Evapotranspiration, seed yield and water use efficiency of drip irrigated sunflower under full and deficit irrigation conditions

Deficit irrigation occurrence while maintaining acceptable yield represents a useful trait for sunflower production wherever irrigation water is limited. A 2-year experiment (2003–2004) was conducted at Tal Amara Research Station in the Bekaa Valley of Lebanon to investigate sunflower response to deficit irrigation. In the plots, irrigation was held at early flowering (stage F1), at mid flowering (stage F3.2) and at early seed formation (stage M0) until physiological maturity. Deficit-irrigated treatments were referred to as WS1, WS2 and WS3, respectively, and were compared to a well-irrigated control (C). Reference evapotranspiration (ET_rye-grass) and crop evapotranspiration (ET_crop) were measured each in a set of two drainage lysimeters of 2 m × 2 m × 1 m size cultivated with rye grass (Lolium perenne) and sunflower (Helianthus annuus L., cv. Arena). Crop coefficients (K_c) in the different crop growth stages were derived as the ratio (ET_crop/ET_rye-grass).

Lysimeter measured crop evapotranspiration (ET_crop) totaled 765 mm in 2003 and 882 mm in 2004 for total irrigation periods of 139 and 131 days, respectively. Daily ET_crop achieved a peak value of 13.0 mm day⁻¹ at flowering time (stage F3.2; 80–90 days after sowing) when LAI was >6.0 m² m⁻². Then ET_crop declined to 6.0 mm day⁻¹ during seed maturity phase. Average K_c values varied from 0.3 at crop establishment (sowing to four-leaf stage), to 0.9 at late crop development (four-leaf stage to terminal bud), to >1.0 at flowering stage (terminal bud to inflorescence visible), then to values <1.0 at seed maturity phase (head pale to physiological maturity). Measured K_c values were close to those reported by the FAO.

Average across years, seed yield at dry basis on the well-irrigated treatment was 5.36 t ha⁻¹. Deficit irrigation at early (WS1) and mid (WS2) flowering stages reduced seed yield by 25% and 14% (P < 0.05), respectively, in comparison with the control. However, deficit irrigation at early seed formation was found to increase slightly seed yield in WS3 treatment (5.50 t ha⁻¹). We concluded that deficit irrigation at early seed formation (stage M0) increased the fraction of assimilate allocation to the head, compensating thus the lower number of seeds per m² through increased seed weight. In this experiment, while deficit irrigation did not result in any remarkable increase in harvest index (HI), water use efficiency (WUE) was found to vary significantly (P < 0.05) among treatments, where the highest (0.83 kg m⁻³) and the lowest (0.71 kg m⁻³) values were obtained from WS3 and WS1 treatments, respectively. Finally, results indicate that irrigation limitation at early flowering (stage F1) and mid flowering (stage F3.2) should be avoided while it can be acceptable at seed formation (stage M0).     

Water balance of centre pivot irrigated pasture in northern Victoria, Australia

The irrigated dairy industry in Australia depends on pasture as a low-cost source of fodder for milk production. The industry is under increasing pressure to use limited water resources more efficiently. Pasture is commonly irrigated using border-check but there is growing interest amongst dairy irrigators to explore the potential for overhead sprinklers to save water and/or increase productivity. This paper reports on a detailed water balance study that evaluated the effectiveness of centre pivot irrigation for pasture production. The study was conducted between 2004/2005 and 2005/2006 on a commercial dairy farm in the Shepparton Irrigation Region in northern Victoria. More than 90% of supplied water (irrigation plus rainfall) was utilized for pasture growth. Deep drainage of respectively 90 and 93 mm was recorded for the two observation seasons. During the 2004/2005 season, deep drainage resulted from large unseasonal summer rainfall events. Over the 2005/2006 season, deep drainage resulted from excess irrigation. The cumulative pasture dry matter (DM) production was 15.5 and 11.3 tonnes DM ha⁻¹ for the two irrigation seasons, with an agronomic water use efficiency (WUE) of 16 and 12 kg DM ha⁻¹ mm⁻¹ respectively. The farmer's intuitive irrigation scheduling was found to be very effective; the pattern of irrigation application closely matched measured pasture water use, prevented water stress and resulted in high irrigation efficiency.     

A rule-based method for the development of crop management systems applied to grain sorghum in south-western France

A generic approach is proposed for the development and testing of crop management systems in contrasting situations of water availability. Ecophysiological knowledge, expertise, regional references and simulation models are combined to devise management strategies adapted to production targets and constraints. The next stage consists of converting these crop management strategies into logical and consistent sets of decision rules. Each rule describes the reasoning which is used to apply a technical decision by taking account of observed or simulated environmental conditions or predicted agronomic risks.

