Impact of Deficit Irrigation on Water Productivity, Yield and Fruit Quality of Tomato under Mediterranean Climate
By Abdallah, A and Hamdy, A
Abstract
The effect of deficit irrigation (DI) on water productivity, crop sensitivity to water stress, physiological performance,yield and quality of tomato under the Mediterranean climate were studied. An open-field experiment was carried out where three irrigation treatments were investigated: 100% (FI=full), DI-75% (Moderate water stress) and DI-50% (Severe water stress). The obtained results showed that the deficit irrigation approach affected the crop water productivity with values greater than that obtained for the full irrigation treatment. On the other hand the deficit irrigation affected negatively the studied parameters: the relative water content (RWC), total chlorophyll, total dry mass, net Co2 assimilation rate and fruit yield and size. However, under the severe deficit irrigation treatments I-50%Etc most of the studied parameters were subjected to notable reduction in their values with respect to those obtained under the 75%ETc irrigation treatments. This Cleary prove that under deficit irrigation practices crop response to moisture stress will vary according to the variation in the crop under investigation. For tomato, irrigation with 75%ETc (Moderate water stress) is the one to be recommended as it gives yield very near to that under full irrigation, provides good saving of irrigation water and improves crop water productivity.
Key words: water productivity, deficit irrigation, tomato and yield quality
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SUMMARY OF MASTER THESIS
Because nitrogen application rate and irrigation amounts typically exceed plant requirements demand in Egypt, drainage to ground water or surface water can result in N movement out of the root zone especially in light textured soils, and this causes a lot of economical and environmental problems, therefore the management of irrigation water and fertilizer and physical properties of soil are important to reduce these problems. The Research Objectives were i) to reduce nitrate leaching to water recourses through the adoption of the improved nitrogen and water management practices. 2)-Evaluating the effectiveness of localized compaction on NO־3 leaching reduction and improvement of nitrogen and water use efficiency in a corn field under different water regimes and different locations of the localized compaction. 3)-Determination of soil nitrate vertical distribution (after crop yielding) as affected by localized compaction treatments. 4)-Calculating compaction dependency and yield response under different water regimes, and different locations of localized compaction treatments.5) -Assessing the relationship between some of physical properties and localized compaction treatments.
To achieve these objectives, the following studies were carried out: field experiment was carried out in 2007 at EL-Boston region, in calcareous, sandy loam soil under furrow irrigation system. Split plot statistical design with two water application rates as a main plots (a) Field capacity= 100% of ETC (I-1), and (b) at saturation (I-2). Nitrogen fertilizer was banded under four treatments of localized compaction (LC) as sub main plots as fellows, (i): The control without compaction (LC-1), (ii): under the fertilizer band (LC-2), (iii): above the fertilizer band (LC-3), and (iv): both above and under the fertilizer band (LC-4).For each irrigation treatment, 120 Kg of nitrogen /fed as ammonium nitrate 33.5 % was applied. The fertilizer was incorporated in depth of 5 cm. The N-fertilizer was splited in two equal doses (at planting and 30 days after planting). Soil samples were collected during the growing season and after harvesting. Plant samples were collected at tasseling.
The obtained results can be summarized as following: The results of this study showed that increasing loads, above the compacting wheel, increased soil bulk density and reduced total porosity at the same level of soil moisture content. Also, soil compaction, by the wheel when the load was 30 kg with the volumetric water content near field capacity, increased soil bulk density from 1.41 up to 1.67 g/cm3. This caused parallel decrease in total porosity (TP) and quickly drainable pores (QDP); and increased the slowly drainable pores (SDP), and fine capillary pores (FCP). Reduced infiltration rate and hydurlic conductivity are resulted from 30 kg load.
Using FAO-CROPWAT software version 4.3 to calculate crop water requirements is a good method in irrigation scheduling. Moreover The results also suggest that irrigation scheduling might be a viable method to reduce groundwater pollution, and that application of optimized minimum amounts of water and nitrogen is required to meet realistic environmental, economic and yield goals.
Irrigation at field capacity significantly increased grain yield, N-uptake, all growth parameters, N- efficiency, water efficiency parameters and chlorophyll A chlorophyll B contents at the same time reduced nitrate leaching from soil profile as compared with irrigation at saturation.
At irrigation at saturation, localized compaction significantly increased grain yield, N-uptake, all growth parameters, N- efficiency, water efficiency parameters and chlorophyll content as compared with control plots and localized compaction under the fertilizer band. At irrigation at field capacity there was no response to localized compaction treatments therefore; localized compaction dependency was small as compared with saturation treatments.
Results of the present study indicate that localized compaction (LC-3), (LC-4) reduced NO־3 leaching and improved N-use efficiency only when irrigation water excessed field capacity. These findings suggest that the (LC-3) may be effective in reducing leaching losses during growing seasons when irrigation was above field capacity.