气候变化下浙江省极端降水时空变化研究

基于CMIP5的18个GCMs模型,通过LARS-WG降尺度模型获得降雨数据,计算了2041-2070年在RCP4.5和RCP8.5两个情景下的11个极端降雨指数,并通过贝叶斯平均法获得两个情景下的集合值,分别与浙江省1971-2000年实测数据的极端指数计算结果进行对比分析,最后探讨了浙江省2041-2070年极端降水时空变化特征,结论如下:(1)浙江省的降雨量在2041-2070年间趋于集中化,整体向极端降雨量和降雨日数增加的方向发展。其中强降雨量R95pTOT和极强降雨量R99pTOT相对基准期的变化最具代表性,上升幅度最大;中雨日数R20 mm和大雨日数R30 mm上升幅度明显高于小雨日数R10 mm。(2)全省降雨在空间分布上趋于极端化,极端降雨由东部沿海向西部递减,东部沿海地区未来极端降雨强度和频率相对其他地区增加明显;(3)RCP4.5和RCP8.5排放情景下极端降雨指数相对基准期的变化相似,相较之下,RCP4.5排放情景下降雨强度和频率增加更为明显,说明该情景下发生极端降雨事件的概率更大。     

Combining an ecological model with remote sensing and GIS techniques to monitor soil water content of croplands with a monsoon climate

Soil water is an important factor affecting photosynthesis, transpiration, growth, and yield of crops. Accurate information on soil water content (SWC) is crucial for practical agricultural water management at various scales. In this study, remotely sensed parameters (leaf area index, land cover type, and albedo) and spatial data manipulated using the geographic information system (GIS) technique were assimilated into the boreal ecosystem productivity simulator (BEPS) model to monitor SWC dynamics of croplands in Jiangsu Province, China. The monsoon climate here is characterized by large interannual and seasonal variability of rainfall causing periods of high and low SWC. Model validation was conducted by comparing simulated SWC with measurements by a gravimetric method in the years 2005 and 2006 at nine agro-meteorological stations. The model-to-measurement R² values ranged from 0.40 to 0.82. Nash-Sutcliffe efficiency values were in the range from 0.10 to 0.80. Root mean square error (RMSE) values ranged from 0.028 to 0.056 m³ m⁻³. Simulated evapotranspiration (ET) was consistent with ET estimated from pan evaporation measurements. The BEPS model successfully tracked the dynamics and extent of the serious soil water deficit that occurred during September-November 2006. These results demonstrate the applicability of combining process-based models with remote sensing and GIS techniques in monitoring SWC of croplands and improving agricultural water management at regional scales in a monsoon climate.     

Water management options based on rainfall analysis for rainfed maize (Zea mays L.) production in Rushinga district, Zimbabwe

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.     

全球降水观测计划IMERG降水产品对中国大陆极端降雨监测能力评估

全球降水观测计划GPM降水产品IMERG(Integrated Multi-satellitE Retrievals for GPM)作为热带降水观测计划TRMM降水产品TMPA(TRMM Multisatellite Precipitation Analysis)的继任者,提供了覆盖范围更大、时间序列更长、精度和时空分辨率更高的降水数据来源。论文以国内809个气象台站2000-2017年逐日降水作为基准数据,选取极端日降水(R95p)、极端降水总量(R95pTOT)、最大日降水量(Rx1day)、最大5日降水量(Rx5day)和大雨日数(R25mm)5种极端降水指标,评价IMERG V06 Final(IMERG)在中国大陆的极端降水探测能力,并与TMPA 3B42V7(TMPA 3B42)的结果进行对比。结果表明:①总体上,各项极端指标下IMERG对极端降雨监测表现优于TMPA 3B42产品;②IMERG除倾向于低估R95p、高估R95pTOT外,其他极端降水指标偏差均低于TMPA 3B42;③在极端降雨的探测上,两个卫星产品在高海拔和干旱地区的探测精度较低,但IMERG V06的表现较TMPA 3B42更好,可靠性更高;④在极端降水频率的表现上,IMERG的频率分布较TMPA 3B42更接近于实测雨量,但在更高强度降水(>100 mm/d)中均存在低估。     

