黄土高原肥水坑施技术下苹果树根系及土壤水分布

为了解黄土丘陵区雨养条件下山地老果园布设肥水坑(water-wertilizer pit,WFP)技术对红富士老果树(Malus pumila Mill)根系及土壤水分空间分布特征的影响,以无肥水坑处理为对照(CK),利用管式TDR系统监测0~300 cm土层土壤含水率,利用根钻法获得21a生旱地果园0~300 cm土层的根系干质量密度。结果表明:WFP能够显著增加果园含水率低值区间(≥40~80 cm土层)土壤含水率,WFP60(60 cm坑深)处理土壤平均含水率增量(145.4%)最显著。WFP40(40 cm坑深)根际土壤湿润区主要集中在≥40~100cm土层,WFP60在≥20~140 cm土层,WFP80(80 cm坑深)主要集中在深层土壤≥140 cm土层。在0~200cm试验土层,WFP60处理土壤多次平均含水率值都最高,为11.02%,依次为WFP40(10.67%)和WFP80(9.80%)。总根系质量密度WFP60处理最大(594.76 g/m3),WFP40(579.08 g/m3)和WFP80(491.82 g/m3)次之,CK最小(372.12 g/m3)。根系在0~100、≥100~200和≥200~300 cm土层中的分配比例为:CK(69.88%、13.74%和16.38)、WFP40(66.04%、14.26%和19.70%)、WFP60(70.35%、24.08%和5.58%)和WFP80(46.54%、15.04%和38.42%),其根系分布与水分分布正相关。该研究表明WFP能够显著改变土壤水分在不同土层深度的分布,坑深越大向下湿润的土体范围也越深;从而显著促进果树根系的生长和根系在不同湿润土层的分配比例关系。总体而言,WFP60处理效果显著好于WFP40和WFP80处理。研究结果将对黄土高原旱地果园集雨和灌溉制度的制定和肥水坑技术的推广提供参考。

Distribution characteristic of soil moisture and roots in rain-fed old apple orchards with water-fertilizer pit on the Loess Plateau

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 WFP80was 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, WFP60and WFP80was 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.