Effect of water quality and quantity to salt balance And changes of physical and chemical properties of saline soil   Yuttachai Anulaxtipun, Somsri Arunin, Prasit Tanprapas and Seri Chaipan   ABSTRACT        Effect of water quality and quantity to salt balance and change of physical and chemical properties of saline soil was carried out in 1991-1992, supported by JICA. There are 3 locations : Ban Bokae, Ban Phra-Yun and Ban Nongbysri where each location is a sub-research. The objective is to study on changing of chemical soil properties emphasizes fluctuation of salt balance in the saline soil profile by water application. This study mimic mini-lysimeter and undisturbed core technique. RCB of 5 treatments with 3 replications were designed. Three water quality were applied in the saline soil profile for example, fresh water value of Ecw = 0.19 dS/m; blended water between fresh water (0.19 dS/m): saline water (4.1 dS/m) that there are 5 proportions of 78:22%, 64:36%, 50:50%, 36:64% and 22:78% by volume respectively. Two saline water were applied in 2 sites. Each site consists of 15 plots of Mini-lysimeter.      These results can be conclude that the optimum rate for apply the amount of fresh water to decrease positive and negative ions which may toxic to plant is the fourth rate (R4) of 452.7 litter/dry season at Ban Bokae. The virgin soil of Ban Bokae ECw was 1.7-2.9 dS/m. After apply fresh water, ECdw of 25 and 65 cm depth declined to 0.32 dS/m. Blending water of 22% fresh water : 78% saline water by volume gave a high repressing power to replace positive and negative toxic charges from the soil profile. Moreover, ECdw declined between 0.77-1.53 dS/m but saline water 4.1 dS/m is low quality to apply for agriculture. The second rate of saline water (171.55 litter/dry season) gave the lowest ECdw of 4.05 dS/m. In Ban Phra-Yun site, the virgin soil ECdw was between 2.95 to 4.56 dS/m. After apply fresh water, ECdw of 25 and 65 cm depth was declined to 0.37 dS/m. The best proportion of blending water is 22%  fresh water: 78% saline water by volume, a high repressing power to replace positive and negative toxic charges from the soil profile. Moreover, ECdw was declined to 1.483-2.417 dS/m and gave the lowest of average ECdw of 1.95 dS/m but saline water 4.1 dS/m is low quality to apply for agriculture. The third rate of saline water (343.10 litter/dry season) gave the lowest ECdw of 3.90-4.15 dS/m. In Ban Nongbysri, there was only one water quality Ecw of 1.6 dS/m to apply and it was found that the rate of 473.31 gave the lowest ECdw of 1.167 dS/m. It should be realized that utilization of saline water for cash crop may cause salt accumulation in the soil profile. However, halophytes or salt tolerant plants should be considered to be planted in salt affected soil and studying is necessary to balance the relationship of soil water and proper plant which give less effect on saline soil distribution.        Keywords : salt balance, mini-lysimeter and undisturbed core technique