Post-harvest Mineral Nitrogen Status in Grower Fields (1994)


This grower trial was undertaken to determine whether residual nitrate and ammonium levels in grower fields were similar to those found in our experiments at NWREC. The data should be useful in indicating which of the major processed vegetable crops leave significant quantities of residual mineral N in the soil at harvest and the extent to which grower cultural practices, particularly fertilizer application, influence the amount of residual N that is available for leaching by heavy winter rainfall.


Effect of Nutri-Phite P Foliar Fertilizer on Onions and Broccoli (1996)


Phosphorus pollution of the Willamette River and its tributaries is a problem affecting agriculture in western Oregon. Many of our soils are high in available (soluble) P, as measured by the tests commonly used to determine plant-availability of P. Consequently, many streams have background levels of P that are conducive to algal blooms and poor water quality for fisheries and recreational use. Agriculture may also contribute to P pollution of streams through the use of large amounts of phosphate fertilizers and is under pressure to reduce P applications.

Effect of Nitrogen Rate and Row Spacing on Sweet Corn Yield and Residual Soil Nitrogen (1996)


Vegetable growers in the Willamette Valley use high rates of nitrogen fertilizers, often exceeding 250 to 300 pounds actual N/acre per season. While growers believe that these rates are necessary to achieve maximum yields and quality, a considerable portion of the applied fertilizer is not taken up by the crop. This has raised concerns that the remaining N may be contributing to nitrate pollution of groundwater. Improved efficiency of nitrogen management may be possible if the fertilizer could be placed for maximum contact with the root system.