Evaluating deficit irrigation management strategies for grain sorghum using AquaCrop

Many wells in the US Central Plains can no longer meet full crop water requirements due to declines in Ogallala aquifer water levels. A study was conducted in Southwest Kansas to determine optimum limited irrigation strategies for grain sorghum. Objectives were to (1) calibrate and validate the AquaCrop model, (2) apply AquaCrop to assess the effect of varying climate, planting dates, and soil types on yield, and (3) evaluate water productivities and optimal irrigation needs. Experimental data of grain sorghum were used to calibrate and validate AquaCrop. Planting date was found to substantially affect biomass and grain yield, and hence, considerably affect water productivities. The highest grain water productivities were obtained with late planting in a wet season. Late planting was associated with lower irrigation requirements. Depending on local conditions, we recommend planting to occur between June 1st and June 10th. Grain sorghum yield was optimized on sandy soils of southwestern Kansas with irrigation of 100–275 mm for early, 150–275 mm for normal and 100–275 mm for late planting. The optimal irrigation on silt loam soils for the corresponding planting dates were 175–350, 175–250 and 125–250 mm, respectively, with the lowest and highest in the range being for the wet and dry climate season conditions. Fluctuations in grain sorghum prices had a substantial impact on economic water productivity. Overall planting grain sorghum under optimum conditions combined with deficit irrigation improved water productivity.     

Validation and testing of the AquaCrop model under full and deficit irrigated wheat production in Iran

Accurate crop development models are important tools in evaluating the effects of water deficits on crop yield or productivity and predicting yields to optimize irrigation under limited available water for enhanced sustainability and profitable production. Food and Agricultural Organization (FAO) of United Nations addresses this need by providing a yield response to water simulation model (AquaCrop) with limited sophistication. The objectives of this study were to evaluate the AquaCrop model for its ability to simulate wheat (Triticum aestivum L.) performance under full and deficit water conditions in a hot dry environment in south of Iran, to study the effect of different scenarios of irrigation (crop growth stages and depth of water applied) on wheat yield. The AquaCrop model was evaluated with experimental data collected during the three field experiments conducted in Ahvaz. The AquaCrop model was able to accurately simulate soil water content of root zone, crop biomass and grain yield, with normalized root mean square error (RMSE) less than 10%. The analysis of irrigation scenarios showed that the highest grain yield could be obtained by applying four irrigations (200 mm) at sowing, tillering, stem elongation and flowering or grain filing stages for wet years, four irrigations (200 mm) at sowing, stem elongation and flowering stages for normal years and six irrigations (300 mm) at sowing, emergence, tillering, stem elongation, flowering and grain filing stages for dry years. The least amount of irrigation water to provide enough water to response to evaporative demand of environment and to obtain high WUE for wet, normal and dry years were 100, 200 and 250 mm, respectively.     

不同生育期水分亏缺对春青稞水分利用和产量的影响

对不同生育期水分亏缺程度对春青稞(Hordeum vulgare)水分利用效率和产量的影响进行了桶栽试验研究。试验处理设充分灌溉处理(2个水分控制下限和秸秆覆盖)以及在全生育期和5个不同生育期的4个水分亏缺程度(轻度、中度、重度和极度)处理,共27个处理。结果表明,在充分灌溉条件下,75%田间持水率水分下限控制处理的春青稞收获指数、籽粒产量和作物水分利用效率大于80%水分处理;秸秆覆盖处理的籽粒产量和水分利用效率在所有试验处理中最大。在全生育期水分亏缺条件下,春青稞籽粒产量均小于充分灌溉处理,且随着水分亏缺程度的增大而显著减小;轻度至重度水分亏缺处理可获得更大的作物收获指数和水分利用效率,但极度水分亏缺却导致最低的籽粒产量、收获指数和水分利用效率。除成熟期水分亏缺处理外,不同生育期水分亏缺处理条件下,春青稞籽粒产量和作物水分利用效率基本随着水分亏缺程度的增大而减小;拔节期、分蘖期和灌浆期水分亏缺对籽粒产量的不利影响较大。地表秸秆覆盖或全生育期轻度至重度水分亏缺处理可提高春青稞水分利用效率。     

