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Agricultural Water Management
Elsevier
Agricultural Water Management

Elsevier

0378-3774

Agricultural Water Management/Journal Agricultural Water ManagementSCIISTPEI
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    Estimation of soil moisture content under high maize canopy coverage from UAV multimodal data and machine learning

    Yin D.Nie C.Jin X.Jiao X....
    15页
    查看更多>>摘要：? 2022 Elsevier B.V.An accurate in-field estimate of soil moisture content (SMC) is critical for precision irrigation management. Current ground methods to measure SMC were limited by the disadvantages of small-scale monitoring and high cost. The development of unmanned aerial vehicle (UAV) platforms now provides a cost-effective means for measuring SMC on a large scale. However, previous studies have considered only single-sensor estimates of SMC, so the combination of multiple sensors has yet to be thoroughly discussed. Additionally, the way in which soil depth, canopy coverage, and crop cultivars affect the SMC-estimation accuracy remains unclear. Therefore, the objectives of this study were to (1) evaluate the SMC-estimation accuracy provided by multimodal data fusion and four machine learning algorithms: partial least squares regression, K nearest neighbor, random forest regression (RFR), and backpropagation neural network (BPNN); (2) discuss the accuracy of the remote-sensing approach for estimating SMC at different soil depths, and (3) explore how canopy coverage and crop cultivars affect the accuracy of SMC estimation. The following results were obtained: (1) Data from multispectral sensors provided the most accurate SMC estimates regardless of which of the four machine learning algorithms was used. (2) Multimodal data fusion improved the SMC estimation accuracy, especially when combining multispectral and thermal data. (3) The RFR algorithm provided more accurate SMC estimates than the other three algorithms, with the highest accuracy obtained by combining data from RGB, multispectral, and thermal sensors with an R2 = 0.78 (0.78) and a relative root-mean-square error of 11.2% (9.6%) for 10-cm-deep (20-cm-deep) soil. (4) UAV-based SMC-estimation methods provided similar, stable performance for SMC estimates at various depths and even yielded smaller relative error for deeper estimates (20 cm). (5) The RFR and BPNN machine learning algorithms both provided relatively accurate SMC estimates for modest canopy coverage (0.2–0.4) but relatively poor estimates for higher (>0.4) or lower (<0.2) canopy coverage. (6) The SMC-estimation accuracy for different maize cultivars (JNK728 and ZD958) did not differ significantly (P < 0.01). These results indicate that UAV-based multimodal data fusion combined with machine learning algorithms can provide relatively accurate and repeatable SMC estimates. This approach can thus be used to monitor SMC and design precision irrigation systems.
      原文链接:
    • NSTL
    • Elsevier

    Assessing soil water recovery after converting planted shrubs and grass to natural grass in the northern Loess Plateau of China

    Liu B.Jia Y.Jia X.Shao M....
    11页
    查看更多>>摘要：? 2022 Elsevier B.V.The Chinese Loess Plateau (CLP) is prone to adverse effects from drought, especially the widespread creation of a dried soil layer (DSL), a problem intensified by revegetation under the Grain for Green Program. Using 13-year soil moisture (SM) data, we compared soil water consumption by planted shrubs (Korshinsk peashrub, KOP), planted grass (purple alfalfa, ALF), and natural grass (NAG) from 2004 to 2016 in the CLP. To assess the soil water recovery processes, long-term (30 years) SM dynamics were simulated using the simultaneous heat and water (SHAW) model based on field data and local meteorological data under two scenarios (A: converting KOP to NAG and B: converting ALF to NAG). The results showed that the decline rates of SM in 1–4 m profiles for NAG (24.0–29.8%) were much lower than those for KOP (47.6–51.4%) and ALF (48.8–50.2%) during the 13-year growth period. Modelling SM dynamics at depths of 1–4 m for 30 years showed that SM gradually increased and that the DSL prevalence could be reduced under scenarios A and B. The complete elimination of DSL requires at least 6 years at 1–4 m under scenario A, 13 years at 2–4 m, and 22 years at 1–2 m under scenario B. Soil water restored to local stable soil water levels requires approximately 19, 13, and 15 years in the 1–2 m, 2–3 m, and 3–4 m profiles, respectively, under scenario A. Soil water recovery will take approximately 28 years in the 2–3 m profile and 27 years in the 3–4 m profile under scenario B. Our results enhance the understanding of the soil water depletion and recovery processes under different vegetation types and can could be used to provide scientific guidance for sustainable ecological restoration in the CLP.
      原文链接:
    • NSTL
    • Elsevier

