A Remote Irrigation Monitoring and Control System for continuous move systems. Part A: description and development

Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology that performed well for on-site control but were very expensive to add remote, real-time monitoring and control aspects that have been made possible by wireless sensor networks and the Internet. A new approach to the monitoring and control of continuous move irrigation systems is described. This system uses a Single Board Computer (SBC) using the Linux operating system to control solenoids connected to individual or groups of nozzles based on prescribed application maps. The main control box houses the SBC connected to a sensor network radio, a GPS (Global Positioning System) unit, and an Ethernet radio creating a wireless connection to a remote server. A C-software control program resides on the SBC to control the on/off time for each nozzle group using a “time on” application map developed remotely. The SBC also interfaces with the sensor network radio to record measurements from sensors on the irrigation system and in the field that monitor performance and soil and crop conditions. The SBC automatically populates a remote database on the server in real time and provides software applications to monitor and control the irrigation system through the Internet.     

The impact of various sprinkler irrigation patterns on spatial soil moisture variation in Vertisols

The objective of this research was to assess the effect of soil cracks on soil moisture distribution under various sprinkler irrigation applications and to identify the optimal irrigation strategy that enhances soil moisture distribution and reduces water drainage for the upper soil layer 0–250 mm. The assessment was made for six irrigation events: the first two were for 10 and 46 mm water applications using a hand shift-set sprinkler system. The second set was for 43 and 19 mm water applications using the lateral move system with fixed sprayer heads and the third pair of events were for 43 and 32 mm water applications using the lateral move system with rotating sprinklers. The experiments were conducted on two adjacent fields at the University of Queensland, Gatton, Australia. Each field was divided into 2 m × 2 m grids that covered 62 sampling locations. For each event, the initial soil moisture content (SMC) was measured at each sampling location before irrigation. After irrigation, catch can readings were recorded for each sampling location. After 12 h overnight, the second set of soil moisture measurements was taken at each location. The area1 distribution of SMC for the studied applications was quantified. An attempt was made to identify the relationship between the applied water uniformity using catch cans and the soil moisture uniformity using gravimetric water content measurements. The study also took into consideration variables that could affect the soil physical and hydrological properties including the field slope, the soil texture, the infiltration rate, the salt content and the soil organic matter content of the two fields. Since the soils were cracking clay Vertisols, further analyses were conducted on the crack dynamics, size and distribution using image analysis techniques. The research findings demonstrated that the cracks were the main contributors to water drainage below 250 mm soil depth due to the micro-run off from the crust surface to the cracks. The cracks ranged from a few millimeters to more than 40 mm in width. It was observed that the cracks which were wider than 15 mm remained open after irrigation for the specified application rates. Improving the irrigation system application uniformity did not always result in higher uniformity of the surface SMC (0–250 mm). The event that best enhanced soil moisture distribution and thus improved soil moisture recharging was observed after the sixth irrigation event when the field received 32 mm water application. The soil was at a relatively high initial SMC of 25%, (which represented 43.3% of the plant available water range) and the sprinkler water uniformity was rather high above 87% Christiansen coefficient of uniformity (CUc). At this SMC, the extent of soil cracking is limited.     

Soil water status mapping and two variable-rate irrigation scenarios

Irrigation is the major user of allocated global freshwaters, and scarcity of freshwater threatens to limit global food supply and ecosystem function—hence the need for decision tools to optimize use of irrigation water. This research shows that variable alluvial soil ideally requires variable placement of water to make the best use of irrigation water during crop growth. Further savings can be made by withholding irrigation during certain growth stages. The spatial variation of soil water supplied to (1) pasture and (2) a maize crop was modelled and mapped by relating high resolution apparent electrical conductivity maps to soil available water holding capacity (AWC) at two contrasting field sites. One field site, a 156-ha pastoral farm, has soil with wide ranging AWCs (116–230 mm m⁻¹); the second field site, a 53-ha maize field, has soil with similar AWCs (161–164 mm m⁻¹). The derived AWC maps were adjusted on a daily basis using a soil water balance prediction model. In addition, real-time hourly logging of soil moisture in the maize field showed a zone where poorly drained soil remained wetter than predicted. Variable-rate irrigation (VRI) scenarios are presented and compared with uniform-rate irrigation scenarios for 3 years of climate data at these two sites. The results show that implementation of VRI would enable significant potential mean annual water saving (21.8% at Site 1; 26.3% at Site 2). Daily soil water status mapping could be used to control a variable rate irrigator.     