The effect of rice straw mulch on evapotranspiration, transpiration and soil evaporation of irrigated wheat in Punjab, India

Soil evaporation (Es) is considered to be a non-productive component of evapotranspiration (ET). So, measures which moderate Es may influence the amount of water available for transpiration (T), the productive component of ET. Field experiments investigating the effects of rice straw mulch on components of the water balance of irrigated wheat were conducted during 2006-2007 and 2007-2008 in Punjab, India, on a clay loam soil. Daily Es was measured using mini-lysimeters, and total seasonal ET was estimated as the missing term in the water balance equation. Mulch lowered total Es over the crop growth season by 35 and 40 mm in relatively high and low rainfall years, respectively. Much of this “saved water” was partitioned into T, which increased by 30 and 37 mm in the high and low rainfall years, respectively. As a result, total ET was not affected by mulch in either year. In both years, there was a trend for higher biomass production and grain yield with mulch, but with significant differences only in 2006-2007. Transpiration efficiency (TE) with respect to grain yield was 18.8-19.1 kg ha⁻¹ mm⁻¹ in 2006-2007, and 14.6-16.4 kg ha⁻¹ mm⁻¹ in 2007-2008. While wheat grown in the presence of mulch tended to lower TE, this was only significant in 2007-2008. The results suggest that while mulching of well-irrigated wheat reduces Es, it does not “save” water because the crop compensates by increased T and reduced TE.     

Climatic water balance,probable rainfall,rice crop water requirements and cold periods in AER 12.0 in India

In this study an analysis was made on spatial variation of climatic water balance, (water surplus, actual evapotranspiration), probabilistic monthly monsoon rainfall and mapping of cold periods in agro-ecological region (AER) 12.0 of India using GIS and models. Since, rice is the dominant crop of the region, crop water requirements of rice was also spatially analyzed in different agro-ecological subregions (AESRs) of the AER 12.0 using CROPWAT 4.0 model and GIS. Study found that as per climatic water balance, large to moderate water surplus (520–70 mm) was available in AESR 12.1. The rainfall surplus of 220–370 mm was computed in AESR 12.2 and 370–520 mm in AESR 12.3 mm. Since winter rainfall is meagre and erratic, this amount of rainfall may be harvested and utilized for providing supplemental irrigation to winter crops or during dry spell of rainy season crops. Study also reveals that at 80% probability level (highly assured) in first month of southwest monsoon (June) 98–156 mm rainfall occurs in AESR 12.1, 103–144 mm in AESR 12.2 and 93–132 mm in AESR 12.3. These amounts of rainfall are sufficient to prepare land and sowing of direct seeded crops like maize, groundnut, blackgram, greengram, pigeonpea, cowpea, etc. that may be done from 24th standard week onwards (11th–7th June) after onset of southwest monsoon in the region. Based on existence of favorable temperature, among different AESRs, cold requiring crops may be tried in the districts of AER 12.1, but before cultivation of these crops, economic feasibility should be properly assessed. In normal rainfall year 450–550 mm, 600–720 mm and 775–875 mm crop water requirement was computed using CROPWAT 4.0 model for autumn rice, winter rice and summer rice, respectively in different AESRs of AER 12.0.     

Agronomic and economic response to furrow diking tillage in irrigated and non-irrigated cotton (Gossypium hirsutum L.)

The Southeast U.S. receives an average of 1300 mm annual rainfall, however poor seasonal distribution of rainfall often limits production. Irrigation is used during the growing season to supplement rainfall to sustain profitable crop production. Increased water capture would improve water use efficiency and reduce irrigation requirements. Furrow diking has been proposed as a cost effective management practice that is designed to create a series of storage basins in the furrow between crop rows to catch and retain rainfall and irrigation water. Furrow diking has received much attention in arid and semi-arid regions with mixed results, yet has not been adapted for cotton production in the Southeast U.S. Our objectives were to evaluate the agronomic response and economic feasibility of producing cotton with and without furrow diking in conventional tillage over a range of irrigation rates including no irrigation. Studies were conducted at two research sites each year from 2005 to 2007. Irrigation scheduling was based on Irrigator Pro for Cotton software. The use of furrow diking in these studies periodically reduced water consumption and improved yield and net returns. In 2006 and 2007, when irrigation scheduling was based on soil water status, an average of 76 mm ha⁻¹ of irrigation water was saved by furrow diking, producing similar cotton yield and net returns. Furrow diking improved cotton yield an average of 171 kg ha⁻¹ and net return by $245 ha⁻¹ over multiple irrigation rates, in 1 of 3 years. We conclude that furrow diking has the capability to reduce irrigation requirements and the costs associated with irrigation when rainfall is periodic and drought is not severe.     