This approach was applied to design crop management systems for grain sorghum (Sorghum bicolor L. Moench.) in south-western France. For spring-sown crops, management (sowing date, plant density, varietal choice, N fertilizer rate and timing) was based on water availability, both for economic and environmental reasons. Specific sets of decision rules were written for irrigated and rainfed conditions. The establishment of rules was based on agronomic principles (e.g. for plant density) or on the application of a simulation model (e.g. for sowing date, variety). N fertilization and irrigation were applied using combined N and water dynamic models.

A novel methodology combining crop diagnosis, analytical trials and crop simulation was developed to evaluate the management systems. An irrigated and a rainfed rule-based management system were compared near Toulouse (S.W. France) from 1995 to 2002. The profitability of rainfed low-input management was confirmed for sorghum in spite of high yields under irrigation (up to 10 t ha⁻¹). The adaptation of sorghum management in rainfed conditions was mainly achieved through early maturing cultivars and by reducing N applications by 65%.     

Irrigation and fertiliser strategies for minimising nitrogen leaching from turfgrass

Establishing and implementing management practices that limit N leaching from agricultural and horticultural land is a priority internationally. Movement of N through soil to surface and ground waters can degrade aquatic systems and compromise water used for drinking, industry and recreation. Reported annual rates of N leaching from turfgrass range from 0 to 160 kg N ha⁻¹ year⁻¹, representing up to 30% of applied N. Irrigation rate, fertiliser regime and turfgrass growth phase influence the amounts of N leached. Nitrogen losses tend to be low (<5% of applied fertiliser N) from established turfgrass that is not over-irrigated, and has received N fertiliser at 200–300 kg N ha⁻¹ year⁻¹. Efficient irrigation management is critical for efficient N use. Irrigation scheduling that does not cause water to move beyond the active rooting zone decreases the amount of N leached from established turfgrass, without being detrimental to, and in some instances enhancing, turfgrass growth and quality. Applying N fertilisers at rates and frequencies that match N requirements decreases N leaching from established turfgrass. Soil disturbance, such as during preparation of areas for planting turfgrass, can increase N leaching. Therefore, the main strategies for minimising N leaching from turfgrass are (i) optimise irrigation regimes, and (ii) ensure N is applied at rates and frequencies that match turfgrass demand. These strategies are particularly important during turfgrass establishment. Further work is required on turfgrass-soil N cycling and partitioning of N applied to turfgrass. Research needs to be conducted for a broad range of turfgrass species, turfgrass ages, soil types and climates.     

灌水模式对油葵耗水量产量及经济效益的影响

通过5种灌水处理模式和对照旱地油葵田间试验,探讨了灌水模式对油葵耗水量、产量、水分利用效率以及经济收入的影响。结果表明,油葵出盘前和灌浆后耗水量比其他时段多50％以上。在油葵不同生育阶段耗水量随着灌水量增加而增加;灌水定额120mm,灌两次水的灌水模式的产量最高,为2268kg／hm^2,而水分利用效率最大值出现在灌水定额66mm的灌水模式,灌水量增加反而使水分利用效率下降。经济分析结果表明,纯收入最高值出现在灌水模式93mm灌二水的处理,为2871元／hm^2,灌水定额增加或减少均导致经济收入下降。统计分析结果表明,干旱年份（全生育期有效降水量123mm）灌二水时,为了兼顾产量、水分利用效率以及经济收入,油葵最佳总灌水量以208-218mm为宜。全生育期有效降水量超过350mm的丰水年份不应该再灌水。     

Effect of salinity on water stress, growth, and yield of maize and sunflower

Maize and sunflower were grown in tanks filled with loam and clay, and were irrigated with water of three different levels of salinity. Predawn leaf-water potential and stomatal conductance were used as parameters for water stress. The predawn leaf-water potential of maize was higher than that of sunflower, but the effect of salinity and soil texture on the predawn leaf-water potential was the same for both crops. The stomatal conductance of sunflower was much higher and more severely affected by salinity and soil texture than the stomatal conductance of maize.

Although salinity had a more serious effect on the development of leaf area and canopy dry matter of sunflower, its effect on evapotranspiration and grain yield was the same for both crops. Soil texture had a stronger effect on the development of leaf area and canopy dry matter of sunflower, which also appeared in the evapotranspiration and grain yield, indicating that sunflower is more sensitive to drought than maize.     

