Soil microbial response, water and nitrogen use by tomato under different irrigation regimes

The objectives of this study were to investigate the effects of full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD) on plant biomass, irrigation water productivity (IWP), nitrogen use efficiency (NUE) of tomato, and soil microbial C/N ratio. The plants were grown in pots with roots split equally between two soil compartments in a climate-controlled glasshouse. During early fruiting stage, plants were exposed to FI, DI, and PRD treatments. In FI, both soil compartments were irrigated daily to a volumetric soil water content of 18%; in PRD, only one soil compartment was irrigated to 18% while the other was allowed to dry to ca. 7-8%, then the irrigation was shifted; in DI, the same amount of water used for the PRD plants was equally split to the two soil compartments. The results showed that, the FI treatment produced significantly higher dry biomasses of leaves, stems, and fresh weight of fruit and water productivity of aboveground dry biomass production than either DI or PRD, however, fruit IWP in DI was 25% higher than that of FI, and harvest index in DI and PRD were 50% and 22% higher than FI, respectively, for the 26% and 23% less water used in the DI and PRD, respectively, than the FI treatment. The DI treatment caused the smallest losses of N and highest N use efficiency by fruit. Both DI and PRD caused a significant increase in the soil microbial C/N ratio, meaning ratio of fungal biomass was high at low soil water contents. The result indicates that more work is needed to link the aboveground N uptake and the underground microbially mediated N transformation under different water-saving irrigation regimes.     

Maize yield response to deficit irrigation during low-sensitive growth stages and nitrogen rate under semi-arid climatic conditions

Knowledge of crop production in suboptimal environmental conditions not only helps to sustain crop production but also aids in the design of low-input systems. The objective of this study was to evaluate the effects of water stress imposed at low-sensitive growth stages (vegetative, reproductive, and both vegetative and reproductive) and level of nitrogen (N) supply (100 and 200 kg ha⁻¹) on the physiological and agronomic characteristics of two hybrids of maize (Zea mays L.). A two-site field experiment was carried out using a randomized complete block design with three replications and a split-factorial arrangement. A water deficit (WD) was induced by withholding irrigation at different stages of crop development. The results showed that proline content increased and the relative water content, leaf greenness, 100-kernel weight and grain yield decreased under conditions of WD. The highest IWUE was obtained when maize endured WD at vegetative stage at two sites. The limited irrigation imposed on maize during reproductive stage resulted in more yield reduction than that during vegetative stage, compared with fully irrigated treatment. The 100-kernel weight was the most sensitive yield component to determine the yield variation in maize plant when the WD treatments were imposed in low-sensitive growth stages. The results of the statistical regression analysis showed liner relationships between RGR during a period bracketing the V₈ or R₃ stages and 100-kernel weight in all the WD treatments. The increase of N supply improved yield and IWUE when maize plant endured once irrigation shortage at vegetative stage. But, the performance of high N fertilizer reduced and eliminated when water deficit imposed once at reproductive stage and twice at vegetative and reproductive stages, respectively. Furthermore, the response of T.C647 hybrid to increase of N supply was stronger than S.C647 hybrid.     

Opportunities for yield increases and environmental benefits through site-specific nutrient management in rice systems of Zhejiang province,China

Environmental pollution by nitrogen (N) leaching or runoff from rice fields and high pesticide use has become a serious concern in China. Average N application is high and fertilizer-N use efficiency is low compared with other major rice growing countries. In Zhejiang, rice farmers apply 150–250 kg ha⁻¹ fertilizer N and 7–10 sprays of pesticides per season to maintain yield levels of 5.5–8.0 t ha⁻¹. Fertilizer and pest management strategies of farmers are not based on plant nutrient demand and pest control requirements. To provide farmers with options for high yielding, yet more resourceful management options, site-specific nutrient management (SSNM) was developed at Zhejiang University in collaboration with the International Rice Research Institute (IRRI). The approach comprises guidelines that allow farmers to adjust domain- and season-specific fertilizer recommendations to actual growing conditions in their fields taking into account plant nutrient demand, indigenous nutrient supply, nutrient use efficiency, as well as socio-economic factors. The main objective of this paper is to evaluate the agronomic performance of SSNM in farmers’ fields in the past seven years (1998–2004). With SSNM, average grain yield increased by about 0.5 t ha⁻¹ over the farmers’ practice, while N use efficiency increased significantly. About 30% of both fertilizer N could be reduced through adoption of SSNM, which would effectively eliminate an unnecessary source of pollution in the rice ecosystem. Larger scale dissemination of SSNM for rice is under way in Zhejiang province, but stronger institutional support is urgently required.     