Controlling factors of sheet erosion under degraded grasslands in the sloping lands of KwaZulu-Natal, South Africa

The current increase in the global demand for food and fresh water and the associated land use changes or misuses exacerbate water erosion which has become a major threat to the sustainability of the soil and water resources. Soil erosion by rainfall and runoff is a natural and geologic phenomenon, and one of the most important components of the global geochemical cycle.Despite numerous studies on crop lands, there is still a need to quantify soil sheet erosion (an erosion form that uniformly removes fertile upper soil horizons) under grasslands and to assess the factors of the environment that control its spatial variation. For that purpose, fifteen 1 m² micro-plots installed within a 23 ha catchment under pasture in the sloping lands of KwaZulu-Natal (South Africa) were monitored during the 2007-2008 rainy season to evaluate runoff (R) and sediment losses (SL). Soil losses computed from the 37 rainfall events with soil erosion averaged 6.45 ton ha⁻¹ year⁻¹with values from 3 to 13 ton ha⁻¹ year⁻¹. SL were significantly correlated with the proportion of soil surface coverage by the vegetation (P < 0.01) whereas the slope gradient, and soil characteristics such as bulk density or clay content were not correlated. R and SL increased as the proportion of soil surface coverage decreased and this trend was used to predict the spatial variations of sheet erosion over the 23 ha catchment. Greater sheet erosion occurred at the catchment plateau and at the vicinity of gully head cuts probably in relation to regressive erosion. Mitigating sheet erosion would require an appropriate management of the soil cover through appropriate management of cattle grazing, especially at places where “natural” erosion is likely to occur.     

Rice growth, yield and water productivity responses to irrigation scheduling prior to the delayed application of continuous flooding in south-east Australia

The majority of rice grown in south-east Australia is continuously flooded for much of its growing season, but reduced irrigation water availability brought about by a combination of drought and environmental flow legislation has presented a need to maintain (or even increase) rice production with less irrigation water. Delaying the application of continuous flooding until prior to panicle initiation can increase input water productivity by reducing non-beneficial evaporation losses from free water and the soil. A field experiment was conducted over two growing seasons, 2008/9 and 2009/10, comparing a conventional dry seeded treatment (the control - continuous flooding from the 3 leaf stage) with delayed continuous flooding (10-20 days prior to panicle initiation) with several irrigation scheduling treatments prior to flooding commencement. In the first year, the delayed water treatments were irrigated at intervals of 40, 80 and 160 mm of cumulative reference evapotranspiration (ETo) prior to delayed continuous flooding, thereby imposing differing degrees of crop water stress. In year 2, the 80 and 160 mm treatments were modified by use of a crop factor (Kc) when the plants were small and the 40 mm treatment was replaced with a continuously flooded treatment throughout the crop duration.Decreases in net water input (irrigation + rain − surface drainage) and increases in input water productivity were achieved by reducing the flush irrigation frequency during the pre-flood period. Savings of 150 and 230 mm (10 and 15%) were achieved in Year 1 from the 80 and 160 mm cumulative ETo irrigation frequency treatments, respectively, in comparison to the control. In the second year, net water input savings of 230 and 330 mm (15 and 22%) were achieved with the 80/Kc and 160/Kc mm treatments, respectively. Input water productivity of the 160 mm treatment was 0.06 kg/m³ (8%) higher than the control in Year 1, while in Year 2 a 0.15 kg/m³ (17%) increase in input water productivity above the control was achieved by the 160/Kc mm treatment. Delaying the application of continuous flooding in the second year greatly extended the period of crop growth suggesting the need for earlier sowing (by 7-10 days) to ensure pollen microspore still occurs at the best time to minimise yield loss due to cold damage. Nitrogen fertiliser management is an important issue when delaying continuous flooding, and nitrogen losses appeared to increase with the frequency of irrigation prior to continuous flooding. This was likely due to increased denitrification from alternate wetting and drying of the soil. Further research is required to determine the most appropriate nitrogen management strategies, and to also better define the optimal pre-flood irrigation frequency.     