Water conservation practices for a river valley irrigated with groundwater

Water conservation strategies for center pivot and furrow irrigation in the Central Platte Valley of Nebraska were evaluated using computer simulation. Irrigation requirements, grain yield, return flow and net depletion (gross irrigation minus return flow) of groundwater were simulated for a period of 29 years for Hord and Wood River silt loam soils. Grain yields were simulated for a typical corn variety for non-limiting water supplies (maximum attainable yield), for two levels of deficit irrigation (irrigation limited to certain growing periods), and for dryland conditions. Additional simulations were performed for a short-season corn, grain sorghum, and soybeans. The impacts of tillage practices on water conservation were also investigated.Center pivot irrigation on the Hord silt loam required 75–125 mm/year less water application than furrow irrigation. For the Wood River silt loam, water applications were the same for both irrigation systems. Applied water depths were reduced by an additional 75–125 mm using deficit irrigation with only a small reduction in yield. Return flow to the groundwater was small for well-managed pivots but high for some furrow irrigation systems based on the assumption that all deep percolation returns to the aquifer in the Central Platte Valley. Net depletion (gross irrigation minus return flow) of the groundwater for a center pivot with LEPA was 50 mm (17%) less than a center pivot with impact sprinklers. Ridge till had a net depletion 50 mm (25%) less than conventional tillage (double disk, plant) for furrow systems.     

不同灌溉定额对向日葵生物量累积动态及产量构成要素的影响

为探究河套灌区向日葵不同播前灌水量及现蕾—开花期复水对地上生物量累积、分配以及产量构成要素的影响,试验以当地常规灌溉量(播前135 mm,复水90 mm)为对照,设置A1(播前108 mm,复水90 mm)、A2(播前81 mm、复水90 mm)、B1(播前108 mm、复水72 mm)和B2(播前81 mm、复水72 mm)4个处理进行对比研究。结果表明,适当减少播前灌水量,向日葵在开花期生物量累积补偿效应表现显著,且充分复水较限制复水的生物累积量提高16.45%~32.24%。相同播前灌水量下,收获期充分复水处理总生物量高于限制复水处理(P0.01),不同复水处理收获期籽粒百分比差异显著(P0.05),且A1处理籽粒占总生物量的百分比最高,达到43.02%。播前适当的减少灌水量(108 mm),充分复水能显著提高(P0.05)经济产量,而相同播前灌水量下,现蕾—开花期减少灌水量会显著降低经济产量(P0.05)。采用隶属函数法综合评价不同灌溉下的产量和产量构成要素、灌溉水分生产率等相关指标,得出A1处理最优。A1处理经济产量、灌溉水分生产率分别较CK显著提高8.47%和23.19%,其原因是平均单株实粒数和结实率的显著提高(P0.05)。研究表明,河套灌区向日葵适宜的灌溉制度为播前灌水108 mm,现蕾-开花期复水90 mm。     

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.     

Effect of timing of a deficit-irrigation allocation on corn evapotranspiration, yield, water use efficiency and dry mass

Water regulations have decreased irrigation water supplies in Nebraska and some other areas of the USA Great Plains. When available water is not enough to meet crop water requirements during the entire growing cycle, it becomes critical to know the proper irrigation timing that would maximize yields and profits. This study evaluated the effect of timing of a deficit-irrigation allocation (150 mm) on crop evapotranspiration (ETc), yield, water use efficiency (WUE = yield/ETc), irrigation water use efficiency (IWUE = yield/irrigation), and dry mass (DM) of corn (Zea mays L.) irrigated with subsurface drip irrigation in the semiarid climate of North Platte, NE. During 2005 and 2006, a total of sixteen irrigation treatments (eight each year) were evaluated, which received different percentages of the water allocation during July, August, and September. During both years, all treatments resulted in no crop stress during the vegetative period and stress during the reproductive stages, which affected ETc, DM, yield, WUE and IWUE. Among treatments, ETc varied by 7.2 and 18.8%; yield by 17 and 33%; WUE by 12 and 22%, and IWUE by 18 and 33% in 2005 and 2006, respectively. Yield and WUE both increased linearly with ETc and with ETc/ETp (ETp = seasonal ETc with no water stress), and WUE increased linearly with yield. The yield response factor (ky) averaged 1.50 over the two seasons. Irrigation timing affected the DM of the plant, grain, and cob, but not that of the stover. It also affected the percent of DM partitioned to the grain (harvest index), which increased linearly with ETc and averaged 56.2% over the two seasons, but did not affect the percent allocated to the cob or stover. Irrigation applied in July had the highest positive coefficient of determination (R²) with yield. This high positive correlation decreased considerably for irrigation applied in August, and became negative for irrigation applied in September. The best positive correlation between the soil water deficit factor (Ks) and yield occurred during weeks 12-14 from crop emergence, during the “milk” and “dough” growth stages. Yield was poorly correlated to stress during weeks 15 and 16, and the correlation became negative after week 17. Dividing the 150 mm allocation about evenly among July, August and September was a good strategy resulting in the highest yields in 2005, but not in 2006. Applying a larger proportion of the allocation in July was a good strategy during both years, and the opposite resulted when applying a large proportion of the allocation in September. The different results obtained between years indicate that flexible irrigation scheduling techniques should be adopted, rather than relying on fixed timing strategies.     