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.     

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

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

The effect of parameter uncertainty on whole-field nitrogen recommendations from nitrogen-rich strips and ramped strips in winter wheat

This paper estimates the relative profitability of using optical reflectance-based measures to predict crop needs for topdress nitrogen application to hard red winter wheat (Triticum aestivum). The data are from nitrogen yield response experiments where midseason optical reflectance data were recorded. Both nitrogen-rich strips and ramped strips are considered. Unlike past research, optimal nitrogen recommendations are calculated with and without accounting for parameter uncertainty. The expected profit-maximizing strategy is to follow the historical extension advice of applying 90 kg ha⁻¹ preplant nitrogen using anhydrous ammonia. This strategy is more profitable than the best optical reflectance-based prediction system by $18.74 ha⁻¹. When anhydrous ammonia is unavailable and preplant nitrogen must be applied as dry urea, the extension recommendation and the optical reflectance-based predictors are not significantly different. Ramped strips are no better than nitrogen-rich strips. Accounting for estimation uncertainty in the parameters increases expected profit by about $10 ha⁻¹.     

Integrating remote sensing, census and weather data for an assessment of rice yield, water consumption and water productivity in the Indo-Gangetic river basin

Crop consumptive water use and productivity are key elements to understand basin water management performance. This article presents a simplified approach to map rice (Oryza sativa L.) water consumption, yield, and water productivity (WP) in the Indo-Gangetic Basin (IGB) by combining remotely sensed imagery, national census and meteorological data. The statistical rice cropped area and production data were synthesized to calculate district-level land productivity, which is then further extrapolated to pixel-level values using MODIS NDVI product based on a crop dominance map. The water consumption by actual evapotranspiration is estimated with Simplified Surface Energy Balance (SSEB) model taking meteorological data and MODIS land surface temperature products as inputs. WP maps are then generated by dividing the rice productivity map with the seasonal actual evapotranspiration (ET) map. The average rice yields for Pakistan, India, Nepal and Bangladesh in the basin are 2.60, 2.53, 3.54 and 2.75 tons/ha, respectively. The average rice ET is 416 mm, accounting for only 68.2% of potential ET. The average WP of rice is 0.74 kg/m³. The WP generally varies with the trends of yield variation. A comparative analysis of ET, yield, rainfall and WP maps indicates greater scope for improvement of the downstream areas of the Ganges basin. The method proposed is simple, with satisfactory accuracy, and can be easily applied elsewhere.     

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.     

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.     

Greenhouse gas implications of water reuse in the Upper Pumpanga River Integrated Irrigation System, Philippines

Enhancing water productivity is often recommended as a “soft option” in addressing the problem of increasing water scarcity. However, improving water productivity, particularly through water reuse, incurs additional investment and may result in increased greenhouse gas (GHG) emissions. In this study, we analysed the water productivity and GHG implications of water reuse through pumping groundwater and creek water, and compare this with gravity-fed canal irrigation in the Upper Pampanga River Integrated Irrigation System (UPRIIS) in the Philippines.Water productivity indicators show that water reuse contributes significantly to water productivity. For example, water productivity with respect to gross inflow (WP_gross) with water reuse (0.19 kg grain/m³) is 21% higher than without water reuse (0.15 kg grain/m³). However, there is a tradeoff between increasing water productivity and water reuse as water reuse increases GHG emissions. The estimated GHG emission from water reuse (pumping irrigation) is 1.47 times higher than without water reuse (gravity-fed canal irrigation). Given increasing concerns about climate change and the need to reduce carbon emissions, we recommend that a higher priority be given to water reuse only in areas where water scarcity is a serious issue.     

Simulating soil water flow and nitrogen dynamics in a sunflower field irrigated with reclaimed wastewater

Soil water flow and nitrogen dynamics were simulated in sunflower field during and after the growing period, in Northern Greece. Soil water and nitrogen dynamics were evaluated using a one-dimensional simulation model based on the Galerkin finite element method. We examined the effects of irrigation with reclaimed wastewater and nitrogen fertilizer applications on plant growth, water and nitrogen distribution in the soil profile, water and nitrogen balance components and nitrogen leaching to groundwater. The model simulated the temporal variation of soil water content with reasonable accuracy. However, an over estimation of the measured data was observed during the simulation period. Relatively good agreement was found between the simulated and measured NH₄-N and NO₃-N concentrations over time and depth, whereas fluctuations at greater depths were relatively small. Most of the cumulative nitrate-N leaching (44.7 kg N ha⁻¹) occurred during the winter.     

