There are a lot of investigations to select the best model to estimate potential evapotranspiration (ET ) in a certain climate or region. In this paper, the types of climate include arid, semiarid, Mediterranean, and very humid. A spatial and temporal study of the ET is the aim of this paper, according to the peak and low events (extreme events) and climate change alarms. For this purpose, 50 years (1961–2010) monthly meteorological data of 18 regions in Iran, with various climates, were collected. For estimating the ET , 5 temperature−based, 5 radiation−based, and 5 mass transfer−based models, were selected with respect to better performance of them in different climates on the basis of past investigations. The results will especially be useful in the regions where the monthly (rather than daily) meteorological data are available. The results appear that the Blaney−Criddle (BC) (root mean square error (RMSE) = 1.32 mm day ) and Abtew (Ab) (RMSE = 0.83 mm day ) are the best models for estimating the ET in the arid and semiarid regions, respectively. While, modified Hargreaves−Samani 2 (MHS2) represents the best performance in the Mediterranean and very humid regions (RMSE = 0.30 mm day & 0.68 mm day , respectively). In addition, radiation—and mass transfer−based models are proper tools to estimate the ET in warm and cold seasons on the basis of improving values of evaluation indices in 40% and 70% of the study area, respectively. Increasing air temperature and decreasing minimum relative humidity for best performance of most models alarms a climate change in most regions of Iran. As a result, the radiation−based models were adapted with climate change better than the temperature−based and particularly mass transfer−based models. Finally, a step by step flowchart was presented for selecting the best model to estimate the ET in each climate.
Unmanned aerial vehicles (UAVs) present an exciting opportunity to monitor crop fields with high spatial and temporal resolution remote sensing capable of improving water stress management in agriculture. In this study, we reviewed the application of different types of UAVs using different remote sensors and compared their performance with ground-truth plant data. Several reflectance indices, such as NDVI, TCARI/OSAVI and PRInorm obtained from UAVs have shown positive correlations related to water stress indicators such as water potential ( ) and stomatal conductance ( ). Nevertheless, they have performed differently in diverse crops; thus, their uses and applications are also discussed in this study. Thermal imagery is also a common remote sensing technology used to assess water stress in plants, via thermal indices (calculated using artificial surfaces as references), estimates of the difference between canopy and air temperature, and even canopy conductance estimates derived from leaf energy balance models. These indices have shown a great potential to determine field stress heterogeneity using unmanned aerial platforms. It has also been proposed that chlorophyll fluorescence could be an even better indicator of plant photosynthesis and water use efficiency under water stress. Therefore, developing systems and methodologies to easily retrieve fluorescence from UAVs should be a priority for the near future. After a decade of work with UAVs, recently emerging technologies have developed more user-friendly aerial platforms, such as the multi-copters, which offer industry, science, and society new opportunities. Their use as high-throughput phenotyping platforms for real field conditions and also for water stress management increasing temporal and resolution scales could improve our capacity to determine important crop traits such as yield or stress tolerance for breeding purposes.
▶ Evapotranspiration (ET) data are derived from a range of measurement systems including lysimeters, eddy covariance, Bowen ratio, water balance (gravimetric, neutron meter, other soil water sensing), sap flow, scintillometry and even satellite-based remote sensing and direct modeling. ▶ These measurement techniques require substantial experimental care and are prone to substantial biases in reported results. ▶ Basic principles of ET measurement systems are reviewed and causes of common error and biases endemic to systems are discussed. ▶ Recommendations are given for reducing error in ET retrievals. ▶ Upper limits on ET measurements and derived crop coefficients are proposed. More and more evapotranspiration models, evapotranspiration crop coefficients and associated measurements of evapotranspiration (ET) are being reported in the literature and used to develop, calibrate and test important ET process models. ET data are derived from a range of measurement systems including lysimeters, eddy covariance, Bowen ratio, water balance (gravimetric, neutron meter, other soil water sensing), sap flow, scintillometry and even satellite-based remote sensing and direct modeling. All of these measurement techniques require substantial experimental care and are prone to substantial biases in reported results. Reporting of data containing measurement biases causes substantial confusion and impedance to the advancement of ET models and in the establishment of irrigation water requirements, and translates into substantial economic losses caused by misinformed water management. Basic principles of ET measuring systems are reviewed and causes of common error and biases endemic to systems are discussed. Recommendations are given for reducing error in ET retrievals. Upper limits on ET measurements and derived crop coefficients are proposed to serve as guidelines. The descriptions of errors common to measurement systems are intended to help practitioners collect better data as well as to assist reviewers of manuscripts and users of data and derived products in assessing quality, integrity, validity and representativeness of reported information. This paper is the first part of a two-part series, where the second part describes recommendations for documentation to be associated with published ET data.