防飘喷头在植保无人飞机水稻病害防治应用研究

为了解植保无人飞机应用文丘里防飘喷头对水稻病害的防效影响。利用植保无人飞机搭载文丘里防飘喷头的方法,分析雾滴沉积特性及水稻纹枯病、稻曲病的防治效率。结果表明：应用文丘里防飘喷头雾滴在冠层上部与下部以及总体沉积量均超过应用常规扇形喷头的雾滴沉积量,相对于小雾滴,植保无人飞机采用大雾滴可以改善雾滴在冠层中的穿透性及喷幅范围内的雾滴分布均匀性;不论是粗雾滴还是细雾滴,植保无人飞机均可以有效防治稻曲病,而且防效优于传统的背负式喷雾器;纹枯病植保无人飞机应用文丘里防飘喷头施药后,其防效达到80%,与背负式喷雾器防效相当,较常规扇形喷头防效提高30%。因此,水稻叶部病害应用文丘里防飘喷头能够达到病害防治要求。     

Effect of irrigation management on soil salinization in Manas River Valley, Xinjiang, China

Abstract The irrigated area of Manas River Valley in Northwest China is an example of the successful reclamation of massive land affected by shallow ground water levels and salinization. To determine the effect of irrigation management practices on soil salinization, soil profiles representing various soil types were sampled. The historical records on the characteristics of irrigation management practices, groundwater level and soil salts accumulation in this region at four key periods, namely: flood irrigation without drainage; flood irrigation with drainage but of low efficiency; irrigation in combination with lined irrigation canals and exploitation of groundwater; and irrigation with the application of water-saving irrigation techniques, were analyzed emphatically. In addition, the salinization status of cultivated land in 2010 and 2020 was also predicted by using analogism according to the relationship between soil salinization and irrigation practices. The results revealed that the application of the traditional irrigation methods, such as flood irrigation and ridge irrigation, resulted in a rapid rising of groundwater level and salts accumulation in soil surface layers. However, with the way of well irrigation and well drainage, the groundwater level and the desalinization in soil layers apparently lowered, leading to a substantial increase of crop yield. Currently, the application of drip irrigation under mulch decreased the salts concentration in soil layers and increased the crop yield. With the continuous application of drip irrigation, the average soil desalinization efficiency in soil layers may increase. It is predicted that the percentage of salinized land would be reduced to 35%–40% when irrigation water is utilized reasonably in 2010. With the high efficient utilization of irrigation water after 2020, the salinized land would remain below 30%. It is concluded that with the improvement of irrigation management, an obvious desalinization would appear in the soil surface layers and the area of salinized land in this study area would gradually narrow, but the land salinization problem would be hard to totally solve. __________ Translated from Journal of China Agricultural University, 2007, 12(1): 22–26 [译自: 中国农业大学学报]     

Crop water stress mapping for site-specific irrigation by thermal imagery and artificial reference surfaces

Variable-rate irrigation by machines or solid set systems has become technically feasible, however mapping crop water status is necessary to match irrigation quantities to site-specific crop water demands. Remote thermal sensing can provide such maps in sufficient detail and in a timely way. In a set of aerial and ground scans at the Hula Valley, Israel, digital crop water stress maps were generated using geo-referenced high-resolution thermal imagery and artificial reference surfaces. Canopy-related pixels were separated from those of the soil by upper and lower thresholds related to air temperature, and canopy temperatures were calculated from the coldest 33% of the pixel histogram. Artificial surfaces that had been wetted provided reference temperatures for the crop water stress index (CWSI) normalized to ambient conditions. Leaf water potentials of cotton were related linearly to CWSI values with R ² = 0.816. Maps of crop stress level generated from aerial scans of cotton, process tomatoes and peanut fields corresponded well with both ground-based observations by the farm operators and irrigation history. Numeric quantification of stress levels was provided to support decisions to divide fields into sections for spatially variable irrigation scheduling.     

