Effect of amount and timing of subsurface drip irrigation on corn yield

A field study was conducted at North Platte, Nebraska in 2007–2009, imposing eight irrigation treatments, ranging from dryland to fully irrigated. Four of the eight treatments allowed for various degrees of water stress only after tasseling and silking. In 2007, corn yield ranged from 8.9 Mg ha^?1 with a season total of 41 mm of irrigation water to 11.5 Mg ha^?1 for the fully irrigated treatment (264 mm of irrigation water). The treatment with the greatest reduction in irrigation water after tasseling and silking (158 mm) had a mean yield of 10.9 Mg ha^?1, only 0.6 Mg ha^?1 less than the fully irrigated treatment. In 2009, yields ranged from 12.6 to 13.5 Mg ha^?1. There were no significant yield differences between the irrigation treatments for several possible reasons: more in-season precipitation and cooler weather required less irrigation water; much of the irrigation water was applied after the most water-stress sensitive stages of tasseling and silking; and lower atmospheric demand allowed for soil water contents well below 50 % management allowed depletion (MAD) not to cause any yield losses.     

The effect of partial wetting of the root zone on yield and water use efficiency in a drip-and sprinkler-irrigated mature grapefruit grove

Summary The effect of partial wetting of the root zone on yield and water use efficiency in a drip- and sprinkler-irrigated mature grapefruit grove was tested in a long-term experiment from 1976 to 1979. Three different percentages of the surface soil areas ( 30%, 40% and 70%) were wetted by the use of single and double drip laterals and sprinklers, respectively. Irrigation frequencies were 3 and 7 days for the drip treatments and 14 and 21 days for the sprinkler-irrigated plots.Two amounts of water, 80% and 100% of the total seasonal water application as previously determined from the soil moisture depletion data (ca. 630 and 800 mm), were applied at the different irrigation intervals for the drip- and sprinkler-irrigated treatments during the irrigation season (April–November). Soil moisture and salinity patterns were determined by the neutron scattering method and by gravimetric sampling. The partition of water extraction from the wet and dry zones in the drip-irrigated treatments was determined. About 86% of the total amount of water depletion was from the wet zone and 14% from the dry zone. Percolation losses in the irrigated treatments receiving 80% of the total seasonal water application decreased as compared with the 100% irrigated plots. Salts accumulated during the irrigation season were leached out by the winter rainfall.The effect of the reduction of irrigation application amount, first introduced in 1976, on the grapefruit yield was cumulative. The average yield (for the three years 1977, 1978, 1979) in the 80%, drip-irrigated plots at 3-day intervals, was 89 t/ha, compared with 98 t/ha in the 100% irrigated plots. The average yields obtained in the sprinkler and trickle irrigation treatments receiving 100% of the water application was 84 t/ha and 100 t/ha, respectively. Yield reductions in the plots receiving reduced water application of 80% were 11% for the drip treatments and 13% for the sprinkler treatment; the extent of the yield reduction varied according to the time interval between irrigations. The fruit quality was up to the required standards in all treatments. Water use efficiency was greater in the drip-irrigated plots than in the sprinkled ones, and also greater in the plots given the reduced water applications (80% of the maximum seasonal amount of the irrigation water applied), as compared with plots receiving the full amount of irrigation.Contribution from the Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan 50–250, Israel. No. 175-E, 1981 series     

Irrigation scheduling of cotton in a climate with uncertain rainfall

Summary An investigation was made of the irrigation requirements of cotton grown in a sub-humid environment with significant but highly variable rainfall. In the first year of the study, no additional yield benefits accrued to subsequent irrigations following a pre-emergent irrigation due to above average rainfall (550 mm) throughout the growing season. In the second year a similar rainfall amount (502 mm) fell but significant yield increases to irrigation resulted due to the uneven distribution of the rainfall. The main effect was associated with later rains which influenced the number of bolls set. The maximum amount of water extracted by cotton from a deep grey cracking clay was 178 mm. It was found that 70% of this amount could be depleted before irrigation without loss of yield. Crop evapotranspiration varied from 607 mm with no irrigation after emergence to 775 mm following three irrigations. Irrigation was associated with significant losses from rainfall runoff. Too frequent irrigation creates a risk that soil will be too wet to permit utilisation of natural rainfall. Therefore, the use of soil water information to maximise the interval between irrigation is proposed as a necessary basis for efficient irrigation management.     

