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I - --ii
I - --ii
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126<br />
ranged from November 22, 1978 to March 15, 1979 and the intervals were more<br />
evenly distributed over this period. 1o ensure good germination in the first date,<br />
an irrigation was given immediately after planting. Except for this, the whole<br />
experiment was raised under rainfed condition. The total seasonal rainfall was<br />
only 246 mm. As an average of 20 genotypes, the November-planted crop yielded<br />
more than 3000 kg/ha, and there was almost a linear decrease in yield as the<br />
planting date was delayed by various intervals up to March 15 (Fig. 2). The<br />
increase in the mean yield was 69, 128, 193 and 277% when the planting was<br />
advanced from March 15 to February 15, January 11, December 17 and Novem<br />
ber 22, respectively. Thus advancing the date of planting even to late or mid<br />
winter proved substantially better than the early spring and late spring plantings.<br />
This observation is interesting from the point of view of the need for flexibility in<br />
the cropping system of the rainfed agriculture in dry areas.<br />
As in 1977-78, the studies in 1978-79 were also conducted under fungicidal<br />
control as the seeds of Ascochyta-resistantcultivars were not available at that<br />
stage for large-scale trials. However, during 1979-80 season, several promising<br />
genotypes with an acceptable degree of tolerance to ascochyta blight became<br />
available. Hence, their response to the spread in the planting date from early<br />
winter to spring, was evaluated under rainfed condition (total seasonal precipitation<br />
427 mm), along with several others making a total of 20 genotypes. Some of<br />
these genotypes were susceptible to ascochyta blight and were thus affected by<br />
the disease in the winter planting, in spite of the fungicidal spray, because of a<br />
heavy buildup of inoculum and favorable weather conditions for the spread of the<br />
disease. The individual yield data of some selected genotypes including four<br />
tolerant and one susceptible (ILC 1929) lines, as also the mean yield of all the 20<br />
genotypes, are presented in Tab. 2.<br />
The yield of ILC 482 cuhivar increased by 69, 145 and 249%, respectively,<br />
under February 13, December 19 and November 20 planting dates over the yield<br />
under March II planting. Averaged over all the genotypes,the planting in winter<br />
(November 20) resulted in a 118% higher yield than from the spring ph,nting<br />
(March 11). These results reemphasize the point that substantial gains in yield<br />
can be obtained by advancing the date of planting and that this advantage is<br />
particularly higher in the genotypes which have resistance to ascochyta blight in<br />
addition to good agronomic characters.<br />
A more detailed analysis of the performance of an ascochyta blight tolerant<br />
cultivar, ILC 482, in relation to the date of planting is provided in Tab. 3. The<br />
yield of straw, which is economically important in the farming systems of the<br />
region, is also increased substantially by winter planting over spring planting,<br />
following a trend parallel to that of grain yield with no major change in the<br />
harvest index. The water-use efficiency of the crop, as computed by relating the<br />
grain yield to the total seasonal precipitation (427 ram), increases in winter<br />
planting following obviously the trend similar to the grain yield.