Macromanagement of deficit-irrigated peanut with sprinkler irrigation

Precision irrigation management and scheduling, as well as developing site- and cultivar-specific crop coefficient (K_c), and yield response factor to water deficit (ky) are very important parameters for efficient use of limited water resources. This study investigated the effect of deficit irrigation, applied at different growth stages of peanut with sprinkler irrigation in sandy soil, on field peanut evapotranspiration (ETc), yield and yield components, and water use efficiencies (IWUE and WUE). Also, yield response factor to water deficit (ky), and site- and cultivar-specific K_c were developed. Four treatments were imposed to deficit irrigation during late vegetative and early flowering, late flowering and early pegging, pegging, and pod formation growth stages of peanut, and compared with full irrigation in the course of the season (control). A soil water balance equation was used to estimate crop evapotranspiration (ETc). The results revealed that maximum seasonal ETc was 488 mm recorded with full irrigation treatment. The maximum value of K_c (0.96) occurred at the fifth week after sowing, this value was less than the generic values listed in FAO-33 and -56 (1.03 and 1.15), respectively. Dry kernels yield among treatments differed by 41.4%. Deficit irrigation significantly affected yields, where kernels yield decreased by 28, 39, 36, and 41% in deficit-irrigated late vegetative and early flowering, late flowering and early pegging, pegging, and pod formation growth stages, respectively, compared with full irrigation treatment. Peanut yields increased linearly with seasonal ETc (R² = 0.94) and ETc/ETp (R² = 0.92) (ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 2.9, was higher than the 0.7 value reported by Doorenbos and Kassam [Doorenbos, J., Kassam, A.H., 1979. Yield response to water. FAO Irrigation and Drainage Paper 33, Rome, Italy, 193 pp.], the high ky value reflects the great sensitivity of peanut (cv. Giza 5) to water deficit. WUE values varied considerably with deficit irrigation treatments, averaging 6.1 and 4.5 kg ha⁻¹ mm⁻¹ (dry-mass basis) for pods and kernels, respectively. Differences in WUE between the driest and wettest treatment were 31.3 and 31.3% for pods and kernels, respectively. Deficit irrigation treatments, however, impacted IWUE much more than WUE. Differences in IWUE between the driest and wettest treatment were 33.9 and 33.9% for pods and kernels, respectively. The results revealed that better management of available soil water in the root zone in the course of the season, as well as daily and seasonal accurate estimation of ETc can be an effective way for best irrigation scheduling and water allocation, maximizing yield, and optimizing economic return.     

Water use efficiency of narrow row cotton

Summary A field experiment was conducted on the west side of the San Joaquin Valley in California to determine water use, crop growth, yield and water use efficiency of Acala (SJ-2) cotton (Gossypium hirsutum L.) grown in 0.5 m spaced rows on a Panoche clay loam soil (Typic Torriorthents). Evapotranspiration was determined by water balance techniques utilizing neutron soil moisture measurements. All neutron measurements were made within a 3 m soil profile in 0.20 m increments. The measured evapotranspiration was compared to climatic estimates of potential evapotranspiration, and to calculations using a one-dimensional soil water balance model that separately computed soil water evaporation and plant transpiration. Crop growth was determined by weekly destructive plant sampling. Leaf area was determined along with dry matter components of leaves, stems, fruiting parts (flowers and squares) and bolls. Final yield was determined by machine harvesting (brush stripper) 720 m² from each plot. Lint yields and fiber quality were determined by sample ginning and fiber analysis at the U.S. Cotton Research Station at Shafter, California. Three irrigation regimes were established that resulted in an evapotranspiration range from a high deficit condition to full irrigation at the calculated atmospheric demand.The measured evapotranspiration of narrow row cotton under a full irrigation regime was 778 mm, 594 mm under a limited irrigation regime and 441 mm under a regime with no post-plant irrigation. The evapotranspiration from these irrigation treatments was accurately simulated by a water balance model. that used inputs of potential evapotranspiration, leaf area index, soil water holding capacity and root development.The average lint yield from narrow row cotton with a full irrigation regime was 1583 kg/ha, the average lint yield from a limited irrigation regime was 1423 kg/ha and the average lint yield from a treatment with no postplant irrigation (fully recharged soil profile at planting) was 601 kg/ha. The full irrigation regime resulted in a dry matter production of approximately 16 t/ha while the limited irrigated regime produce 11 t/ha and the no-postplant irrigation regime produced 7 t/ha of dry matter. The fiber quality results indicated significant (0.05 level) differences only in 50% span length and micronaire, with the 2.5% span length, uniformity index, elongation and strength indicating no difference.Cotton lint yield was found to be directly related to total evapotranspiration although the relationship was slightly non-linear while dry matter yield was found to be linearly related to evapotranspiration. Both lint and dry matter yield were found to have a linear relationship to estimated transpiration from the water balance model calculations.Contribution from the Unived States Department of Agriculture, Agricultural Research Service, Western Region and the University of California     

