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146<br />
creases rapidly and rainfall frequency decreases, that measurable differences in<br />
E, and E. occur. This is an important point when comparing winter and spring<br />
grown chickpeas since all root and shoot growth during winter is thus effectively<br />
"free" in terms of moisture use.<br />
In March, April and May there was little difference in evapotranspiration<br />
between winter-sown crops at a given site, although the densely planted ILC 72<br />
treatment tended to use more water than the standard density treatments. During<br />
this period E, of winter-sown crops was significantly greater than the springsown<br />
crops at all sites.<br />
As winter-sown crops approached maturity at the two drier sites (Tel Hadya<br />
and Brida) total E, values between germination and maturity were found to be<br />
very similar in spite of the earlier maturity date of ILC 482. Nevertheless,<br />
densely planted ILC 72 continued to have a slightly higher total moisture use<br />
than either of the standard density treatments. In addition, at these two sites the<br />
final total moisture use of the spring-sown crop was similar (though sightly lower)<br />
to the winter-sown crops. In contrast, at the wettest site (Jindiress) where considerably<br />
more moisture was stored in the soil profile (Fig. IA, B), the winter-sown<br />
longer maturity ILC 72 used significantly more moisture than both the winterand<br />
spring-sown ILC 482. This point is discussed in more detail in the next<br />
section in which depth and efficiency of moisture extraction by chickpeas are<br />
considered.<br />
Utilizing the final harvest data (Table 7) the water-use efficiency (WUE) of<br />
both total drymatter and seed production was calculated in terms of kg/ha/mm<br />
of moisture used. Considering WUE of total drymatter production, it can be seen<br />
from Table 3 that the densely planted ILC 72 and winter-sown ILC 482 treatments<br />
achieved very similar WUE values at any given site, but were higher than<br />
the standard density ILC 72 treatment. All winter-sown crops achieved much<br />
greater WUE values than those obtained for the spring-sown crops, particularly<br />
at the two wettest sites, Jindiress and Tel Hadya.<br />
In terms of seed yield also, the winter planting of ILC 482 achieved a far<br />
higher water-use efficiency than the spring sowing resulting in a 119, 150 and a<br />
32% increase in WUE at Jindiress, Tel Hadya and Brida, respectively. Due to the<br />
very different harvest index of the erect and spreading cultivars, the spreading<br />
cultivar gave a consistently better WUE than the erect types at all sites.<br />
Comparing the WUE for an individual treatment across sites for both total<br />
drymatter production and seed yield, it is interesting to note the general decrease<br />
in WUE as one moves from wettest to driest site. This is partly due to differential<br />
stress during the period of potential flower and seed abortion resulting in a<br />
tendency for lower harvest indices at the drier sites, but it is likely to be attributed<br />
more to the differential ground cover achieved at each site. The moisture loss<br />
due to E, (soil surface evaporation) can be calculated on a daily basis from the<br />
empirical formula: