into subplots with varying amounts of 0, 67, 134, 201, and 268
kg N/ha inorganic N fertilizer. Each of the 25 different subplots
(five different main plots multiplied by five different amounts of
N fertilizer) were replicated four times to insure reliable data.
All these subplots were randomly placed within the main plot. A
border row of untreated plants were on each side of the plot.

 The samples were collected by removing the top ear leaf from
five random plants in each subplot and placed in a paper bag that
was marked with the cover crop, date, and plot number. Table 1 is
an example of the randomized setup of a main plot. The plot number
was determined by three factors: replication number (1-4),
manipulation type (tillage/subsoil 1-5), and the amount of added
amount of N fertilizer (1-5).

Table 1. Example of the randomization of a field plot of corn
following either crimson clover or rye
 --------------NORTH DIRECTION----------------
 134* 132 135 131 133



 152 151 153 155 154



 141 145 142 143 144



 113 114 111 112 115



 125 121 124 122 123

* 1 no.=replication no.1; 2d no.=management scheme; and
 3rd no.=nitrogen rates.

 All corn ear leaf samples were put through a leaf area index
meter (L1-3100). The sum of the five ear leaf areas represented
the leaf area for that subplot treatment. The samples were then
placed back in their bags and dried in a forced air oven at 70 C
for 24 hours and weighed on an analytical balance (Mettler PN 2210)
for dry matter weights. Then, all five leaves from each subplot
were ground in a Wiley mill to pass through a 2.00 mm stainless
steel screen. These ground samples were stored in air tight,
sterile plastic bags until they were analyzed. The tops of the
bags were opened and placed in a forced air oven at 70 C for four
hours then removed and resealed to insure no water contamination.