不同节水灌溉方式对小麦产量及水分利用效率的影响

为探讨不同节水灌溉方式对小麦产量及水分利用效率的影响,在通许试验基地进行了节水灌溉方式(滴灌、微喷灌、喷灌和小白龙)及灌水量(45、90、135mm)的大田试验,分别于拔节和灌浆前期灌水。结果表明:小麦收获时土壤储水量表现为滴灌微喷灌喷灌小白龙,总耗水量以滴灌和微喷灌方式下较少;小麦千粒重随灌水量增加有降低趋势,且在微喷灌方式下明显高于其他处理,而小麦群体、穗长、小穗数和穗粒数均以滴灌方式下表现较佳;灌水能增加小麦产量,水分利用效率随灌水量的增加而降低;以滴灌135 mm的产量最高,水分利用效率以滴灌45mm处理为最高。4种节水灌溉方式中,滴灌更有利于增产和节水,其次为微喷灌。     

灌溉增氧技术对玉米产量和根系生长的影响

为了揭示灌溉、施肥和增氧三者耦合作用对玉米产量及根系生长的影响,以鲜食玉米“晶甜3号”为研究对象,选取灌溉量、液肥量、增氧量为影响因素,以玉米“晶甜3号”的产量及根系生长为评价指标进行正交试验研究。结果表明:对玉米产量影响大小顺序依次为灌溉量、增氧量和液肥量,对根干重影响大小顺序为增氧量、灌溉量和液肥量。运用Design-Exper10.0对数据完成方差分析和显著性检验,确定了最佳工艺参数组合:当灌溉量为3600m³/hm²、液肥量为650kg/hm²、增氧量为2000m³/hm²时,理论的玉米产量为9987kg/hm²,根干重为30.25g。试验结果与优化结果相符,满足玉米农艺性状要求。     

Crop water deficit estimation and irrigation scheduling in western Jilin province,Northeast China

Jilin province is one of the main dryland grain production areas in China. Recently, limited supplemental irrigation, using groundwater in the semi-arid western area of the province, has developed rapidly to improve the low grain productivity caused by rainfall variability. Research was conducted to estimate the actual crop water requirements and identify the timing and magnitude of water deficits of the main crops such as corn (Zea mays L.), soybean (Glycine max L.) and sorghum (Sorghum bicolor L.). Using the guidelines for computing crop water requirements in FAO Irrigation and Drainage paper 56 and historical rainfall distributions, the crop water requirements, ETc and the crop water deficits of corn, soybean and sorghum were calculated. Based on the water deficit analysis, a recommended average supplemental irrigation schedule was developed. Crop production was compared to full irrigation and to a rainfed control in a field experiment.On average, compared to the rainfed control, the full irrigation and the average supplemental irrigation treatments of corn, increased yields 49.0 and 43.9%, respectively; soybean yields of those treatments increased by 41.0 and 34.7%, and sorghum yields of those treatments increased by 55.5 and 46.3%. A supplemental irrigation schedule can be used in the semi-arid western Jilin province to improve crop yields.     