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.     

Incorporation of ridge and furrow method of rainfall harvesting with mulching for crop production under semiarid conditions

A plastic-covered ridge and furrow rainfall harvesting (PRFRH) system combined with mulches was designed to increase water availability to crops for improving and stabilizing agricultural production in the semiarid Loess region of northwest China. The system was built by shaping the soil surface with alternate ridges and furrows along the contour. The plastic-covered ridges served as a rainfall harvesting zone and furrows as a planting zone. Some materials were also used to mulch the furrows to increase the effectiveness of the harvested water. This system can make better utilization of light rain by harvesting rainwater through the plastic-covered ridge. The field experiment (using corn as an indicator crop) showed that grain yields in the PRFRH system with mulches in 1998 and 1999 were significantly higher than the controls, with an increase of 4010–5297 kg per ha (108–143%). In most treatments, the water use efficiencies (WUE) were in excess of 2.0 kg m⁻³. The WUE values of corn in this system were 1.9 times greater than the controls in 1998 and 1.4 times greater than the controls in 1999. The plastic-covered ridge led to a yield increase of 3430 kg per ha (92%) in 1998 and of 1126 kg per ha (21%) in 1999 compared with the uncovered ridge. On average, the additional mulches in the furrow brought about a yield increase of 8–25%. Based on the results of this study and other researches, this technique can increase corn grain yield by 60–95% in drought and average years, 70–90% in wet years, and 20–30% in very wet years. The PRFRH system had the potential to increase crop yield and produced greater economic benefit, therefore it could be used in regions dominated by light rainfall of low intensity where crops generally fail due to water stress.     

Yield and fruit development in mango (Mangifera indica L. cv. Chok Anan) under different irrigation regimes

‘Chok Anan’ mangoes are mainly produced in the northern part of Thailand for the domestic fresh market and small scale processing. It is appreciated for its light to bright yellow color and its sweet taste. Most of the fruit development of on-season mango fruits takes place during the dry season and farmers have to irrigate mango trees to ensure high yields and good quality. Meanwhile, climate changes and expanding land use in horticulture have increased the pressure on water resources. Therefore research aims on the development of crop specific and water-saving irrigation techniques without detrimentally affecting crop productivity.The aim of this study was to assess the response of mango trees to varying amounts of available water. Influence of irrigation, rainfall, fruit set, retention rate and alternate bearing were considered as the fruit yield varies considerably during the growing seasons. Yield response and fruit size distribution were measured and WUE was determined for partial rootzone drying (PRD), regulated deficit irrigation (RDI) and irrigated control trees.One hundred ninety-six mango trees were organized in a randomized block design consisting of four repetitive blocks, subdivided into eight fields. Four irrigation treatments have been evaluated with respect to mango yield and fruit quality: (a) control (CO = 100% of ET_c), (b) (RDI = 50% of ET_c), (c) (PRD = 50% of ET_c, applied to alternating sides of the root system) and (d) no irrigation (NI).Over four years, the average yield in the different irrigation treatments was 83.35 kg/tree (CO), 80.16 kg/tree (RDI), 80.85 kg/tree (PRD) and 66.1 kg/tree (NI). Water use efficiency (WUE) calculated as yield per volume of irrigation water was always significantly higher in the deficit irrigation treatments as compared to the control. It turned out that in normal years the yields of the two deficit irrigation treatments (RDI and PRD) do not differ significantly, while in a dry year yield under PRD is higher than under RDI and in a year with early rainfall, RDI yields more than PRD. In all years PRD irrigated mangoes had a bigger average fruit size and a more favorable fruit size distribution.It was concluded that deficit irrigation strategies can save considerable amounts of water without affecting the yield to a large extend, possibly increasing the average fruit weight, apparently without negative long term effects.     

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。     

Crop coefficient, yield response to water stress and water productivity of teff (Eragrostis tef (Zucc.)