华北典型区冬小麦区域耗水模拟与灌溉制度优化

以经校验Aquacrop模型模拟了不同土壤条件下冬小麦水分与产量响应关系,结合北京大兴区土壤分布及其冬小麦实际种植情况,对模型模拟结果进行区域尺度拓展,以此为基础分析了研究区不同灌溉制度下冬小麦耗水量、产量及水分生产率的变化规律,并推荐了与华北地区水资源实际情况相适宜的冬小麦亏缺灌溉制度。结果表明:应用Aquacrop模型能较好模拟冬小麦生育期内土壤墒情和冠层覆盖度的动态变化过程及其生物量与产量情况,可利用经校验后的模型进行冬小麦水分与产量响应关系研究。灌溉定额在300 mm范围内,随着灌溉量增加,耗水量增大;在灌水次数相同条件下,灌溉日期不同,因蒸腾量变化导致耗水量差异显著。在相同处理下总体上降水多年份产量较高,而不同处理之间随着灌溉量增加产量增大;在灌水次数相同情况下,灌溉关键生育时段选择对冬小麦产量形成及水分生产率提高至关重要。以冬小麦增产提效为原则,在灌1水情况下重点保障拔节-抽穗阶段的需水;灌2水情况下重点保障返青-拔节、抽穗-乳熟阶段需水;灌3水情况下重点保障返青-拔节、拔节-抽穗、抽穗-乳熟阶段需水。针对华北水资源严重短缺实际,建议北京大兴区冬小麦采用灌2水的亏缺灌溉制度,较灌4水情况下的灌溉量与耗水量分别减少140、65 mm,能确保75%产量。可见,在与华北类似的资源性缺水区域,选择适宜亏缺灌溉制度,能大幅降低区域灌溉量与耗水量,在稳定区域冬小麦产量及涵养地下水源方面具有重要的现实意义。     

Soil texture, climate and management effects on plant growth, grain yield and water use by rainfed maize–wheat cropping system: Field and simulation study

In sub-mountain tract of Punjab state of India, maize (Zea mays, L.) and wheat (Triticum aestivum L.) crops are grown as rainfed having low crop and water productivity. To enhance that, proper understanding of the factors (soil type, climate, management practices and their interactions) affecting it is a pre-requisite. The present study aims to assess the effects of tillage, date of sowing, and irrigation practices on the rainfed maize–wheat cropping system involving combined approach of field study and simulation. Field experiments comprising 18 treatments (three dates of sowing as main, three tillage systems as subplot and two irrigation regimes as the sub-subplot) were conducted for two years (2004–2006) and simulations were made for 15 years using CropSyst model. Field and simulated results showed that grain yields of maize and wheat crops were more in early July planted maize and early November planted wheat on silt loam soil. Different statistical parameters (root mean square error, coefficient of residual mass, model efficiency, coefficient of correlation and paired t-test) indicated that CropSyst model did fair job to simulate biomass production and grain yield for maize–wheat cropping system under varying soil texture, date of planting and irrigation regimes.     

Using AquaCrop to derive deficit irrigation schedules

Straightforward guidelines for deficit irrigation (DI) can help in increasing crop water productivity in agriculture. To elaborate such guidelines, crop models assist in assessing the conjunctive effect of different environmental stresses on crop yield. We use the AquaCrop model to simulate crop development for long series of historical climate data. Subsequently we carry out a frequency analysis on the simulated intermediate biomass levels at the start of the critical growth stage, during which irrigation will be applied. From the start of the critical growth stage onwards, we simulate dry weather conditions and derive optimal frequencies (time interval of a fixed net application depth) of irrigation to avoid drought stress during the sensitive growth stages and to guarantee maximum water productivity. By summarizing these results in easy readable charts, they become appropriate for policy, extension and farmer level use. We illustrate the procedure to derive DI schedules with an example of quinoa in Bolivia. If applied to other crops and regions, the presented methodology can be an illustrative decision support tool for sustainable agriculture based on DI.     

AquaCrop模型的适用性及应用初探

AquaCrop模型是FAO新推出的以水分为驱动的作物生长模型。为了评价其在华北地区的适用性,于2009-2010年在中国水利水电科学研究院大兴试验站进行了夏玉米水分处理试验,其中2010年的试验数据用于参数率定,2009年的试验教据用于模型验证,并在此基础上对模型参数进行敏感性分析。结果表明,AquaCrop模型能够...     