The effect of system innovations on water productivity in subsistence rainfed agricultural systems in semi-arid Tanzania

Rainfed subsistence farming systems in sub-Saharan Africa generally obtain low crop yields as a result of highly erratic rainfall seasons. This paper presents results of research conducted to test the effects of improvements in farming techniques for subsistence rainfed systems. The research was carried out in the Makanya catchment of northern Tanzania where rainfall of less than 600 mm a⁻¹ and spread over two agricultural seasons per year is clearly insufficient to support staple food crops under the present farming systems in the area. The research sought to prove that, with improved efficiency in tillage techniques, grain yields can improve even under the existing challenging hydro-climatic conditions. The research tested farming system innovations (SIs) at four sites located within a spatial distance of 10 km where a combination of runoff diversion (RD), on-site rain water harvesting (WH) and conservation tillage (CT) were compared against the traditional farming methods of hand-hoeing under strict rainfed conditions (Control). For RD, runoff generated from natural storms was directed into infiltration pits dug along the contour with the excavated soil deposited upward of the trenches (fanya juus). The impact of these techniques on maize yields under different SIs was investigated.The results showed that the innovations resulted in increased maize grain yields of up to 4.8 t ha⁻¹ compared against current averages of less than 1 t ha⁻¹. The average productivity of the available water over four seasons was calculated to range between 0.35 and 0.51 kg m⁻³. For the SIs that were tested, the distribution of yields within a cultivated strip showed variations with better yields obtained on the down slope side of the cultivated strip where ponding effects resulted in higher water availability for infiltration and storage. However, due to the large seasonal climate variability, statistical analysis did not show significant differences in the yields (p < 0.05) between different cultivation techniques.The study showed that there is scope to improve grain yields with the little available rainfall through the adoption of techniques which promote water availability and retention within the field. The re-partitioning of water within the field creates mitigation measures against the impact of dry spells and allows alternative cropping in addition to the traditional maize cultivated in the rainfall seasons.     

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.     

Effect of different pre-sowing water application depths on wheat yield under spate irrigation in Dera Ismael Khan District of Pakistan

Spate irrigation is a method of flood water harvesting, practiced in Dera Ismael Khan (D.I. Khan), Pakistan for agricultural production for the last several hundred years in which during monsoon period flood water is used for irrigation before wheat sowing. A field study on the effect of different pre-sowing water application depths on the yield of wheat was conducted during 2006-2007. The spate irrigation command areas normally receive the flood water as a result of rainfall on the mountains during the months of July to September, which also carries a significant amount of sediment load. The flood water flows in different torrents and is diverted through earthen bunds to the fields for irrigation with depth of water application ranging from 21 to 73 cm and resulted in sediment deposition of 1.8-3.6 cm per irrigation. In this study, the effect on wheat yield of three different pre-sowing water application depths (D1 < 30 cm, D2 = 30-45 cm and D3 > 45 cm) were studied under field conditions. Fifteen fields with field sizes of about 2-3 ha were randomly selected, in each field five samples were collected for analysis of soil physical properties, yield and yield components. Five major soil texture classes (silty clay, clay loam, silty clay loam, silt loam and loam) were found in the area with water-holding capacity ranging from 23% to 36.3% (on a volume basis) and bulk density varied from 1.35 to 1.42 g cm⁻³. About 36% more grain yield was obtained from loam soil fields, followed by silt loam (24%) as compared to wheat grown on silty clay soil condition. The maximum wheat grain yield of 3448 kg ha⁻¹ was obtained from fields with water application depths of 30-45 cm and the lowest wheat yield was recorded in fields with water application depths greater than 45 cm. On-farm application efficiencies ranged from 22% to 93% with an overall average of about 49%. Due to large and uneven fields, a lot of water is lost. In general, the application efficiency decreased with increasing water application depth. Based on the results of this research, in arid to semi-arid environments, for optimum wheat yield under spate irrigation, the pre-sowing water application depth may be about 30-45 cm (September to July) and under or over irrigation should be avoided.     