Integrated effect of transplanting date, cultivar and irrigation on yield, water saving and water productivity of rice (Oryza sativa L.) in Indian Punjab: Field and simulation study

Individual effect of different field scale management interventions for water saving in rice viz. changing date of transplanting, cultivar and irrigation schedule on yield, water saving and water productivity is well documented in the literature. However, little is known about their integrated effect. To study that, field experimentation and modeling approach was used. Field experiments were conducted for 2 years (2006 and 2007) at Punjab Agricultural University Farm, Ludhiana on a deep alluvial loamy sand Typic Ustipsamment soils developed under hyper-thermic regime. Treatments included three dates of transplanting (25 May, 10 June and 25 June), two cultivars (PR 118 inbred and RH 257 hybrid) and two irrigation schedules (2-days drainage period and at soil water suction of 16 kPa). The model used was CropSyst, which has already been calibrated for growth (periodic biomass and LAI) of rice and soil water content in two independent experiments. The main findings of the field and simulation studies conducted are compared to any individual, integrated management of transplanting date, cultivar and irrigation, sustained yield (6.3-7.5 t ha⁻¹) and saved substantial amount of water in rice. For example, with two management interventions, i.e. shifting of transplanting date to lower evaporative demand (from 5 May to 25 June) concomitant with growing of short duration hybrid variety (90 days from transplanting to harvest), the total real water saving (wet saving) through reduction in evapotranspiration (ET) was 140 mm, which was almost double than managing the single, i.e. 66 mm by shifting transplanting or 71 mm by growing short duration hybrid variety. Shifting the transplanting date saved water through reduction in soil water evaporation component while growing of short duration variety through reduction in both evaporation and transpiration components of water balance. Managing irrigation water schedule based on soil water suction of 16 kPa at 15-20 cm soil depth, compared to 2-day drainage, did not save water in real (wet saving), however, it resulted into apparent water saving (dry saving). The real crop water productivity (marketable yield/ET) was more by 17% in 25th June transplanted rice than 25th May, 23% in short duration variety than long and 2% in irrigation treatment of 16 kPa soil water suction than 2-days drainage. The corresponding values for the apparent crop water productivity (marketable yield/irrigation water applied) were 16, 20 and 50%, respectively. Pooled experimental data of 2 years showed that with managing irrigation scheduling based on soil water suction of 16 kPa at 15-20 cm soil depth, though 700 mm irrigation water was saved but the associated yield was reduced by 277 kg ha⁻¹.     

Modelling of water and nitrogen balances in the ponded water and soil profile of rice fields in Northern Greece

This paper presents a water and nitrogen balance model for the surface ponded water and soil profile system of rice (Oryza sativa L.) fields. The model estimates the daily water balance components, as well as, the daily losses and transformations of nitrogen. Data from two neighbouring rice fields during the growing season of 2005 in the Thessaloniki plain of Northern Greece were used for the application of the model. The data set of field A was used for the calibration of the model, while the data set from the field B for validation of model. Simulation results of total inorganic nitrogen in the soil and runoff water exhibited reasonable agreement with the measured data during calibration and verification of the model. Significant amounts of applied irrigation water were lost through surface runoff and deep percolation into the groundwater. The sum of nitrogen inputs from fertilization, mineralization and irrigation water were 292.7 and 280.4 kg ha⁻¹ for field A and B, respectively. Nitrogen uptake by algae in ponding water and plants was one of the main processes of nitrogen reduction in the rice field systems with an amount of 125.7 and 131.8 kg ha⁻¹ for field A and B, respectively. Leaching through percolated water was the other significant process with 118.3 and 120.8 kg ha⁻¹, respectively. Gaseous losses of nitrogen (via volatilization and denitrification) were also substantial processes of nitrogen reduction in the flooded compartment. The study showed that the simple model presents important results for the water and nitrogen management in rice fields. This information can be used for irrigation water saving and prevention of water resources contamination in rice-based agroecosystems.     

