severe resource shortage and waste of resource in agricultural production make it necessary to assess efficiency to increase productivity with high efficiency and ensure sustainable agricultural development. This paper adopted an input-oriented data envelopment analysis (DEA) method with the assumption of variable returns to scale to evaluate agricultural production efficiency of 100 major irrigation districts in Northwest China in 2010. Major findings of this paper were as follows: firstly, the average value of total technical efficiency, pure technical efficiency and scale efficiency of those irrigation districts in Northwest China were 0.770, 0.825 and 0.931, respectively; secondly, 30% of irrigation districts were technically efficient, while 42% and 32% of them showed pure technical and scale efficiency respectively. Among inefficient decision-making units, total technical efficiency score varied from 0.313 to 0.966, showing significant geographical differences, but geographical differences of pure technical efficiency was more consistent with that of total technical efficiency; thirdly, input redundancy was evident. Inputs of agricultural population, irrigation area, green water, blue water, consumption of fertilizer and agricultural machinery could be reduced by 34.88%, 40.19%, 43.85%, 47.10%, 41.53% and 42.21% respectively without reducing agricultural outputs. Furthermore, irrigation area, green water and blue water had relatively high slack movement though Northwest China which is short of water resources. Based on these results, this paper drew the following conclusions: First, there is huge potential for Northwest China to improve its agricultural production efficiency, and agro-technology not input scale had greater influence on improvement. Second, farmers needed proper guidance in order to reduce agricultural inputs and it is time to centralize agricultural management for overall agricultural inputs regulation and control.
Most animals, including humans, produce natural sex hormones such as estrogens: 17β-estradiol (E2) and estrone (E1). These compounds are able to disrupt the reproductive systems of living organisms at trace concentrations (ng·L − 1 ). This experiment tests the hypothesis that 1% slow pyrolysis biochar-amended sandy soil could retain significant amount of estrogens (E1, E2) from poultry manure in its second year of application. The experiment was conducted over 46 days and consisted of a series of lysimeters containing sandy soil with biochar-amended topsoil. The application rate of poultry manure was kept at 2.47 kg·m − 2 . The biochar held a significant concentration of hormone during the first year of its application. However, in the following year (current study), there was no significant retention of hormones in the biochar-amended soil. During the first year after application, the biochar was fresh, so its pores were available for hydrophobic interactions and held significant concentration of hormones. As time passed there were several biotic and abiotic changes on the surface of the biochar so that after some physical fragmentation, pores on the surface were no longer available for hydrophobic interactions. The biochar started releasing dissolved organic carbon, which facilitated greater mobility of hormones from poultry manure down the soil profile.
In semi-arid regions of the Loess Plateau, water deficiency restricts plant performance. Panicum virgatum (switchgrass), which is a highly versatile grass, had been introduced to the Plateau as a restoration species. To determine if prechilling stratification (PCS) and sulfuric acid scarification (SAS) can optimize establishment,P. virgatum cvs Pathfinder, Trailblazer and Alamo were tested under different ambient water potentials by measuring germination and root and shoot growth along water potential gradients under laboratory conditions. Both PCS and SAS improved total germination percentage (TGP), with PCS being more beneficial. The effect of PCS and SAS on mean germination time (MGT) weakened gradually with increasing drought stress. Both PCS and SAS showed no obvious effect on promoting root and shoot growth. Both PCS and SAS reduced base water potential requirement for reaching 50% germination of Pathfinder and Trailblazer, with this effect greater for PCS. These results indicate that embryo dormancy may be a major factor limiting germination ofP. virgatum under drought conditions. Pathfinder appears to be more suitable for a semi-arid environment, whereas Alamo appears to be unsuitable for drought conditions. Given the large difference between predicted value and measured value, the reliability and applicable scope of linear regression estimated Y50 needs further investigation, specification and optimization.
Five cotton cultivars and their parents were tested for induction of germination of Orobanche cumana Wallr. (sunflower broomrape) seeds in pot and field experiments. Germination rates induced by cotton root extracts were the highest followed by stem extracts then leaf extracts. Cotton seedlings at the six-leaf stage induced higher germination than seedling at the two- and four-leaf stage, in all five cotton cultivars and their parents. In the field, the highest concentration of cotton root extracts gave the highest germination rate of O. cumana, and the lowest concentration of cotton root extracts gave the lowest germination rate. Methanol extracts of cotton rhizosphere soil gave the highest germination of O. cumana. In general, the root, stem and leaf extracts were more active at the six-leaf stage than other seedling stages. In conclusion, extracts of cotton rhizosphere soil and tissues have high activity in the seedling stage. Extracts of cotton across the whole growing season were able to induce O. cumana germination but displayed significant cultivar interactions.