Irrigation is an important measure for increasing grain production. Improving water use efficiency in agriculture is expected to play a very important role in ensuring food and water security in China, since there is a serious problem between food supply and limited water resources in China. The present state and future trend of water and food security in China were analyzed, while the importance of irrigation in ensuring China food security was highlighted based on the analysis of the evolution of irrigation water productivity in recent 60 years and its relationships with changes of crop yield, cropping pattern, fertilization and irrigation water use. Research progresses and practical application on high-efficient agricultural water use in China were introduced, and two successful cases of improving agricultural water productivity in China were presented, one was to improve crop water use efficiency by the novel irrigation method based on crop physiological responses, and the other was to improve the regional water productivity by the integrative methods in the Shiyang River Basin of Northwest China. The major research areas needed to focus on in the future were discussed, which include responses of crop water demand to changing environment and associated spatio-temporal optimization of water allocation, multi-processes hydrologic cycle of irrigated land under strong influences of human activities, integrated measures for improving multi-scale agricultural water use efficiency, and interactions between grain production, water resources and ecological system and its sustainability analysis in a systematic way.
Irrigation with wastewater supports agricultural production and the livelihoods of millions of smallholder farmers in many parts of the world. Considering the importance of better wastewater management at the local and national levels, there is a need for updated national data on wastewater generation, treatment, and use, which would also assist in regional and global wastewater assessments. While searching data and literature in published or electronic forms for 181 countries, we find that only 55 countries have data available on all three aspects of wastewater – generation, treatment, and use. The number of countries with one or two aspects of wastewater generation, treatment, and use is 69, while there is no information available from 57 countries. Of the available information, only 37% of the data could be categorized as recent (reported during 2008–2012). The available data suggest that high-income countries on average treat 70% of the generated wastewater, followed by upper-middle-income countries (38%), lower-middle-income countries (28%), and low-income countries, where only 8% of the wastewater generated is treated. The availability of current information on wastewater generation, treatment, and use is crucially important for policy makers, researchers, and practitioners, as well as public institutions, to develop national and local action plans aiming at safe and productive use of wastewater in agriculture, aquaculture, and agroforestry systems. The country level information aggregated at the regional and global levels would help in identifying the gaps in pertinent data availability and assessing the potential of wastewater in food, feed, and fish production at different scales.
Deficit irrigation (DI) has been widely investigated as a valuable and sustainable production strategy in dry regions. By limiting water applications to drought-sensitive growth stages, this practice aims to maximize water productivity and to stabilize – rather than maximize – yields. We review selected research from around the world and we summarize the advantages and disadvantages of deficit irrigation. Research results confirm that DI is successful in increasing water productivity for various crops without causing severe yield reductions. Nevertheless, a certain minimum amount of seasonal moisture must be guaranteed. DI requires precise knowledge of crop response to drought stress, as drought tolerance varies considerably by genotype and phenological stage. In developing and optimizing DI strategies, field research should therefore be combined with crop water productivity modeling.
In its broadest sense, water productivity (WP) is the net return for a unit of water used. Improvement of water productivity aims at producing more food, income, better livelihoods and ecosystem services with less water. There is considerable scope for improving water productivity of crop, livestock and fisheries at field through to basin scale. Practices used to achieve this include water harvesting, supplemental irrigation, deficit irrigation, precision irrigation techniques and soil–water conservation practices. Practices not directly related to water management impact water productivity because of interactive effects such as those derived from improvements in soil fertility, pest and disease control, crop selection or access to better markets. However, there are several reasons to be cautious about the scope and ease of achieving water productivity gains. Crop water productivity is already quite high in highly productive regions, and gains in yield (per unit of land area) do not necessarily translate into gains in water productivity. Reuse of water that takes place within an irrigated area or a basin can compensate for the perceived losses at the field-scale in terms of water quantity, though the water quality is likely to be affected. While crop breeding has played an important role in increasing water productivity in the past, especially by improving the harvest index, such large gains are not easily foreseen in the future. More importantly, enabling conditions for farmers and water managers are not in place to enhance water productivity. Improving water productivity will thus require an understanding of the biophysical as well as the socioeconomic environments crossing scales between field, farm and basin. Priority areas where substantive increases in water productivity are possible include: (i) areas where poverty is high and water productivity is low, (ii) areas of physical water scarcity where competition for water is high, (iii) areas with little water resources development where high returns from a little extra water use can make a big difference, and (iv) areas of water-driven ecosystem degradation, such as falling groundwater tables, and river desiccation. However, achieving these gains will be challenging at least, and will require strategies that consider complex biophysical and socioeconomic factors.