不同灌水策略对夏玉米水分利用效率和产量构成要素的影响

于2013—2014年在河南商丘开展了5个灌水处理(T1:苗期水45 mm+拔节水60 mm+灌浆水60 mm+成熟期水45mm,T2:苗期水45 mm+拔节水60 mm+灌浆水60 mm,T3:拔节水60 mm+灌浆水60 mm,T4:拔节水60 mm,T5:灌浆水60 mm)的田间试验,研究了不同灌水处理对夏玉米阶段耗水量、总耗水量、产量、水分利用效率、收获穗数、穗粒数、百粒质量、行粒数的影响。结果表明,夏玉米不同生长阶段灌水处理的耗水量均显著大于不灌水处理(P0.05),且随着整个生育期灌水次数和灌水量的增加,总耗水量显著提高。2013年和2014年,灌拔节水和灌浆水处理(T3)的总耗水量显著低于T1处理(P0.05),产量分别下降8.0%和8.9%,水分利用效率则分别提高5.3%和0.5%。灌水显著影响了夏玉米的收获穗数、穗粒数和百粒质量。2 a的苗期灌水处理(T1和T2)显著提高了夏玉米的收获穗数(P0.05),拔节期和灌浆期灌水处理(T3)的穗粒数和百粒质量均显著大于只灌拔节水(T4)和只灌灌浆水(T5)的处理(P0.05),但收获穗数差异不显著。在节水灌溉的条件下,黄淮海平原夏玉米主产区要实现较高的产量和水分利用效率,灌拔节水和灌浆水是最基本的灌水策略。     

Subsurface drip irrigation for corn production: a review of 10 years of research in Kansas

Kansas State University initiated studies in 1989 to develop the methodology for successful application of subsurface drip irrigation (SDI) for corn production on the deep silt loam soils of the Central Great Plains, USA. Irrigation water use for corn can be reduced by 35–55% when using SDI compared with more traditional forms of irrigation in the region. Irrigation frequency has not been a critical issue when SDI is used for corn production on the deep silt loam soils of the region. A dripline spacing of 1.5 m has been found to be most economical for corn grown in 0.76 m spaced rows. Nitrogen fertigation was a very effective management tool with SDI, helping to maximize corn grain yield, while obtaining high efficiencies of nitrogen and water use. The research SDI systems have been utilized since 1989 without replacement or major degradation. SDI systems lasting 10–20 years are cost competitive for corn production with the more traditional forms of irrigation in the Great Plains for certain field sizes.Communicated by P. Thorburn     

Evaluation of crop water stress index for LEPA irrigated corn

This study was designed to evaluate the crop water stress index (CWSI) for low-energy precision application (LEPA) irrigated corn (Zea mays L.) grown on slowly-permeable Pullman clay loam soil (fine, mixed, Torrertic Paleustoll) during the 1992 growing season at Bushland, Tex. The effects of six different irrigation levels (100%, 80%, 60%, 40%, 20%, and 0% replenishment of soil water depleted from the 1.5-m soil profile depth) on corn yields and the resulting CWSI were investigated. Irrigations were applied in 25 mm increments to maintain the soil water in the 100% treatment within 60–80% of the “plant extractable soil water” using LEPA technology, which wets alternate furrows only. The 1992 growing season was slightly wetter than normal. Thus, irrigation water use was less than normal, but the corn dry matter and grain yield were still significantly increased by irrigation. The yield, water use, and water use efficiency of fully irrigated corn were 1.246 kg/m², 786 mm, and 1.34 kg/m³, respectively. CWSI was calculated from measurements of infrared canopy temperatures, ambient air temperatures, and vapor pressure deficit values for the six irrigation levels. A “non-water-stressed baseline” equation for corn was developed using the diurnal infrared canopy temperature measurements as T _c–T _a = 1.06–2.56 VPD, where T _c was the canopy temperature (°C), Ta was the air temperature (°C) and VPD was the vapor pressure deficit (kPa). Trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Both the dry matter and grain yields decreased with increased soil water deficit. Minimal yield reductions were observed at a threshold CWSI value of 0.33 or less for corn. The CWSI was useful for evaluating crop water stress in corn and should be a valuable tool to assist irrigation decision making together with soil water measurements and/or evapotranspiration models. Received: 19 May 1998     

Different indices to characterize water use pattern of micro-sprinkler irrigated onion (Allium cepa L.)