A model for assessing crop response to salinity

CropSyst, a management-oriented crop growth model, was modified to assess crop response to salinity. The effect of salinity was included in the existing water uptake module by adding an osmotic component to the soil water potential and developing a function to account for salinity effects on root permeability. The effect of salinity on water uptake is the link to simulate crop growth reduction. A qualitative analysis showed that the model simulated expected trends of crop response to salinity as affected by cultivar tolerance, atmospheric vapor pressure deficit, and soil water availability. Comparisons with data from sprinkler line experiments were performed for barley grown at Zaragoza (Spain) in 1986 and 1989, and corn at Davis, Calif. and Fort Collins, Colo. in 1975. These experiments included different salinity and irrigation levels. At Davis, the model simulated well the effect of salinity/irrigation treatments on water use, biomass, and crop yield, with values for the Willmot index of agreement (d) generally better than 0.94 (a value of 1.0 implying perfect agreement). At Fort Collins, simulation of grain yield was less satisfactory (d fluctuated between 0.83 and 0.90), but the agreement was good for crop water use and biomass (d generally better than 0.96). The lower performance for grain yield was attributed to large and erratic variations in the observed harvest index. The agreement between simulated and observed values tended to be lower at Zaragoza, with d values fluctuating between 0.84 and 0.91 for biomass and yield in the 2 years included in this evaluation. Unusually high measured yields in 1989 and erratic variation in 1986 were attributed to small sample size. The small size (increased measurement error) of samples typically obtained in sprinkler line source experiments tends to limit their use for evaluation of simulation models.     

Assessment of the FAO AquaCrop model in the simulation of rainfed and supplementally irrigated maize, sugar beet and sunflower

Farming in Serbia is traditionally rainfed. Analyses show that drought events of varying severity are frequent in this region, although there is no specific pattern. There is a distinct need for an objective assessment of the impact of drought on strategic field crops, to solve the dilemma whether irrigation is required or not. For this reason, and based on available field data, the FAO AquaCrop water driven model was selected to simulate yield and irrigation water use efficiency (IWUE) for three major field crops (maize, sunflower, and sugar beet), under two scenarios: (1) natural water supply and adequate supply of nutrients, and (2) supplementary irrigation and adequate supply of nutrients. The experiments presented here were conducted between 2000 and 2007 in northern Serbia, where chernozem soil is prevalent. Data of 2003 cropping seasons were used for local calibration, whereas the remaining years for validation. Results were such that local calibration resulted in very minor changes of AquaCrop coefficients (e.g., maize basal crop coefficient, sunflower harvest index, etc.). Simulated maize yield levels exhibited the greatest departure from measured data under irrigation conditions (−3.6 and 3.3% during an extremely dry and an extremely wet year, respectively). Simulated sunflower yield levels varied by less than 10% in 8 out of 10 comparisons. The most extreme variation was noted during the extremely wet year. The difference between simulated and measured values in the case of sugar beet was from −10.2 to 12.2%. Large differences were noted only in two or three cases, under extreme climatic conditions. Statistical indicators - root mean square error (RMSE) and index of agreement (d) - for all three crops suggested that the model can be used to highly reliably assess yield and IWUE. This conclusion was derived based on low values of RMSE and high values of d (in the case of maize and sugar beet 0.999 for both yield and IWUE, and in the case of sunflower 0.999 for yield and 0.884 for IWUE). It is noteworthy that under wet conditions, the model suggested that sunflower and sugar beet do not require irrigation, as confirmed by experimental research. These data are significant because they show that the AquaCrop model can be used in impartial decision-making and in the selection of crops to be given irrigation priority in areas where water resources are limited.     