Deficit irrigation and nitrogen effects on seed cotton yield, water productivity and yield response factor in shallow soils of semi-arid environment

A field experiment was conducted for 2 years to investigate the effects of deficit irrigation, nitrogen and plant growth minerals on seed cotton yield, water productivity and yield response factor. The treatment comprises six levels of deficit irrigation (Etc 1.0, 0.9, 0.8, 0.7, 0.6 and 0.5) and four levels of nitrogen (80, 120, 160 and 200 kg N ha⁻¹). These were treatments superimposed with and without plant growth mineral spray. Furrow irrigation treatments were also kept. Cotton variety Ankur-651 Bt was grown during 2006 and 2007 cotton season. Drip irrigation at 1.0 Etc saved 26.9% water and produced 43.1% higher seed cotton yield over conventional furrow irrigation (1.0 Etc). Imposing irrigation deficit of 0.8 Etc caused significant reduction in seed cotton yield to the tune of 9.3% of the maximum yield. Further increase in deficit irrigation from 0.7 Etc to 0.5 Etc significantly decreased seed cotton yield over its subsequent higher irrigation level. Decline in the yield under deficit irrigation was associated with reduction in number of bolls plant⁻¹ and boll weight. Nitrogen at 200 kg ha⁻¹ significantly increased mean seed cotton yield by 36.3% over 80 kg N ha⁻¹. Seed cotton yield tended to increase linearly up to 200 kg N ha⁻¹ with drip Etc 0.8 to drip Etc 1.0. With drip Etc 0.6-0.5, N up to 160 kg ha⁻¹ provided the highest yield, thereafter it had declined. Foliar spray of plant growth mineral (PGM) brought about significant improvement in seed cotton yield by 14.1% over control. The water productivity ranged from 0.331 to 0.491 kg m⁻³ at different irrigation and N levels. On pooled basis, crop yield response factor of 0.87 was calculated at 20% irrigation deficit.     

Short staple cotton under micro and level-basin irrigation methods

Summary Advanced irrigation methods and water management practices are needed for high yields with minimum water applications: A three-year study using recently introduced surface-micro and level-basin irrigation methods was conducted in central Arizona on a nonuniform sandy loam soil to determine optimum water placement and irrigation frequency. Several newer, short staple cotton (Gossypium hirsutum L.) cultivars and different row spacings were also evaluated. Precision micro and level-basin irrigation systems achieved maximum lint yields of more than 2,000 kg/ha and lint water use efficiencies in excess of 0.21 kg/m³. A single micro line per every two rows irrigated daily averaged about 25% more lint cotton than every furrow, level-basin treatment irrigated every two weeks. With a micro irrigation line per every three rows, yields were reduced by an average of 15% and as much as 33% compared with a micro line per every two rows. The cotton production on the narrow row (0.75 m) spacing with a 33% higher plant population outyielded the conventional row (1.0 m) spacing by about 15% in the third year. In addition, some of the newer cotton cultivars had a lower water requirement than the ones prevalent 10 years ago. In the future, cotton growers should be able to irrigate with less water by using improved irrigation systems and water management practices.Contribution of the U.S. Department of Agriculture, Agricultural Research Service, Pacific West Area     

