Abstract:
Abstract: The purpose of improving saline-alkali soil is to enhance soil physical and chemical properties, benefit crop growth, and ultimately realize high efficient and productivity. However, the current improving methods are faced with challenges of heavy workload, high cost, etc., which limit the promotion and application of saline-alkali soil at a large scale. In order to overcome above shortages, a modified method named punching and filling sand (PFS) was proposed. This research aimed at studying the influence of PFS method on water and salt transport process by irrigation experiments, and exploring the feasibility of PFS as an efficient measure of desalinization. The PFS method was divided into 2 steps, firstly punching vertical holes in the experiment fields, and secondly filling sand into the holes. From May to June in 2016, a series of irrigation experiments were carried out, and the experimental field was located at Shiji Countryside Cooperative in Zhongtang town, Binhai district, Tianjin (38°46′N, 117°13′E). The experimental site belonged to the coastal saline-alkali soil area, which was typical in northern China. The soil in experimental site was classified as coastal solonchak with a bad structure and permeability. Under 3 kinds of irrigation amount (600, 900 and 1 200 m3/hm2) condition, 3 kinds of punching depth (5, 10, and 15 cm, respectively) and 3 kinds of punching density (30, 60, and 90 holes/m2, respectively) were considered as 2 independent variables in the experimental design (3 replicates). Meanwhile, the irrigation experiments without punching treatment were also tested as the control group (CK). The outer diameter of the punching tube was 16 mm. Soil samples were respectively collected after 5, 10, 15, 20 and 25 days of irrigation, i.e. the duration of each monitoring period was 25 days. The soil water content was determined by oven drying method and the soil salinity was measured by a DDS-11A type conductivity meter. The results showed that the desalinization rate increased with the increasing of irrigation amount. After 25 days, in 600 m3/hm2 irrigation amount condition, the desalinization rate of 0-30 cm soil layer was negative (from -11.5% to ?6.9%), and in 1 200 m3/hm2 irrigation amount condition, the desalinization rate of 0-30 cm soil layer was positive (2.2%-14.3%). The PFS method affected water infiltration, after 25 days of 1200 m3/hm2 irrigation, ≥10 cm punching depth treatment decreased water storage of 0-30 cm soil layer by 8.7%-16.1% (P<0.05), compared with CK (without punching treatment). In addition, compared with CK, the PFS method with ≥10 cm punching depth treatments increased total desalinization amount by 50.7%-98.8% in top 0-30 cm soil layer after 25 days of irrigation. The punching density had no significantly influence on water storage under the same punching depth (P>0.05). However, the total desalination amount was greatly affected by the punching density. At the punching depth of 5 and 10 cm, the punching density of 30 and 60 holes/m2 was not significantly (P>0.05) different in total desalination amount, and the total desalination amount of both treatments was lower than that at 90 holes/m2 (P<0.05). However, at the punching depth of 15 cm, the total desalination amount for the punching density of 90 and 60 holes/m2 was not significantly different (P>0.05) but significantly higher than that at 30 holes/m2 (P<0.05). The results indicated that the PFS method affected water and salt transport significantly, and the PFS method had been proved to be an effective measure to improve coastal saline land in northern China. Considering current agricultural machinery equipment and local agronomic standard, 10 cm punching depth and 30 holes/m2 punching density were recommended as an adaptable PFS project. This study can provide valuable information for the agricultural practice of farmland in coastal saline-alkali soil area.