Effects of different water supply regimes on water use and yield performance of spring wheat in a simulated semi-arid environment

This research explores the limited irrigation strategies based on root-to-shoot communication that exists in spring wheat, and examines the effects of root-sourced signals on water use and yield performance of three genotypes of spring wheat (Triticum aestivum) under three different irrigation regimes. Four treatments, CT (well-watered management), DIu (supplying water to the upper layer to maintain soil moisture in the entire pot at 50–60% of field water capacity (FWC)), and DId (supplying water to the lower layer to maintain soil moisture in the entire pot at 50–60% FWC), were employed. The treatment DIu was used to simulate frequent post-sowing irrigation with small amount of water in each time, and DId was used to simulate pre-sowing irrigation with the same amount of water. Plants were grown in cylinder pots outdoors. A non-hydraulic root signal was induced from seedling to tillering stage in the treatment DId. But after the jointing stage, the signal resulted in a reduction in root biomass and root length in the upper layer and an increase in root biomass and root length in the middle layer as compared with the treatment DIu. The water use efficiencies of the three genotypes were the highest in the treatment DId and the lowest in the treatment DIu for the genotypes A and C. This suggests that under the conditions of the same amount of water supply frequent post-sowing irrigation to the upper soil layer had lower water use efficiency and grain yield, whereas pre-sowing irrigation to the lower soil layer tended to have higher grain yield and higher water use efficiency.     

Water use and water-use efficiency of wheat and barley in relation to seeding dates,levels of irrigation and nitrogen fertilization

Response of timely and late seeded wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) to three levels of irrigation and four rates of nitrogen was investigated under pre-seeding irrigation. Water extraction pattern and water use of these crops varied markedly. Barley outyielded wheat by 27 and 9%, but used 9 and 21 mm less water, when one and two irrigations were given at critical stages, respectively. These results indicate the possibilities of considerable saving of water (100 mm) for barley without any decrease in grain yield and increased water-use efficiency (WUE) of wheat and barley by irrigating at critical stages as compared to irrigation at 75% depletion of available soil water (ASW). In general WUE decreased with increase in irrigation frequency and delay in seeding.Nitrogen fertilization with marginal additional water use (4–9%) increased yield linearly (45–98%) and thus increased WUE of wheat and barley. This additional water was extracted from below 60 cm depth at tensions ? 1.5 MPa and particularly in maximum growth and reproductive stages. These results suggest that barley should be preferred to wheat under medium to severe water stress and late seeding conditions.     

改进CERES-Maize模型在玉米膜下滴灌模式下的适用性

针对CERES-Maize模型没有覆膜处理模块而无法从机理上实现对覆膜玉米生长发育及产量形成过程进行模拟的问题,依据作物生长发育的有效积温原理,利用膜地增温对有效气积温的补偿效应,量化覆膜地温对气温的补偿值,改进模型气象模块中的气温输入数据,同时将模型中影响腾发量及水量平衡计算的冠层能量消光系数K调整为0.5,构建了适宜于膜下滴灌的改进型CERES-Maize模型,并依据2014和2015年膜下滴灌玉米田间试验数据对改进模型进行验证.结果表明覆膜地积温对气积温的增温补偿系数C_c:播种-出苗期为0.45,出苗~抽雄前期为0.20;随着K降低,地上生物量与籽粒产量的相对误差绝对值ARE降低并趋近于0;改进后的模型能够较好地模拟覆膜玉米开花期天数、成熟期天数、收获期地上生物量和籽粒产量,其模拟值和实测值的ARE分别为0.58%,0.37%,7.65%和16.95%,相对均方根误差RRMSE分别为0.84%,0.51%,8.75%和17.50%.     

Genotypic differences of maize in grain yield response to deficit irrigation

This study was undertaken to investigate genotypic differences of five maize cultivars in grain yield response to two different modes of deficit irrigation, conventional deficit irrigation and partial root zone irrigation. Three irrigation treatments were implemented: (1) FULL irrigation, the control treatment where plant water requirement, 100% Class-A pan evaporation, was fully met and the furrows on both sides of the plant rows were irrigated; (2) partial root zone irrigation (PRI), 35% deficit irrigation, compared to FULL treatment, was applied in every other furrow thus irrigating only one side of the plant rows. The furrows irrigated were alternated every irrigation; (3) conventional deficit irrigation (CDI), the same amount of water as PRI was applied in furrows on both sides of the plant rows, similar to FULL irrigation treatment. Five maize cultivars (P.31.G.98, P.3394, Rx:9292, Tector and Tietar) showing extreme growth response to water stress were selected out of ten cultivars tested with earlier completed greenhouse-pot experiment. A split-plot experimental design, comprising three irrigation treatments and five maize cultivars with four replicates, was used during two years of work, in 2005 and 2006. Total of nine irrigations, with one-week irrigation interval, were annually applied using a drip-irrigation system. Soil water status was monitored using a neutron moisture gauge, in addition to measuring leaf water potential and above-ground biomass production throughout the growing season. Grain yield and other yield attributes were measured at harvest as well as assessing differences in plant root distributions. Decrease in grain yield and harvest index of the tested cultivars, compared to FULL treatment, was proportionally less under PRI than CDI. Whether or not a significant yield advantage can be obtained under PRI compared to CDI showed significant (P < 0.05) genotypic variability. Tector and Tietar among the tested cultivars of maize showed significantly higher grain yield (P < 0.05) under PRI than CDI. The yield advantage of the genotypes (P.3394 and Tector) under PRI compared to CDI seems related to their enhanced root biomass developed under PRI.     