Genotypic differences of maize in grain yield response to deficit irrigation

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

水钾耦合对北疆机采棉水钾利用效率及产量的影响

【目的】探索不同土壤含水率区间与钾肥施用量之间的耦合效应,优化机采棉灌水和钾肥施用方案。【方法】以膜下滴灌棉花为研究对象,设计了3个土壤含水率(田间持水率的40%～60%、60%～80%和80%～100%,W1、W2、W3)和3个施钾水平(30、60和90 kg/hm~2,K1、K2、K3),研究了机采棉的株高、叶面积指数、生物量和产量。【结果】土壤含水率为田间持水率的60%～80%时,钾肥对棉花株高的增益效果更加明显;施钾量在30 kg/hm~2和60 kg/hm~2时,土壤含水率能显著提高株高的日增长量。叶面积指数随着施钾量和灌水量的增加而增加。土壤含水率为田间持水率的60%～80%且施钾量为90 kg/hm~2时,最有利于棉花生物量的形成。土壤含水率为田间持水率的60%～80%时,棉花单株有效铃数和籽棉产量最多,且籽棉产量和有效铃数随着施钾量的增加而增加,W2K3处理的籽棉产量最高(7 579.78 kg/hm~2),有效铃数最高(9.03个/株)。钾肥能促进棉花单铃质量的形成,但是单株有效铃数的增加会减缓钾肥对棉花单铃质量的促进作用。当灌水水平一致时,钾肥生产效率随着施钾量的增加而显著降低。在土壤含水率为田间持水率的80%～100%且施钾量为90 kg/hm~2时,棉花的水分利用效率最低。【结论】土壤含水率为田间持水率的60%～80%且施钾量为90 kg/hm~2为适宜的灌水施肥方案,有利于生物量向生殖生长倾斜,获得较高的水钾利用效率以及棉花籽棉产量。     

施氮对中国棉田产量和水分利用效率影响的Meta分析

为系统分析不同气候条件、土壤基础条件和农田管理措施条件下施氮对棉花产量和水分利用效率的影响,收集了国内外已发表的103篇中英文文献,筛选其中37篇文献,共获得301组产量和127组水分利用效率数据。基于Meta分析方法定量分析了不同生产条件下施氮对棉花产量和水分利用效率的影响,同时利用偏相关分析找出施氮条件下棉花产量和水分利用效率的主要影响因素。结果表明,以不施氮为对照,施氮能够显著提高棉花的产量和水分利用率。在年均降水量200～500 mm的地区施氮对产量和水分利用率的提高作用最为明显,效应量分别为34.02%和54.15%;施氮对产量和水分利用率的提高作用均随着日照时数的增大而增大。当土壤pH值为6～8时,施氮对棉花产量和水分利用效率的提高作用最为明显,效应量分别为28.52%和24.59%;在不同土壤质地中施氮对产量和水分利用效率的提高作用均表现为在砂土中效应量最大,分别为46.71%和26.29%;随着施肥频次的增加,施氮对棉花产量和水分利用率的提高作用逐渐增大;施氮对产量的提高作用随灌水量的增加而增加,对水分利用率的提高作用随灌水量的增加呈先增加后降低趋势。当施氮量为300～...     

Water use and yield responses of cotton to alternate partial root-zone drip irrigation in the arid area of north-west China

A field experiment was carried out over 2 years to investigate the effect of partial root-zone irrigation applied using drip irrigation on the water use and yield of cotton (Gossypium hirsutum) in oasis fields of arid north-west China. Two irrigation treatments, i.e., conventional drip irrigation (CDI, both sides of plant row watered) or alternate drip irrigation (ADI, both sides of plant row alternatively watered) were applied under plastic mulch. Three irrigation levels (i.e., 15, 22.5, 30 mm during 2004 and 12, 18, 24 mm during 2005) were applied at each irrigation. Monitoring of soil water contents in the ADI treatment indicated a change in root-zone uptake in response to the irrigation method, although there existed some lateral soil water movement from the wetted side to the dry side after each watering. Stomatal conductance in ADI was lower than that of CDI when compared at the same irrigation level. Reduced stomatal conductance and water loss resulted in higher water use efficiency (WUE) in the ADI treatment. About 31-33% less total irrigation water was applied using the ADI method when compared to that of the CDI treatment with a similar seed cotton yield. ADI also yielded 11% more pre-frost seed cotton than CDI in 2005, indicating a better lint quality and higher price. These results suggest that ADI should be a useful water-saving irrigation method in arid oasis fields where cotton production is heavily dependent on irrigation and water resources are scarce.     