Ten consecutive years of regulated deficit irrigation probe the sustainability and profitability of this water saving strategy in loquat

The successful application of postharvest regulated deficit irrigation (RDI) over ten consecutive years (from season 1999/2000 to season 2007/2008) confirms the sustainability of this strategy for producing ‘Algerie’ loquat. Postharvest RDI consisting in a reduction of watering (between 45 and 80% depending on the season) from early June until the end of August, improved loquat profitability by increasing fruit value and by reducing water consumption with respect to fully irrigated trees (control). The increase in fruit value in RDI trees was due to a consistent improvement in harvest earliness as a result of an earlier blooming. Water savings of around 20% did not diminish yield nor fruit quality. Water use efficiency in RDI trees rose by over 30%. Water productivity reached 9.5 € m⁻³ of water applied in RDI trees versus 6.6 € m⁻³ in control trees. The most noticeable effect of RDI on vegetative growth was a significant and progressive decline in trunk growth. The canopy volume seems to be strongly influenced by pruning and no significant effects were detected in this parameter. Our results confirm the suitability of RDI in loquat and the economic benefits of saving water during the summer.     

Assessing yield optimization and water reduction potential for summer-sown and spring-sown maize in Pakistan

Agricultural food production in arid and semi-arid regions faces the challenge to ensure high yields with limited supply of water. This raises the question to which extent irrigation supply can be reduced without detriment to yield. Our study focuses on the yield-water uptake relationship for maize in the moderate water stress range in order to determine the onset of stress-induced dry-matter and yield losses. Compensatory plant responses under moderate stress levels are discussed in relation to seasonal climatic conditions.Summer-sown and spring-sown maize were irrigated with a decreasing amount of water in a field experiment in Pakistan. Water supply ranged from 100% water required to maintain soil at field capacity (FC) to 40% of FC. The average dry-matter and yield levels were slightly higher for summer-sown (15.0 Mg ha⁻¹) compared to spring-sown maize (13.1 Mg ha⁻¹). The onset of significant dry-matter and yield reduction started at the least irrigation treatment in both seasons. The amount of water required to avoid production losses was 272 mm in the summer-sown maize during the autumn growing season, and 407 mm for the spring-sown maize in the summer season, when the evaporative demand of the atmosphere was +27% higher. Water use efficiency (WUE_ET), normalized by vapour pressure deficit, of the summer-sown maize which was 10.0 kg kPa m⁻³, was +15% higher compared to the spring-sown crop; while the irrigation water productivity (2.9 kg m⁻³) was +11% more. WUE_ET increased over the whole range of applied water deficits for summer-sown maize, while the spring-sown crop showed a decreasing WUE_ET in the less irrigated treatment. Due to the higher efficiency in summer-sown maize, the potential in irrigation reduction without production losses (129 mm) was higher compared to the spring-sown maize (57 mm). Our results showed that in Pakistan water saving irrigation practices can be applied without yield loss mainly during the cooler growing season when the crop can efficiently compensate a lower total water uptake by increased use efficiency. For spring-sown maize the increasing evaporative demand of the atmosphere towards summer implies a higher risk of yield losses and narrows the range to exploit higher irrigation water productivity under moderate water deficit conditions.     

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.     