In the semi-arid region of Tigray, Northen Ethiopia a two season experiment was conducted to measure evapotranspiration, estimate yield response to water stress and derive the crop coefficient of teff using the single crop coefficient approach with simple, locally made lysimeters and field plots. During the experiment we also estimated the water productivity of teff taking into account long-term rainfall probability scenarios and different levels of farmers’ skills. During the experimental seasons (2008 and 2009), the average potential evapotranspiration of teff ranged from 260 to 317 mm. The total seasonal water requirement of teff was found to lower in contrast to the assumptions of regional agronomists that teff water requirement is comparable to that of wheat and barley (375 mm). The average single crop coefficient values (k_c) for the initial, mid and late season stages of teff were 0.8-1, 0.95-1.1 and 0.4-0.5, respectively. The seasonal yield response to water stress was 1.04, which indicates that teff exhibits a moderately sensitive and linear response to water stress. The results suggest that teff is likely to give significantly higher grain yield when a nearly optimal water supply is provided. The study showed that, in locations where standard equipment is not affordably available, indicative (rough) crop evapotranspiration values can be obtained by using field plots and employing locally made lysimeters. The difference in economic water productivity (EWP) and the crop water productivity (CWP) for teff were assessed under very wet, wet, normal, dry and very dry scenarios. In addition two groups of farmers were evaluated, a moderately (I) and a highly skilled (II) group. The results showed that higher EWP and CWP were obtained under very wet scenario than very dry scenario. There was also a 22% increase in EWP and CWP under group II compared to group I farmers. The increase was due to a 22% reduction in unwanted water losses achieved through use of improved technology and better irrigation skills. Both EWP and CWP can be used to evaluate the pond irrigation water productivity (IWP) for a given climate, crop and soil type, and skill and technology level of the farmer. For special crops like teff extra criteria may be needed in order to properly evaluate the pond irrigation water productivity. During the experimental seasons, a high IWP for teff was attained when about 90% of the optimal water need of the crop was met. IWP can be used as an indicator as how much supplementary irrigation has to be applied in relation to the rainfall and other sources of water supply in order to assure greatest yield from a total area. However, the supplemental irrigation requirement of the crops may vary with season due to seasonal rainfall variability.     

Supplemental irrigation effect on canola yield components under semiarid climatic conditions

With the availability of irrigation water, supplemental irrigation in winter-grown crops, such as lentil, wheat, and barley, has been intensely practiced to prevent crop yield losses due to the incidence of intermittent drought stress. In the crop growing seasons of 2006-2007 and 2008-2009, a study was conducted to determine the effect of supplemental irrigations on Canola (Brassica napus L. cv. Elvis F1) under the semiarid climatic conditions of the Harran plain, Sanliurfa, Turkey. A sprinkler irrigation system was used to irrigate the study plots. The irrigation treatments included 0.0, 0.25, 0.50, 0.75, and 1.0 (full irrigation) of Class-A pan evaporation amounts. The full irrigation treatment during both years consisted of 250 and 225 mm, respectively. In turn, crop water use values during the same years and treatments were 462 and 449 mm. In general, plant height and 1000 seed weight ranged from 140 to 165 cm and from 2.5 to 3.3 g, respectively, and these variables significantly differed among irrigation treatments (p < 0.05). Crop yield and above ground biomass measurements were affected by irrigation treatments and varied from 1094 to 3943 kg ha⁻¹ and from 6746 to 18,311 kg ha⁻¹, respectively (p < 0.05). Similarly, harvest index values were affected (p < 0.05) and ranged from 0.16 to 0.23 on average. The water use efficiency obtained in the different treatments indicated a strong positive relationship between crop yield and irrigation. Overall, our results indicate that supplemental irrigation substantially increased canola yield; however, for an optimum yield, full irrigation is suggested.     

咸水灌溉对土壤水热盐变化及棉花产量和品质的影响

为了充分利用咸水资源,采用田间对比试验,研究了1、3、5、7 g/L等4个矿化度咸水(分别用S1、S2、S3、S4表示)灌溉对棉田土壤水热盐变化特征及棉花长势、产量和纤维品质的影响。结果表明,棉花生育期内各处理0~40 cm土层土壤含水率及地下5 cm处土壤温度总体上都随着灌溉水矿化度的增加而增大,但差异不大;处理间土壤电导率差异明显,灌溉水矿化度愈高,土壤电导率愈大,棉花生育期结束后,降雨对各处理盐分的淋洗率介于29.40%~40.40%。土壤水分和盐分剖面分布受制于土壤质地、降雨和棉花蒸发蒸腾耗水;干旱时期,土壤干燥,盐分表聚,湿润时期与之相反。棉花成苗率、株高、单株最大叶面积和霜前花率均随着灌溉水矿化度的增加而降低,籽棉产量从大到小依次为S2、S1、S3和S4,其中,S4与S1处理间的差异达显著水平。咸水灌溉通过改变马克隆值对纤维品质产生了负面影响,尤其是S4处理。研究结果可为丰富棉花咸水灌溉技术体系提供理论支撑。     

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.     