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。     

Effects of salinity and fertigation practice on cotton yield and N recovery

The purpose of optimal water and nutrient management is to maximize water and fertilizer use efficiency and crop production, and to minimize groundwater pollution. In this study, field experiments were conducted to investigate the effect of soil salinity and N fertigation strategy on plant growth, N uptake, as well as plant and soil ¹⁵N recovery. The experimental design was a 3 × 3 factorial with three soil salinity levels (2.5, 6.3, and 10.8 dS m⁻¹) and three N fertigation strategies (N applied at the beginning, end, and in the middle of an irrigation cycle). Seed cotton yield, dry matter, N uptake, and plant ¹⁵N recovery significantly increased as soil salinity level increased from 2.5 to 6.3 dS m⁻¹, but they decreased markedly at higher soil salinity of 10.8 dS m⁻¹. Soil ¹⁵N recovery was higher under soil salinity of 10.8 dS m⁻¹ than those under soil salinity of 6.3 dS m⁻¹, but was not significantly different from that under soil salinity of 2.5 dS m⁻¹. The fertigation strategy that nitrogen applied at the beginning of an irrigation cycle had the highest seed cotton yield and plant ¹⁵N recovery, but showed higher potential loss of fertilizer N from the root zone. While the fertigation strategy of applying N at the end of an irrigation cycle tended to avoid potential N loss from the root zone, it had the lowest cotton yield and nitrogen use efficiency. Total ¹⁵N recovery was not significantly affected by soil salinity, fertigation strategy, and their interaction. These results suggest that applying nitrogen at the beginning of an irrigation cycle has an advantage on promoting yield and fertilizer use efficiency, therefore, is an agronomically efficient way to provide cotton with fertilizer N under the given production conditions.     

Effects of fixed partial root-zone drying irrigation and soil texture on water and solute dynamics in calcareous soils and corn yield

Water dynamics and salt distribution in the soil were studied under Fixed Partial Root zone Drying irrigation (FPRD) conditions in corn fields in Northern Greece. FPRD irrigation technique was applied without deficit treatment in two calcareous soils, a sandy clay loam and a sandy loam. Soil water content was recorded in the vertical profile of 0.6 m with the use of capacitance sensors in the row and interrow positions of plants. Salt built-up was monitored to the depth of the root zone, bi-weekly, by measuring electrical conductivity (EC_e) and the concentrations of soluble cations Ca²⁺, Mg²⁺, Na⁺ and K⁺ of the saturation extract on irrigated and non irrigated interrow positions. Soil moisture distribution and salt built-up in soil were used to evaluate the potentials and constraints of FPRD efficiency to sustain plant growth and crop production as a low cost drip irrigation technique. The results indicated that FPRD application on both soils was capable of supplying sufficient amounts of water on plant row. Soil analyses showed that salts accumulated to high levels in the soil surface and decreased in depth at the non irrigated interrow positions. Spatial and temporal variability of salt movement and distribution in the soil profile of 0.6 m were ascribed to soil textural differences. The development and yield of corn plants for both soils reached the usual standards for the area with a minor decrease in the sandy loam soil.     

Drip irrigation with saline water for oleic sunflower (Helianthus annuus L.)

The field experiments were carried out in 2007 and 2008 to study the effects and strategies of drip irrigation with saline water for oleic sunflower. Five treatments of irrigation water with average salinity levels of 1.6, 3.9, 6.3, 8.6, and 10.9 dS/m were designed. For each treatment, 7 mm water was applied when the soil matric potential (SMP) 0.2 m directly underneath the drip emitters was below −20 kPa, except during the seedling stage. To ensure the seedling survival, 28 mm water was applied after sowing during the seedling stage. Results indicate that amount of applied water decreases as salinity level of irrigation water increases. The emergence will be delayed when the salinity level of irrigation water is higher than 6.3 dS/m, but these differences will be alleviated if there is rainfall during emergence period. The final emergence percentage is not changed when salinity level of irrigation is less than 6.3 dS/m, and the percentage decreases by 2.0% for every 1 dS/m increase when the salinity level of irrigation water is above 6.3 dS/m, but the decreasing rate will be reduced if there is rainfall. The plant height and yield decrease with the increase of salinity of irrigation water. The height of plants decreases by 0.6-1.0% for every 1 dS/m increase in salinity level of irrigation water. The yield decreases by 1.8% for every 1 dS/m increase in salinity level of irrigation water, and irrigation water use efficiency (IWUE) increases with increase in salinity of irrigation water. The soil salinity increases as the salinity of irrigation water increasing after drip irrigation with saline water in the beginning, but the soil salinity in soil profile from 0 to 120 cm depths can be maintained in a stable level in subsequent year irrigation with saline water. From the view points of yield and soil salt balance, it can be recognized even as the salinity level of irrigation water is as high as 10.9 dS/m, saline water can be applied to irrigate oleic sunflower using drip irrigation when the soil matric potential 0.2 m directly under drip emitter is kept above −20 kPa and the beds are mulched in semi-humid area.     

