Abstract:
Abstract: Soil water is the key factor that limits vegetative growth and productivity in semiarid ecosystem, and the process of water uptake by the root system is of key importance for the effective management of irrigation. The relationships between soil water and plant have been reported for a wide range. However, there is very limited information about the relationships among soil water, fine root distribution and water-fertilizer pit (WFP) depth. This study was conducted to investigate the distribution characteristics of soil moisture and roots for 21-year-old 'Fushi' apple trees (Malus pumila Mill) under the WFP technology. The apple trees had a planting distance of 4 m between trees and 5 m between tree rows, and were planted on a typical rain-fed orchard with 15° slope. Three WFP treatments (with 3 replicates) were used in mature apple orchard, i.e., WFP40 (pit depth of 40 cm), WFP60 (pit depth of 60 cm) and WFP80 (pit depth of 80 cm), and CK (without WFP technology) as the controlled trial. c (Luoyang shovel) was used to obtain fine roots from 3 different horizontal positions, and soil moisture (volumetric) was measured by the time domain reflectometer (TDR) system with a measuring tube of 3 m at 20 cm increment in a vertical direction. The results showed that: 1) The low soil moisture content zone appeared in 40-80 cm soil profile of the CK, and the WFP significantly promoted the increase of the soil moisture content in the region. The average soil moisture content increment (145.4%) under WFP60 was the maximum, WFP40 was the next (133.4%) and WFP80 was the minimum (76.6%). 2) The vertical variations of soil moisture content had the same tendency under WFP40 and WFP60 treatments, which was that the moisture content firstly increased and next decreased and then increased again with the increase of soil depth in the vertical direction, and WFP80 showed the opposite tendency. The wetted area under WFP40 was concentrated in 40-100 cm soil profile and WFP60 was in 20-140 cm and WFP80 was below 140 cm, and the depth of the wetted area moved down with the depth of the pit (WFP). In the horizontal direction, the soil moisture content decreased with the increase of horizontal distance. The mean moisture content under WFP60 was the maximum, which was 11.60% and 10.45% in 0-100 and 100-200 cm experimental soil profile, respectively. And under WFP40, it was 10.93% and 10.41%, respectively; and WFP80 was 9.33% and 10.27%, respectively. 3) In 0-300 cm soil layer, the total root dry weight density under CK, WFP40, WFP60 and WFP80 was 372.12, 579.08, 594.76 and 491.82 g/m3, respectively. The root system distribution proportion in 0-100, ≥100-200 and ≥200-300 cm soil profile was as follows: CK (69.88%, 13.74% and 16.38%), WFP40 (66.04%, 14.26% and 19.70%), WFP60 (70.35%, 24.08% and 5.58%) and WFP80 (46.54%, 15.04% and 38.42%), and the distribution of root had relation with the spatial change of soil water. The result showed that the WFP technology could change the spatial distribution of soil water, which affected the root system distribution proportion in the soil profile with different depth, and the deeper the WFP got, the deeper the wetted area reached. Thus, the WFP technology is beneficial to roots by helping them absorb water and nutrients in a wider wetted area and improving drought resistance. Our results show that the application effect of WFP60 is better than WFP40 and WFP80.