Yield and quality response of drip irrigated broccoli (Brassica oleracea L. var. italica) under different irrigation regimes, nitrogen applications and cultivation periods

The experiment aimed at evaluating the yield and quality response of broccoli (Brassica oleracea L. var. italica) to applied irrigation water and nitrogen by drip irrigation method during the spring and autumn cultivation periods of 2007. Irrigation water was applied based on a ratio of Class A pan evaporation (k_cp = 0.50, 0.75, 1.00 and 1.25) with 7 days interval. Also, the effect of four nitrogen levels (0 kg ha⁻¹, 150 kg ha⁻¹, 200 kg ha⁻¹ and 250 kg ha⁻¹) was compared with each treatment. The seasonal evapotranspiration in the treatments varied from 233 mm to 328 mm during the spring period and from 276 mm to 344 mm during the autumn period. The highest broccoli yield was obtained in the spring period as 11.02 t ha⁻¹ and in the autumn period as 4.55 t ha⁻¹. In general, there were statistical differences along nitrogen does with respect to yield and yield components while there were no statistically significant differences in the yield and yield components among irrigation regimes. Both yield and yield parameters in the spring period were found to be higher than that of the autumn period due to the low temperature and high rainy days in autumn. Irrigation water use efficiency (IWUE) ranged from 3.78 kg m⁻³ to 14.61 kg m⁻³ during the spring period and from 1.89 kg m⁻³ to 5.93 kg m⁻³ during the autumn period. On the other hand, nitrogen use efficiency (NUE) changed as 37.32-73.13% and 13.08-22.46% for spring and autumn season, respectively.     

Runoff nitrogen from a large sized paddy field during a crop period

Nutrient load management is an important environmental issue because nutrient loads from farmlands degrade surface waters as a result of anthropogenic eutrophication. Nitrogen load from a large sized paddy field during the crop period was examined from the results of field measurements carried out in 2004. The 1.5 ha paddy field was located east of Biwa Lake. Irrigation water volume and ponded water depth were continuously observed. Field measurements were carried out at least once a week to analyze total nitrogen (TN) concentration in the irrigation water and ponded water. Daily inflow and outflow of nitrogen was obtained by multiplication of the nitrogen concentration and transported water volume, consisting of irrigation, precipitation, evapotranspiration, percolation and surface discharge. Water outflow volume was calculated by a tank model that consisted of three small tanks connected to represent ponded water depth differences in the large paddy field. The calculated nitrogen load was 18.8 kg ha⁻¹, with 7.2 kg ha⁻¹ from surface drainage and 11.6 kg ha⁻¹ from percolation loss. The runoff nitrogen value of 18.8 kg ha⁻¹ was within the range of the reported values investigated in a medium-sized paddy field. The observed value was close to the value for a low percolation flux paddy field where less irrigation water has been applied. These results suggest that less irrigation water keep runoff nitrogen low. This also indicates that irrigation water management can reduce nitrogen load from large sized paddy fields.     

Evaluation of the influence of irrigation methods and water quality on sugar beet yield and water use efficiency

Rapid urbanization and industrialization have increased the pressure on limited existing fresh water to meet the growing needs for food production. Two immediate responses to this challenge are the efficient use of irrigation technology and the use of alternative sources of water. Drip irrigation methods may play an important role in efficient use of water but there is still limited information on their use on sugar beet crops in arid countries such as Iran. An experiment was conducted to evaluate the effects of irrigation method and water quality on sugar beet yield, percentage of sugar content and irrigation water use efficiency (IWUE). The irrigation methods investigated were subsurface drip, surface drip and furrow irrigation. The two waters used were treated municipal effluent (EC = 1.52 dS m⁻¹) and fresh water (EC = 0.509 dS m⁻¹). The experiments used a split plot design and were undertaken over two consecutive growing seasons in Southern Iran. Statistical testing indicated that the irrigation method and water quality had a significant effect (at the 1% level) on sugar beet root yield, sugar yield, and IWUE. The highest root yield (79.7 Mg ha⁻¹) was obtained using surface drip irrigation and effluent and the lowest root yield (41.4 Mg ha⁻¹) was obtained using furrow irrigation and fresh water. The highest IWUE in root yield production (9 kg m⁻³) was obtained using surface drip irrigation with effluent and the lowest value (3.8 kg m⁻³) was obtained using furrow irrigation with fresh water. The highest IWUE of 1.26 kg m⁻³ for sugar was obtained using surface drip irrigation. The corresponding efficiency using effluent was 1.14 kg m⁻³. Irrigation with effluent led to an increase in the net sugar yield due to an increase in the sugar beet root yield. However, there was a slight reduction in the percentage sugar content in the plants. This study also showed that soil water and root depth monitoring can be used in irrigation scheduling to avoid water stress. Such monitoring techniques can also save considerable volumes of irrigation water and can increase yield.     