沙地喷灌土壤基质势调控对土壤水分分布和马铃薯产量的影响

[目的]制定砂质土壤马铃薯的喷灌灌溉制度。[方法]选择“夏波蒂”(抗旱性弱)和“费乌瑞它”(抗旱性强)2种不同抗旱能力的马铃薯品种,通过2a的田间试验,研究了不同土壤基质势阈值对土壤水分状况、马铃薯产量与灌溉水利用效率等的影响,以确定马铃薯适宜的土壤基质势阈值来指导灌溉。2012年布置了3个处理,在马铃薯定苗后分别控制垄中心20cm深度处土壤基质势阈值为-20、-30和-40kPa,2013年增加了1个-10kPa处理。[结果]大型喷灌机灌溉条件下监控垄中心20cm深度处土壤基质势可较好地调控马铃薯农田的土壤水分状况;①指导灌溉的土壤基质势阈值越高,马铃薯生育期内0~30cm深度平均土壤基质势越高,并且变化幅度越平缓;土壤基质势阈值越低,0~30cm深度平均土壤基质势越低,且变化越剧烈;40cm深度以下土壤水分状况与土壤基质势阈值的关系不明显。②不同抗旱能力马铃薯品种的产量都随着土壤基质势阈值的降低而线性降低,当阈值低于-15.8 kPa时,土壤基质势每降低1kPa,产量降低1.8%,且主要表现在大薯(W≥250g)和中薯(150g≤ W<250g)质量的降低,单株结薯个数基本不受影响。③灌溉水利用效率随着土壤基质势的降低而线性增加,表现为土壤基质势每降低1 kPa,灌溉水利用效率升高1.3%。[结论]砂质土壤大型喷灌机灌溉或类似农业生产条件下,推荐监控垄中心20cm深度处土壤基质势来指导施肥灌溉,并且土壤基质势阈值建议为-15.8 kPa左右,在淀粉积累期之后可考虑适当地降低土壤基质势阈值,以获得高产和较高的灌溉水利用效率。     

Effects of irrigation strategies and soils on field grown potatoes: Yield and water productivity

Yield and water productivity of potatoes grown in 4.32 m² lysimeters were measured in coarse sand, loamy sand, and sandy loam and imposed to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. PRD and DI as water-saving irrigation treatments received 65% of FI after tuber bulking and lasted for 6 weeks until final harvest. Analysis across the soil textures showed that fresh yields were not significant between the irrigation treatments. However, the same analysis across the irrigation treatments revealed that the effect of soil texture was significant on the fresh yield and loamy sand produced significantly higher fresh yield than the other two soils, probably because of higher leaf area index, higher photosynthesis rates, and “stay-green” effect late in the growing season. More analysis showed that there was a significant interaction between the irrigation treatments and soil textures that the highest fresh yield was obtained under FI in loamy sand. Furthermore, analysis across the soil textures showed that water productivities, WP (kg ha⁻¹ fresh tuber yield mm⁻¹ ET) were not significantly different between the irrigation treatments. However, across the irrigation treatments, the soil textures were significantly different. This showed that the interaction between irrigation treatments and soil textures was significant that the highest significant WP was obtained under DI in sandy loam. While PRD and DI treatments increased WP by, respectively, 11 and 5% in coarse sand and 28 and 36% in sandy loam relative to FI, they decreased WP in loamy sand by 15 and 13%. The reduced WP in loamy sand was due to nearly 28% fresh tuber yield loss in PRD and DI relative to FI even though ET was reduced by 9 and 11% in these irrigation treatments. This study showed that different soils will affect water-saving irrigation strategies that are worth knowing for suitable agricultural water management. So, under non-limited water resources conditions, loamy sand produces the highest yield under full irrigation but water-saving irrigations (PRD and DI) are not recommended due to considerable loss (28%) in yield. However, under restricted water resources, it is recommended to apply water-saving irrigations in sandy loam and coarse sand to achieve the highest water productivity.     