Uniformity testing of variable-rate center pivot irrigation control systems

As water supplies become limited, agricultural water use needs to become more efficient to maintain current productivity levels. The efficiency of center pivot and linear move irrigation systems can be increased by matching the amount and rate of water application to specific soil conditions that vary in the field. Such site-specific application can be achieved by variable-rate control systems. Although such systems are being developed, their effects on center pivot and linear move uniformity have not been documented. The uniformity along the length of a center pivot and a linear move irrigation system was measured at two system movement speeds and three variable-rate settings. One variable-rate system is commercially available using pneumatically actuated solenoid valves to turn groups of sprinklers ON and OFF at fractions of a minute corresponding to the cycle rate, for example a 50% cycle rate is 30 s ON and 30 s OFF. The other variable-rate system used commonly available electric solenoid valves to accomplish the same task. Overall, the coefficient of uniformity and low quarter distribution uniformity averaged 93% and 0.90, respectively for the center pivot irrigation system; 84% and 0.74 for the linear move system. The results were not significantly (P > 0.05) affected by wind speed, cycling rate, or system movement speed. The type of nozzle did influence the uniformity because of the distinctly different application characteristics of rotator, fixed plate, and wobbling low pressure sprinklers. Thus, the variable-rate technologies tested under the conditions presented in this paper had at least as good uniformity as the center pivot and linear move systems when functioning in non-variable-rate mode.Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the University of Florida or the University of Georgia and does not imply approval of a product or exclusion of others that may be suitable.     

水氮处理对复播油葵产量和水氮利用效率的影响

为探明不同水氮处理对复播油葵生长、产量及水氮利用效率的影响,采用裂区设计,设置不同灌水处理:低水处理(2 250 m³·hm^-2)、中水处理(3 750 m³·hm^-2)、高水处理(5 250 m³·hm^-2)和不同施氮处理:不施氮处理(0 kg·hm^-2)、低氮处理(120 kg·hm^-2)、中氮处理(240 kg·hm^-2)、高氮处理(360 kg·hm^-2)进行大田小麦复播油葵试验。结果表明:复播油葵氮素吸收量、氮肥利用效率随灌水量的增加而增加;施氮量在0~240 kg·hm^-2时,复播油葵的产量随着施氮量的增加而增加,施氮量超过240 kg·hm^-2时增加不显著;随灌水量的增加,复播油葵耗水量增加,水分利用效率先增加后降低,且均在施氮240 kg·hm^-2和360 kg·hm^-2处理间无显著差异。本试验条件下,生育期内灌水5 250 m³·hm^-2(高水)、施氮360 kg·hm^-2(高氮)时,复播油葵的产量为3 598 kg·hm^-2,生育期内中水3 750 m³·hm^-2、中氮240 kg·hm^-2时,复播油葵的单盘粒重、千粒重和产量表现一致,产量为3 518 kg·hm^-2,综合考虑各因素,中水中氮的处理为产量和效益兼优的最佳组合。     

Prediction of plant water status in almond and walnut trees using a continuous leaf monitoring system

Persistent drought conditions in the Central valley of California demands efficient irrigation scheduling tools such as precision or variable rate irrigation (VRI). To assist VRI scheduling, an experiment was conducted in almond and walnut orchards using a sensor system called ‘leaf monitor’, which was developed at UC Davis to detect plant water status. A Modified Crop Water Stress Index (MCWSI) was calculated to quantify plant water status using leaf temperature and environmental data collected by the leaf monitor. This technique also took into account spatio-temporal variability of plant water status. Stem water potential (SWP), which is considered a standard method for determining plant water stress (PWS), was also measured simultaneously. Relationships between measured deficit stem water potential (DSWP), which is the difference between SWP and the saturated baseline, and MCWSI were developed for both crops based on data collected during the 2013 and 2014 growing seasons. A linear relationship was found in the case of walnut crop with a coefficient of determination (r²) value of 0.67. A quadratic relationship was found in the case of almonds with a coefficient of multiple determination (R²) value of 0.75. Moreover, these results highlighted that at lower PWS of below 0.5 MPa of DSWP, almonds crops did not show any decrease in transpiration rate. However, when the stress level exceeded 0.5 MPa of DSWP, transpiration rate tended to decrease. On the other hand, walnut crop showed decrease in transpiration rate even at low PWS of below 0.5 MPa of DSWP. Temporal variability was noticed in PWS as it was found that coefficients of saturation baseline used for MCWSI method changed significantly throughout the season. MCWSI values estimated before an irrigation event was used to calculate the irrigation amount for low frequency variable rate irrigation (VRI) based on the relationship found between MCWSI and DSWP, and VRI led to an average 39% reduction in water usage as compared to the fixed 100% ET replacement irrigation method for all trees. Based on the results, leaf monitor showed potential for use as an irrigation scheduling tool.