Climate change is expected to intensify the existing risks, particularly in regions where water scarcity is already a concern, as well as create new opportunities in some areas. Efforts to develop adaptation strategies for agricultural water management can benefit from understanding the risks and adaptation strategies proposed to date. This understanding may assist in developing priorities for the adaptation of water resources for irrigation. Here we characterise the main risks across European regions and evaluate adaptation strategies by reviewing over 168 highly relevant publications that appeared in the last 15 years. Based on this extensive database we characterise the effort and benefit of a number of agronomic and policy measures, aiming to develop concrete adaptation plans and responding to concrete regional challenges. The adaptation choices consider current technological perspectives and do not project future technological change; we are certain that technological change will shape some choices for adaptation in the coming decades. The greatest scope for action is in improving adaptive capacity and responding to changes in water demands, however the implementation requires revamping current water policy, adequate training to farmers and viable financial instruments. These results aim to assist stakeholders as they take up the adaptation challenge and develop measures to reduce the vulnerability of the sector to climate change.
The volume of wastewater generated by domestic, industrial and commercial sources has increased with population, urbanization, improved living conditions, and economic development. The productive use of wastewater has also increased, as millions of small-scale farmers in urban and peri-urban areas of developing countries depend on wastewater or wastewater polluted water sources to irrigate high-value edible crops for urban markets, often as they have no alternative sources of irrigation water. Undesirable constituents in wastewater can harm human health and the environment. Hence, wastewater irrigation is an issue of concern to public agencies responsible for maintaining public health and environmental quality. For diverse reasons, many developing countries are still unable to implement comprehensive wastewater treatment programs. Therefore in the near term, risk management and interim solutions are needed to prevent adverse impacts from wastewater irrigation. A combination of source control, and farm-level and post-harvest measures can be used to protect farm workers and consumers. The WHO guidelines revised in 2006 for wastewater use suggest measures beyond the traditional recommendations of producing only industrial or non-edible crops, as in many situations it is impossible to enforce a change in the current cash crop pattern, or provide alternative vegetable supply to urban markets. There are several opportunities for improving wastewater management via improved policies, institutional dialogues and financial mechanisms, which would reduce the risks in agriculture. Effluent standards combined with incentives or enforcement can motivate improvements in water management by household and industrial sectors discharging wastewater from point sources. Segregation of chemical pollutants from urban wastewater facilitates treatment and reduces risk. Strengthening institutional capacity and establishing links between water delivery and sanitation sectors through inter-institutional coordination leads to more efficient management of wastewater and risk reduction.
Rainfed agriculture plays and will continue to play a dominant role in providing food and livelihoods for an increasing world population. We describe the world's semi-arid and dry sub-humid savannah and steppe regions as global hotspots, in terms of water related constraints to food production, high prevalence of malnourishment and poverty, and rapidly increasing food demands. We argue that major water investments in agriculture are required. In these regions yield gaps are large, not due to lack of water , but rather due to inefficient management of water, soils, and crops. An assessment of management options indicates that knowledge exists regarding technologies, management systems, and planning methods. A key strategy is to minimise risk for dry spell induced crop failures, which requires an emphasis on water harvesting systems for supplemental irrigation. Large-scale adoption of water harvesting systems will require a paradigm shift in Integrated Water Resource Management (IWRM), in which rainfall is regarded as the entry point for the governance of freshwater, thus incorporating green water resources (sustaining rainfed agriculture and terrestrial ecosystems) and blue water resources (local runoff). The divide between rainfed and irrigated agriculture needs to be reconsidered in favor of a governance, investment, and management paradigm, which considers all water options in agricultural systems. A new focus is needed on the meso-catchment scale, as opposed to the current focus of IWRM on the basin level and the primary focus of agricultural improvements on the farmer's field. We argue that the catchment scale offers the best opportunities for water investments to build resilience in small-scale agricultural systems and to address trade-offs between water for food and other ecosystem functions and services.
