THE EFFECTS OF RECLAMATION PROGRAMME ON SOIL IMPROVEMENT AND CROP YIELD
The soil was characterized by heavy texture with an average of 23.5 mmhos/cm and high exchangeable sodium percentage, salinity and alkalinity exist in all soil profiles.
Sufficiency of water in Shavour project necessitated an improvement programme to decrease the salinity and alkalinity through leaching practices and rice cultivation with clover cropping preceding it.
The programme was as follows:
- Leaching was accomplished in fields of 1000 m2 with 500 mm of water.
It was concluded that at this stage salinity and alkalinity were only reduced on the top soil layers and leached salts were accumulated in the sub layers which was an indication of insufficient leaching water.
Samples were taken from irrigation and drainage water during the course of experiment and it was observed that the salt concentration in drained water was 10 g/l, 10 times more than that of irrigation water.
- Leaching and rice cultivation. Rice cultivation in continuation to leaching process with 2500 mm irrigation water was done.
The EC, E.S.P., P, cations and anions in soil saturated extract, CaSO4 and CaCO3 were reduced to a considerable extent.
The analysis of drained water indicated that the concentration of the soluble salts was 9 g/l which was 13.5 times more than that of irrigation water.
This also indicates that rice cultivation supplemented the leaching processes. Inspite of decreased salinity and alkalinity a yield of 724 kg/ha was produced. This helps to recover the initial investment.
- Clover cropping: to improve the physical soil conditions clover was cultivated followed by rice. Inspite of improved soil physical conditions the programme could bring about reduced salinity to some extent and alkalinity to a greater extent. It was observed that CaCO3 and CaSO4 extent of the soil increased compared to rice only, but it was not hasardous. A yield of 17 ton/ha counted for some recovery of the incurred expenses. The comparison studies and statistical analysis during 3 courses of the programme indicated that variations were significant at any stage or after completion of a programme and it is concluded that 100 m spacing and 500 m length of tile drains were quite adequate.