IRRIGATION SCHEDULING FOR SWEET PEPPER - Management, Performance, and Applications of Micro Irrigation Systems - page 178

According to the procedure described above, percolation occurred on those days
when the estimated moisture content exceeded the fi eld capacity moisture content
(0.39 for Year 1 and 0.35 during Year 2). On those days, the water in excess of the fi eld
capacity was assigned to PERC and the moisture content set equal to the fi eld capacity.
This can be seen in Fig. 3 for those days in which the moisture content curve touched
the dashed horizontal line associated with the fi eld capacity moisture content. Figure
4 shows the estimated percolation during the Year 1 and Year 2. During the April 6,
2002 rainfall event of 175 mm, 43 mm were converted to percolation. During the April
10th, 2003 rainfall event of 97 mm, 31 mm were converted to percolation. Recall that
only 25% of the rainfall was allowed to infi ltrate, which was equal to 44 mm on April
6, 2002 and 24 mm on April 10, 2003. In the latter case 18 mm of irrigation was also
applied, which together (24 mm + 18 mm) equaled 42 mm. In this case 31 mm was
lost to percolation and 11 mm was stored in the root zone. Table 2 shows the Year 1
and Year 2 seasonal components of the water balance.

FIGURE 4 Estimated percolation past the root zone during the Year 1 and Year 2 seasons.

TABLE 2 Components of the seasonal water balance for Years 1 and 2.

TABLE 3 Nitrate, ammonium and nitrate plus ammonium (Total) leached during Year 1 and 2
for the four experimental treatments.