Drip irrigation

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A large number of experiments have been conducted regarding the beneficial effects of drip irrigation over other methods, like sprinkler or surface irrigation. Advantages of drip irrigation include the saving of water, the efficient utilisation of applied nutrients, water having a higher salt content can be used for irrigation and less weed intensity as a result of less surface area wetted.

Capsicum plants irrigated with water containing 95 mg/L and having electrical conductivity of 0.6 mmhos/cm had a higher content of soluble and diffusible ions in the leaves when irrigated by sprinkler than when irrigated by drip, while there was no significant difference in yield between the two methods (Gornat et al., 1973).

Sprinkler and drip irrigation were compared on green pepper in an arid tract of Jerusalem in Israel. Yield, leaf growth and root development of pepper plants (cv. Califernia Wonder) were all greater with drip than with sprinkler irrigation (Goldberg and Shmueli, 1970).

Pepper plants of cv. California Wonder were drip irrigated at a constant frequency of one to two days with different amounts of water based on evaporation from a class A pan. The amount of water applied was 0.82, 0.95, 1.33 and 1.75 of the pan evaporation. Irrigation at 1.33 of the pan evaporation resulted in the highest yield of pepper (Shmueli and Goldberg, 1972).

An investigation was made in Tamil Nadu, India, to find out the water requirement of chilli crop variety K-l and its response to drip irrigation. There was a saving of 62% of water by drip irrigation. Yield of the crop increased by 25% and reduced weed infestation by 50% (Sivanappan etal., 1978; Sivanappaa, 1979).

In another study conducted in Israel, yields obtained under a drip system was 74t/ha, while in a sprinkler system it was 59 t/ha. The yield difference was attributed to lesser nitrate nitrogen in the root zone in drip (60—150ppm) compared to 250—300ppm in sprinkler system (Sagiv etal., 1978).

Methods of micro irrigation system

Among the various kinds of micro irrigation systems, namely, rotary, micro sprinkler, stationary micro sprinkler, canewall, drip irrigation, online drippers and drip irrigation microtube tested on a clay soil, the canewall drip tape recorded the highest benefit: cost (B : C) ratio (2.84%) and net extra income. However, the net extra income was the maximum with the stationary microsprinkler with B : C ratio of 2.74% (Shinde and Firake, 1998).

Prabhakar and Hebbar (1998) observed that the micro irrigation system produced 17—29% higher marketable yield and the microtube irrigation system resulted in a significant reduction in investment costs.

In a greenhouse experiment, Capsicum plants were grown using either the nutrient film technique (NFT) or rockwool, with drip irrigation. Plants grown using NFT gave a higher yield than those grown in rockwool and took up more water due to a higher leaf area index. However, the higher evaporation from the rockwool meant that total water consumption in the rockwool system was much higher than in the NFT system (Abou Hadid et al., 1993).

Drip irrigation and disease incidence

Drip irrigation increases chilli yield by providing either favourable soil moisture conditions or unfavourable conditions for disease incidence. Jin Haixie et al. (1999) observed that drip irrigation created a higher marketable green chilli yield than the alternate row furrow irrigation. Phytophthora root rot disease incidence in the infested plots was significantly higher under alternate row furrow irrigation than drip irrigation. There was no disease development in the unin-fested plots regardless of the irrigation method. The disease decreased green chilli yield by 55% and the combined yield (green + red chilli) by 36% compared to that in uninfested plots in alternate row furrow irrigation. A similar effect was also observed in the infection of Phytophthora capsici, causing mortality in green house grown Capsicum (Rista et al., 1995) and in the open production of Capsicum (Biles et al., 1992). Cafefilho and Duniway (1996) found that Phytophthora root rot of pepper could be reduced in a low rainfall area by positioning the drip emitters away from plant stems with a subsurface location (15 cm below soil). De Qiang and other workers (1996) also observed flood irrigation to be one of the reasons for the incidence of southern Sclerotium blight in chilli in China.

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