冬小麦生物量和产量的AquaCrop模型预测

以华北地区冬小麦为研究对象,将AquaCrop作物生长模型应用到滴灌、喷灌、漫灌中,对模型主要参数如气象、土壤、作物特性等进行调整,并对作物产量和生物量模拟的有效方法进行了研究。模拟结果表明,产量和收获时地上部分生物量的模拟值与实测值较为接近且略高于实测值,模型性能指数均高于0.95。产量模拟效果优于生物量,滴灌模拟效果最好。     

不同水分条件下秸秆覆盖对冬小麦生长的影响

在充分灌溉、轻度水分胁迫和重度水分胁迫条件下,秸秆覆盖可以有效降低作物需水量,同无秸秆覆盖对照相比分别降低了14.42%、9.58%和6.47%。秸秆覆盖可以提高土壤的保墒作用;各种水分条件下,秸秆覆盖对于作物产量都有着显著影响。     

Modeling the potential for closing quinoa yield gaps under varying water availability in the Bolivian Altiplano

In the Bolivian Altiplano, the yields of rainfed quinoa are relatively low and highly unstable. We use a validated crop water productivity model to examine the potential of closing quinoa yield gaps in this region. We simulate the expectable yields under rainfed cultivation and under different deficit irrigation (DI) strategies using the AquaCrop model for the Northern, Central and Southern Bolivian Altiplano. Simulated DI scenarios include a reference strategy avoiding stomatal closure during all sensitive growth stages and allowing drought stress during the tolerant growth stages (DI₀) and various restrictive deficit irrigation strategies (DI_i) representing cases when water resources are limited. We obtain a logistic crop water production function for quinoa by plotting the seasonal actual evapotranspiration versus total grain yield. Due to the large scatter, this function only indicatively provides expectable yields. From the scenario analysis, we derive yield probability curves for the 3 agro-climatic regions. DI, without restriction in irrigation water during the drought sensitive growth stages, is able to close the yield gaps in the Northern, Central and Southern Bolivian Altiplano, and would guarantee a high and stable level of water productivity (WP). The yields of quinoa under rainfed cultivation during dry years are only 1.1, 0.5 and 0.2 Mg ha⁻¹ in the Northern, Central and Southern Bolivian Altiplano, whereas under DI₀ they are 2.2, 1.6 and 1.5 Mg ha⁻¹, respectively. Under limited water availability for irrigation, these stable yield levels decrease, most drastically in the Southern Bolivian Altiplano. Below a minimum water availability of 600 m³ per ha and 700 m³ per ha in the Central and Southern Bolivian Altiplano, respectively, the application of DI for quinoa is not significantly effective and should be avoided to save valuable resources. The yield probability curves we derive can serve as input for stochastic economic analysis of DI of quinoa in the Bolivian Altiplano.     

Calibration and use of CROPGRO-soybean model for improving soybean management under rainfed conditions

Crops such as soybean (Glycine max L.) are grown predominantly under rainfed conditions where water is a major limiting factor and the interannual variability in rainfall pattern is high. Crop modeling has proven a valuable tool to evaluate the long-term consequences of weather patterns, but the candidate crop models must be tested and calibrated for new regions prior to their use as extrapolation tools to predict optimum cultivar choice and sowing dates. The objectives of this paper were to calibrate the CROPGRO-soybean model for growth and yield under rainfed conditions in Galicia, northwest Spain, and then to use the calibrated model to establish the best sowing dates for three cultivars at three locations in this region. The starting point of the calibration process was the CROPGRO-soybean version previously calibrated for non-limiting water conditions. The original model, when simulated versus rainfed soybean field data sets, tended to simulate more severe water stress than actually occurred. In order to calibrate growth and yield for the actual soil we tried several ways for the modelled crop to have access to more water. Modifications were made on soil depth, water holding capacity, and root elongation rate. In addition, other changes were made to predict accurately the observed water-stress induced acceleration of maturity. Long-term simulations with recorded weather data showed that soybean is more sensitive to planting date under irrigated than rainfed management, in the three studied Galician locations.     

