RECLAMATION AND AMELIORATION OF SALINE-SODIC SOIL USING GYPSUM AND HALOPHYTIC GRASSES: CASE OF GOLINA-ADDISALEM IRRIGATION SCHEME, RAYA KOBO VALLEY, ETHIOPIA

Abstract

In the Golina-Adisalem irrigation scheme, 500 ha irrigated land is becoming salt-affected. This relatively recent agricultural threat in the study area has never been comprehensively managed until now. Rehabilitation of salt-affected field into productive lands using drainage is expensive and the application of leaching by far is not feasible in shallow water table areas. The alternative way is chemical amendment and bioremediation. Therefore, the field experiment was conducted from January to May 2019 to evaluate the possibility of using gypsum soil amendment and halophytic grasses on modification of properties of saline-sodic soil, and the effects of gypsum on the performance of grasses. The gypsum levels (0%, 75%, 100%, 125% G) and halophytic grasses (0H, RG, PG) were set in factorial RCBD design with three replication. Composite soil samples before the experiment and from each treatment after 1 st and 2nd harvest with 0-20, 20-40, 40-60 cm depths were collected for laboratory analysis. Deep percolated water samples (at 1.5 m depth) were collected from the gypsum received and control plots. The gypsum rates mixed to the top 20 cm soil layer 20 days prior to planting. The laboratory analysis revealed that after the 1st and 2nd harvest the soil pHe, ECe, SAR and ESP in the three soil columns were highly significantly (P<0.01) affected by the main effects of gypsum, grasses and by their interaction. After the 1st harvest, the lowest pHe, ECe, SAR and ESP was recorded from the soils treated with a combination of RG+125% G and PG+125% G, whereas the highest values recorded from the soil of the control plot. After the 2 nd harvest, combination of RG+125% and PG+125% G in contrasting with the control treatment exhibits more pronouncedly decreased the pHe from 8.54, 8.66, 8.77 to 7.23, 7.29, 7.51, ECe from 20.1, 16.31, 11.4 to 4.62, 4.89, 4.31dS m -1 ,SAR from 50.12, 54.23, 57.29 to 10.78, 15.81, 16.38 and ESP from 57.37, 66.22, 72.26 % to 8.93, 8.66, 9.47 % for 0-20, 20-40, 40-60 cm respectively. The reclamation efficiency of RG+125% G was statistically equal (≈) with PG+125% G. The highest infiltration rates were noted from soils treated with RG+125% G (6.3 cm/hr) and PG+125% G (5.92 cm/hr); while the lowest value (1.22 cm/hr) was recorded from the control treatment. After the two experimental season, the concentration of Na+, Ca2+, mg2+, ECw and TDS in the deep percolated water does not appears much change by surface gypsum application. However, the biomass yield in the saline-sodic field had highly significantly (p<0.01) affected by gypsum application. The highest biomass yields (10.56 and 13.2 t/ha) with highest net benefits (187,153.47 and 255,319.44 ETB/ha) were obtained in saline-sodic soil that treated with RG+125% G for first and second harvest respectively followed by PG+125% G. Whereas, the lowest biomass yield (5.73 and 7.14 t/ha) was recorded from the normal field which treated by PG+0% G for first and second harvest respectively. From the result, it could be concluded that combined application of RG+125% G and PG+125% G was the most efficient treatment with respect to a faster decreased pHe, ECe, SAR, ESP and it enhances soil infiltration rate, reached high biomass yield with high net benefit as well as getting acceptable tissue quality for forage provision