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1.
Landsat Thematic Mapper (TM) measurements have been utilized to derive land-use patterns from a supervised multi-spectral classification. Independently, the water use of crops, perennial vegetation, surface water impoundments, and barren land has been assessed using a radiation and energy balance approach using the same Landsat images. The land-use classification had an overall accuracy of 85%, which is acceptable for a heterogeneous tropical watershed with abundant small-scale landscape features. Actual evaporation of the various land use types was verified on physical consistency by applying the inverse Penman-Monteith equation, taking the evaporation estimations from remote sensing as input. The surface resistance to evaporation was found to be similar to resistances experimentally obtained elsewhere, but in similar climatic conditions. A new calculation procedure for time integration of actual evaporation under conditions of very limited surface observations is outlined and applied to the 26,000-ha Kirindi Oya watershed in southern Sri Lanka. The annual watershed evaporation deviated 4% from evaporation derived as the residual water balance term. This new technique, based on Landsat measurements, helps in identifying the evaporative depletion of various land-use categories, which is an important input for water management evaluation procedures. The major finding is that a significant amount of irrigation water is used by the perennial vegetation in the vicinity of the irrigation systems. 相似文献
2.
In many countries, irrigation water is usedfor several purposes other than irrigatingfield crops. In Sri Lanka, irrigationwater from canals, wells, and reservoirs isused for domestic purposes, industry,livestock, and fisheries, and it alsocontributes to sustain the environment. However, policy makers and water managersin irrigation systems only take intoaccount water used for irrigating the fieldcrops and sometimes water used for domesticpurposes. Owing to the failure torecognize the different uses and users ofwater, the water in irrigation systems hasbeen undervalued. This paper presents theenvironmental impact of irrigation and aframework for valuing water for itsmultiple and often competing uses,especially focusing on water uses forecological services, in this case wetlands.The south coastal area of Sri Lanka wasselected as a site for a case study, including2,610 ha of irrigated area and adownstream wetland area of 2,250 ha whichhas five lagoons. This wetland areacombines coastal, marine and freshwaterecosystems in a tropical environment inwhich distinct plant and animal speciescoexist in a delicate balance. All users ofwater and other resources, and theirenvironmental problems were identified. Thispaper discusses the policy and managementimplications of valuing water for competinguses. 相似文献
3.
Maize (Zea mays L.), the dominant and staple food crop in Southern and Eastern Africa, is preferred to the drought-tolerant sorghum and pearl millet even in semi-arid areas. In semi-arid areas production of maize is constrained by droughts and poor rainfall distribution. The best way to grow crops in these areas is through irrigation, but limited areal extent, increasing water scarcity, and prohibitive development costs limit the feasibility of irrigation. Therefore, there is need for a policy shift towards other viable options. This paper presents daily rainfall analysis from Rushinga district, a semi-arid location in Northern Zimbabwe. The purpose of the rainfall analysis was to assess opportunities and limitations for rainfed maize production using 25 years of data. Data was analysed using a variety of statistical methods that include trend analysis, t-test for independent samples, rank-based frequency analysis, Spearman's correlation coefficient and Mann-Whitney's U test. The results showed no evidence of change in rainfall pattern. The mean seasonal rainfall was 631 mm with a standard deviation (SD) of 175 mm. December, January and February consistently remained the major rainfall months. The results depicted high inter-annual variability for both annual and seasonal rainfall totals, a high incidence of droughts ≥3 out of every 10 years and ≥1 wet year in 10 years. Using the planting criteria recommended in Zimbabwe, most of the plantings would occur from the third decade of November with the mode being the first decade of December. This predisposes the rainfall to high evaporation and runoff losses especially in December when the crop is still in its initial stage of growth. On average 5 to more than 20 days dry spells occupy 56% of the rainy season. Seasonal rainfall exhibited negative correlation (P < 0.001; R = −0.746) with cumulative dry spell length, and wet years were free from dry spells exceeding 20 days. The most common dry spells (6-10 days), are in the range in which irrigated crops survive on available soil water. Therefore, they can be mitigated by in situ rainwater harvesting (RWH) and water conservation. The potential evapotranspiration of a 140-day maize crop was estimated to be 540 mm. Consequently, short season maize cultivars that mature in less than 140 days could be grown successfully in this area in all but drought years. However, sustainable maize production can only be achieved with careful management of the soil as a medium for storing water, which is essential for buffering against dry spells. To this end soil restorative farming systems are recommended such as conservation farming, in situ RWH techniques for dry spell mitigation and a cropping system that includes drought-tolerant cereal crops as for example sorghum and pearl millet, and perennial carbohydrate sources as for example cassava to provide stable crop yields. 相似文献
4.