Tuber yield, water and fertilizer productivity in early potato as affected by a combination of irrigation and fertilization

Excessive amounts of irrigation water and fertilizers are often utilized for early potato cultivation in the Mediterranean basin. Given that water is expensive and limited in the semi-arid areas and that fertilizers above a threshold level often prove inefficacious for production purposes but still risk nitrate and phosphorous pollution of groundwater, it is crucial to provide an adequate irrigation and fertilization management. With the aim of achieving an appropriate combination of irrigation water and nutrient application in cultivation management of a potato crop in a Mediterranean environment, a 2-year experiment was conducted in Sicily (South Italy). The combined effects of 3 levels of irrigation (irrigation only at plant emergence, 50% and 100% of the maximum evapotranspiration - ETM) and 3 levels of mineral fertilization (low: 50, 25 and 75 kg ha⁻¹, medium: 100, 50 and 150 kg ha⁻¹ and high: 300, 100 and 450 kg ha⁻¹ of N, P₂O₅ and K₂O) were studied on the tuber yield and yield components, on both water irrigation and fertilizer productivity and on the plant source/sink (canopy/tubers dry weight) ratio. The results show a marked interaction between level of irrigation and level of fertilization on tuber yield, on Irrigation Water Productivity and on fertilizer productivity of the potato crop. We found that the treatments based on 50% ETM and a medium level of fertilization represent a valid compromise in early potato cultivation management. Compared to the high combination levels of irrigation and fertilization, this treatment entails a negligible reduction in tuber yield to save 90 mm ha⁻¹ year⁻¹ of irrigation water and 200, 50 and 300 kg ha⁻¹ year⁻¹ of N, P₂O₅ and K₂O, respectively, with notable economic savings for farmers compared to the spendings that are usually made.     

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

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

The effects of irrigation methods with effluent and irrigation scheduling on water use efficiency and corn yields in an arid region

A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m³ ha⁻¹ water applied, and the minimum water saving was obtained using FI with 6822 m³ ha⁻¹. The predicted irrigation water requirements using the Penman-Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m³ ha⁻¹. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 10³ kg ha⁻¹) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 10³ kg ha⁻¹). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m⁻³) and the minimum was obtained with the FI method (1.43 kg m⁻³). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.     

Management trends and responses to water scarcity in an irrigation scheme of Southern Spain

Improvement of irrigation management in areas subjected to periods of water scarcity requires good knowledge of system performance over long time periods. We have conducted a study aimed at characterizing the behaviour of an irrigated area encompassing over 7000 ha in Southern Spain, since its inception in 1991. Detailed cropping pattern and plot water use records allowed the assessment of irrigation scheme performance using a simulation model that computed maximum irrigation requirements for every plot during the first 15 years of system operations. The ratio of irrigation water used to maximum irrigation requirements (Annual Relative Irrigation Supply, ARIS) was well below 1 and oscillated around 0.6 in the 12 years that there were no water supply restrictions in the district. The ARIS values varied among crops, however, from values between 0.2 and 0.3 for sunflower and wheat, to values approaching 1 for cotton and sugar beet. Farmer interviews revealed some of the causes for the low irrigation water usage which were mainly associated with the attempt to balance profitability and stability, and with the lack of incentives to achieve maximum yields in crops subsidized by the Common Agricultural Policy (CAP) of the European Union. The response to water scarcity was also documented through interviews and demonstrated that the change in crop choice is the primary reaction to an anticipated constraint in water supply. Water productivity (value of production divided by the volume of irrigation water delivered; WP) in the district was moderate and highly variable (around 2€ m⁻³) and did not increase with time. Irrigation water productivity (increase in production value due to irrigation divided by irrigation water delivered) was much lower (0.65€ m⁻³) and also, it did not increase with time. The lack of improvement in WP, the low irrigation water usage, and the changes in cropping patterns over the first 15 years of operation indicate that performance trends in irrigated agriculture are determined by a complex mix of technical, economic, and socio-cultural factors, as those that characterized the behaviour of the Genil-Cabra irrigation scheme.     

