LB Natk Irrigation scheduling

The scheduling of irrigation can be made based on weather or soil moisture conditions as follows:

Cumulative pan evaporation

Irrigation scheduling based on evaporation values indicated that irrigation at 40 mm cumulative pan evaporation (CPE) exhibited the highest dry matter production, fruit yield, N uptake and water use efficiency (Prabhakar and Naik, 1997). Pulekar et al. (1990) also reported the highest yield of green chilli when the crop was irrigated at 36 mm CPE.

IWICPE ratio

The irrigation water (IW) to CPE ratio (IW/CPE) has been found to be a useful criteria for scheduling irrigation. The highest yield of chilli was recorded at IW/CPE ratios ranging from 0.75 to 0.90, depending on varieties and locations (Mary and Balakrishnan, 1990; Censur and Buzescu, 1998; Chartzoulakis and Drosos, 1998; Selvaraj et al., 1998; Subramanian et al., 1998). However, the highest water use efficiency was observed at 0.5 IW/CPE (Palled et al., 1988).

Available soil moisture depletion

While irrigating, enough water is to be applied to bring the soil moisture content of the effective rooting zone up to the field capacity. This is the quantity of water that the soil will hold against the pull of gravity. Add water when the moisture in the root zone has been depleted. In a study on the influence of different irrigation regimes on the off-season Capsicum, Boicet et al. (1989) found that irrigation throughout the vegetative cycle when soil water level had decreased to 85% field capacity resulted in the highest total yield, highest yield of grade one fruits, the largest fruits, and the highest average number of flowers per plant. This treatment also produced the best returns. While for Capsicum cv. California Wonder irrigation at 40% and 60% of available soil moisture gave the highest fruit yield in India (Hegde, 1989b).

Soil moisture tension

Irrigating the field when the soil moisture tension reaches a specified value is a useful method for scheduling irrigation. The soil moisture tension is measured by using tensiometers. Irrigation when soil moisture tension exceeded 1 atm increased the yield of chilli without affecting the number of fruits (Basaccu and Garibaldi, 1971).

Smittle et al. (1994) studied the effect of water regimes on yield and water use of bell pepper. Irrigation regimes consisted of applying water when the soil water tension at 10 cm exceeded 25, 50 or 75 kPa during crop growth. Yield and water use were greatest when irrigation was applied at 25 kPa. Using plastic tunnels with trickle irrigation, the highest yield was produced when irrigation was applied at 15 kPa (Dyko and Kaniszewski, 1989).

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