Soil and Water
תחום או ענף אגרוטכנולוגיה; ירקות
תאריך עדכון 29/9/2011
תיאור מלא Optimizing irrigation frequency and volume for peppers irrigated with saline water
S. Kramer, E. Kenig – Extension Service (SHA'AM), Ministry of Agriculture
A. Ben-Gal - Gilat Research Center, Agricultural Research Organization, Ministry of Agriculture
R. Offenbach, A. Maduel, M. Kapun - Central and Northern Arava R&D
Email for correspondence: firstname.lastname@example.org
The increase in the amount of area cultivated by each farmer together with the addition of new families to the Arava region have negatively affected the water restriction for all growers. Together with the increase in water consumption in recent years, the quality of irrigation water has deteriorated as a result of the increased salinity of the local well water. The practice of growers using excessive irrigation to ensure that the crop will never lack for water and that excess salts are washed out of the root zone has worsened the state of the depleted water reserves. The results of experiments to evaluate the feasibility of irrigating based on tensiometer readings have taught us that irrigation in the field can be timed so that the plants receive the amount of water they need, corresponding to the effects of changes in the weather. The average amount of water applied daily decreased in all treatments as the days became shorter and temperatures fell. The frequency of irrigation changed according to increases in the quantity of water applied at the time that tensiometer reading was observed in the field. According to the obtained results, the efficiency of irrigation was improved in all treatments without any damage to yield levels.
In an experiment conducted in pepper in a greenhouse at the Zohar Experimental Station in Sodom Valley during the 2009/10 growing season, we evaluated three irrigation programs that were carried out based on continuous tensiometer readings, which were used to determine ahead of time the amount of water to be applied when the tensiometer reading was received. The actual frequency of irrigation was the result of a combination of a threshold value for activating the irrigation system and the quantity of water to be supplied when the tensiometer reading was received. The choice of a value for which the water potential was relatively low (absolute value) in combination with a water quantity of 4 mm led to once-a-day irrigation. The use of a similar threshold value with a water quantity of 1 mm led to irrigation at a frequency of 3-5 times per day. The use of a threshold value for which the water potential was very low and a water quantity of 0.2 mm led to a irrigation at a frequency of 25 times per day. In two additional treatments, we started and stopped irrigation based on threshold values that had been determined ahead of time. The amount of water applied was a function of these values. In a treatment in which the starting and stopping of irrigation was controlled by a shallow tensiometer, plants were watered twice a day during warm periods and once a day during the winter. Turning on the irrigation based on the readings of a shallow tensiometer and turning it off based on the readings of a deep tensiometer led to once-a-day irrigation for most of the growing season. In all of the treatments, the amount of water applied each day decreased as the days became shorter and the air became cooler. From the end of the winter, the quantity and frequency of irrigation increased as the days became warmer and longer.
We examined two characteristics of pepper development: A) the lateral growth of the plants, which was monitored from three weeks after the plants were transplanted through January 5, 2010; and B) the numbers of internodes and fruit. No differences in these characteristics were observed between the treatments. We also monitored changes in the salinity of the soil solution at four depths and two locations relative to the dripper: next to the dripper and 10 cm away from it along the length of the branch. In the treatment in which 0.2 mm of water were applied when the tensiometer reading was received, the electrical conductivity of the soil solution increased beginning in mid-November, when the amount of daily irrigation began to be gradually decreased. In the treatment in which1 mm of water was applied, the electrical conductivity of the soil remained stable throughout the growing season. This treatment also had the highest yield, 6.57 tons/dunam. In the treatment in which an irrigation quantity of 4 mm was applied, there was an increase in the electrical conductivity of the soil solution from the beginning of January, parallel to the move to irrigating once every two days and a decrease in the daily irrigation level to 2 mm. This treatment had the lowest yield, 5.74 tons/dunam. The high level of salinity in the root zone during the winter explains why the fruits in this treatment were particularly small. In the treatment in which the irrigation was turned on according to the readings of a shallow tensiometer and turned off based on the readings of a deep tensiometer, large irrigation amounts of 4-5 mm per day were applied throughout most of the period. In late January and early February, the daily irrigation amount was decreased to 3 mm and there was a parallel, moderate increase in the salinity of the soil solution. In the treatment in which irrigation was turned on and off based on the readings of a shallow tensiometer, the amount of water applied daily decreased to 1.8 mm that were applied each time the system was turned on, from mid-January through the beginning of March. During this period, there was an initial moderate increase in the electrical conductivity of the soil solution and, over time, there was an increase in the rate at which the electrical conductivity values were increasing. As the weather became warmer and we began to irrigate twice a day (for a total amount of 4 mm or more), the electrical conductivity decreased sharply.
These results demonstrate the need to apply irrigation volumes that exceed consumption, even during the winter, in order to maintain a relatively low and stable level of salinity in the root zone. These processes occur in all crops irrigated with saline water.
We would like to thank the Scientist’s Fund of the Ministry of Agriculture and Rural Development for funding Research Program no. 08-1498-870.
מלות מפתח greenhouse vegetable production, pepper, water conservation
מחבר Shlomo Kramer, Elisha Kenig, Alon Ben Gal, Rivka Offenbach, Ami Maduel, Moran Kapun
תאריך יצירה 29/9/2011
תאריך עדכון 14/3/2012