Effects of precipitation patterns and temperature trends on soil water available for vineyards in a Mediterranean climate area

The objective of this paper is to analyse the impact of temperature increases and irregular rainfall distribution, associated with climate change, on water availability for rainfed vineyards cultivated in a Mediterranean climate area. The study includes the analysis of the interrelations between precipitation distribution, temperature, evapotranspiration and runoff rates, and the resulting water storage in vineyards soils of the Penedès region (NE Spain). A hierarchical cluster analysis was applied to classify the years according to water availability. The influence of water stored into the soil on yield for some one of the main vine varieties cultivated in the area is analysed. A vineyard, representative of the land management practices in this area, was selected for soil moisture monitoring and runoff evaluations, as well as for grape yield, which was compared with yields recorded in other plots.According to rainfall distribution and water availability, the 12 analysed years represent five different situations: wet years with positive and negative water balance; dry years; years with average annual rainfall but irregularly distributed throughout the year leading to a negative water balance; and extreme situations. Significant water deficits were observed in years in which total rainfall amount was above the annual average in the area, being similar to those observed in dry years: in 8 of the 12 analysed years deficits higher than 100 mm (up to 309 mm) during the growing period (budbreak-harvest) were recorded. At annual scale, 42% of the analysed years recorded deficits ranging between 27.7 and 191.4 mm. In the driest years, and those with more irregular rainfall distribution, soil moisture contents below the wilting point were reached. The high intensity rainfalls, producing important runoff losses (in many cases out of the periods in which crop water needs are higher), together with the increasing temperature trends, which give rise to significant evapotranspiration increases (values up to 32% higher than the average were recorded during the study period), are the main responsible factors for the water deficits recorded during grape development. Winegrape yield was influenced by the water stored into the soil, bloom-veraison or during budbreak-bloom depending on the variety.     

咸水灌溉对棉花耗水特性和水分利用效率的影响

采用田间对比试验,连续3 a研究了1、3、5、7 g/L 4个矿化度咸水(记作S1、S2、S3、S4)灌溉对棉田土壤水盐、土壤蒸发、棉花阶段耗水量、籽棉产量和水分利用效率的影响。结果表明,棉花生育期内根系层土壤含水率和电导率有随灌溉水矿化度的增加而增大的趋势,土壤电导率增加尤为明显;年际间,各处理土壤含水率和电导率差异非常大,经过连续3 a灌溉,根系层土壤电导率均未逐年增加。S3和S4处理的平均土壤蒸发强度大于S1处理,S2与S1处理间的差异很小;7 g/L以下咸水灌溉对棉花耗水过程产生了一定影响,但对总耗水量影响并不明显。3 a的平均籽棉产量和水分利用效率由大到小顺序均为:S2、S1、S3、S4,S2比S1处理增产2.43%,水分利用效率增加1.15%,S3和S4比S1处理减产1.67%和8.88%,水分利用效率降低0.25%和7.31%,其中,S2和S3与S1处理间差异不显著,S4处理产量和水分利用效率降低显著。     

Subsurface drip irrigation of corn in the United States Mid-South

Although rainfall in the United States Mid-South is sufficient to produce corn (Zea mays L.) without irrigation in most years, timely irrigation has been shown to increase yields. The recent interest in ethanol fuels is expected to lead to increases in US corn production, and subsurface drip irrigation (SDI) is one possible way to increase application efficiency and thereby reduce water use. The objective of this study was to determine the response of SDI-irrigated corn produced in the US Mid-South. Field studies were conducted at the University of Arkansas Northeast Research and Extension Center at Keiser during the 2002-2004 growing seasons. The soil was mixed, with areas of fine sandy loam, loamy sand, and silty clay. SDI tubing was placed under every row at a depth of approximately 30 cm. Three irrigation levels were compared, with irrigation replacing 100% and 60% of estimated daily water use and no irrigations. The split plot treatment was hybrid, with three hybrids of different relative maturities. Although the 3-year means indicated significantly lower yields for a nonirrigated treatment, no significant differences were observed among the treatments in 2003 or 2004. A large difference was observed in 2002, the year with the least rainfall during the study period, but no difference was detected between the two irrigated treatments in any year. The treatment with the lower water application had the higher irrigation water use efficiency. Although the results of this study suggested that replacing 60% of the estimated daily evapotranspiration with SDI is sufficient for maximum corn yields, additional observations will be needed to determine whether corn production with SDI is feasible in the region and to develop recommendations for farmers choosing to adopt the method. Improved weather forecasting and crop coefficient functions developed specifically for the region should also contribute to more efficient irrigation management.     