远红光阶段辐照对水稻幼苗生长及水分利用效率研究

以水稻“绿旱639”为研究对象,在水稻的种期(T1)、芽期(T2)和苗期(T3)分别进行远红光辐照,并设置对照组(CK)。通过测算水稻幼苗的生理指标、生长特性以及水分利用效率,研究了阶段辐照下远红光对水稻幼苗的生长及水分利用效率影响。结果表明：种期进行辐照水稻幼苗的叶面积比芽期和苗期分别增加了15.82％和20.46％。芽期进行辐照水稻幼苗的相对生长速率比种期和苗期分别增加了23.10％和37.01％,根长、根冠比、净同化速率等指标的增长幅度均大于种期和苗期辐照。苗期进行辐照水稻幼苗的叶片水分利用效率与种期和芽期辐照相比,分别增加了16.60％和23.07％。综上,在水稻幼苗的芽期进行远红光辐照,可以有效促进水稻幼苗的生长。在水稻幼苗的苗期进行远红光辐照,可以显著提高水稻幼苗的水分利用效率。本研究从光学农业角度为提高水稻以及其他作物水分利用效率提供了参考。     

Water pillow irrigation compared to furrow irrigation for soybean production in a semi-arid area

Field studies were done in 2003 and 2006 to evaluate the performance of water pillow (WP) irrigation as an alternative to furrow irrigation (FI) for soybean growth in semi-arid climatic conditions. There were four irrigation treatments: two of which (FI and WP_1.0) were full irrigation, in that the water deficit in the soil profile (0.9 m) was brought to field capacity in 10-day intervals. The other two treatments (WP_0.75 and WP_0.50) were deficit irrigation treatments, and received 75% and 50% of WP_1.0 irrigation amount. The highest seed yield was achieved with the WP_1.0 treatment. Irrigation water use efficiency (IWUE) and water use efficiency (WUE) were influenced significantly by the irrigation methods and levels (P ≤ 0.05). The highest values of WUE and IWUE were obtained by the WP_0.75 and WP_0.50 treatment, respectively, in both study years. However, the smallest irrigation amount resulted in lower total yield for the WP_0.50 treatment, and is not recommended. In conclusion, the WP_0.75 treatment is recommended for soybean production in order to attain higher values of IWUE and WUE, and to conserve water and maximize yield with the same volume of water.     

Effect of mulching on soil and plant water status, and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment

Mulching is one of the important agronomic practices in conserving the soil moisture and modifying the soil physical environment. Wheat, the second most important cereal crop in India, is sensitive to soil moisture stress. Field experiments were conducted during winter seasons of 2004-2005 and 2005-2006 in a sandy loam soil to evaluate the soil and plant water status in wheat under synthetic (transparent and black polyethylene) and organic (rice husk) mulches with limited irrigation and compared with adequate irrigation with no mulch (conventional practices by the farmers). Though all the mulch treatments improved the soil moisture status, rice husk was found to be superior in maintaining optimum soil moisture condition for crop use. The residual soil moisture was also minimum, indicating effective utilization of moisture by the crop under RH. The plant water status, as evaluated by relative water content and leaf water potential were favourable under RH. Specific leaf weight, root length density and dry biomass were also greater in this treatment. Optimum soil and canopy thermal environment of wheat with limited fluctuations were observed under RH, even during dry periods. This produced comparable yield with less water use, enhancing the water use efficiency. Therefore, it may be concluded that under limited irrigation condition, RH mulching will be beneficial for wheat as it is able to maintain better soil and plant water status, leading to higher grain yield and enhanced water use efficiency.     

Crop coefficient, yield response to water stress and water productivity of teff (Eragrostis tef (Zucc.)

In the semi-arid region of Tigray, Northen Ethiopia a two season experiment was conducted to measure evapotranspiration, estimate yield response to water stress and derive the crop coefficient of teff using the single crop coefficient approach with simple, locally made lysimeters and field plots. During the experiment we also estimated the water productivity of teff taking into account long-term rainfall probability scenarios and different levels of farmers’ skills. During the experimental seasons (2008 and 2009), the average potential evapotranspiration of teff ranged from 260 to 317 mm. The total seasonal water requirement of teff was found to lower in contrast to the assumptions of regional agronomists that teff water requirement is comparable to that of wheat and barley (375 mm). The average single crop coefficient values (k_c) for the initial, mid and late season stages of teff were 0.8-1, 0.95-1.1 and 0.4-0.5, respectively. The seasonal yield response to water stress was 1.04, which indicates that teff exhibits a moderately sensitive and linear response to water stress. The results suggest that teff is likely to give significantly higher grain yield when a nearly optimal water supply is provided. The study showed that, in locations where standard equipment is not affordably available, indicative (rough) crop evapotranspiration values can be obtained by using field plots and employing locally made lysimeters. The difference in economic water productivity (EWP) and the crop water productivity (CWP) for teff were assessed under very wet, wet, normal, dry and very dry scenarios. In addition two groups of farmers were evaluated, a moderately (I) and a highly skilled (II) group. The results showed that higher EWP and CWP were obtained under very wet scenario than very dry scenario. There was also a 22% increase in EWP and CWP under group II compared to group I farmers. The increase was due to a 22% reduction in unwanted water losses achieved through use of improved technology and better irrigation skills. Both EWP and CWP can be used to evaluate the pond irrigation water productivity (IWP) for a given climate, crop and soil type, and skill and technology level of the farmer. For special crops like teff extra criteria may be needed in order to properly evaluate the pond irrigation water productivity. During the experimental seasons, a high IWP for teff was attained when about 90% of the optimal water need of the crop was met. IWP can be used as an indicator as how much supplementary irrigation has to be applied in relation to the rainfall and other sources of water supply in order to assure greatest yield from a total area. However, the supplemental irrigation requirement of the crops may vary with season due to seasonal rainfall variability.     