Effects of elevated CO2 concentration,irrigation and nitrogenous fertilizer application on the growth and yield of spring wheat in semi-arid areas

In this paper, we discuss the effect of elevated CO₂ concentration, irrigation and nitrogenous fertilizer application on the growth and yield of spring wheat in semi-arid areas. A field experiment was conducted at the Dingxi Agricultural Experiment Station during 2000–2002. According to the experimental design, the CO₂ concentration increased to 14.5, 40 and 54.5 μmol mol⁻¹, respectively, by NH₄HCO₃ (involving CO₂) application, direct application of CO₂ gas and combination of fertilizer NH₄HCO₃ plus CO₂ application, which are equal to CO₂ concentration of the Earth's atmosphere in the next 5, 15 and 20 years. The fertilizer application was divided into three levels: application of NH₃NO₃ (250 kg h m⁻²), NH₄HCO₃ (500 kg h m⁻²) and no fertilizer. Irrigation was divided into two levels: with 90 mm irrigation in the growth period and without irrigation. They can be combined as eight treatments. Each treatment was replicated three times. The results showed that elevated CO₂ concentration owing to CO₂ application leads to remarkable increase in leaf area index (LAI) and shoot biomass, and also generates the higher value of leaf area duration (LAD) that can benefit the photosynthesis in the growth stage and yield increase in crop compared than the no CO₂ application treatment. When CO₂ concentration elevated by 14.5, 40 and 54.5 μmol mol⁻¹ with irrigation and fertilization, correspondingly, the grain yield increased by 6.3, 13.1 and 19.8%, respectively, whereas without irrigation and fertilization, the grain yield increased by only 4.2% when CO₂ concentration increased to 40 μmol mol⁻¹. Meanwhile, irrigation and fertilization can result in larger and deeper root system and have significantly positive influences on higher value of root/shoot (R/S) and water use efficiency. The grain yields in irrigation, irrigation plus NH₃NO₃ application and irrigation plus application of NH₄HCO₃ treatments are 73.4, 148.0 and 163.6% higher than that of no-irrigated and no-fertilized treatment, suggesting that both irrigation and fertilizer application contribute to remarkable increase of crop yield. In all treatments, the highest water use efficiency (WUE, 7.24 kg h m⁻² mm⁻¹) and grain yield (3286 kg h m⁻²) consistently occurred in the treatment with 90 mm irrigation plus fertilizer NH₄HCO₃ and elevated CO₂ concentration (54.5 μmol mol⁻¹), suggesting that this combination has an integrated beneficial effect on improving WUE and grain yield of spring wheat. These results may offer help to maintain and increase the crop yields in semi-arid areas.     

Irrigation evaluation based on performance analysis and water accounting at the Bear River Irrigation Project (U.S.A.)

The purpose of this work is to contribute to the development of a combined approach to evaluate irrigated areas based on: (1) irrigation performance analysis intended to assess the productive impacts of irrigation practices and infrastructures, and (2) water accounting focused on the hydrological impacts of water use. Ador-Simulation, a combined model that simulates irrigation, water delivery, and crop growth and production was applied in a surface irrigated area (1213 ha) located in the Bear River Irrigation Project, Utah, U.S.A.. A soil survey, a campaign of on-farm irrigation evaluations and an analysis of the database from the Bear River Canal Company and other resources were performed in order to obtain the data required to simulate the water flows of the study area in 2008. Net land productivity (581 US$ ha⁻¹) was 20% lower than the potential value, whereas on-farm irrigation efficiency (IE) averaged only 60%. According to the water accounting, water use amounted to 14.24 Mm³, 86% of which was consumed through evapotranspiration or otherwise non-recoverable. Gross water productivity over depleted water reached 0.132 US$ m⁻³. In addition, two strategies for increasing farm productivity were analyzed. These strategies intended to improve water management and infrastructures raised on-farm IE to 90% reducing the gap between current and potential productivities by about 50%. Water diverted to the project was reduced by 2.64 Mm³. An analysis based on IE could lead to think that this volume would be saved. However, the water accounting showed that actually only 0.91 Mm³ would be available for alternative uses. These results provide insights to support the decision-making processes of farmers, water user associations, river basin authorities and policy makers. Water accounting overcomes the limitations and hydrological misunderstandings of traditional analysis based on irrigation efficiency to assess irrigated areas in the context of water scarcity and competitive agricultural markets.     

