滴灌频率对温室小西瓜生长势、产量及品质的影响

在日光温室栽培条件下研究不同滴灌频率对西瓜长势、产量及品质的影响,以确定温室西瓜种植最佳的滴灌频率和灌溉量。结果表明:不同灌溉频率对西瓜生长过程中叶面积和长势的影响较小。其中在整个果实发育期以每7d灌水1次,共浇灌3次,总灌溉量为65m3的处理效果最佳,667m2西瓜产量3564.6kg,中心可溶性固形物13.62%,是本试验条件下温室栽培小西瓜最优的灌溉频率和灌溉量,不仅小西瓜高产优质,同时又省工省时节水。     

Agronomic and economic response to furrow diking tillage in irrigated and non-irrigated cotton (Gossypium hirsutum L.)

The Southeast U.S. receives an average of 1300 mm annual rainfall, however poor seasonal distribution of rainfall often limits production. Irrigation is used during the growing season to supplement rainfall to sustain profitable crop production. Increased water capture would improve water use efficiency and reduce irrigation requirements. Furrow diking has been proposed as a cost effective management practice that is designed to create a series of storage basins in the furrow between crop rows to catch and retain rainfall and irrigation water. Furrow diking has received much attention in arid and semi-arid regions with mixed results, yet has not been adapted for cotton production in the Southeast U.S. Our objectives were to evaluate the agronomic response and economic feasibility of producing cotton with and without furrow diking in conventional tillage over a range of irrigation rates including no irrigation. Studies were conducted at two research sites each year from 2005 to 2007. Irrigation scheduling was based on Irrigator Pro for Cotton software. The use of furrow diking in these studies periodically reduced water consumption and improved yield and net returns. In 2006 and 2007, when irrigation scheduling was based on soil water status, an average of 76 mm ha⁻¹ of irrigation water was saved by furrow diking, producing similar cotton yield and net returns. Furrow diking improved cotton yield an average of 171 kg ha⁻¹ and net return by $245 ha⁻¹ over multiple irrigation rates, in 1 of 3 years. We conclude that furrow diking has the capability to reduce irrigation requirements and the costs associated with irrigation when rainfall is periodic and drought is not severe.     

Analysis of surface irrigation systems with WinSRFR—Example application

WinSRFR is an integrated software package for analyzing surface irrigation systems. Software functionalities and technical features are described in a companion article. This article documents an example application. The analyzed field is a graded basin (close-ended border) irrigation system. The event analysis tools of WinSRFR are used first to evaluate performance of the irrigation system and estimate its infiltration and hydraulic roughness properties. Performance contours in the Operations Analysis World are then used to optimize irrigation system inflow rate and cutoff time. The adequacy of the existing design is examined with the performance contours provided in the Physical Design World. Hydraulic and practical constraints are considered in finding an optimal operation or design solution. Finally, sensitivity analyses are used to demonstrate the robustness of the solutions.     

Association of root, specific leaf area and SPAD chlorophyll meter reading to water use efficiency of peanut under different available soil water

Drought is the major abiotic constraint affecting peanut productivity and quality worldwide. There is a pressing need to improve the water use efficiency (WUE) of rain-fed peanut production. Breeding varieties with higher water use efficiency is seen as providing part of the solution. The objectives of this work were to (i) evaluate genetic variation in WUE, harvest index, root dry weight, specific leaf area (SLA) and SPAD chlorophyll meter reading (SCMR) among peanut genotypes in response to different available soil water levels and (ii) assess the relevance of root dry weight, SLA and SCMR to WUE in peanut under receding soil moisture levels. Two greenhouse experiments were conducted in the dry and rainy seasons in 2002/2003. The 11 peanut genotypes (ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60-3 and Tifton-8) and three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW] were laid out in a factorial randomized complete block design (RCBD) with six replications. At 37, 67, and 97 day after sowing (DAS), data were recorded for SLA and SCMR. Root dry weight, harvest index (HI) and WUE were recorded at harvest. Drought reduced WUE, root dry weight and HI. Across both seasons, Tifton-8 and ICGV 98300 had high WUE and also had large root systems under drought conditions. ICGV 98324 and Tifton-8 had low SLA and high SCMR under stressed and non-stressed condition. Under drought conditions, ICGV 98324 had high HI and Tifton-8 had low HI. Root dry weight had a greater contribution to WUE under well-watered and mild drought (2/3 AW). Under severe drought (1/3 AW), SLA showed a more important contribution to WUE than the other traits. Traits that were associated to high WUE under drought conditions were different among different peanut genotypes. ICGV 98300 maintained high root dry weight under 2/3 AW and ICGV 98324 maintained low SLA and high SCMR under 1/3 AW. Tifton-8 had both large root systems and low SLA associated with high WUE.     