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 (kc) 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. 相似文献
5.
《Agricultural Water Management》1996,32(1):37-48
Microirrigation techniques can be used to improve irrigation efficiency on vegetable gardens by reducing soil evaporation and drainage losses and by creating and maintaining soil moisture conditions that are favourable to crop growth. Water balance experiments in Zimbabwe showed that over 50% of the water applied as surface irrigation on traditional irrigated gardens can be lost as soil evaporation. This result gives an indication of the potential improvement in irrigation efficiency that can be achieved by adopting irrigation methods that reduce soil evaporation at the same time as minimising losses due to drainage and canopy interception. During the period 1985 to 1995, irrigation trials and experiments were carried out in south-east Zimbabwe and northern Sri Lanka with the main aim of comparing and quantifying the benefits of using simple microirrigation techniques on traditional vegetable gardens. This paper reviews the results of these trials and experiments. Microirrigation techniques that were evaluated included low-head drip irrigation, pitcher irrigation and subsurface irrigation using clay pipes. Of these methods, subsurface irrigation using clay pipes was found to be particularly effective in improving yields, crop quality and water use efficiency as well as being cheap, simple and easy to use. The comparative advantages of subsurface irrigation were maintained for a range of crops grown under different climatic conditions. Good results were also obtained with subsurface irrigation when irrigation was carried out using with poor quality irrigation water. 相似文献
6.
不同灌溉方式对水稻需水量和生长的影响 总被引：4，自引：0，他引：4
利用桶栽试验,研究了在不同灌溉方式及不同蒸发渗漏处理下的水稻需水量和对水稻生长的影响。结果表明:水稻以拔节孕穗期需水强度最高,无水层、干干湿湿和70%水分处理需水量分别比有水层处理减少42.5%、51.3%和57.6%;水稻叶面蒸腾量、棵间蒸发量与田间渗漏量占总耗水量的百分比分别为60.1%、16.4%和23.5%;干干湿湿处理水分利用率达到1.6 kg/m3,叶片光合速率最大,收获指数最高,从节水和增效的角度看,以干干湿湿灌溉最佳。 相似文献
7.
注水补灌,也称注射灌溉,是指采用特制的注水补灌设备直接向农作物和树木根部土壤注灌水（或水、肥、药液）的一种抗旱节水方法,用很少量的水保障农作物和造林的成活率,最大限度地提高水资源利用率,解决了干旱缺水季节农作物补水保丰产的难题。该技术与设备同集雨窖储水利用和地膜覆盖相组合,抗旱节水效果更为显著,具有投资少、易操作、成本低等特点。 相似文献
8.
C. Shanthi de Silva 《Agricultural Water Management》2008,95(3):271-282
Soil-water conditions for ricefields located in valleys in micro-catchments are simulated using a daily soil-water balance model. The crop is primarily rainfed but there is also limited irrigation water. The simulation covers a complete year and includes features such as rainfall, irrigation releases, runoff from uplands, actual evaporation and evapotranspiration, percolation losses through the bed and bunds of the ricefield, standing water in the field and overflows from the ricefield. A specific location in Sri Lanka is selected to illustrate the approach. The impacts of different conditions are explored including alternative irrigation releases, increased losses through the bed and bunds of the ricefield and a lower overflow from the ricefield. Simulations indicate that ricefields which are towards the valley sides have an increased inflow due to runoff from adjacent uplands; this can lead to improved rice yields. However, reducing heights of the bunds to half the original value results in substantial overflows during periods of high rainfall while the number of days without submergence almost doubles. This uncomplicated model is consistent with the limited field data and information available; it provides a realistic representation of the important processes and indicates why poor crop yields often occur. 相似文献
9.