Biochar is an amendment that can be used for enhancing soil water storage which may increase crop productivity. The objective of this study was to investigate the effects of biochar on physiology, yield and quality of tomato under different irrigation regimes. From early flowering to fruit maturity stages, the plants were subjected to full irrigation (FI), deficit irrigation (DI) and partial root-zone drying irrigation (PRD) and two levels of biochar (0% and 5% by weight). In FI, the plants were irrigated daily to pot water holding capacity while in DI and PRD, 70% of FI was irrigated on either the whole or one side of the pots, respectively. In PRD, irrigation was switched between sides when the soil water content of the dry side decreased to 15%. The results showed that addition of biochar increased the soil moisture contents in DI and PRD, which consequently improved physiology, yield, and quality of tomato as compared with the non-biochar control. However, leaf N content and chlorophyll content index (CCI) were decreased significantly in biochar treated plants. Furthermore, given a same irrigation volume, PRD offered advantages over DI in improving water use efficiency, leaf relative water content, membrane stability index and fruit yield. Overall, fruit quality was improved under reduced irrigation (i.e. DI and PRD) as compared with FI. It was concluded that incorporation of biochar under DI and particularly, PRD might be a novel approach to improve water productivity and quality of tomato.
► Plastic film, corn straw, biodegradable film, and liquid film were applied as mulches ridge and furrow cultivation. ► Mulching does not change seasonal water consumption, but can change water availability during critical growth stages. ► Cultivation with ridge and furrow mulching improved soil moisture availability, and promoted maize growth. ► Plastic-covered ridges and straw-covered furrow was the most efficient for maize production in the Loess Plateau, China. Field experiments were conducted from 2008 to 2010 in the Weibei Highlands of China to determine the effects of cultivation with ridge and furrow mulching on soil temperature, moisture, and maize ( L.) growth and yield. Ridges were covered with plastic film in all the treatments. Different furrow treatments were mulched with plastic film (PE film) (PP), biodegradable film (PB), maize straw (PS), and liquid film (PL). For the control (CK), ridges were covered with plastic film and the furrows received no mulching. Compared with CK, the soil water storage and soil temperature in furrow were significantly higher with the PP and PB treatments 0–60 days after planting (DAP), evapotranspiration was significantly higher at 60–90 DAP, but significantly lower at 120–140 DAP. The PS treatment had the highest soil water storage and the lowest temperature, while evapotranspiration was significantly lower at 0–60 DAP but significantly higher at 120–140 DAP, when compared with CK. Soil water storage and temperature were slightly higher with the PL treatment during the maize-growing season when compared with CK, but there were no significant differences in evapotranspiration. The three-year mean maize yields with PP, PB, and PS were significantly increased by 13.0%, 13.8%, and 15.0%, respectively, while water use efficiency increased by 9.8%, 10.2%, and 11.6%, compared with CK. Net income and input/output was highest with PS, and the three-year average net income increased by 1888.0 Chinese yuan (CNY) ha , compared with the control. Soil moisture and temperature conditions were improved, while the maize yield and net income were increased, when ridges were covered with plastic film and the furrows were mulched with straw. Therefore, this treatment may be considered the most efficient for maize production in the rainfed area of the Loess Plateau, China.