     

A dynamic knowledge model for water management in maize

Farmland irrigation management and model establishment are always core and difficult contents in crop simulation. This research was focused on exerting the establishment theory of knowledge model, and applying the systematic analysis method and mathematic modeling technology to knowledge expression system of maize water management. Based on soil water balance, a dynamic knowledge model with systematic and wide-application characteristics for maize water management was developed, after periodically quantifying the relationship of irrigation ration between cultivars’ characteristics and environmental factors. Cases were studied on the knowledge model with the data sets of normal year in different eco-sites and those of different rain years in the same eco-sites. The results showed that there was no difference in water saving in normal years under different eco-sites, irrigation schedule changes with eco-sites greatly; but a more obvious difference in different rain years of the same eco-sites existing, with 8.6% and 31.9% of water saving in both more rainfall and normal rainfall years, respectively. Additionally, irrigation in the seedling stage did not change with year types, but it did in Knurling and filling stages. This can be concluded that the irrigation regime designed by the model is well coherent to the actual planting system, which indicated that the model had good decision-making and applicability __________ Translated from Transactions of the Chinese Society of Agricultural Engineering, 2007, 23(6): 165–169 [译自: 农业工程学报]     

Nutrient Management Zones for Citrus Based on Variation in Soil Properties and Tree Performance

Site-specific soil management can improve profitability and environmental protection of citrus groves having large spatial variation in soil and tree characteristics. The objectives of this study were to identify soil factors causing tree performance decline in a variable citrus grove, and to develop soil-specific management zones based on easily measured soil/tree parameters for variable rate applications of appropriate soil amendments. Selected soil properties at six profile depths (0–1.5 m), water table depth, ground conductivity, leaf chlorophyll index, leaf nutrients and normalized difference vegetation index were compared at 50 control points in a highly variable 45-ha citrus grove. Regression analysis indicated that 90% of spatial variation in tree growth, assessed by NDVI, was explained by average soil profile properties of organic matter, color, near-infrared reflectance, soil solution electrical conductivity, ground conductivity and water table depth. Regression results also showed that soil samples at the surface only (0–150 mm) explained 78% of NDVI variability with NIR and DTPA-extractable Fe. Excessive available copper in low soil organic matter areas of the grove apparently induced Fe deficiency, causing chlorotic foliage disorders and stunted tree growth. The semivariograms of selected variables showed a strong spatial dependence with large ranges (varied from 230 m to 255 m). This grove can be divided into different management zones on the basis of easily measured NDVI and/or soil organic matter for variable rate application of dolomite and chelated iron to improve tree performance.     

Coupling effects of irrigation and nitrogen fertilization on grain protein and starch quality of strong-gluten winter wheat