Alternative cropping strategies for assured and efficient crop production in upland rainfed rice areas of eastern India based on rainfall analysis

The productivity of rice in rainfed upland soils of eastern India is very low (<1 t/ha) and unstable because of erratic monsoon, moisture deficit during dry spells, light textured with less fertile soils and several biological constraints (weeds, pests and diseases). Keeping the urgent need of augmenting the productivity of vast rainfed upland rice ecosystem of eastern India (4.3 million ha), crop diversification technology was generated through on-farm research trials in representative upland rice soils of eastern India after analyzing agro-climatic (rainfall variability, probability and onset of effective monsoon) and edaphic (soil water retention properties) constraints and prospects. Based on rainfall analysis, direct seeded, low water requiring, rice substituted alternative upland crops namely maize, groundnut, pigeonpea, greengram and blackgram (sole or intercropping) was sown in light textured upland rice soils on 24th meteorological weeks (11–17 June) in 3 years 2000–2002 with two to three summer ploughings during pre-monsoon shower (May). Study revealed that in deficit rainfall years (2000 and 2002), when rice yield was affected adversely in light textured upland, higher rice equivalent yield and rain water use efficiency were obtained from groundnut+pigeonpea intercropping followed by sole groundnut and sole pigeonpea. Study also revealed that productivity of rice substituted crops in the same upland did not fluctuate much between rainfall excess (2001) and rainfall deficit years (2002 and 2000). Double cropping in rainfed upland rice soils was also explored through maize–horsegram/sesamum rotation with increased productivity and rainwater use efficiency. The crop diversification technology was found to be very effective for drought mitigation.     

Rainfall concentration for increasing corn production under semiarid climate

The ridge and furrow farming of rainfall concentration (RC) system is being promoted to increase water availability to crops for improving and stabilizing agricultural production in the semiarid Loess region of northwest China. In the system, plastic-covered ridges serve as rainfall harvesting zones and furrows serve as planting zones. In recent years, however, the current RC practices are still confined to rural family units for very limited supplemental irrigation purposes. To adopt this system for large-scale use in the semiarid region and bring it into full play, it is necessary to test the befitting rainfall range for RC farming. A field study (using corn as an indicator crop) combined with rainfall simulation was designed to determine the effects of RC practices on soil water content, crop yield and water use efficiency (WUE) under three rainfall levels (230 mm, 340 mm and 440 mm) during the growing seasons of 2006 and 2007. The results indicated that with the rainfalls ranging within 230-440 mm, RC system can increase soil water content in 0-100 cm and temperature conditions in the topsoil (0-10 cm) in furrows by 5-12% and 0.7-1 °C, respectively. The corn seedlings emerged 1-2 days earlier, the developmental stages generally occurred earlier, and the plant height and total dry matter all significantly increased (P < 0.05). In 2006, compared to conventional flat (CF) practice, the grain yield and WUE in the RC system increased by 75.4% and 73.3%, respectively at 230 mm rainfall, and by 36.7% and 40.2%, respectively at 340 mm rainfall, but there was no significant difference between the RC₄₄₀ and CF₄₄₀ patterns. In 2007, the grain yield and WUE were 82.8% and 77.4%, respectively higher in the RC₂₃₀ plots than in the CF₂₃₀ plots, 43.4% and 43.1%, respectively higher in the RC₃₄₀ plots than in the CF₃₄₀ plots, and 11.2% and 9.5%, respectively higher in the RC₄₄₀ plots than in the CF₄₄₀ plots. Combining yield and WUE, it could be concluded that the optimal rainfall upper limit for RC system is below 440 mm rainfall in the experiment. In the case of corn, the adoption of RC practice in the 230-440-mm rainfall area will make the system more attractive during the whole growth period and offer a sound opportunity for sustainable farming under semiarid climate.     

