| Study of movement of water and salts in dry red soil under drip irrigation with brackish water |
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| DOI：10.7606/j.issn.1000-7601.2019.02.06 |
| Key Words: drip irrigation with brackish water dry red soil water and salt migration salinity wetting front |
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| Abstract: |
| In order to better understand the water and salt transport of brackish water drip irrigation in dry red soil region, single and double point source infiltration experiments with different irrigation salinity (2.88 g·L-1, 4.86 g·L-1 and 8.33 g·L-1) and single point source infiltration experiments with different dripper discharge (2.68 L·h-1, 3.74 L·h-1, 4.68 L·h-1) were carried out on red soil with a bulk density of 1.2 g·cm-3. The effects of dripper discharge and salinity on water and salt transport in red loam soil were analyzed. The results showed that under the fixed salinity (2.88 g·L-1), the movement rate of wetting front was fast and stable after 150 seconds, and the average advancing rate was 1.65 cm·s-1 under 3.74 L·h-1dripper discharge. The final wetting depth was 22 cm, which meets the irrigation requirements. Its comprehensive performance was better than 4.68 L·h-1dripper discharge and effectively saved irrigation water. Under certain conditions (3.74 L·h-1), the propulsive depth of wetting front increased with increasing salinity, and its velocity was 2.88 g·L-1<4.86 g·L-1<8.33 g·L-1, and the propulsive depth was 21.5 cm, 22.4 cm and 22.78 cm, respectively. In the double point source experiment, the water content of the dripper with salinity of 8.33 g·L-1 and 4.86 g·L-1 was about 0.4 g·g-1, while the salt content of the dripper with salinity of 8.33 g·L-1was about 0.4%, which was not suitable for the cropgrowth. When the water salinity of 4.86 g·L-1was irrigated, a low salinity area with salinity of about 0.1% was formed in the intersection part. When the dripper flow rate was 3.74 L·h-1, comparing the same infiltration depth of single and double point source infiltration tests, it is found that increasing salinity made the surface wetting ratio increase from 87% to 90.8%. The intersection time at 8.33 g·L-1 salinity was 16 minutes earlier than that at 2.88 g·L-1 salinity.The salinity at 0~15 cm soil layer at 8.33 g·L-1 of drip water salinity at the same wetting position increased by 37% over that at the single point source. When the salinity was not more than 4.86 g·L-1, the salt content increase ratio was almost negative. While the irrigation salinity was at 4.86 g·L- 1, salt accumulation was not significant and the water content was high. When using drip irrigation with brackish water in dry red soil area of Yunnan Province where irrigation water resources are scarce, the drip flow rate of 3.74 L·h-1with ≤4.86 g·L-1salinity of brackish water can be used for crop cultivation practice. |
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