    Supplemental irrigation increases grain yield, water productivity, and nitrogen utilization efficiency by improving nitrogen nutrition status in winter wheat

    Lin X.Wang W.Zhang B.Wang D....
    9页
    查看更多>>摘要：? 2022Supplemental irrigation (SI) is considered as one of the effective water management practices for improving grain yield and nitrogen utilization efficiency (NUtE) in winter wheat (Triticum aestivum L.). However, whether SI increases grain yield and NUtE by improving the N status in winter wheat is unclear. Based on a two-year field experiment (2017–2018, 2018–2019), we studied the effects of different levels of SI (i.e., no SI (J0), volumetric soil water content at100% field capacity at 20 cm (J20), and volumetric soil water content at 100% field capacity at 40 cm (J40)) and winter wheat cultivars (i.e., large spike-type Shannong23 (SN23) and multi spike-type Shannong29 (SN29)) on grain yield, NUtE and N status in winter wheat of the North China Plain. Our results indicated that, grain yield had a significant positive correlation with the amount of photosynthetic N (PN) at anthesis. With an increase in the N accumulation in shoots at anthesis (NAA), the amount of PN increased first and then remained stable, whereas the amount of reserve N (RN) increased continuously. Compared with SN29, SN23 allocated more N to PN and storage RN and less to structural N (SN) and accumulation RN at anthesis and had higher NUtE. Supplemental irrigation at jointing stage significantly increased the amount of NAA and pre-anthesis N redistributed to grains, and its contribution to grains, while the highest grain yield, NUtE, and water productivity (WP) were reached in J20 and not J40. WP was positively related to the amount of NAA and was also affected by the N nutrition index (NNI) at anthesis. The NNI of winter wheat under J20 treatment is optimal (approximated 1). In J40, with the higher irrigation amount, actual crop evapotranspiration (ETc act), the amounts of NAA and RN, and the NNI at anthesis increased further, but the amounts of PN and grain yield were not affected, which explained the reductions in NUtE and WP. Overall, moderate SI increased winter wheat grain yield and NUtE by improving N nutrition status as indicated by the NNI. And the NNI at anthesis is an important indicator to help manage irrigation and improve grain yield, NUtE, and WP in winter wheat on the North China Plain.
      原文链接:
    • NSTL
    • Elsevier

    A new approach for estimating spatial-temporal phreatic evapotranspiration at a regional scale using NDVI and water table depth measurements

    Zhao T.Zhu Y.Yang J.Mao W....
    21页
    查看更多>>摘要：? 2022 Elsevier B.V.Accurate estimation of the spatial-temporal distribution of phreatic evapotranspiration (ET) is critical for managing water resources and preventing soil salinization in arid and semiarid agricultural areas where substantial water-saving efforts are needed. Traditional phreatic ET estimation approaches either are for small scales or cannot consider spatial and/or temporal variations in phreatic ET. This study developed a new approach for estimating the spatial-temporal phreatic ET based on the normalized difference vegetation index (NDVI) and measured water table depths. The NDVI was used to calculate the actual evapotranspiration (ETc act) by scaling it with the reference crop evapotranspiration (ETo). The water table depths measured during the periods of no other factors (i.e., precipitation, irrigation and groundwater extraction) were used to establish an equation used to estimate the phreatic ET contribution coefficient (defined as the ratio of phreatic ET to the corresponding ETc act). To improve estimation accuracy, a time-related correction factor was considered in the equation for estimating the phreatic ET. The new approach was used to estimate monthly phreatic ET with a spatial resolution of 250 m in the Hetao irrigation district, located in arid Northwest China. The estimated phreatic ET at different spatial and temporal scales matched well with the groundwater balance model results. The results show that the spatial distribution of phreatic ET is affected by both natural factors (e.g., land cover types) and human activities (e.g., groundwater extraction, planted crops). In the Hetao irrigation district, phreatic ET contributes an average of 24.4% to ETc act during the non-freezing-thawing period (from June to November), demonstrating the essential role of phreatic ET in supporting crop growth and the general ecological environment in arid areas with shallow water table depths. The new approach of estimating spatial-temporal phreatic ET may be used for designing effective and efficient water resource management policies at the regional scale.
      原文链接:
    • NSTL
    • Elsevier