Soil salinity in Aceh after the December 2004 Indian Ocean tsunami

The 2004 Indian Ocean tsunami inundated about 37,500 ha of coastal farmland in Aceh, and crops planted after the tsunami were severely affected by soil salinity. This paper describes the changes of soil salinity over time on tsunami affected farms and the implications for resuming crop production after natural disasters.Soil salinity and salt leaching processes were assessed across the tsunami affected region by measuring soil apparent electrical conductivity (ECa) using an electromagnetic induction soil conductivity instrument (EM38) combined with limited soil analysis. The ECa was measured 5 times between August 2005 and December 2007 in both the vertical (EMv) and horizontal (EMh) dipole orientations at 23 sites across Aceh. The level of salinity and direction of salt movement were assessed by comparing changes in mean profile ECa and relative changes in EMv and EMh.Eight months after the tsunami the average soil salinity in the 0-1.2 m soil depth varied from ECe 22.6 to 1.6 dS m⁻¹ across sites in the affected region and three years after the tsunami it varied from 13.0 to 1.4 dS m⁻¹. Soil salinity tended to be higher in rice paddy areas that trapped saline tsunami sediments and held seawater for longer periods. Leaching of salts occurred slowly by both vertical displacement and horizontal movement in surface waters. Hence, soil salinity persisted at a level which could reduce crop production for several years after the 2004 tsunami. High soil salinity persisted three years after the tsunami even though there had been more than 3000-7000 mm of accumulated rainfall to leach salts. The slow leaching is likely to have been due to the loss of functional drainage systems and general low relief of the affected areas.Monitoring of soil salinity with EM38 assisted local agricultural extension agencies to identify sites that were too saline for crops and determine when they were suitable for cropping again. The methodology used in this study could be used after similar disasters where coastal agriculture areas become inundated by seawater from storm surges or future tsunamis.     

How much land is needed for global food production under scenarios of dietary changes and livestock productivity increases in 2030?

Growing global population figures and per-capita incomes imply an increase in food demand and pressure to expand agricultural land. Agricultural expansion into natural ecosystems affects biodiversity and leads to substantial carbon dioxide emissions.Considerable attention has been paid to prospects for increasing food availability, and limiting agricultural expansion, through higher yields on cropland. In contrast, prospects for efficiency improvements in the entire food-chain and dietary changes toward less land-demanding food have not been explored as extensively. In this study, we present model-based scenarios of global agricultural land use in 2030, as a basis for investigating the potential for land-minimized growth of world food supply through: (i) faster growth in feed-to-food efficiency in animal food production; (ii) decreased food wastage; and (iii) dietary changes in favor of vegetable food and less land-demanding meat. The scenarios are based in part on projections of global food agriculture for 2030 by the Food and Agriculture Organization of the United Nations, FAO. The scenario calculations were carried out by means of a physical model of the global food and agriculture system that calculates the land area and crops/pasture production necessary to provide for a given level of food consumption.In the reference scenario - developed to represent the FAO projections - global agricultural area expands from the current 5.1 billion ha to 5.4 billion ha in 2030. In the faster-yet-feasible livestock productivity growth scenario, global agricultural land use decreases to 4.8 billion ha. In a third scenario, combining the higher productivity growth with a substitution of pork and/or poultry for 20% of ruminant meat, land use drops further, to 4.4 billion ha. In a fourth scenario, applied mainly to high-income regions, that assumes a minor transition towards vegetarian food (25% decrease in meat consumption) and a somewhat lower food wastage rate, land use in these regions decreases further, by about 15%.     

Soil random roughness and depression storage on coffee farms of varying shade levels

Water availability in rainfed coffee agroecosystems is an important factor in determining the production success of the crop. In this study, an estimate of soil water capture and storage was conducted in order to understand the differences of soil water availability among coffee farms or various management intensities, distinguished here by differences in shade cover level. Measurements of effective soil depression storage, leaf litter and soil moisture were taken in each of the sites. These measurements were taken to better understand how different shade coffee systems may gain or lose opportunities to keep water within the system due to contributions of shade. Three sites of varying shade were chosen in the Soconusco region of Chiapas, Mexico. The medium (30-50% cover) shade site was found to be more effective for precipitation capture when compared to the low (10-30% cover) shade site because of a larger value of effective depression storage (t-test, p = 0.05) due to increased soil roughness. This conclusion was supported by significantly higher soil moisture measurements in the medium shade site when compared to the low shade site in the dry season (repeated measure GLM, p = 0.001). The high shade (60-80% cover) site was found to have a greater slope than the other two sites, yielding smaller effective storage capacities; yet the high shade site was able to retain 15% of the available rainfall during the dry season through surface storage, possibly because of greater leaf litter and other shade contributions. Farmers may consider the use of shade trees within coffee farms as a practical method toward preserving water within the agroecosystem.