Effect of irrigation amounts applied with subsurface drip irrigation on corn evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate

Quantifying the local crop response to irrigation is important for establishing adequate irrigation management strategies. This study evaluated the effect of irrigation applied with subsurface drip irrigation on field corn (Zea mays L.) evapotranspiration (ETc), yield, water use efficiencies (WUE = yield/ETc, and IWUE = yield/irrigation), and dry matter production in the semiarid climate of west central Nebraska. Eight treatments were imposed with irrigation amounts ranging from 53 to 356 mm in 2005 and from 22 to 226 mm in 2006. A soil water balance approach (based on FAO-56) was used to estimate daily soil water and ETc. Treatments resulted in seasonal ETc of 580–663 mm and 466–656 mm in 2005 and 2006, respectively. Yields among treatments differed by as much as 22% in 2005 and 52% in 2006. In both seasons, irrigation significantly affected yields, which increased with irrigation up to a point where irrigation became excessive. Distinct relationships were obtained each season. Yields increased linearly with seasonal ETc (R² = 0.89) and ETc/ETp (R² = 0.87) (ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 1.58 over the two seasons. WUE increased non-linearly with seasonal ETc and with yield. WUE was more sensitive to irrigation during the drier 2006 season, compared with 2005. Both seasons, IWUE decreased sharply with irrigation. Irrigation significantly affected dry matter production and partitioning into the different plant components (grain, cob, and stover). On average, the grain accounted for the majority of the above-ground plant dry mass (≈59%), followed by the stover (≈33%) and the cob (≈8%). The dry mass of the plant and that of each plant component tended to increase with seasonal ETc. The good relationships obtained in the study between crop performance indicators and seasonal ETc demonstrate that accurate estimates of ETc on a daily and seasonal basis can be valuable for making tactical in-season irrigation management decisions and for strategic irrigation planning and management.     

基于Meta分析的中国灌溉冬小麦产量及水分利用效率影响因素研究

【目的】目前针对灌溉冬小麦产量与水分利用效率影响因素的研究大多集中于某一特定区域,研究结果零散,针对上述问题,揭示宏观尺度下灌溉冬小麦产量和水分利用效率的影响因素。【方法】综合已发表的田间试验数据,采用Meta分析方法得出灌溉在不同地区的增产效应和水分效应,在异质性检验的基础上,通过Meta亚组分析探究灌溉定额、降雨量和平均气温等对冬小麦产量和水分利用效率的影响机制。【结果】与生育期不灌溉相比,灌溉使冬小麦总体增产39.34%,水分利用效率提高3.39%;增产率随灌溉定额的增加而增大,增幅最终趋于稳定,水分利用效率随灌溉定额的增加呈先增加后减少的趋势,当灌溉定额>240 mm时,冬小麦相对水分利用效率变化率显著降低11.29%;随着生育期平均温度上升,灌溉冬小麦增产效应显著提高,生育期均温>9℃时,冬小麦增产率高达45.81%;生育期降雨量对灌溉冬小麦产量影响显著,生育期降雨量处于干旱年份时灌溉增产效应最明显,增产率为72.48%。【结论】灌溉定额为60~120 mm更有利于提高冬小麦产量和水分利用效率。     

The wheat yields and water-use efficiency in the Loess Plateau: straw mulch and irrigation effects