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.     

Response of vanilla (Vanilla planifolia A.) intercropped in arecanut to irrigation and nutrition in humid tropics of India

A 5-year field trial to assess the impact of microsprinkler irrigation and nutrition on vanilla grown as intercrop in arecanut plantation was conducted on a laterite soil. Pooled analysis indicated that microsprinkler irrigation at 1.0 Epan resulted in significantly higher green bean yield (842 kg ha⁻¹) than 0.75 Epan (579 kg ha⁻¹). Organic manure application in the form of vermicompost (720 kg ha⁻¹) and FYM (768 kg ha⁻¹) and recommended NPK (718 kg ha⁻¹) produced green bean yield at par with recycling of gliricidia prunings (625 kg ha⁻¹). Irrigation at 1.0 Epan proved superior by registering maximum benefit:cost (B:C) ratio of 2.25 compared to 1.62 at 0.75 Epan. The highest B:C ratio was obtained with recommended NPK (2.27) followed by recycling of gliricidia prunings (2.10), vermicompost (1.87), vermicompost + arecanut husk mulching (1.80) and FYM (1.64). The soil pH increased by 0.4 units in 2008 compared with the pre-experimental soil pH of 5.6 in 2004. Nutrition alone and in combination with irrigation had significant impact on soil pH. Organic manure application increased the soil pH (6.1-6.2) significantly over recommended NPK (5.6) at the end of experiment in 2008. Significant variation in soil organic carbon (SOC) was noticed due to different nutrition treatments. Application of vermicompost and FYM significantly increased the SOC content by 38-54% in 2008 over initial levels in 2004. Bray's P availability was influenced by nutrition and its interaction with irrigation. Application of FYM continuously for 4 years has resulted in significant increase in Bray's P content (41.3 mg kg⁻¹) compared to other nutrition treatments (9.4-17.2 mg kg⁻¹). Irrigation equivalent to 0.75 Epan (223 mg kg⁻¹) increased the K availability significantly over 1.0 Epan (172 mg kg⁻¹). The K availability was significantly higher in recommended NPK (416 mg kg⁻¹) than in other organic treatments (98-223 mg kg⁻¹) at 0-30 cm soil depth. Overall, vanilla responded well to irrigation and nutrition in arecanut-based cropping system with a better economic output and improved soil fertility.     

Different drip irrigation regimes affect cotton yield, water use efficiency and fiber quality in western Turkey

Decreasing in water availability for cotton production has forced researchers to focus on increasing water use efficiency by improving either new drought-tolerant cotton varieties or water management. A field trial was conducted to observe the effects of different drip irrigation regimes on water use efficiencies (WUE) and fiber quality parameters produced from N-84 cotton variety in the Aegean region of Turkey during 2004 and 2005. Treatments were designated as full irrigation (T₁₀₀, which received 100% of the soil water depletion) and those that received 75, 50 and 25% of the amount received by treatment T₁₀₀ on the same day (treatments T₇₅; T₅₀ and T₂₅, respectively). The average seasonal water use values ranged from 265 to 753 mm and the average seed cotton yield varied from 2550 to 5760 kg ha⁻¹. Largest average cotton yield was obtained from the full irrigation treatment (T₁₀₀). WUE ranged from 0.77 kg m⁻³ in the T₁₀₀ to 0.98 kg m⁻³ in the T₂₅ in 2004 growing season and ranged from 0.76 kg m⁻³ in the T₁₀₀ to 0.94 kg m⁻³ in the T₂₅ in 2005 growing season. The largest irrigation water use efficiency (IWUE) was observed in the T₂₅ (1.46 kg m⁻³), and the smallest IWUE was in the T₁₀₀ treatment (0.81 kg m⁻³) in the experimental years. A yield response factor (k_y) value of 0.78 was determined based on averages of two years. Leaf area index (LAI) and dry matter yields (DM) increased with increasing water use for treatments. Fiber qualities were influenced by drip irrigation levels in both years. The results revealed that well-irrigated treatments (T₁₀₀) could be used for the semi-arid climatic conditions under no water shortage. Moreover, the results also demonstrated that irrigation of cotton with drip irrigation method at 75% level (T₇₅) had significant benefits in terms of saved irrigation water and large WUE indicating a definitive advantage of deficit irrigation under limited water supply conditions. In an economic viewpoint, 25.0% saving in irrigation water (T₇₅) resulted in 34.0% reduction in the net income. However, the net income of the T₁₀₀ treatment is found to be reasonable in areas with no water shortage.     

