POTENTIAL USE OF POLYACRYLAMIDES (PAM) IN AUSTRALIAN IRRIGATED AGRICULTURE S.Sivapalan

Hardsetting soils are common in Australia and adversely affect crop performance and management. The possibility of ameliorating degraded hardsetting soils using anionic PAM conditioner was investigated. 84% increase in germination of cotton seeds was achieved by treating the soil with PAM at the rate of 7 kg ha-1. The productivity of coarse textured soils is mostly limited by their low water holding capacity and excessive deep percolation losses that reduce the efficiency of water use by plants. The amount of water retained by a sandy soil against a 0.01 MPa pressure increased by 23 and 95 % by adding small amounts (0.03 and 0.07% by weight, respectively) of PAM to the soil. Consequently there were substantial increases in water use efficiency of soybean plants grown in soils treated with 0.03 (12×) and 0.07 % (19×) PAM. Another experiment with soybeans was conducted in soils treated with 0-0.5 % of PAM under 3-7 days irrigation interval. It revealed that 0.05 % PAM in soil with 4 days irrigation interval and 0.1 % PAM in soil with 5 days irrigation interval enabled the plants to achieve grain yields higher than that of control soil with 3 days irrigation interval. PAM was tested for its effectiveness in reducing the turbidity of water as an alternative to, and in conjunction with gypsum. Turbidity reduction was most effective with low molecular weight (5-8 million) anionic PAM under a split application strategy. However, PAM/gypsum combinations reduced the turbidity of water by more than 99 % relative to the control. It was also noted that PAM with small amounts of gypsum did not increase the cumulative infiltration of the treated soil