Effects of irrigation and nitrogen fertilization on the grain yield, protein composition, protein quality, starch composition and starch pasting properties of a strong-gluten winter wheat were investigated in a high fertility field. Compared with non-irrigation treatment, grain yields under irrigation treatments were significantly increased, but the content of grain protein, monomeric protein and flour wet gluten was reduced. There were no significant differences in the above parameters between the irrigation treatments. Nitrogen application could significantly increase grain yield under low irrigation frequency (W₀ and W₁), while the neglected effect on yield was observed with high irrigation frequency (W₂ and W₃). With the increase of irrigation frequency, the glutenin content leveled off, but the changes of glutenin composition were not uniform, in which the soluble glutenin content was increased, while the insoluble glutenin content and polymerization index (the ratio of insoluble glutenin to total glutenin) were reduced. Both dough development time and stability time became shorter with the increased irrigation frequency. Nitrogen application improved the content of all grain protein fractions and grain quality, in which the increased degree in non-gluten protein (albumin and globulin) was higher than gluten protein (gliadin and glutenin), and the increased degree in soluble glutenin was found higher than that of insoluble glutenin. The interactive effects of irrigation and nitrogen on starch composition were significant. Starch content and amylopectin content was increased as irrigation frequency added in non-nitrogen treatment. Compared to non-irrigation treatment, irrigation significantly increased the starch content and the amylopectin content in nitrogen application treatment, but the starch and amylopectin content had no significant difference between irrigation treatments. Amylose content and the ratio of amylose to amylopectin were reduced while RVA indexes (peak viscosity, breakdown, final viscosity and setback) were increased as irrigation frequency was increased. Nitrogen application significantly improved the amylopectin content and decreased the amylose content in lower frequency irrigation, while the amylopectin content was decreased and the amylose content was enhanced by nitrogen application in higher frequency irrigations. __________ Translated from Plant Nutrition and Fertilizer Science, 2007, 13(3): 361–367 [译自: 植物营养与肥料学报]     

Real-time nozzle flow uniformity when using automatic section control on agricultural sprayers

Automatic section control (ASC) has been readily adopted by US producers on sprayers because it can improve operator productivity and decrease overlap or input usage leading to economic savings while reducing environmental impacts. However, there is limited knowledge about nozzle flow dynamics when shutting ON/OFF of boom-sections or nozzles and the possible impact on application accuracy. Therefore, an investigation was conducted to evaluate system response in managing real-time nozzle off-rate and flow uniformity across the boom, for a typical agricultural sprayer using ASC. An 18.3-m sprayer was outfitted with commercially available individual nozzle and boom-section control. Tests were conducted to simulate sprayer moving out of point rows into a no-spray zone and then reentry into the spray zone by selecting two point row scenarios having 20° and 70° angles. Ten high frequency response pressure sensors were randomly mounted across the boom to measure nozzle pressure. The nozzle pressures were converted to nozzle flow, using the manufacturers pressure versus flow relationship, to calculate nozzle flow rate delay time, settling time, percent off-rate (percent difference between actual and target nozzle flow rate) and nozzle flow uniformity (CV), considering only ON boom-sections. Auto-boom scenarios were conducted with and with-out flow compensation while auto-nozzle scenarios were conducted without flow compensation. Results indicated that nozzle flow rate settling time varied from 0.4 to 14.4 s and nozzle off-rate between 36.6% and +28.7% for 70° point row auto-boom tests when exiting and reentering point rows. When exiting point rows, over-application occurred whereas reentry resulted in under-application during flow compensated tests. Nozzle flow uniformity (CV) were more than 50% for a short duration (<1.0 s) when reentering point rows, during all tests. Compensation testing for 20° point row reentry highlighted the constraint of the control system to respond to certain situations where feedback response times could not match target rates rapidly set for the controller. Overall results indicated that system response time can impact nozzle off-rate and can vary with point row angle.     

Control of individual microsprinklers and fault detection strategies

Based on yield variability in orchards, it is evident that many trees receive too much or too little water and fertilizer under uniform management. Optimizing water and nutrient management based on the demand of individual trees could result in improved yield and environmental quality. A microsprinkler sensor and control system was developed to provide spatially variable delivery of water and fertilizer, and a prototype was installed in a nectarine orchard. Fifty individually addressable microsprinkler nodes, one located at every tree, each contained control circuitry and a valve. A drip line controller stored the irrigation schedule and issued commands to each node. Pressure sensors connected to some of the nodes provided lateral line pressure feedback. The system was programmed to irrigate individual trees for specific durations or to apply a specific volume of water at each tree. Time scheduled irrigation demonstrated the ability to provide microsprinkler control at individual trees, but also showed variation in discharge because of pressure differences between laterals. Volume scheduled irrigation used water pressure feedback to control the volume applied by individual microsprinklers more precisely, and the average error in application volume was 3.7%. Fault detection was used to check for damaged drip lines and clogged or damaged emitters. A pressure monitoring routine automatically logged errors and turned off the microsprinklers when drip line breaks and perforations caused pressure loss. Emitter diagnosis routines correctly identified clogged and damaged microsprinkler emitters in 359 of 366 observations. Irrigation control at the individual tree level has many useful features and should be explored further to characterize fully the benefits or disadvantages for orchard management.     