► In spring maize growing period of a sub-humid area, fallow field with wheat straw mulch had a fallow efficiency of 35%. ► Fallow field mulched with plastic sheets had a fallow efficiency of 46.1%. ► Largest water loss by evaporation occurred during the hottest part of summer. ► Maize plant canopy significantly reduced evaporation due to uptake of soil water and shading of the soil surface. A field experiment was conducted in a dry sub-humid area to study the effect of plastic sheet mulch and wheat straw mulch on water loss by evaporation (E) under fallow and cropped conditions and water use by transpiration (T) under cropped conditions. Results showed that during the entire spring maize ( L.) growing period with 305.1 mm water of precipitation and irrigation from April 22 to August 28, fallow plots mulched with wheat straw conserved 106.9 mm water in the 0–200 cm soil layer with a fallow efficiency of 35% while those mulched with plastic sheets conserved 140.6 mm water with a fallow efficiency of 46.1%. Although plastic film and wheat straw mulch significantly reduced water loss by E compared to non-mulch that had typically a fallow efficiency of 10–15%, water loss by E was still serious, with the largest water losses occurring during the hottest part of summer (July and August). During this period, it was difficult to reduce E, even when mulch was properly applied. In contrast, water losses due to E were much lower when maize plants were grown on the plots. In this case, maize plants continuously took up water from soil, leading to a reduction in the amount of soil water available for E. The large canopy shaded the soil surface and reduced water loss by evaporation. Only 20 mm, or 6.3% water was estimated lost by evaporation for maize grown on plots covered with plastic mulch. We developed a regression equation between shoot dry matter and transpiration amounts from plastic sheet mulched plots to estimate water loss by E in non-mulched and wheat straw mulched plots. Results showed that non-mulched plots lost 30.2% and wheat straw mulched plots lost 24.5% of the water received during the maize-growing season to E.
► Water use concepts and performance descriptors are useful in defining water conservation and saving. ► New indicators are proposed which include consideration of water reuse and distinctions between beneficial and non-beneficial water uses. ► In addition, an analysis of water productivity concepts useful both in irrigation and elsewhere is provided. ► Attention is given to economic issues in water productivity. ► Case study applications at irrigation farm and system scales are included. Water use concepts and performance descriptors that may be useful in defining conservation and saving of water are discussed with the aim of improving the overall performance and productivity of water use. New indicators are proposed which include consideration of water reuse and aim to assist in identifying and providing clear distinctions between beneficial and non-beneficial water uses. An analysis of productivity concepts useful both in irrigation and elsewhere is provided together with suggestions for where commonly used terms, such as the broadly used “water use efficiency” among others, would be better avoided in irrigation engineering and given much more narrowly defined meanings in agronomy and biological sciences. Particular attention is given to economic issues in water productivity. The analysis is completed with various case study applications at irrigation farm and system scales. It is recommended that a set of terms (not necessarily those developed here) be widely adopted that will provide a basis for easy, certain communication and provide widespread common understanding of the issues which must be faced to develop approaches to achieve efficient water use.
Approximately, seventy (70) percent of world water use including all the water diverted from rivers and pumped from underground is used for agricultural irrigation, so that the reuse of treated municipal wastewater for purposes such as agricultural and landscape irrigation reduces the amount of water that needs to be extracted from natural water sources as well as reducing discharge of wastewater to the environment. Thus, treated municipal wastewater is a valuable water source for recycling and reuse in the Mediterranean countries and other arid and semi-arid regions which are confronting increasing water shortages. Treated wastewater reuse in agriculture is a common practice in the Mediterranean countries and there is a considerable interest in the long-term effects of treated wastewater on crops intended for human consumption. This paper reviews the fundamentals of agricultural irrigation using treated municipal wastewater and the status of municipal wastewater reuse in Greece and Spain with studies related to the effects on soils and plants.
Innovative irrigation practices can enhance water efficiency, gaining an economic advantage while also reducing environmental burdens. In some cases the necessary knowledge has been provided by extension services, helping farmers to adapt and implement viable solutions, thus gaining more benefits from irrigation technology. Often investment in technological improvements has incurred higher water prices, however, without gaining the full potential benefits through water efficiency. Farmers generally lack adequate means and incentives to know crops’ water use, actual irrigation applications, crops’ yield response to different water management practices, and thus current on-farm water-efficiency levels. Those general difficulties are illustrated by our two case studies investigating options, stimuli and difficulties to improve water-efficient practices. The two areas have strong stimuli for improvement but lack a knowledge-exchange system to help farmers and resource managers identify scope for improvements. Partly for this reason, farmers’ responsibility for efficient water management has been displaced to hypothetical prospects, e.g. extra supplies from reuse of treated wastewater or a long-term low water pricing. In both cases a displaced responsibility complements the default assumption that farmers’ irrigation practices already have adequate water-use efficiency. Under current circumstances, agricultural water management will maintain the unknown water-efficiency level and farmers will have weaker incentives to make efforts for more efficient practices. A continuous knowledge-exchange is necessary so that all relevant stakeholders can share greater responsibility across the entire water-supply chain. On this basis, more water-efficient management could combine wider environmental benefits with economic advantage for farmers.