Water and nitrogen interaction on soil profile water extraction and ET in maize-wheat cropping system

In the present study, water and nitrogen interaction on soil profile water extraction and evapo-transpiration (ET) was investigated taking a field experiment on a clay loam soil (Typic Haplustept) at the Indian Agricultural Research Institute, New Delhi with four consecutive crops (maize-wheat-maize-wheat) taken from July 2002 to April 2004. Three levels of water regime, namely W1, W2 and W3 referring to limited, medium and maximum irrigation were applied to each crop depending on the seasonal rainfall and the critical crop growth stage. The three water regimes were used with five nitrogen levels from T1 to T5, (T1, 0% N; T2, 75% N; T3, 100% N; T4, 150% N; T5, 100% N from organic source) in a split plot design for the four crops grown in sequence.Significant water and nitrogen interaction was observed for ET and soil profile water extraction pattern. Averaged across nitrogen treatments, ET in W2 and W3 were higher by 17 and 26%, respectively than W1 in maize 2002 and by 12 and 19% in maize 2003. In case of wheat, ET in W2 and W3 were higher by 27 and 58% than W1 in 1st crop and by 37 and 70% in 2nd crop. The effect of nitrogen regime, however, was prominent in both crops of maize and wheat, with significantly higher profile soil moisture depletion in T4 of each water regime. In all cases, lowest water depletion was observed in control plots receiving 0% N.In both crops, water extraction from surface 60 cm was highest in W3 followed by W2 and W1. In maize, the % extraction from 0 to 60 cm layer varied from 71 to 76% (W1), 70-79% (W2) and 75-82% (W3), whereas the values for wheat were 70-77, 72-79 and 75-83% for W1, W2 and W3, respectively. The 90-120 cm layer contributed only 3-14% to total water extraction in both the crops. From 90 to 120 cm layer, higher extraction was observed in W1 as compared to W3. The extraction values in W1, W2 and W3 in maize were 9-13, 7-14 and 3-9, respectively, whereas the corresponding values in wheat were 8-14, 5-12 and 3-7% for the three water regimes. Effect of nitrogen treatments on water extraction from deeper layer was observed with higher extraction in highest fertilized treatment (T4) as compared to other treatments.     

Yield and water use efficiency of cauliflower under varying irrigation frequencies and water application methods in Lower Gangetic Plain of India

A field study (1999-2000 to 2001-2002) was carried out to optimize the irrigation frequency and suitable water application methods for cauliflower with a view to increase curd yield (CY) and water use efficiency (WUE). Check Basin (CB), Each Furrow (EF) and Alternate Furrow (AF) methods were tested with three irrigation frequencies depending on the attainment of soil matric potential (Ψ_m) value at 0.2 m depth as: −0.03 MPa (F₁), −0.05 MPa (F₂) and −0.07 MPa (F₃). Maximum CY was recorded under F₁ and decreased by 10.4 and 31.4%, respectively under F₂ and F₃ frequencies. In contrast, WUE decreased by 9.3% from F₃ to F₁. Highest CY and WUE obtained under CB followed by EF and AF methods. Furrow application methods saved 12-24% irrigation water over CB method. Maximum soil water stress coefficient (K_s) recorded at curd development stage in comparison to other stages. Both seasonal evapotranspiration (ET_a) and yield-moisture stress index (Kys) recorded positive linear relationships with CY. Present study shows a crop response factor of 0.822 for cauliflower. In this region, cauliflower should be irrigated with check basin method at an interval of 8-10 days.     

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.