Development and validation of fuzzy logic inference to determine optimum rates of N for corn on the basis of field and crop features

A fuzzy inference system (FIS) was developed to generate recommendations for spatially variable applications of N fertilizer. Key soil and plant properties were identified based on experiments with rates ranging from 0 to 250 kg N ha⁻¹ conducted over three seasons (2005, 2006 and 2007) on fields with contrasting apparent soil electrical conductivity (EC_a), elevation (ELE) and slope (SLP) features. Mid-season growth was assessed from remotely sensed imagery at 1-m² resolution. Optimization of N rate by the FIS was defined against maximum corn growth in the weeks following in-season N application. The best mid-season growth was in areas of low EC_a, high ELE and low SLP. Under favourable soil conditions, maximum mid-season growth was obtained with low in-season N. Responses to N fertilizer application were better where soil conditions were naturally unfavourable to growth. The N sufficiency index (NSI) was used to judge plant N status just prior to in-season N application. Expert knowledge was formalized as a set of rules involving EC_a, ELE, SLP and NSI levels to deliver economically optimal N rates (EONRs). The resulting FIS was tested on an independent set of data (2008). A simulation revealed that using the FIS would have led to an average N saving of 41 kg N ha⁻¹ compared to the recommended uniform rate of 170 kg N ha⁻¹, without a loss of yield. The FIS therefore appears to be useful for incorporating expert knowledge into spatially variable N recommendations.     

Restoring soil health to reduce irrigation demand and buffer the impacts of drought

Irrigation consumes three quarters of global water withdrawals each year. Strategies are needed to reduce irrigation water use, including increasing the efficiency of transfer methods and field application. Comprehensive restoration of soil health, specifically through organic matter amendments, can substantially reduce irrigation demand and increase crop yield. A program to restore severely degraded and desertified soils by incorporating coarse woodchips into the soil successfully increased rainfall capture and elevated soil moisture for several weeks between rainfall events at both Ningxia, north-west China and North Dakota, USA. With addition of fertilizer, woodchip incorporation further increased growth of wheat and alfalfa. Comprehensive soil health assessment of remnant grasslands was used to develop target reference soil profiles by which to guide restoration efforts. Given that most agricultural soils are degraded to some degree, soil health restoration can provide a powerful strategy toward achieving global food and water security.     

一种窄行距条播密植作物微喷带高效节本喷灌方法

为高效利用灌溉水资源和喷灌设施微喷带,在山西临汾开展了窄行距条播密植作物微喷带高效节本喷灌方法的探讨,其具体方法为：在与窄行距条播密植作物种植方向相垂直的方向安装引水带,在与引水带相垂直方向上安装输水管;在与输水管垂直方向上安装微喷带,在卡套后方插入微喷带U型固定卡;当一季作物喷灌完成后,将引水带移出农田,拔出微喷带U型固定卡,将每个四通连接的一对微喷带沿着输水管的方向折叠捆绑置于搁置带;当下茬作物播种完成后,将引水带移入农田安装,解开微喷带绑绳拉开微喷带并插入微喷带U型固定卡。结果表明,该方法较传统(微喷带沿作物种植行向铺设于行间)方法改善了窄行距条播密植作物中、后期喷灌的效果,节水效果显著,耕地利用率提高16.5%,每茬作物每公顷可节约搬运、安装、拆卸费用525-600元。该项研究为微喷带节水灌溉设施的节本高效利用及大面积推广提供了技术支撑。     

