Technical Abstract: Management options for reducing drainage water volumes on the west side of the San Joaquin Valley of California such as reuse of saline drainage water and water table control have the potential to adversely impact crop yields due to a build up in boron concentration. An earlier experiment had shown that extrapolation of soil tests to field conditions provided poor predictability of B content of melons. Consequently, three tests for extractable soil B were evaluated for their ability to predict conditions of potential B toxicity of melons under controlled conditions. Melons were grown for 95 days in containers of soil that had been pretreated with solutions containing B concentrations as great as 5.3 mmol/L. Extractable soil B was determined using ammonium acetate, DTPA-sorbitol and a 1:1 aqueous soil extract at the beginning and end of the experiment. The B treatments caused various deleterious effects on melon growth and development. Fresh and dry plant matter decreased significantly with increasing B concentrations; while B concentration of plant leaves, stems, and fruits increased significantly with increasing B. The number of days to first flowering was significantly delayed from 35 days at B treatments < 2 mmol/L to 51 days at B treatments > 3 mmol/L. Fruit set was completely inhibited at the highest B treatment of 5.3 mmol/L. Plant analysis revealed a highly significant relationship between soil extract B and leaf, stem, and fruit B content. Correlation coefficients for plant stems and fruits were much higher than for plant leaves. Correlation coefficients for all soil tests were almost equivalent, althouth the highest values were obtained for the DTPA-sorbitol extract indicating the greatest predictive capability. The soil tests are well able to predict B damage to melons in a container experiment.