A combined monitoring-modelling analysis of the past operation of the Thup Salao irrigation scheme (Thailand) is performed with a view to developing an improved operational strategy. The IMSOP computer model was used to simulate the operation of the delivery system using monitoring operational data since its commissioning (1988–1991). Temporal deviations of up to 80% are observed between the planned irrigation supply, the requirement irrigation delivery and the actual irrigation delivery in the wet season and up to 20% in the dry season. A real-time rainfall adjustment of the planned delivery scheduling resulted in a substantial improvement in the ability to match crop water demand and use rainfall more effectively. This suggests that a dual scheduling strategy consisting of seasonal (tactical) planning and real-time adjustment is required to improve operational performance. 相似文献
10.
灌水模式对油葵耗水量产量及经济效益的影响 总被引：2，自引：0，他引：2
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。 相似文献
11.
Recent droughts in the humid southeastern United States have focused attention on the need for and use of supplemental irrigation. Total annual rainfall amounts are sufficient for most crops in the region. However, erratic distribution of rainfall and the low water-holding capacities of most soils in the region cause frequent drought stresses in many crops. An on-farm study was conducted in southeastern Alabama to evaluate the effects of farmers' irrigation scheduling decisions on soil moisture variations in peanut fields irrigated with center-pivot irrigation systems. The study showed that the way irrigation was practiced in this high rainfall area often caused soil moisture deficit (SMD) level higher than the desired SMD limit during over 20% of the 140-day growing season. This is partially due to farmers' tendency to delay irrigation in anticipation of rainfall which may or may not occur, as rainfall during the growing season is often erratic and local. In contrast SMD in non-irrigated fields was higher than the SMD limit for half of the growing season.Abbreviations SMD
soil moisture deficit
- ET
evapotranspiration
- Reff
effective rainfall
- WHC
water holding capacity 相似文献
12.
《Agricultural Water Management》1996,31(3):253-267
Scarcity of water is a critical limitation to adoption of modern technology for increasing productivity of traditional rainfed rice growing areas of eastern Madhya Pradesh, India. The shortage of water results from uneven distribution of rains, significant gaps between rain events and field water losses rather than from low seasonal or annual rainfall totals. A feasible strategy to alleviate this limitation is to harvest excess rainwater in a farm pond during the wet season and use the conserved water for crop production in both wet (as insurance against drought) and dry seasons by adopting suitable crop and cropping systems. The results of water balance in a 1.05 ha field, on which a farm pond was built using 0.09 ha area, showed that 28–37% of seasonal rainfall was available as surface runoff from microcatchment (0.66 ha growing soybean, peanut and pigeonpea) for collection in the pond. This was sufficient for saving rice in a 0.30 ha area (in the lower side of the field) from drought stress, and for establishment of chickpea and mustard (in 0.90 ha) in the post-rainy season after harvest of rainy season crops. Soybean, peanut and pigeonpea, grown in the microcatchment during the rainy season, utilized respectively 371–726, 364–733 and 535–920 mm water in evapotranspiration (E,) and deep percolation (P). Rice grown below the pond required 28–317 mm water in different seasons to save the crop from in-season drought stress which commonly occurred during vegetative and reproductive stages. Water requirement (E, + P) of rice was 816–1342 mm in different seasons. Residual soil moisture after rainy season soybean, peanut and rice was sufficient (172–203 mm) to support post rainy season crops of chickpea and mustard. However, the losses of moisture from the soil surface layer after harvest of rainy season crops were rapid (7–23 mm), which necessitated a light irrigation (21–45 mm) for establishment of chickpea and mustard in the post-rainy season. The water balance results of soybean-mustard, peanut-mustard and peanut-chickpea were near identical to soybean-chickpea cropping. Similarly the water balance of rice-mustard was identical to Corresponding author. rice-chickpea in the vertisols. Soybean-mustard and rice-chickpea were the suitable and economical cropping systems for the microcatchment and service area of the farm pond. 相似文献
13.