Comparison of drip and sprinkler irrigation strategies on sunflower seed and oil yield and quality under Mediterranean climatic conditions

This study compares the effects of different irrigation regimes on seed yield and oil yield quality and water productivity of sprinkler and drip irrigated sunflower (Helianthus annus L.) on silty-clay-loam soils in 2006 and 2007 in the Mediterranean region of Turkey. In sprinkler irrigation a line-source system was used in order to create gradually varying irrigation levels. Irrigation regimes consisted of full irrigation (I₁) and three deficit irrigation treatments (I₂, I₃ and I₄), and rain-fed treatment (I₅). In the drip system, irrigation regimes included full irrigation (FI-100), three deficit irrigation treatments (DI-25, DI-50, DI-75), partial root zone drying (PRD-50) and rain-fed treatment (RF). Irrigations were scheduled at weekly intervals both in sprinkler and drip irrigation, based on soil water depletion within a 0.90 m root zone in FI-100 and I₁ plots. Irrigation treatments influenced significantly (P < 0.01) sunflower seed and oil yields, and oil quality both with sprinkler and drip systems. Seed yields decreased with increasing water stress levels under drip and sprinkler irrigation in both experimental years. Seed yield response to irrigation varied considerably due to differences in soil water contents and spring rainfall distribution in the experimental years. Although PRD-50 received about 36% less irrigation water as compared to FI-100, sunflower yield was reduced by an average of 15%. PRD-50 produced greater seed and oil yields than DI-50 in the drip irrigation system. Yield reduction was mainly due to less number of seeds per head and lower seed mass. Soil water deficits significantly reduced crop evapotranspiration (ET), which mainly depends on irrigation amounts. Significant linear relationships (R² = 0.96) between ET and oil yield (Y) were obtained in each season. The seed yield response factors (ky_seed) were 1.24 and 0.86 for the sprinkler and 1.19 and 1.06 for the drip system in 2006 and 2007, respectively. The oil yield response factor (ky_oil) for sunflower was found to be 1.08 and 1.49 for both growing seasons for the sprinkler and 1.36 and 1.25 for the drip systems, respectively. Oil content decreased with decreasing irrigation amount. Consistently greater values of oil content were obtained from the full irrigation treatment plots. The saturated (palmitic and stearic acid) and unsaturated (oleic and linoleic acid) fatty acid contents were significantly affected by water stress. Water stress caused an increase in oleic acid with a decrease in linoleic acid contents. The palmitic and stearic acid concentrations decreased under drought conditions. Water productivity (WP) values were significantly affected by irrigation amounts and ranged from 0.40 to 0.71 kg m⁻³ in 2006, and from 0.69 to 0.91 kg m⁻³ in 2007. The PRD-50 treatment resulted in the greatest WP (1.0 kg m⁻³) and irrigation water productivity (IWP) (1.4 kg m⁻³) in both growing seasons. The results revealed that under water scarcity situation, PRD-50 in drip and I₂ in sprinkler system provide acceptable irrigation strategies to increase sunflower yield and quality.     

Response of cotton to various levels of nitrogen and water applied to normal and paired sown cotton under drip irrigation in relation to check-basin