Regional partnerships to assist public-private investments in irrigation systems

Public-private partnerships have been implemented throughout the world since the 1970s with mixed results. This is mainly due to the lack of long run commitments from governments and other parties involved, lack of scientific understanding regarding clear short-term and long-term potential biophysical and socio-economic, policy and legal consequences, and lack of trust between the partners. We present a Regional Irrigation Business Partnership (RIBP) model, which is capable of efficiently utilising research output and government policies for sustainable public-private irrigation planning and investment. Unlike other public-private partnership models, the RIBP is based on robust assessment of biophysical, hydrologic, socio-economic, political and legal aspects of water management. The RIBP model provides a crucial link between research and infrastructure investments while minimising short-term and long-term risks. The business investment framework involves iterative feedback from research and policy for identifying markets, defining products and establishing a legislatively and institutionally acceptable route to market as part of the feasibility assessment process. The RIBP model is based on the principle that sharing risks, rewards, and responsibilities coupled with sufficient investment incentives will motivate actors in water management to invest in irrigation infrastructure that saves water and generates better outcomes for the environment. We describe application of the RIBP model in the Coleambally Irrigation Area in New South Wales, Australia.     

MIRRIG: A decision support system for design and evaluation of microirrigation systems

The decision support system (DSS) MIRRIG has been developed to support the design of microirrigation systems and to advise farmers as a result of field evaluations. It is written in Visual Basic 6.0, runs in a Windows environment, and uses a database with information on emitters and pipes available in the market, as well as on crops, soils and the systems under design. MIRRIG is composed by design and simulation models and a multicriteria analysis model that ranks alternative design solutions based upon an integration of technical, economic and environmental criteria. User friendly windows are adopted for handling the databases and to manage the sub-models. The model allows creating and comparing a set of design alternatives relative to the pipe system and the emitters, either drip or microsprinkling emitters. For each alternative, the pipe system is sized and the irrigation system is simulated to produce performance, environmental and economic indicators. These include uniformity of water application, potential for contamination with agrochemicals due to water percolation, and installation and operation costs. Those indicators are used as attributes of the selected criteria. All alternatives are then compared and ranked through multicriteria analysis where the weights giving the relative importance of the adopted criteria are defined by the user. These procedures allow selecting the best design alternative and solving the complexities involved in the design of microirrigation systems. The model is available from the website www://ceer.isa.utl.pt/cms or by contacting cpedras@ualg.pt.     

Using ESAP software for predicting the spatial distributions of NDVI and transpiration of cotton

Observations of the normalized difference vegetation index (NDVI) from aerial imagery can be used to infer the spatial variability of basal crop coefficients (Kcb), which in turn provide a means to estimate variable crop water use within irrigated fields. However, monitoring spatial Kcb at sufficient temporal resolution using only aerial acquisitions would likely not be cost-effective for growers. In this study, we evaluated a model-based sampling approach, ESAP (EC_e Sampling, Assessment, and Prediction), aimed at reducing the number of seasonal aerial images needed for reliable Kcb monitoring. Aerial imagery of NDVI was acquired over an experimental cotton field having two treatments of irrigation scheduling, three plant density levels, and two N levels. During both 2002 and 2003, ESAP software used input imagery of NDVI on three separate dates to select three ground sampling designs having 6, 12, and 20 sampling locations. On three subsequent dates during both the years, NDVI data obtained at the design locations were then used to predict the spatial distribution of NDVI for the entire field. Regression of predicted versus imagery observed NDVI resulted in r² values from 0.48 to 0.75 over the six dates, where higher r² values occurred for predictions made near full cotton cover than those made at partial cover. Prediction results for NDVI were generally similar for all three sample designs. Cumulative transpiration (Tr) for periods from 14 to 28 days was calculated for treatment plots using Kcb values estimated from NDVI. Estimated cumulative Tr using either observed NDVI from imagery or predicted NDVI from ESAP procedures compared favorably with measured cumulative Tr determined from soil water balance measurements for each treatment plot. Except during late season cotton senescence, errors in estimated cumulative Tr were between 3.0% and 7.3% using observed NDVI, whereas they were they were between 3.4% and 8.8% using ESAP-predicted NDVI with the 12 sample design. Thus, employing a few seasonal aerial acquisitions made in conjunction with NDVI measurements at 20 or less ground locations optimally determined using ESAP, could provide a cost-effective method for reliably estimating the spatial distribution of crop water use, thereby improving cotton irrigation scheduling and management.     

