Uptake and cycling of nitrogen (N) in mature trees are not well understood.
Fertilizer-N uptake, partitioning, and use-efficiency were studied in standard strain
'Topred Delicious' and spur strain 'Redspur Delicious' mature apple trees {Malus
domestica Borck) on 'Malling 7A' (M.7A) rootstocks. The treatments consisted of a
ground application in spring,...
A better understanding of grass seed crop and soil fertility is necessary to
improve fertilizer practices and preserving water quality in Willamette Valley,
Oregon, where 55% of land-use is in grass seed production that directly impacts
adjacent waterways containing native protected fish species. I determined tillage
effects on soil N...
Potatoes require adequate nitrogen to produce quality tubers and high yields. Organic farming practices are designed to build soil nutrient levels
gradually. In organic systems, nitrogen (N) enters the soil in the form of crop residue and amendments (e.g., manures, composts, and specialty products).
Much of the N added to...
The CERES-Wheat Crop Growth and Development model treats temperature,
nitrogen and water stresses as limiting factors. For each day the model calculates a
stress index for temperature, N and water, compares the magnitude of the indices,
and then adjusts the calculated daily potential growth using the index of the most...
Nutrient management plans for crops require estimates of plant-available nitrogen (PAN) provided by application of manure or compost. Recent developments have stimulated interest in utilizing manure nitrogen (N) as a resource. These factors include the following:
• Increased cost of N fertilizers
• Increased value of PAN from manure on...
Estimates of nitrogen (N) available from long-term application of organic
amendments are required to balance N inputs with crop N requirements. Two studies
were conducted to (1) determine N mineralized from organic amendments (manures
and composts) during year 2 after application, and (2) compare plant-available N
(PAN) determined via in...
According to the United States Geological Survey, 9 percent of wells in the Willamette Valley exceed the EPA’s 10 ppm drinking water standard for nitrogen in the NO3– compound, or NO3–-N. A study of 281 domestic drinking water wells in Lane County showed that 22 percent of the wells exceeded...
In order to properly utilize organic amendments as nitrogen sources, reliable methods
to estimate plant-available nitrogen (PAN) are needed. The objectives of this study
were to (1) evaluate the use of crop and soil responses in fertilizer N equivalence
(FNE) calculations, (2) examine the relationships between the C/N ratio, total...
Cover crop selection and management depend on many factors, among them the cover crop’s ability to accumulate dry matter (i.e., residues) and nitrogen (N). Dry matter provides energy for soil organisms, contributes to soil organic matter, improves tilth, and acts as a sink for nutrients.
Although legumes have been widely studied for their nitrogen-fixing ability, it is uncertain to what extent legume cover crops achieve their nitrogen-fixing potential under the climatic conditions encountered in western Oregon. Furthermore, it is unknown what factors control the proportions of legume cover crop N that are either sequestered into...