Field experiments were conducted for 2 years to investigate the effects of various levels of nitrogen (N) and methods of cotton planting on yield, agronomic efficiency of N (AEN) and water use efficiency (WUE) in cotton irrigated through surface drip irrigation at Bathinda situated in semi-arid region of northwest India. Three levels of N (100, 75 and 50% of recommended N, 75 kg ha⁻¹) were tested under drip irrigation in comparison to 75 kg of N ha⁻¹ in check-basin. The three methods of planting tried were; normal sowing of cotton with row to row spacing of 67.5 cm (NS), normal paired row sowing with row to row spacing of 35 and 100 cm alternately (NP) and dense paired row sowing with row to row spacing of 35 and 55 cm alternately resulting in total number rows and plants to be 1.5 times (DP) than NS and NP. In NS there was one lateral along each row, but in paired sowings there was one lateral between each pair of rows. Consequently the number of laterals and quantity of water applied was 50 and 75% in NP and DP, respectively, as compared with NS in which irrigation water applied was equivalent to check-basin.Drip irrigation under NS resulted in an increase of 258 and 453 kg ha⁻¹ seed cotton yield than check-basin during first and second year, respectively, when same quantity of water and N was applied. Drip irrigation under dense paired sowing (DP) in which the quantity of irrigation water applied was 75% as compared with NS, further increased the yield by 84 and 101 kg ha⁻¹ than NS during first and second year, respectively. Drip irrigation under NP, in which the quantity of water applied and number of laterals used were 50% as compared with drip under NS, resulted in a reduction in seed cotton yield of 257 and 112 kg ha⁻¹ than NS during first and second year, respectively. However, the yield obtained in NP under drip irrigation was equivalent to yield obtained in NS under check-basin during first year but 341 kg ha⁻¹ higher yield was obtained during second year. The decrease in N applied, irrespective of methods of planting, caused a significant decline in seed cotton yield during both the years. Water use efficiency (WUE) under drip irrigation increased from 1.648 to 1.847 and from 0.983 to 1.615 kg ha⁻¹ mm⁻¹ during first and second year, respectively, when the same quantity of N and water was applied. The WUE further increased to 2.125 and 1.788 kg ha⁻¹ mm⁻¹ under DP during first and second year, respectively. The agronomic efficiency of nitrogen was higher in drip than check-basin during both the years when equal N was applied. The WUE decreased with decrease in the rate of N applied under fertigation but reverse was true for AEN. It is evident that DP under drip irrigation resulted in higher seed cotton yield, WUE and AEN than NS and also saved 25% irrigation water as well as cost of laterals.     

Forage quality, water use and nitrogen utilization efficiencies of pearl millet (Pennisetum americanum L.) grown under different soil moisture and nitrogen levels

The increasing scarcity of water for irrigation is becoming the most important problem for producing forage in all arid and semi-arid regions. Pearl millet is a key crop in these regions which needs relatively less water than other crops. In this research, a field study was conducted to identify the best combination of irrigation and nitrogen (N) management to achieve acceptable pearl millet forage both in quantity and quality aspects. Pearl millet was subjected to four irrigation treatments with interaction of N fertilizer (0, 75, 150 and 225 kg ha⁻¹). The irrigation treatments were 40%, 60%, 80% and 100% of total available soil water (I₄₀, I₆₀, I₈₀ and I₁₀₀, respectively). The results showed that increasing moisture stress (from I₄₀ to I₁₀₀) resulted in progressively less total dry matter (TDM), leaf area index (LAI), and nitrogen utilization efficiency (NUzE), while water use efficiency (WUE) and the percentage of crude protein (CP%) increased. The highest TDM and LAI were found to be 21.45 t ha⁻¹ and 8.65, in I₄₀ treatment, respectively. TDM, WUE, CP% and profit responses to N rates were positive. The maximum WUE of 4.19 kg DM/m³ was achieved at I₁₀₀ with 150 kg N ha⁻¹. The results of this research indicate that the maximum profit of forage production was obtained in plots which were fully irrigated (I₄₀) and received 225 kg N ha⁻¹. However, in the situation which water is often limited and not available, application of 150 kg N ha⁻¹ can produce high forage quality and guaranty acceptable benefits for farmers.     

Carbon and nitrogen cycling in a tropical Brazilian soil cropped with sugarcane and irrigated with wastewater

Carbon (C) and nitrogen (N) dynamics in agro-systems can be altered as a consequence of treated sewage effluent (TSE) irrigation. The present study evaluated the effects of TSE irrigation over 16 months on N concentrations in sugarcane (leaves, stalks and juice), total soil carbon (TC), total soil nitrogen (TN), NO₃⁻-N in soil and nitrate (NO₃⁻) and dissolved organic carbon (DOC) in soil solution. The soil was classified as an Oxisol and samplings were carried out during the first productive crop cycle, from February 2005 (before planting) to September 2006 (after sugarcane harvest and 16 months of TSE irrigation). The experiment was arranged in a complete block design with five treatments and four replicates. Irrigated plots received 50% of the recommended mineral N fertilization and 100% (T100), 125% (T125), 150% (T150) and 200% (T200) of crop water demand. No mineral N and irrigation were applied to the control plots. TSE irrigation enhanced sugarcane yield but resulted in total-N inputs (804-1622 kg N ha⁻¹) greater than exported N (463-597 kg N ha⁻¹). Hence, throughout the irrigation period, high NO₃⁻ concentrations (up to 388 mg L⁻¹ at T200) and DOC (up to 142 mg L⁻¹ at T100) were measured in soil solution below the root zone, indicating the potential of groundwater contamination. TSE irrigation did not change soil TC and TN.     

Management evaluation of Water Users Associations using benchmarking techniques

The development of different tools to evaluate the performance of Water Users Associations (WUAs) is an important practice for improving water and energy management, together with other production costs. One of these tools is the Benchmarking technique, which is based on the comparison between different WUAs to determine the best practices in each of them.In this paper, a Benchmarking process is applied to seven WUAs located in Castilla-La Mancha (Spain) during three irrigation seasons (2006-2008). The performance indicators developed by the International Programme for Technology and Research in Irrigation and Drainage (IPTRID) are used, while new indicators dealing with production and energy are proposed. The goals of this paper are to group WUAs with the same characteristics, using performance and energy indicators, and to reduce the set of indicators using statistical methods. The most important indicators, easy to obtain and yielding result in maximum information are retained for further use.Three proposals reducing the initial number of indicators were proposed, with an aim of being useful for future applications based on characterizing WUAs. Indicators results highlighted that irrigable areas can be grouped based on the application of drip irrigation systems and those with sprinkler irrigation systems. When using groundwater resources, no significant differences were observed for energy consumption between these irrigation systems. This can be explained by the indicator energy load index (ICE, m), which had similar values in all WUAs analyzed. According to annual irrigation water supply per unit irrigated area (V_TSr, m³ ha⁻¹), the highest values (between 5200 m³ ha⁻¹ and 6800 m³ ha⁻¹) were obtained in WUAs with sprinkler irrigation systems, which contained crops characterized by high water requirements, compared to the V_TSr (less than 1800 m³ ha⁻¹) of WUAs with drip irrigation systems, with crops that required less volume of irrigation water. Regarding production efficiency indicators, in drip irrigation systems the high presence of vineyards, almond and olive trees, crops with low water requirements, explained high values of gross margin per unit irrigation delivery (MBVs, € m⁻³)(close to 0.82 € m⁻³) in comparison with sprinkler irrigation systems (close to 0.36 € m⁻³).     

Yield and quality of melon grown under different irrigation and nitrogen rates

During 2 years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to investigate the effects of different nitrogen (N) and irrigation (I) levels on fruit yield, fruit quality, irrigation water use efficiency (IWUE) and nitrogen applied efficiency (NAE). The statistical design was a split-plot with four replications, where irrigation was the main factor of variation and N was the secondary factor. In 2005, irrigation treatments consisted of applying daily a moderate water stress equivalent to 75% of ETc (crop evapotranspiration), a 100% ETc control and an excess irrigation of 125% ETc (designated as I₇₅, I₁₀₀ and I₁₂₅), while the N treatments were 30, 85, 112 and 139 kg N ha⁻¹ (designated as N₃₀, N₈₅, N₁₁₂ and N₁₃₉). In 2006, both the irrigation and N treatments applied were: 60, 100 and 140% ETc (I₆₀, I₁₀₀ and I₁₄₀) and 93, 243 and 393 kg N ha⁻¹ (N₉₃, N₂₄₃ and N₃₉₃). Moderate water stress did not reduce melon yield and high IWUE was obtained. Under severe deficit irrigation, the yield was reduced by 22% mainly due to decrease fruit weight. The relative yield (yield/maximum yield) was higher than 95% when the irrigation depth applied was in the range of 87-136% ETc. In 2006, the interaction between irrigation and N was significant for yield, fruit weight and IWUE. The best yield, 41.3 Mg ha⁻¹, was obtained with 100% ETc at N₉₃. The flesh firmness and the placenta and seeds weight increased when the irrigation level was reduced by 60% ETc. The highest NAE was obtained with quantities of water close to 100% ETc and increased as the N level was reduced. The highest IWUE was obtained with applications close to 90 kg N ha⁻¹. The I₂₄₃ and I₃₉₃ treatments produced inferior fruits due to higher skin ratios and lower flesh ratios. These results suggest that it is possible to apply moderate deficit irrigation, around 90% ETc, and reduce nitrogen input to 90 kg ha⁻¹ without lessening quality and yields.     