Estimation of water levels in a main drainage canal in a flat low-lying agricultural area using artificial neural network models

The Chiyoda basin is located in the Saga Prefecture of the Kyushu Island, Japan, and lies next to the tidal compartment of the Chikugo River, into which excess water in the basin is drained away. This basin has a total area of approximately 1100 ha and is a typical flat and low-lying agricultural area. The estimation of the water levels at the gates and along the main drainage canal is a crucial issue that has recently been the subject of much research. At these locations farmers and managers need to control the operation of the irrigation and drainage systems during periods of cultivation. An attempt has been made to apply a feed-forward artificial neural network (FFANN) to model and estimate the water levels in the main drainage canal. The study indicated that the artificial neural network (ANN) could successfully model the complex relationship between rainfall and water levels in this flat and low-lying agricultural area. Input variables and the model structure were selected and optimized by trial and error, and the accuracy of the model was then evaluated by comparing the simulated water levels with the observed ones during an irrigation period in July 2007. The water levels at two locations, located upstream and downstream of a main drainage canal, were investigated by using a time series at intervals of 20, 30, and 60 min. At these intervals, rainfall and tide water levels in the Chikugo River were measured, and the backward time-step numbers of the input variables of rainfall and tide water level were searched. For the upstream location, the optimal combination yielding good agreement between the observed and estimated water levels was obtained when the interval of the time series was 60 min. The number of backward time-steps of the input variables of rainfall and tide water level were 5 and 4, respectively. In contrast to the downstream location, the optimal combination was obtained for the interval time series of 20 min with 4 backward time-steps for both the input variables of rainfall and tide water level. The present study could provide farmers and managers with a useful tool for controlling water distribution in the drainage basin, and reduce the cost of installing water level observation points at many locations in the main drainage canal.     

Soil moisture tension and phosphate fertilization on yield components of A-7573 sweet corn (Zea mays L.) hybrid, in Campeche, Mexico

The effect of moisture tension and doses of phosphate fertilization on yield components of sweet corn A-7573 (Zea mays L.) hybrid, in a Calcium Vertisol were evaluated. Four levels of soil moisture tension, ranging from −5 to −80 kPa, and three levels of phosphate fertilization: 60, 80, and 100 kg ha⁻¹ were studied. In order to evaluate the effect of the experimental treatments, plant growth, development, and yield were monitored. Treatments were distributed using the randomized complete block design (RCB) for divided plots of experimental units. ANOVA analysis indicated that the effects on more humid treatments (−5 and −30 kPa) were statistically equivalent, however were different from the effect of −55 kPa treatment, which in turn was statistically different from the effect of the driest treatment (p ≤ 0.01). On the other hand, 80 and 100 kg ha⁻¹ phosphate doses were statistically equal among them, but different from the lowest dose in almost all cases (p ≤ 0.01), which suggests that 80 kg ha⁻¹ P₂O₅ application is sufficient to satisfy the nutritional requirements of the A-7573 hybrid. Both stress caused by the lack of water and the one due to deficiency of phosphorus affect all variables under study, however none of them showed interaction between irrigation and fertilization treatments. Irrigation of sweet corn crop is advisable when soil moisture tension grows to −30 kPa at 0-30 cm depth and to apply a phosphate fertilization dose of 80 kg ha⁻¹ is also recommended; using this management, sweet corn expected average length and fresh weight are 30.8 cm and 298 g, respectively, and their average yield is around 16.5 t ha⁻¹. In accordance with regression equations obtained, the maximum values in the evaluated response variables are obtained for a rank from −14.4 to −22.2 kPa in soil moisture tension. The greater efficiency in the use of irrigation water for sweet corn was of 36 kg ha⁻¹ for every millimetre laminate of watering applied, found in the −30 kPa treatment of soil moisture tension.     

The effects of irrigation methods with effluent and irrigation scheduling on water use efficiency and corn yields in an arid region

A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m³ ha⁻¹ water applied, and the minimum water saving was obtained using FI with 6822 m³ ha⁻¹. The predicted irrigation water requirements using the Penman-Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m³ ha⁻¹. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 10³ kg ha⁻¹) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 10³ kg ha⁻¹). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m⁻³) and the minimum was obtained with the FI method (1.43 kg m⁻³). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.