Yashvir S. Chauhan 《Agricultural Water Management》2010,97(3):457-464
The growing demand for maize (Zea mays L.) in intensive livestock and other industries has opened up fresh opportunities for further expansion of the maize industry in Australia, which could be targeted in relatively water rich semi-arid tropical (SAT) regions of the country. This crop simulation study assessed the potential productivity and water requirements of maize peanut (Arachis hypogaea L.) rotations for the SAT climatic zone of Australia using the Agricultural Production Systems Simulator (APSIM) model. APSIM was configured to simulate maize (Pioneer hybrid 3153) either in the dry (May-October) or wet season (November-April) and peanut (cv. Conder) in the following season for three soils found at Katherine (14.48°S, 132.25°E) from 1957 to 2008. The simulated mean total yield potential of the dry season maize and wet season peanut (DMWP) rotation (15-19.2 t/ha) was about 28% greater than the wet season maize-dry season peanut (WMDP) rotation because of the higher yield potential of maize in the dry season compared to in the wet season. These high yields in the DMWP rotation have been achieved commercially. The overall simulated irrigation water requirement for both rotations, which varied from 11.5 to 13.8 ML/ha on different soils, was similar. The DMWP rotation had 21% higher water use efficiency. Similar yield and water use efficiency advantages of the DMWP rotation were apparent for eight other agriculturally important locations in the Northern Territory, Western Australia and Queensland. The simulations for Katherine also suggested that the irrigation requirement of the two rotations could increase by 17.5% in El-Nino years compared to La-Nina years for only a small gain in yield, which has implications for climate change scenarios. 相似文献
14.
全球气候变暖大背景下,黄土高原总体呈现暖干化趋势,未来干旱还可能会加剧。为了全面了解黄土高原旱涝时空变化特征,为黄土高原应对旱涝灾害提供决策依据,根据黄土高原及周边263个气象站的降水数据划分降水水平年,以标准化降水指数（SPI）为指标,分析了黄土高原地区不同水平年年际及年内旱涝特征。结果显示,黄土高原在丰、平、枯水年均有不同程度的干旱发生。丰水年黄土高原干旱面积占5.7%,雨涝面积占40.9%;平水年干旱面积占12.7%,雨涝面积占19.3%;枯水年干旱面积占44.4%,雨涝面积占17.9%。不同水平年的干旱区域存在差异。不同水平年内春旱较重,丰水年和平水年雨季开始后干旱逐渐缓解,枯水年雨季不能有效缓解春季以来的干旱,且秋涝明显,各水平年年内干旱的时空分布存在显著差异。不同水平年年际和年内旱涝差异大且变化频繁,为了确保黄土高原农业生产旱涝保收,应合理布设小型水利工程与田间灌溉设施。 相似文献
15.