Irrigation strategies to improve the water use efficiency of wheat-maize double cropping systems in North China Plain

Water is the most important limiting factor of wheat (Triticum aestivum L.) and maize (Zea mays L.) double cropping systems in the North China Plain (NCP). A two-year experiment with four irrigation levels based on crop growth stages was used to calibrate and validate RZWQM2, a hybrid model that combines the Root Zone Water Quality Model (RZWQM) and DSSAT4.0. The calibrated model was then used to investigate various irrigation strategies for high yield and water use efficiency (WUE) using weather data from 1961 to 1999. The model simulated soil moisture, crop yield, above-ground biomass and WUE in responses to irrigation schedules well, with root mean square errors (RMSEs) of 0.029 cm³ cm⁻³, 0.59 Mg ha⁻¹, 2.05 Mg ha⁻¹, and 0.19 kg m⁻³, respectively, for wheat; and 0.027 cm³ cm⁻³, 0.71 Mg ha⁻¹, 1.51 Mg ha⁻¹ and 0.35 kg m⁻³, respectively, for maize. WUE increased with the amount of irrigation applied during the dry growing season of 2001-2002, but was less sensitive to irrigation during the wet season of 2002-2003. Long-term simulation using weather data from 1961 to 1999 showed that initial soil water at planting was adequate (at 82% of crop available water) for wheat establishment due to the high rainfall during the previous maize season. Preseason irrigation for wheat commonly practiced by local farmers should be postponed to the most sensitive growth stage (stem extension) for higher yield and WUE in the area. Preseason irrigation for maize is needed in 40% of the years. With limited irrigation available (100, 150, 200, or 250 mm per year), 80% of the water allocated to the critical wheat growth stages and 20% applied at maize planting achieved the highest WUE and the least water drainage overall for the two crops.     

Effects of deficit irrigation on the yield and yield components of drip irrigated cotton in a mediterranean environment

A field study on cotton (Gossypium hirsutum L., cv.) was carried out from 2005 to 2008 in the Çukurova Region, Eastern Mediterranean, Turkey. Treatments were designated as I₁₀₀ full irrigation; DI₇₀, DI₅₀ and DI₀₀ which received 70, 50, and 0% of the irrigation water amount applied in the I₁₀₀ treatment. The irrigation water amount to be applied to the plots was calculated using cumulative pan evaporation that occurred during the irrigation intervals. The effect of water deficit or water stress on crop yield and some plant growth parameters such as yield response, water use efficiencies, dry matter yield (DM), leaf area index (LAI) as well as on lint quality components was evaluated. The average seasonal evapotranspiration ranged from 287 ± 15 (DI₀₀) to 584 ± 80 mm (I₁₀₀). Deficit irrigation significantly affected crop yield and all yield components considered in this study. The average seed cotton yield varied from 1369 ± 197 (DI₀₀) to 3397 ± 508 kg ha⁻¹ (I₁₀₀). The average water use efficiency (WUE_ET) ranged from 6.0 ± 1.6 (I₁₀₀) to 4.8 ± 0.9 kg ha⁻¹ mm⁻¹ (DI₀₀), while average irrigation water use efficiency (WUE_I) was between 9.4 ± 3.0 (I₁₀₀) and 14.4 ± 4.8 kg ha⁻¹ mm⁻¹ (DI₅₀). Deficit irrigation increased the harvest index (HI) values from 0.26 ± 0.054 (I₁₀₀) to 0.32 ± 0.052 kg kg⁻¹ (DI₅₀). Yield response factor (Ky) was determined to be 0.98 based on four-year average. Leaf area index (LAI) and dry matter yields (DM) increased with increasing water use. This study demonstrated that the full irrigated treatment (I₁₀₀) should be used for semiarid conditions with no water shortage. However, DI₇₀ treatment needs to be considered as a viable alternative for the development of reduced irrigation strategies in semiarid regions where irrigation water supplies are limited.