Saline water in supplemental irrigation of wheat and barley under rainfed agriculture

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Abstract

In the Mediterranean climate, rainfed cereal crops are planted in autumn and harvested in late spring, relying on the rains during this period for the conclusion of their cycle; the vagaries of rains, however, often put at risk the final harvest. The present research was aimed at investigating the possibility of applying supplemental irrigation to wheat and barley during their sensitive phenophases of flowering and seed formation using brackish water with salinity levels generally considered too high for its use (EC of 3–9 dS/m). Results showed the possibility of securing high yields, with mean reductions of only 21% in barley and 25% in wheat compared to the fully, fresh-water irrigated control, through the application of limited amounts of brackish water. The sustainability of the practice is presumably high, due to the limited amounts of added salts, which can be easily leached out even by a modest precipitation.

Introduction

Given the importance of worldwide rainfed cereal production and its dependence on climatic vagaries with consequent fluctuations in yield, it is felt that it is appropriate to dedicate some efforts to investigate the possibility of stabilizing the production levels through supplemental irrigation (SI). SI is a common practice in rainfed agriculture in Mediterranean-type climates (Duivenbooden et al., 1999), particularly for those staple crops, such as wheat and barley, which are particularly sensitive to the droughts frequently occurring in late spring, that coincide with the phenophases of flowering and seed formation.

According to FAO and ICARDA (1987), SI can stabilize and increase the outputs in quantity and in quality in regions where rainfall does not allow optimal crop development. The conjunctive use of water resources (i.e. irrigation water to supplement rainfall) can, in fact, increase considerably the efficiency of the use of water resources as a whole for the production of food and fibre.

Oweis et al. (1992) defined SI as the addition of limited water amounts (rainfall being the principal source of water) to the crop during periods when rain fails to provide essential moisture for plant growth, thus improving yield significantly and stabilizing it from year to year. Soil moisture shortage can cause marked reductions in production, which can be completely lost if a severe water stress occurs during critical crop stages.

Since a major, well known problem facing agriculture today is the shortage of freshwater resources, the challenge is to maintain crop production without impairing the balance of good quality water: an obvious solution is consequently to explore the sustainable use of non-conventional water resources (Pereira, 1994). When the availability of freshwater is limited, agriculture is likely to be forced to make increasing use of non-conventional waters, either brackish water or sewage effluents (Hamdy, 1999).

Brackish water is actually an interesting potential resource for irrigation: many recent research developments particularly in plant breeding and selection, soil, crop and water management, irrigation and drainage technology suggest how saline water might be used for irrigating crops with minimum adverse effects on the soil–plant–aquifer system (Hamdy, 1996). The use of saline or brackish water in SI is particularly attractive due to the limited water amounts typically needed by SI, which makes it relatively easy to maintain a favourable salt balance in the soil, ultimately protecting the fertility in the long term; however, the use of brackish waters puts some constraints on the selection of the irrigation system (e.g. sprinkling systems cannot be used).

Section snippets

Materials and methods

An experiment was conducted during the season 2002–2003 with wheat (Triticum sa tivum) and barley (Hordeum vulgare) in a greenhouse of the Mediterranean Agronomic Institute of Bari, Italy. The Institute is located at an altitude of 72 m above msl and a latitude of 41°03′; the greenhouse was coated with PVC sheets and thermostatically controlled to maintain the temperature around 20 °C.

The experimental setup included 72 PVC containers with a diameter of 400 mm, a depth of 60 cm and a net capacity,

Results

The total water amount applied to every pot after sowing as a result of the experimental design was:

  • T1: 46 L to wheat and barley (equivalent to 366 mm).

  • T2: 25 L of freshwater to wheat, 27 to barley (199 mm and 215 mm, respectively).

  • T3–T5: 5 L of freshwater (40 mm) + 20 L of brackish water (159 mm) to wheat and 5 L of freshwater (40 mm) + 22 L of brackish water (175 mm) to barley.

  • T6: 16 L to wheat, 18 to barley (mm 127 and 143, respectively).

Plant response in terms of final height, leaf area and dry matter

Discussion and conclusions

The goal generally pursued in irrigated agriculture is the achievement of the highest yield per unit land surface; only in relatively recent times was it realized that such a goal entails a wasteful use of water resources and the principles of deficit irrigation were developed (e.g. English, 1990), aiming to obtain the highest yield per unit of water. However, although representing an appreciable step towards a more rational use of water, adopting deficit irrigation principles implies the

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  • FAO and ICARDA, 1987. Consultation on supplementary irrigation—Rabat, Morocco, 7–9 December...
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