垄作小麦产量及水分生产效率的试验研究

为探讨豫西地区冬小麦节水栽培的生产措施,在大田试验条件下,研究了在3种灌水处理下,垄作冬小麦耗水量、干物质积累、产量和水分生产效率的对比情况。结果表明,在不同灌水次数的条件下,随着灌水次数的增加,垄作冬小麦耗水量和地上干物质积累量逐渐增加,产量和水分生产效率先升高后降低。在相同灌水次数下,垄作冬小麦耗水量低于平作,干物...     

Deficit irrigation under water stress and salinity conditions: The MOPECO-Salt Model

In both arid and semi-arid areas the use of saline water for irrigation is a common practice, even though it may cause a drop in crop yield and progressive soil salinization. In order to determine the most suitable irrigation strategy for higher yield, profitability, and soil salinity management of certain crops, the MOPECO-Salt Model has been developed. This model was first validated in the Eastern Mancha Agricultural System in Albacete (Spain) through a test carried out on onion crop in April-September 2009, where the simulated yield was 2% lower than the observed one. The model was then tested at Tal Amara Research Station in the Central Bekaa Valley Agricultural System (Lebanon) using data from a 5-year experiment on the effects of deficit irrigation on two cultivars of potato (Spunta: July-October 2001, and June-September 2002; and Agria: March-August 2004, 2005, and 2007). Furthermore, these results were compared with those obtained through AquaCrop, which does not currently assess crop response to salinity. Differences between observed and simulated yields were lower than 3% for MOPECO-Salt and up to 12% for AquaCrop. According to findings from simulations, the irrigation strategies without leaching fraction employed in both areas are remediable since the off-season rainfall is sufficient to wash out soluble salts supplied with irrigation water. Results showed that as much as 14.4% water could be saved when this strategy was adopted for onion crops.     

滴灌施肥下水氮供应对夏玉米产量、硝态氮和水氮利用效率的影响

【目的】寻找滴灌夏玉米最佳施氮量。【方法】本试验在测坑-防雨棚设施条件下进行,试验设置2个灌水定额,分别为50 mm(WH为充分灌溉)25 mm(WL为限水灌溉);4个氮肥水平,即0、90、180、270 kg/hm~2,分别以N0、N1、N2和N3表示。采用完全区组设计,共计8个处理,3次重复。研究了滴灌施肥条件下,灌水定额和氮肥互作对土壤水分消耗、NO3--N运移积累以及夏玉米产量和水氮利用效率的影响。【结果】灌水、氮肥及其交互作用均显著影响夏玉米地上部干物质量、籽粒产量和水氮利用效率。限水灌溉条件下,玉米拔节期—灌浆初期发生中轻度水分亏缺,对后期产量形成产生显著影响,但限水灌溉显著提高了土壤贮水的消耗量和水分利用效率。在2种灌溉水平下,施氮量与产量均成抛物线关系,充分灌溉条件下施氮量264.3 kg/hm~2时为转折点,限水灌溉条件下施氮量176.9 kg/hm2为转折点。充分灌溉条件下,随着施氮量的增加氮肥农学利用率呈增加趋势;但在限水灌溉条件下,随着施氮量的增加氮肥农学利用率表现出降低的趋势。随着施氮量增加,各土层土壤硝态氮量显著增加,且60～100 cm土层硝态氮累积所占比例增加。与充分灌溉相比,限水灌溉作物吸氮量降低,各生育期土壤中硝态氮残留增加。【结论】玉米产量对氮素的响应与供水量相关,水分亏缺下,产生最大产量需要的氮素用量随之降低。因此,生产中应根据土壤含水率调整施氮量,以实现最高产量和水肥利用效率。