Rain-fed maize production in semi-arid areas of the Loess Plateau in China is constrained by low temperatures and water limitations during the early growth stage. Traditionally, gravel mulching was an effective strategy to increase soil temperature and moisture and, therefore, crop production; this method was recently replaced by plastic film mulching with the onset of industrial development. This study aimed to evaluate the effects of the two mulching methods on the crop growth, yield, and water-use efficiency of maize ( L.). Three treatments [non-mulched (CK, control), gravel-mulched (GM) and plastic film-mulched (FM)] were compared in 2010 and 2011 at the experimental station. Compared to CK, both gravel and plastic film mulching increased the cumulative soil thermal time (TT ) by 150–220 °C over the growing season. During seedling stage, the FM treatment increased the TT by 50 °C in 2010 and by 79 °C in 2011, which was higher than that caused by GM treatment by 37 °C and 41 °C, respectively. The higher soil temperatures in the FM treatment significantly accelerated maize growth and development more than the GM treatment. The FM treatment stimulated the highest growth rate during vegetative stages, as indicated by a greater leaf area index and the intercepted photosynthetically active radiation, and consistently produced the highest shoot biomass throughout the growing season. Compared with the CK, the grain yields increased by 17.0% and 28.3% in 2010, and 70.2% and 87.5% in 2011 (a colder year) for the GM and FM treatments, respectively. Similarly, water-use efficiency was improved by 15% and 23% in 2010, and by 51% and 90% in 2011 for the GM and FM treatments, respectively. Overall, we concluded that plastic film mulching, compared to gravel mulching, was more effective at counteracting the region's water limitations and low temperatures.
Agricultural systems as well as other ecosystems generate ecosystem services, i.e., societal benefits from ecological processes. These services include, for example, nutrient reduction that leads to water quality improvements in some wetlands and climatic regulation through recycling of precipitation in rain forests. While agriculture has increased ‘provisioning’ ecosystem services, such as food, fiber and timber production, it has, through time, substantially impacted other ecosystem services. Here we review the trade-offs among ecosystem services that have been generated by agriculture-induced changes to water quality and quantity in downstream aquatic systems, wetlands and terrestrial systems. We highlight emerging issues that need urgent attention in research and policy making. We identify three main strategies by which agricultural water management can deal with these large trade-offs: (a) improving water management practices on agricultural lands, (b) better linkage with management of downstream aquatic ecosystems, and (c) paying more attention to how water can be managed to create multifunctional agro-ecosystems. This can only be done if ecological landscape processes are better understood, and the values of ecosystem services other than food production are also recognized.
In the semi-arid region of the Loess Plateau in China, the use of alternative field management practices is essential for sustainable agriculture. The purpose of this study was to investigate the effect of mulching and fertilization on the soil temperature, soil water content, soil nitrate-N content and grain yield of maize. The experiment was conducted over three consecutive years and used randomly assigned field plots with five replicates. The six treatments consisted of no fertilizer without plastic film (CK), no fertilizer with plastic film (ZM), basal fertilizer without plastic film (BN), basal fertilizer with plastic film (BM), basal and top dressing without plastic film (BTN) and basal and top dressing with plastic film (BTM). The soil temperature of the 10-cm mulching treatment was significantly higher than that of the no-mulching treatment, and the average soil temperature of the mulching treatment increased by 2.3 °C before July and nearly 1.2 °C after July. The soil water content in the mulching treatment was significantly higher than that in the no-mulching treatment at 0–60 cm, which was not significantly different from the 140–200 cm depth. The trend in the soil nitrate-N content distribution revealed symmetrical shapes along the center of the furrows, and the standard symmetrical distribution reduced gradually with an increase in soil depth under the plastic film mulching conditions. The soil nitrate-N content under basal fertilizer was 1.65 times higher than that without fertilizer at 0–10 cm at 36 days after sowing. The soil nitrate-N content in the topsoil was reduced from 48.67 to 30.77 mg/kg after 58 days. We found that plastic film mulching with basal fertilizer increased maize yield by 10.61%, 9.48%, and 15.36%, and top dressing increased the yield by 16.61%, 20.94%, and 12.24% over the three consecutive years. A treatment involving plastic film mulching, basal fertilizer and top dressing is recommended. Further studies are required to investigate the effect of mulching on increased soil temperature, soil water content and soil nitrate-N content, which simultaneously affect yield, and to determine the effects on the field microclimate.