Fertilizer placement under irrigation in Washington

The movement of nitrogen, phosphorus, and potassium in a mixed fertilizer applied to Sagemoor fine sandy loam under irrigation was investigated in order to determine the importance of localized fertilizer placement when irrigation water might move the fertilizer in the soil. It was found that highly soluble nitrogen and potassium fertilizers did not penetrate downwards with the water to any appreciable extent, but they did tend to move laterally with the water. The strongest-concentrations were found from 4 to 8 inches from the fertilizer band after the water had penetrated over 4 feet into the soil with 12- and 24-hour irrigations. The movement of phosphorus was negligible as determined by fifth normal nitric acid extracts. Since there was only a limited fertilizer movement in the soil with irrigation, the importance of localized fertilizer placement studies was evident. Fertilizer placement studies were accordingly made in field trials with corn and beans, using nitrogen and phosphorus fertilizers in the form of sulfate of ammonia and treble superphosphate, respectively. It was evident from the data obtained that fertilizers placed with the seed, 1 inch above the seed, or 2 inches directly below the seed were unsatisfactory methods of placement. With applications of 84 pounds of nitrogen per acre as ammonium sulfate, the best placement methods for corn were, in the order named, two bands 2 inches to the side and 2 inches below the seed, a single band 2 inches to the side and 2 inches below the seed, and a single band 4 inches to the side and 2 inches below the seed. With applications of 42 pounds of nitrogen per acre as ammonium sulfate, the single band 4 inches to the side and 2 inches below the wed gave the best results, although application in two bands 4 inches to the side and 2 inches below the seed and a single band 2 inches to the side and 2 inches below the seed were satisfactory. No increase in corn yield was evident from the addition of either 52.5 pounds or 105 pounds of P(2)O(5) as treble superphosphate per acre with the various localized placement methods. When large amounts of nitrogen fertilizer alone or in combination with a phosphorus fertilizer were applied to beans, increases in yields were negative or doubtful in most cases. With smaller amounts of fertilizer applied to beans such as 31.5 pounds of nitrogen per acre as ammonium sulfate or in combination with 42 pounds of P(2)O(5) per acre as treble superphosphate, it was found that certain placements were less injurious to the stand than others. The best results were obtained with placements in two bands 4 inches to the side and 2 inches below the seed. No definite yield increases of beans were obtained on this soil from the use of the nitrogen fertilizer alone or in combination with the phosphorus fertilizer. Had this crop been more responsive to fertilizer, the effects of the different placements would probably have been modified.