    Optimizing irrigation amount and potassium rate to simultaneously improve tuber yield, water productivity and plant potassium accumulation of drip-fertigated potato in northwest China

    Zhang S.Fan J.Zhang F.Wang H....
    13页
    查看更多>>摘要：? 2022 Elsevier B.V.High crop water productivity (WPc) and fertilizer use efficiency are the key to ensuring the sustainable development of agriculture in water-deficient areas, such as the northwest China. In order to determine the irrigation amount and potassium rate for optimizing potato yield, plant potassium accumulation and WPc of drip-irrigated potato, a two-year field experiment was conducted on the Loess Plateau of northwest China, with three irrigation levels (W1: 60% ETc, W2: 80% ETc and W3: 100% ETc, where ETc is the crop evapotranspiration) and four potassium levels (K0: kg ha?1, K1: 135 kg ha?1, K2: 270 kg ha?1 and K3: 405 kg ha?1). The results showed that leaf area index, chlorophyll content, aboveground dry matter, tuber yield, starch, vitamin C content and WPc generally increased with the increase of irrigation amount, while they first increased and then decreased with the increasing potassium rate. The trends of reducing sugar and potassium use efficiency were contrary to the above trends. The residue of available potassium in the soil increased with the increase of potassium rate, but decreased with the increase of irrigation amount. Irrigation amount and potassium rate had interaction effects on chlorophyll content, dry matter, tuber yield, reducing sugar, plant potassium accumulation and potassium use efficiency. To ensure high-yield, high-quality, water-saving and fertilizer-saving potato production, a water input (irrigation plus effective rainfall) range of 498–520 mm combined with a potassium rate range of 201–393 kg ha?1 was recommended. These results can provide a theoretical basis for the rational application of irrigation water and potassium fertilizer to improve tuber yield, quality and soil environment of drip-irrigated potato in northwest China.
      原文链接:
    • NSTL
    • Elsevier

    Increasing available water capacity as a factor for increasing drought resilience or potential conflict over water resources under present and future climate conditions

    Brazdil R.Maca P.Eitzinger J.Trnka M....
    16页
    查看更多>>摘要：? 2022The close relationship between the onset and severity of agricultural and hydrological drought is considered self-evident, yet relatively few studies have addressed the effects of applying agricultural drought adaptation to hydrological drought characteristics. The present study applies a model cascade capable of simultaneously considering the interactions between agricultural and hydrological droughts. The study area covers all river basins in the Czech Republic and includes the periods of 1956–2015 (baseline) and 2021–2080 (future). The model cascade was shown to explain 91% of the variability in the seasonal and annual accumulated runoff and allows for the analysis of increasing/maintaining/decreasing available water capacity (AWC) across the 133 defined basins with a total area of c. 78,000 km2. The study reports that the probability and extent of agricultural drought increased over the entire period with higher AWC scenario showing slower pace of such increase especially from April to June. The trends in the extent or severity of hydrological droughts were of low magnitude. The future climate has been projected through the use of ensembles of five global (CMIP5) and five regional (EURO-CORDEX) climate models. The results showed a significant increase in the duration of agricultural drought stress and in the area affected throughout the year, particularly in July–September. The hydrological drought response showed a marked difference between areas with a negative and positive climatic water balance, i.e., areas where long-term reference evapotranspiration exceeds long-term precipitation (negative climatic water balance) and where it does not (positive climatic water balance). The overall results indicate that increasing soil AWC would decrease the frequency and likely also impact of future agricultural droughts, especially during spring. This result would be especially true if the wetter winters predicted by some of the models materialized. Hydrological droughts at the country level are estimated to become more pronounced with increasing AWC, particularly in catchments with a negative climatic water balance.
      原文链接:
    • NSTL
    • Elsevier