《Agricultural Water Management》2005,73(1):21-41
Semi-arid agro-ecosystems are characterized by erratic rainfall and high evaporation rates leading to unreliable agricultural production. Total seasonal rainfall may be enough to sustain crop production, but its distribution and occurrence of intra-season dry spells (ISDS) and off-season dry spells (ODS) affect crop production. Rainwater harvesting (RWH) and management, especially on-farm storage ponds for supplemental irrigation offers an opportunity to mitigate the recurrent dry spells. Farm ponds are small runoff storage structures of capacities ranging from 30 to 100 m3 used mainly for supplemental irrigation of kitchen gardens, and sometimes for domestic and livestock water supply. The main objective of the study was to evaluate the hydrological and economic performance of farm ponds with the view of assessing their contributions to water and food security in semi-arid agro-systems of Kenya. Agro-hydrological evaluation of on-farm runoff storage systems entailed field survey, monitoring of water losses, analysis of rainy seasons and dry spell occurrence, soil moisture and water balance, estimation of supplemental irrigation requirement (SIR) and farm-level cost-benefit analysis of cabbage production using low-head drip irrigation system. Significant water losses through seepage and evaporation, which accounted on average for 30–50% of the stored runoff, is one of the factors that affect the adoption and up-scaling of on-farm water storage systems. Frequency analysis of rainfall revealed that there is 80% probability of occurrence of dry spells exceeding 10 and 12 days during the long rains and short rains, respectively. The occurrence of off-season (after rainfall cessation) dry spells was more pronounced than intra-seasonal (within the rainy season) dry spells. The length of intra-seasonal (10–15 days) was less than off-season dry spells (20–30 days). The occurrence of off-season dry spells coincides with the critical crop growth stage, in particular flowering and yield formation stages. A 50 m3 farm pond with a drip system irrigation system was found adequate to meet supplemental irrigation requirement for a kitchen garden of 300–600 m2 planted with a 90 days growing period cabbages. The cost-benefit analysis showed that farm ponds are feasible solutions to persistent crop failures in semi-arid areas which dominant most countries in Sub-Saharan Africa (SSA). 相似文献
16.
《Agricultural Water Management》2002,55(1):15-35
Efficient irrigation regimes are becoming increasingly important in commercial orchards. Accurate measurements of the components of the water balance equation in olive orchards are required for optimising water management and for validating models related to the water balance in orchards and to crop water consumption. The aim of this work was to determine the components of the water balance in an olive orchard with mature ‘Manzanilla’ olive trees under three water treatments: treatment I, trees irrigated daily to supply crop water demand; treatment D, trees irrigated three times during the dry season, receiving a total of about 30% of the irrigation amount in treatment I; and treatment R, rainfed trees. The relationships between soil water content and soil hydraulic conductivity and between soil water content and soil matric potential were determined at different depths in situ at different locations in the orchard in order to estimate the rate of water lost by drainage. The average size and shape of the wet bulb under the dripper was simulated using the Philip’s theory. The results were validated for a 3 l h−1 dripper in the orchard. The water amounts supplied to the I trees during the irrigation seasons of 1997 and 1998 were calculated based on the actual rainfall, the potential evapotranspiration in the area and the reduction coefficients determined previously for the particular orchard conditions. The calculated irrigation needs were 418 mm in 1997 and 389 mm in 1998. With these water supplies, the values of soil water content in the wet bulbs remained constant during the two dry seasons. The water losses by drainage estimated for the irrigation periods of 1997 and 1998 were 61 and 51 mm, respectively. These low values of water loss indicate that the irrigation amounts applied were adequate. For the hydrological year 1997–1998, the crop evapotranspiration was 653 mm in treatment I, 405 mm in treatment D and 378 mm in treatment R. Water losses by drainage were 119 mm in treatment I, 81 mm in treatment D and 4 mm in treatment R. The estimated water runoff was 345 mm in treatments I and R, and 348 mm in treatment D. These high values were due to heavy rainfall recorded in winter. The total rainfall during the hydrological year was 730 mm, about 1.4 times the average in the area. The simulated dimensions of the wet bulb given by the model based on the Philip’s theory showed a good agreement with the values measured. In a period in which the reference evapotranspiration was 7.9 mm per day, estimations of tree transpiration from sap flow measurements, and of evaporation from the soil surface from a relationship obtained for the orchard conditions, yielded an average daily evapotranspiration of 70 l for one I tree, and 48 l for one R tree. 相似文献
17.