Maize Nitrogen Response as Affected by Soil Type and Drainage Variability

Site-specific application of nitrogen (N) to maize (Zea mays L.) may provide economic and environmental benefits. Variations in soil drainage and texture within fields are often believed to cause localized differences in soil N availability and therefore are a potential basis for site-specific N fertilizer application. The objective of this study was to evaluate the effect of imposed variations in drainage conditions in two soils on early season soil water conditions, soil nitrate levels, and crop response to N fertilizer. Maize was grown for three years following conversion from sod. Two soil drainage regimes and three N rates (22, 100 and 134 kg ha^–1) were experimentally imposed on plots on two soil types, a clay loam and a loamy sand. Soil water potential and soil nitrate content were intensively monitored for the 0–150 and 150–300 mm soil layers during the early growing season. Early season soil water potentials showed small effects of drainage variability at the 75 and 225 mm depths. However, the clay loam soil experienced prolonged periods of saturation after significant precipitation, while the loamy sand never experienced such conditions. Soil nitrate levels were strongly affected by cropping history, but were also subjected to losses as a result of precipitation and short-term soil saturation. Maize N response was minimally affected by differences in soil drainage conditions in all 3 years. In years with a wet spring, justification exists for higher N fertilizer rates on finer-textured soils. This study therefore showed only moderate potential for varying N application within fields based on soil type and drainage conditions, but suggests that seasonal differences in N dynamics greatly affect maize N response.     

华北平原春玉米滴灌均匀系数对土壤水氮时空分布的影响

【目的】研究滴灌均匀系数及土壤特性对土壤水氮时空分布的影响,定量评价现行标准的适宜性。【方法】试验在华北平原进行,供试作物为春玉米,滴灌均匀系数（CU）设置0.66（低）、0.81（中）和0.99（高）3个水平,灌水量设置灌溉需水量的50%（低）、75%（中）和100%（高）3个水平,监测不同生育阶段的土壤水分和硝态氮含量。【结果】土壤含水量均匀系数在生育期内大于0.85（2009年）和0.80（2010年）,低灌水均匀系数处理与中、高灌水均匀系数处理没有明显区别,远大于滴灌均匀系数（0.66）,初始含水量均匀系数的影响大于滴灌均匀系数,灌水量的影响较小。滴灌均匀系数对硝态氮均匀系数的影响不显著。【结论】在华北平原半湿润地区,滴灌均匀系数不是影响春玉米生育期内土壤水氮分布的主要因素,现行微灌均匀系数标准（CU≥0.80）可适当降低,以降低系统投资。     

Analysis on water requirement and water-saving amount of wheat and corn in typical regions of the North China Plain

This paper studied the variation characters on wheat and corn water consumption and irrigation watersaving amount under different water conditions (ample irrigation level, farmers conventional irrigation level and optimizing irrigation level). The water use efficiency and water saving potential of optimizing treatment and farmers’ conventional irrigation treatment were analyzed respectively. The objective of this study was to provide theoretical supporting for popularization and application of optimizing irrigation measures. Crop water requirement under sufficient water supply was calculated by Penman equation. We obtained crop water consumption under conventional treatment and optimizing treatment by field experiment. The main results showed that the irrigation amount of wheat and corn was too much under farmers’ conventional irrigation level and basically satisfied their water requirement, therefore, the water-saving amount was smaller while water-saving potential was bigger compared with the optimizing irrigation treatment. The grain yield under optimizing irrigation treatment was improved or appreciably reduced compared with that under conventional irrigation treatment, while the water consumption and irrigation amount of optimizing irrigation treatment was lower, with a higher water use efficiency. Therefore, the optimizing irrigation treatment could achieve a stable yield and high water efficiency at the same time. Moreover, when the optimizing irrigation measure was adopted, the grain yield reached 5940 kg/hm², water-saving amount reached 91mm for winter wheat, and the grain yield reached 7743 kg/hm², with water-saving amount of 49mm for summer corn in the piedmont region of Taihang Mount. The grain yield got 7710 kg/hm², with water-saving amount of 20mm for winter wheat in Heilonggang Plain. Therefore, the water-saving amount in the piedmont region of Taihang Mountain was obviously higher than that in Heilonggang Plain. Thus, the piedmont region of Taihang Mountain in the North China Plain is viewed as the key district for water-saving.