    Improving wheat yield by optimizing seeding and fertilizer rates based on precipitation in the summer fallow season in drylands of the Loess Plateau

    Qiu W.Ma X.Cao H.Huang T....
    9页
    查看更多>>摘要：? 2022 Elsevier B.V.Precipitation has been recognized as the dominant factor driving crop grain yields and large yield variations in drylands, which suggests that some agricultural management practices can be optimized to achieve high yields and benefits. In this study, we investigated 804 farmers' wheat fields from 2015 to 2018 in the dryland area of the Loess Plateau in China and analyzed the relationships between wheat yield and the influence factors (including precipitation, wheat sowing rate, fertilizer inputs, and soil nutrients) to propose optimized agricultural management practices for wheat production. The results showed that wheat grain yield followed a linear plateau pattern relative to the precipitation in the summer fallow season, with a yield of 5344 kg ha?1 obtained at a precipitation of 203 mm. In the L203 group (precipitation in the summer fallow season less than 203 mm), the Low-yield subgroup (0–33th in grain yield group (in order from low to high)) had a lower sowing rate, kernel weight, kernel number and spike number than the High-yield subgroup (68–100th in grain yield group); different levels of phosphorous (P) and potassium (K) fertilizer overuse were found among the three yield subgroups. However, in the H203 group (precipitation in the summer fallow season greater than 203 mm), differences in only kernel and spike numbers and nitrogen (N) fertilizer application rate were observed among the Low-, Moderate-, and High-yield subgroups. Additionally, there were no differences in the soil organic matter (SOM), total N or pH in the three subgroups in either L203 or H203, but significant differences in soil mineral N, available P and K were observed among the three subgroups (except mineral N in L203). Based on these results, the wheat sowing rate and fertilizer input rates can be optimized to increase wheat yield and farmers’ income and promote agricultural management for dryland wheat production on the Loess Plateau.
      原文链接:
    • NSTL
    • Elsevier

    Environmental and biophysical effects of evapotranspiration in semiarid grassland and maize cropland ecosystems over the summer monsoon transition zone of China

    Li H.Yue P.Zhang Q.Ren X....
    15页
    查看更多>>摘要：? 2022 The AuthorsAccurate quantification of semiarid energy partitioning and actual evapotranspiration (ETc) is necessary to understand the variability in regional energy and the water cycle, which is expected to intensify under climate change. The seasonal and interannual variability in surface energy and ET and its responses to environmental and biophysical factors of grassland and cropland with maize (Zea mays), and ecosystems over the East Asian summer monsoon transition zone of China, were investigated using multiyear (2003–2008) eddy covariance measurements. The study sites received 65–84% of the annual precipitation (Pr) during the East Asian summer monsoon (EASM; June–August), with the lowest values in the weak EASM years of 2004 and 2007. Seasonal and interannual variations in the portioning of net radiation to turbulent fluxes were mainly controlled by Pr via changes in soil water content (SWC) and vegetation growth. Drastic changes in the Bowen ratio, vegetation growth, and energy fluxes occurred after the onset of EASM. During the cool winter and dry spring and autumn, the sensible heat flux was the largest component of the energy balance, and the latent heat flux dominated during warm and wet periods of summer. Monthly ET was 24.8 and 25.6 mm for the grassland and cropland, respectively, and they peaked at 89.0 mm and 113.9 mm, respectively, in July. Monthly ET was positively correlated with monthly Pr, Ta, the soil water drought stress index, normalized difference vegetation index (NDVI), the surface conductance (Gs), and the Priestley–Taylor coefficient (ET/ETeq) during the growing seasons (April–September). Annual ET varied from 215 to 373 mm in grassland and from 227 to 390 mm in cropland, with the lowest value during the severe drought year of 2007. Interannual variations in ET were primarily controlled by annual effective precipitation frequency, and interannual variations in summer ET were modulated by the summer monsoon duration period through changes in summer Pr, SWC, and vegetation growth.
      原文链接:
    • NSTL
    • Elsevier

