Estimation of Net Water Requirement of Different Phenological Stages of Canola in Isfahan Province

In recent years, canola cultivation in Iran has been considered as oil production, and in 2014-2015, it has been allocated to 7.7% of the cultivation area of industrial products of the country. The yield of canola oil and seeds depends on the availability of sufficient water resources during the growth period. In the Mediterranean, with the cultivation of canola autumn, the high- temperature occurs in the stages of formation and growth of seeds in the spring can increase the water requirement of this plant and irrigation management at this time is important in increasing plant yield. Due to the weather conditions of each area, type of variety and soil conditions may vary the need for canola. In one study in Hamedan water use efficiency of canola in two ways drip and furrow irrigation were calculated as 1.09 and 0.63 kg m-3, respectively. The present study was conducted with the purpose of evaluating the net water requirement of canola plant in different cities of Isfahan province into different climatic zones and considering the phonological stages.

In order to estimate the net water requirement of canola under two different climates (arid-cold winter with temperatures above freezing point - hot summer A-C-W) and (Semi-arid-cold winter with a temperature equal to or less than zero-hot summer SA-K-W) in Isfahan province, a research was conducted in 2014-2015 using a completely randomized, unbalanced design. The study was carried out in different cities of Isfahan province, which have canola cultivation. The required statistical information was obtained from 28 stations of synoptic and climatologic meteorology in Isfahan province and some neighboring provinces. Soil data was used to calculate the soil evaporation coefficient (Ke), which describes the evaporation component in the trait (ETc). In order to calculate the soil properties, in addition to the sampling of existing fields, a database of 1600 soil profiles in the Soil and Water Research Department of Isfahan province was also used. The plant growth stages were considered based on FAO’s 56 irrigation and drainage journal. For analyzing data in each climate, a completely randomized, unbalanced design (with inequality repeat) was used, and the meanings were compared with Duncan’s multiple range test (at 5% level).

There was a significant difference (α=1%) between the different cities in terms of total water consumption and the net water requirement of different phenological growth stages. In the SA-K-W climate, the net water requirement for each hectare of canola cultivated in the cities of Fereydoun Shahr, Friedan, Golpayegan, Khansari, Semirom, Tiran and Karvan, Shahreza, Chadegan, Dehaghan, and Boein va Mian Dasht was 3936, 4069, 4258, 4011, 3991, 4147, 3964, 3961, 4035 and 4055 m-3, respectively. In the SA-K-W climate (with ten cities), the net water requirement of canola was estimated at 4,000 m-3 ha-1. The difference between the highest and the least water requirement in this climate were 322 m-3 ha-1 and related to cities of Frieden and Fereydoun City, respectively. In the climate of A-C-W (12 cities), canola net water requirement was 892 m-3 ha-1 more than the net water requirement of this crop in the SA-K-W climate. On average, the initial, developmental, and (middle and final) net water requirements of the canola in the A-C-W climate were 540, 2150, and 2200 m-3 ha-1, respectively. The net irrigation requirement estimated for each ha-1 of canola cultivation in Isfahan, Ardestan, Khomeini Shahr, Falavarjan, Kashan, Lenjanat, Naein, Najaf Abad, Natanz, Shahin Shahr, Mobarakeh, and Borkhar cities was 4747. 4807. 4797, 5,105, 4885, 4908, 4750, 4785, 4974, 4971, 4879 and 5097 m-3, respectively.

Based on the results of the 10 cities in the SA-K-W climate, canola production per hectare requires an average of 4,000 cubic meters of net water per hectare. In the A-C-W climate of 12 cities, the average net water requirement per hectare was 4892 m-3. The difference in water requirement between this climate and the climate of SA-K-W was related to the middle and late stages of canola growth.