不同灌水量对盆栽棉花产量和品质的影响

在盆栽条件下,以华杂棉H318为试验材料,参照自然蒸发量,设置5个灌溉比例,研究不同灌水量对棉花产量、品质及水分利用效率的影响。结果表明,随灌水量增加,成铃率和单株铃数增加,籽棉产量上升,水分利用效率呈先升后降的趋势。不同灌水量对棉花的纤维品质影响不大,马克隆值随灌水量的增加而降低。综合考虑棉花的产量、品质以及水分利用效率,灌水量80%为最佳的灌水比例。     

Magnetic treatment of irrigation water: Its effects on vegetable crop yield and water productivity

This study examines whether there are any beneficial effects of magnetic treatment of different irrigation water types on water productivity and yield of snow pea, celery and pea plants. Replicated pot experiments involving magnetically treated and non-magnetically treated potable water (tap water), recycled water and saline water (500 ppm and 1000 ppm NaCl for snow peas; 1500 ppm and 3000 ppm for celery and peas) were conducted in glasshouse under controlled environmental conditions during April 2007 to December 2008 period at University of Western Sydney, Richmond Campus (Australia). A magnetic treatment device with its magnetic field in the range of 3.5-136 mT was used for the magnetic treatment of irrigation water. The analysis of the data collected during the study suggests that the effects of magnetic treatment varied with plant type and the type of irrigation water used, and there were statistically significant increases in plant yield and water productivity (kg of fresh or dry produce per kL of water used). In particular, the magnetic treatment of recycled water and 3000 ppm saline water respectively increased celery yield by 12% and 23% and water productivity by 12% and 24%. For snow peas, there were 7.8%, 5.9% and 6.0% increases in pod yield with magnetically treated potable water, recycled water and 1000 ppm saline water, respectively. The water productivity of snow peas increased by 12%, 7.5% and 13% respectively for magnetically treated potable water, recycled water and 1000 ppm saline water. On the other hand, there was no beneficial effect of magnetically treated irrigation water on the yield and water productivity of peas. There was also non-significant effect of magnetic treatment of water on the total water used by any of the three types of vegetable plants tested in this study. As to soil properties after plant harvest, the use of magnetically treated irrigation water reduced soil pH but increased soil EC and available P in celery and snow pea. Overall, the results indicate some beneficial effect of magnetically treated irrigation water, particularly for saline water and recycled water, on the yield and water productivity of celery and snow pea plants under controlled environmental conditions. While the findings of this glasshouse study are interesting, the potential of the magnetic treatment of irrigation water for crop production needs to be further tested under field conditions to demonstrate clearly its beneficial effects on the yield and water productivity.     

微咸水造墒对棉花生长发育及产量的影响研究

采用小区对比试验方法,研究了河北低平原区旱地等雨播种（HD）、播前淡水造墒（S1）以及矿化度为2.2g/L（S2.2）和5g/L（S5）微咸水造墒等不同处理对棉花生长发育和产量的影响。结果表明,棉花生育期内HD处理0～100cm土壤含水率明显低于3种造墒处理;S5处理0～40cm土壤盐分含量最高,但降雨淋洗效果较为显著...     

Cotton response to high frequency surface irrigation

High frequency irrigation with surface irrigation methods has been proposed as a means to increase cotton productivity in cases where drip irrigation or other pressurized systems are not economically justifiable. Field studies were conducted in 1993 and 1994 to evaluate the effects of surface irrigation frequency on the growth, lint yield and water use for a semi-determinate cotton cultivar in central Arizona. Cotton was grown in level basins on a sandy loam under three irrigation treatments defined as low frequency irrigation for the whole season (L), high frequency irrigation for the whole season (H), and low frequency irrigation until the initiation of rapid fruiting, high frequency during rapid fruiting, and low frequency after rapid fruiting (LHL). The treatments were governed by the percentage of allowable soil water depletion within the effective root zone, and the allowable depletion targets for low and high frequency irrigation were 55 and 30%, respectively. An irrigation scheduling program calculated the soil water depletion within the estimated cotton root depth on a daily basis for each treatment and was used to project the dates and amounts for treatment irrigations. In 1993, seven, 14, and 11 irrigations and in 1994 eight, 13 and 10 irrigations were given to the L, H, and LHL treatments, respectively. The total amount of water applied including rainfall differed among the treatments by 4% in 1993 and by 1% in 1994. Soil water measurements indicated that actual soil water depletion within the estimated cotton root depth immediately before treatment irrigations was close to the intended treatment allowable depletion targets for the majority of the growing season. Cotton growth and lint yields were maximized under the H treatment, and yields in this treatment averaged 15 and 21% more lint than the L treatment for the first and second seasons, respectively. The LHL treatment, although not as effective in increasing crop productivity as the H treatment, out yielded the low frequency treatment by an average of 10% in the two seasons. Crop evapotranspiration determined from the soil water balance was 8 and 9% higher for the H than the L treatment and 3 and 5% higher for the LHL than the L treatment in 1993 and 1994, respectively.     