降水、灌溉和品种对玉米产量和水分利用效率的影响 总被引：4，自引：0，他引：4
8年田间试验结果表明,玉米产量明显受降水和灌溉的影响。玉米苗期灌溉最为关键,是保证高产的基础。在只灌溉苗水而没有其他灌溉条件下,夏玉米产量与7、8月份降水密切相关,而与生长季节的降水总量关系不明显。除了极干旱年份(季节降雨量小于200 mm)外,随着灌溉量增加,玉米水分利用效率(WUE)降低。玉米最优灌溉制度为:干旱年份,除了苗期的1次灌溉外,在拔节和扬花期分别实施2次灌溉;常年和湿润年份,除了出苗水外,在抽穗到扬花期的8月初实施1次灌溉。3年的田间试验结果表明,当地种植的不同玉米品种之间产量最大相差20%,水分利用效率差异在12%~19%。因此,将适宜的品种与优化的灌溉制度相结合,是提高华北平原夏玉米产量和水分利用效率的有效途径。 相似文献
18.
In Northern India, insufficient soil moisture and excessively high soil temperatures are reported to restrict growth of crops during the hot, dry months of April–June. A 3-year field experiment was conducted to evaluate the effects of three irrigation schedules based on ratios of 0.50, 0.75 and 1.00 times pan evaporation, and two levels of paddy straw mulch of 0 and 6 tons/ha on yield and quality of sugarcane for a sandy loam. The differential irrigations were restricted to 10–12 weeks before the monsoon season.Both irrigation and straw mulching had favourable effects on plant height and yield. Cane yield increased by an average of 13.8% for the 1.00 over the 0.50 times pan evaporation. Similarly, yield averaged 13.8% higher with mulch than without it. Interestingly, the pan evaporation ratio of 0.50 with mulch gave a higher yield than the ratio 1.00 without mulch. For the same yield, irrigation under mulching averaged 34 cm less than under no mulch. These beneficial effects were attributed to better soil moisture and temperature regimes with mulching. Irrigation and mulching had no effect on the quality of cane juice. These results indicate that straw mulching and early season irrigation to sugarcane based on 1.00 times pan evaporation is a promising practice for increasing sugarcane production in subtropical areas. 相似文献
19.
《Agricultural Water Management》2005,72(3):209-222
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. 相似文献
20.
Eastern India receives higher average annual rainfall (1000–2000 mm) but 80% of it occurs within the June–September (rainy season), whereas the winter season (November–March) is dry. Due to a shortage of soil moisture, most rainfed areas of the region remain fallow during the winter season and cultivation (mainly rice) is confined to the rainy season only (June–September). To explore the possibility of double cropping in the rainfed rice areas, three oilseed crops, viz., linseed (Linum usitatissimum L.), safflower (Carthamous tinctorious L.), mustard (Brassica juncea L.), were grown in a representative rainfed area of eastern India, i.e. Dhenkanal, Orissa, during the dry/winter season by applying irrigation water at phonological stages. Study revealed that with three supplemental irrigations, the highest WUE was achieved by safflower followed by linseed with the mean values being 3.04 and 2.59 kg ha−1 mm−1, respectively. Whereas, with one irrigation, the highest water use efficiency (WUE) was achieved for safflower (1.23 kg ha−1 mm−1) followed by linseed (0.93 kg ha−1 mm−1). Of the three crops studied, safflower withdrew maximum water followed by mustard and crops were shown to use 90–105 mm more water than linseed. With three irrigations, average maximum rooting depths were 1.66, 1.17 and 0.67 m for safflower, mustard and linseed, respectively, which were 13.5, 10.6 and 11.4% higher than for single irrigated crops because of more wet sub soils and decrease of soil strength. The crop growth parameters like leaf area, dry biomass were also recorded with different levels of irrigation. The research work amply revealed the potential of growing these low water requiring oilseed crops in rice fallow during dry/winter season utilizing limited irrigation from harvested rainwater of rainy season. Crop coefficients (Kc) of three winter season oilseed crops were derived using field water balance approach. Study showed that LAI was significantly correlated with Kc values with the R2 values of 0.91, 0.89 and 0.94 in linseed, safflower and mustard, respectively. When LAI exceeded 3.0, the Kc value was 1 in safflower and mustard whereas in linseed corresponding LAI was 2.5. Study revealed that the Kc values for the development and mid season stage were slightly higher to that obtained by the procedure proposed by FAO, which might be due to local advection. 相似文献