    Farmers’ incremental adaptation to water scarcity: An application of the model of private proactive adaptation to climate change (MPPACC)

    Zobeidi T.Yaghoubi J.Yazdanpanah M.
    11页
    查看更多>>摘要：? 2022To support effective adaptation in the agriculture sector through policy and practice, it is essential to know how farmers, as the primary decision-makers regarding land use, understand and respond to water scarcity. Using the model of private proactive adaptation to climate change (MPPACC) as a basic framework for the study, the research investigated the effects of cognitive factors on maladaptation in farmers’ incremental adaptation to water scarcity as a climate risk. Data were collected during face-to-face interviews with 250 farmers of irrigated lands in Khuzestan province, Iran. The structural equation modeling results showed that the research model predicted 49% of the variance in adaptive behavior and 24% of the variance in maladaptation. These results provide strong empirical evidence for the hypothesis that maladaptation has an important and negative effect on determining adaptive behaviors (β = ?.33). Moreover, perceived susceptibility (β = ?.42, β =.38), perceived cost (β = ?.21, β = ?.32), and perceived self-efficacy (β =.31, β = ?.29) directly affected both adaptive behavior and maladaptation. This study contributes to the literature by: i) adding to the limited number of studies on the MPPACC; ii) confirming the efficiency of this model in the water scarcity context, as the MPPACC can be used to understand behavior of people faced with an environmental threat; and iii) improving knowledge regarding the impact of belief in climate change on the constructs of the MPPACC.
      原文链接:
    • NSTL
    • Elsevier

    Soil water and salinity dynamics under the improved drip-irrigation scheduling for ecological restoration in the saline area of Yellow River basin

    Dong S.Wang G.Ma Q.Kang Y....
    11页
    查看更多>>摘要：? 2022The drip-irrigation scheduled by different soil matric potential (SMP) thresholds at different stages according to soil water and salt management purposes was usually adopted for revegetation in saline-alkali land. To reveal the desalinization mechanism of this multi-stage drip-irrigation scheduling, a 3-year field trial, adopting this method for revegetation, was conducted in an arid saline area. The trial consisted of 5 irrigation treatments marked S1-S5, with their SMP that monitored directly under drip emitter at 0.2 m depth correspondingly controlled higher than ? 5, ? 10, ? 15, ? 20 and ? 25 kPa. Results showed the SMP threshold of ? 5 kPa during the unified irrigation stage induced a leaching fraction (LF) of 42.6% and a minimum recharge amount (MRA) from groundwater of zero, thus resulting the relative desalinization rate (RDR) of 91.8% in 0–120 cm soil layer. When treatment applied, the average electrical conductivity of the saturated soil extracts (ECe) in 0–40 cm among three growing seasons in S1-S5 treatments linearly increased from 0.90 to 1.73 dS/m as SMP threshold decreased from ? 5 to ? 25 kPa, resulting from the LF correspondingly decreasing from 18.4% to 2.5% and the MRA increasing from 0 to 21.4 mm. The inter-annual salt dynamic indicated a salt equilibrium state was formed in 80–120 cm soil layer when the SMP threshold was set higher than ? 10 kPa and that was formed in 40–80 cm soil layer if the SMP threshold was set between ? 20 and ? 15 kPa. This study found the SMP threshold controlled the LF and MRA, and eventually determined the dynamics of soil salinity, which explained the efficient desalinization mechanism under the multi-stage drip-irrigation scheduling. A key SMP threshold of ? 5 kPa for rapid soil leaching stage and that of ? 20 kPa for precise salt regulating stage were recommended for vegetation construction in the low-lying saline area.
      原文链接:
    • NSTL
    • Elsevier