The amount of water used by any crop largely depends on the extent to which the soil water depletion from the root zone is being recharged by appropriate depth of irrigation. To test this hypothesis a field study was carried out in November–March of 2002–2003 and 2003–2004 on a sandy loam (Aeric haplaquept) to quantify the effect of depth of irrigation applied through micro-sprinklers on onion (Allium cepa L.) bulb yield (BY) and water use patterns. Seven irrigation treatments consisted of six amounts of sprinkler applied water relative to compensate crop (K_c) and pan (K_p) coefficient-based predicted evapotranspiration loss from crop field (ET_p) (i) 160% of ET_p (1.6ET_p); (ii) 1.4ET_p; (iii) 1.2ET_p; (iv) 1.0ET_p; (v) 0.8ET_p; (vi) 0.6ET_p; (vii) 40 mm of surface applied water whenever cumulative pan evaporation equals to 33 mm. Water use efficiency (WUE), net evapotranspiration efficiency (WUE_ET) and irrigation water use efficiency (WUE_I) were computed. Marginal water use efficiency (MWUE) and elasticity of water productivity (EWP) of onion were calculated using the relationship between BY and measured actual evapotranspiration (ET_c). Yield increased with increasing sprinkler-applied water from 0.6 to 1.4ET_p. Relative to the yield obtained at 0.6ET_p, yield at 1.0ET_p increased by 23–25% while at 1.4ET_p it was only 3–9% greater than that at 1.0ET_p. In contrast, yield at 1.6ET_p was 9–12% less than that at 1.4ET_p. Maximum WUE (7.21 kg m⁻³) and WUE_ET (13.87 kg m⁻³) were obtained under 1.0ET_p. However, the highest WUE_I (3.83 kg m⁻³) was obtained with 1.2ET_p. The ET_c associated with the highest WUE was 20% less than that required to obtain the highest yields. This study confirmed that critical levels of ET_c needed to obtain maximum BYs, or WUE, could be obtained more precisely from the knowledge of MWUE and EWP.     

新疆滴灌施肥棉花生长和产量的水肥耦合效应

在新疆石河子棉花种植区,研究了滴灌施肥棉花生长和产量的水肥耦合效应.试验设置3个灌水水平和5个NPK施肥水平.结果表明,滴灌施肥条件下,灌水量对株高、有效铃数、百铃质量、籽棉产量、水分利用效率和灌溉水利用效率影响均在0.05水平下具有统计学意义,对和叶面积指数的影响在0.01水平下具有统计学意义,其变化随着灌水量的增加而增加;施肥对株高、叶面积指数、有效铃数、百铃质量和籽棉产量影响在0.01水平下具有统计学意义,水肥交互作用对单株有效铃数、百铃质量和籽棉产量影响在0.01水平下具有统计学意义.施肥过高对作物生长有一定的抑制作用.灌水量为60%ET_c,施肥量为300 kg/hm²∶120 kg/hm²∶60 kg/hm²(ω_N∶ω_P2O5∶ω_K2O)时氮、磷、钾的利用效率均最高,灌水量为100%ET_c,施肥量为150 kg/hm²:60 kg/hm²∶30 kg/hm²(ω_N∶ω_P2O5∶ω_K2O)时氮、磷、钾养分回收率最高.从产量、水分利用效率和肥料偏生产力等角度综合考虑,灌水量100%ET_c、300 kg/hm²∶120 kg/hm²∶60 kg/hm²(ω_N∶ω_P2O5∶ω_K2O)为最佳滴灌施肥策略.     

Evaluation on the irrigation and fertilization management practices under the application of treated sewage water in Beijing, China

Irrigation and fertilization management practices play important roles in crop production. In this paper, the Root Zone Water Quality Model (RZWQM) was used to evaluate the irrigation and fertilization management practices for a winter wheat–summer corn double cropping system in Beijing, China under the irrigation with treated sewage water (TSW). A carefully designed experiment was carried out at an experimental station in Beijing area from 2001 to 2003 with four irrigation treatments. The hydrologic, nitrogen and crop growth components of RZWQM were calibrated by using the dataset of one treatment. The datasets of other three treatments were used to validate the model performance. Most predicted soil water contents were within ±1 standard deviation (S.D.) of the measured data. The relative errors (RE) of grain yield predictions were within the range of −26.8% to 18.5%, whereas the REs of biomass predictions were between −38% and 14%. The grain nitrogen (N) uptake and biomass N uptake were predicted with the RE values ranging from −13.9% to 14.7%, and from −11.1% to 29.8%, respectively. These results showed that the model was able to simulate the double cropping system variables under different irrigation and fertilization conditions with reasonable accuracy. Application of RZWQM in the growing season of 2001–2002 indicated that the best irrigation management practice was no irrigation for summer corn, three 83 mm irrigations each for pre-sowing, jointing and heading stages of winter wheat, respectively. And the best nitrogen application management practice was 120 kg N ha⁻¹ for summer corn and 110 kg N ha⁻¹ for winter wheat, respectively, under the irrigation with TSW. We also obtained the alternative irrigation management practices for the hydrologic years of 75%, 50% and 25%, respectively, in Beijing area under the conditions of irrigation with TSW and the optimal nitrogen application.     

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。