Evapotranspiration and water use of full and deficit irrigated cotton in the Mediterranean environment in northern Syria

Cotton (Gossypium hirsutum L.) is the most important industrial and summer cash crop in Syria and many other countries in the arid areas but there are concerns about future production levels, given the high water requirements and the decline in water availability. Most farmers in Syria aim to maximize yield per unit of land regardless of the quantity of water applied. Water losses can be reduced and water productivity (yield per unit of water consumed) improved by applying deficit irrigation, but this requires a better understanding of crop response to various levels of water stress. This paper presents results from a 3-year study (2004-2006) conducted in northern Syria to quantify cotton yield response to different levels of water and fertilizer. The experiment included four irrigation levels and three levels of nitrogen (N) fertilizer under drip irrigation. The overall mean cotton (lint plus seed, or lintseed) yield was 2502 kg ha⁻¹, ranging from 1520 kg ha⁻¹ under 40% irrigation to 3460 kg ha⁻¹ under 100% irrigation. Mean water productivity (WP_ET) was 0.36 kg lintseed per m³ of crop actual evapotranspiration (ET_c), ranging from 0.32 kg m⁻³ under 40% irrigation to 0.39 kg m⁻³ under the 100% treatment. Results suggest that deficit irrigation does not improve biological water productivity of drip-irrigated cotton. Water and fertilizer levels (especially the former) have significant effects on yield, crop growth and WP_ET. Water, but not N level, has a highly significant effect on crop ET_c. The study provides production functions relating cotton yield to ET_c as well as soil water content at planting. These functions are useful for irrigation optimization and for forecasting the impact of water rationing and drought on regional water budgets and agricultural economies. The WP_ET values obtained in this study compare well with those reported from the southwestern USA, Argentina and other developed cotton producing regions. Most importantly, these WP_ET values are double the current values in Syria, suggesting that improved irrigation water and system management can improve WP_ET, and thus enhance conservation and sustainability in this water-scarce region.     

Yield and fibre quality of cotton cultivars as affected by the build-up of sodium in the soils with sustained sodic irrigations under semi-arid conditions

Cotton is commonly grown in many arid and semi-arid regions of the world having sodic ground waters. A field plot study was, therefore, conducted for 2 years to study the effect of sustained sodic irrigation on yield and fibre quality of two hirustum cotton cultivars (F-505 and F-846) and one arborium cultivar (LD-327). The exchangeable sodium percentage (ESP) of 0–30 cm soil under sustained canal water (CW) irrigation treatment was 3.5 whereas long-term irrigations (for more than 10 years) with sodic waters having residual sodium carbonate (RSC) of 5, 10 and 15 me l⁻¹ resulted in ESP bulid-up of 16.4, 39.6 and 56.2, respectively. These sodic waters were used for irrigation in the respective plots, for both years of the study. High ESP of the soil decreased the growth (in terms of plant height) and yield of all the three cotton cultivars. The rate of decline in plant height at 50, 80 and 140 days of sowing (DAS) was maximum in F-505 and minimum in F-846. Compared with CW treatment, relative seed-cotton yield under 16.4, 39.6 and 56.2 ESP levels obtained with respective sodic water treatments for 2 years were 99, 70 and 69%, respectively in F-846, 101, 46 and 29%, respectively in F-505 and 98, 67 and 49%, respectively in LD-327. Similar trends were observed in case of boll number per square metre and boll weight. The cultivar F-846 produced heavier bolls than the other two cultivars under ESP levels of 56.2 obtained under RSC₁₅ treatment which helped this cultivar to perform relatively better. The harmful effect of sodic waters on fibre quality (2.5% span length, micronaire value and bundle strength) were also not observed in the case of F-846. A slight deterioration in fibre quality was, however, observed in cultivars F-505 and LD-327 at an ESP of 56.2 in the soil.