טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentTal Shkolnik
SubjectEvaluation of Water Saving Means, Mulch and Cover Crops,
in Young Orchards
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Furman Alex
Dr. Egozi Roey
Full Thesis textFull thesis text - English Version


Abstract

In the first years of orchard's life, 60-90% of the orchard's floor is exposed because of small tree canopy and the common practice of using herbicides to prevent weeds. This results in soil surface directly exposed to the kinetic energy of the rainfall droplets. The energy that is transferred to the soil's surface leads to a series of processes that develop a physical crust at the soil surface. As a result, the soil’s surface physical properties change, including a decrease of the surface hydraulic conductivity. By that, soil water content and water available to the trees decrease, runoff volume and soil erosion increase. This causes a damage to the fields and its surrounding. One of the solutions that have been examined in order to increase the amount of infiltration from precipitation and at the same time reducing soil erosion is protecting the soil surface by mulch and cover crop (CC).

The main goal of this research is to study the effect of soil mulch and cover crops on the water balance components at young orchards as affected by. This was done by investigating the different hydrological processes in the two main seasons in Israel, the wet winter and dry summer.

Our research area is a young orchard in the “Sharon” region. Three treatments were considered, (1) CC of Oat and Vicia villosa between the rows, mulch cover on the ridge; (2) CC of local wild flora between the rows, mulch on the ridge; (3) CC of Oat and Vicia villosa between the rows only. The treatments were compared to control treatment of bare soil and ridge. We measured runoff with a total of 12 flumes down the slope of the row. The volumetric water content in each treatment was measured by time domain transmittance sensors in all four treatments. The sensors were installed in three depths which represent near surface (10 cm), the root zone (50 cm), and the region beneath the root zone (180 cm). In addition, rain was measured using rain gauges on site.

The results show that there are several major hydraulic advantages for the cover layer during the span of the entire year. In the winter, a significantly higher amount of water turns into runoff when the soil is bare. Nevertheless, for the small rainfall events infiltration is higher when the ridge soil is expose, but during the large events, the average infiltration is higher when the soil is mulched. Between the rows infiltration is consistency higher when the soil is exposed. During the dry season, the soil temperature under mulch is more moderate than under the bare soil, and decreases evaporation rate. By that, the mulch keeps a higher soil moisture content during the dry season which results in more available water for the trees.