|Abstract or Summary
- A study was made to evaluate the effect of different rates of N
fertilization on Nugaines wheat. The variable N treatments provided
different N regimes as a basis for evaluating potential diagnostic
tests for assessing the N status of the wheat plant. The crop was
grown in Lane county during the 1968 growing season on soil of the
To evaluate the treatment effects the yield of grain and dry
matter, number of culms per foot of drill-row, leaf percentage,
grain protein, test weight, and concentration and uptake of nutrients
(N, P, K, Ca and Mg) were measured. The preliminary evaluation
of the diagnostic tests for assessing the N status of the wheat plant
were conducted by comparing the relative sensitivity of the above
parameters to the different rates of applied N. First approximations
of the critical levels were estimated from graphs of grain yield against the various analytical measurements.
The application of N increased grain yield, dry matter production,
the concentration of nitrate-N, N, P and K in the plant tops.
The application of 200 pounds of N per acre decreased the test weight
and increased the protein content of the grain. This same rate of
N fertilization produced an increase in the number of culms per foot
of drill-row and the plant leaf percentage.
The concentration of nitrate-N, total N, P, K, Ca, and Mg
in the plant tops decreased with time irrespective of N treatment as
the plants matured. The concentration of nitrate-N in the upper
leaves was greater than the concentration of nitrate-N in the lower
leaves at the boot stage of growth. The total uptake of these
nutrients with time corresponded to increases in yield of dry matter.
A suitable approach for assessing the N status of the wheat
plant appeared to be that of measuring the level of total N in the plant
tops or the level of nitrate-N in the plant leaves during the latter
part of April. At this time the critical level for total N in the plant
tops was about 2.8% and the critical level for nitrate-N in the plant
leaves was about 300 parts per million. Greater precision was
attained in the measurement of total N concentration in plant tops
than for the concentration of nitrate-N in the leaves.
The critical-level approach for dry matter production, culms
per foot of drill-row, and leaf percentage appeared to have limited
value for assessing the N status of the wheat plant.