SOIL MOISTURE CONTENT, SOIL SALINITY AND WATER USE EFFICIENCY UNDER SURFACE DRIP AND FLOOD IRRIGATION IN CONTINUOUS CROPPING PLASTIC GREENHOUSE OF EASTERN CHINA

Soil salinization with excessive soil nitrate, has become the main limiting factor and major challenge for plastic greenhouse cultivation. This paper studied the effects of drip irrigation on saline soil remediation and crop growth. Six lower limit of irrigation treatments were tested: (1) T1: 50% of field capacity (FC, seedling stage, S1) ~ 60% of FC (flowering and fruit setting stage, S2) ~ 55% of FC (fruiting stage, S3), surface drip irrigation with subsurface drainage; (2) T2: 50% of FC (S1) ~ 70% of FC (S2) ~ 65% of FC (S3), surface drip irrigation with subsurface drainage; (3) T3: 50% of FC (S1) ~ 80% of FC (S2) ~ 75% of FC (S3), surface drip irrigation with subsurface drainage; (4) T4: 50% of FC (S1) ~ 70% of FC (S2) ~ 65% of FC (S3), flood irrigation with subsurface drainage; (5) CK1: 50% of FC (S1) ~ 70% of FC (S2) ~ 65% of FC (S3), surface drip irrigation without subsurface drainage; (6) CK2: 50% of FC (S1) ~ 70% of FC (S2) ~ 65% of FC (S3), flood irrigation without subsurface drainage. Under the same irrigation lower limit, the soil moisture content with drip irrigation was higher than the flood irrigation. In the drip irrigation with buried subsurface pipe, irrigation water and soil moisture content increased with the increase of the lower limit of irrigation. Irrigation in the lower limit of drip irrigation treatment reduced irrigation water and increase water use efficiency. The soil salt content decreased with the increase of the lower limit of irrigation. The soil salinity of the root area can be effectively regulated by drip irrigation. Use subsurface drainage, in 0-20 cm soil layer, with the increase of drip irrigation lower limit, soil salinity showed the tendency of decrease, and soil salt of drip irrigation treatment was significantly lower than the flood irrigation in the same irrigation lower limit; in 20-40 cm soil layer, the soil salinity content of T4 was significantly higher than T1, T2 and T3. The soil nitrate nitrogen content in the subsurface pipe region was reduced with the increasing irrigation lower limit. In 0-20 cm soil layer, the soil nitrate nitrogen content of drip irrigation treatments was significantly lower than the non-subsurface pipe region with the same lower limit of irrigation; but in 20-40 cm soil layer, there was no significant difference in the soil nitrate between T2 (subsurface pipe region) and T4 (non-subsurface region). After transplanting 16 days, the daily water consumption of tomato are increased with