The yield of spring wheat (Triticum aestivum L.), one of the major crops planted in the Loess Plateau, China, is mainly affected by available water. Straw mulch and irrigation are efficient ways of influencing wheat yield and water-use efficiency. To develop better semiarid crop and water management practices, a 13-year experiment in spring wheat monoculture was conducted at the Dingxi Soil and Water Conservation Institute of the Loess Plateau. The influence of rainfall during the growing season (March–July) on yields of rain-fed wheat was studied for 13 years (1982–1992 and 1997–1998). The influence of straw mulch and irrigation on wheat yield, and water-use efficiency, was studied for 2 years (1997–1998). We found that growing season rainfall had a significant (P < 0.05) influence on biomass and grain yield of spring wheat in rain-fed conditions during the 13 years. Both biomass and grain yield were very low and varied significantly due to the low and significant variability of growing season rainfall. Straw mulch increased wheat yields significantly during both dry (1997) and wet (1998) years. It increased biomass and grain yield by 37 and 52%, respectively, in 1997, and by 20 and 26%, respectively, in 1998. Straw mulch also significantly decreased evapotranspiration (P < 0.05), soil water depletion (P < 0.01), and increased water-use efficiency (P < 0.001). Biomass and grain yield both increased (P < 0.01 orP < 0.001) with increasing irrigation in 1997 and 1998. The three irrigation levels increased the biomass yield from 34 to 66% in 1997, and from 34 to 77% in 1998. The irrigation levels also increased grain yield from 53 to 102% in 1997, and from 22 to 57% in 1998. Water-use efficiency for biomass and grain yield also increased with increasing irrigation. On the other hand, irrigation water-use efficiency for biomass and grain yield decreased with increasing irrigation. The results suggest that higher crop yields in the semiarid Loess Plateau may be achieved by using irrigation, or a proper combination of straw mulch and irrigation.     

Optimizing the yield of winter wheat by regulating water consumption during vegetative and reproductive stages under limited water supply

To ensure sustainable agricultural water use in water shortage regions, practices of deficit irrigation should be adopted. This study investigated the performance of winter wheat (Triticum aestivum L.) under limited water supply from 2005 to 2011, a six-season field test on the North China Plain. The test was comprised of four treatments: rain-fed, single irrigation applied at sowing to obtain a good level of soil moisture at the start of crop growth (I1s), single irrigation applied during recovery to jointing (I1r), and full irrigation supplied as three irrigations (control, I3). The results showed that grain yield was significantly correlated with rainfall before heading and with evapotranspiration (ET) after heading (P < 0.01) under rain-fed conditions. The average contribution of soil water stored before sowing to seasonal ET was 90, 103, and 145 mm for rain-fed, I1s, and I1r, respectively, during the six seasons. A smaller root length density (RLD), which restricted utilization of deep soil water by the crop, was one of the reasons for the lower yield with rain-fed and I1s treatments compared with the I1r treatment in dry seasons. The results also showed that the limited irrigation applied from recovery to jointing stage (Treatment I1r) significantly promoted vegetative growth and more efficient soil water use during the reproductive (post-heading) stage, resulting in a 21.6 % yield increase compared with that of the I1s treatment. And although the average yield of the I1r treatment was 14 % lower than that of the full irrigation treatment, seasonal irrigation was reduced by 120–140 mm. With smaller penalties in yield and a larger reduction in applied irrigation, I1r could be considered a feasible irrigation practice that could be used in the NCP for conservation of groundwater resources.     

The effect of deficit irrigation with treated wastewater on sweet corn: experimental and modelling study using SALTMED model

This study investigated the impact of using treated wastewater and deficit irrigation on yield, water productivity, dry matter and soil moisture availability. The experiment included six treatments of deficit irrigation with treated wastewater during the 2010 and 2011 seasons and two deficit irrigation treatments combined with 3 organic amendment levels during the 2012 season. The experimental and SALTMED modelling results indicated that regulated deficit irrigation when applied during vegetative growth stage could stimulate root development, increase water and nutrient uptake and subsequently increase the yield. The organic amendment has slightly improved yield under full irrigation but had relatively small effect under stress conditions. The SALTMED model results supported and matched the experimental results and showed similar differences among the different treatments. The model proved its ability to predict soil moisture availability, yield, water productivity and total dry matter for three growing seasons under several deficit irrigation strategies using treated wastewater. The high values of the coefficient of determination R ² reflected a very good agreement between the model and observed values. The SALTMED model results generally confirm the model’s ability to predict sweet corn growth and productivity under deficit irrigation strategies in the semi-arid region.     

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.