Influência da poda de folhas de alface e chicória, na época do transplante, sobre a precocidade de colheita e produção

Resumo

Two experiments on lettuce and endive pruning at the transplanting time were carried out, in order to check the practice used by vegetable growers of this region. The pruning is done by the growers for the purpose of avoiding shocks to the plant and to have a better success in transplanting.

Four pruning treatments were used for each species, in a latin square design.

Lettuce transplants having 6 or 7 visible leaves were used.

Plants without pruning were used as controls.  In the second treatment, the oldest leaves were cut off at the base, leaving the four youngest ones. The third treatment was similar to the second, except that transplants were kept with the two youngest leaves. The fourth treatment had all leaves cut four centimeters above the transition zone between the roots and stem.

Endive transplants were also selected and only the ones with 5 or 6 visible leaves, were used except the cotyledons if still present. Plants without pruning were used as controls. In the second and third treatments, the transplants were prunned to 3 and 2 youngest leaves, and in the fourth treatment all the leaf blades were cut off 5 centimeters above the transition zone between the roots and the stem.

All plants had the transplants weighted just before and alter the pruning treatments, in order to determine the loss on their fresh weight (summary of these data is given in table I).

Lettuce plants were harvested when they had a good, solid head. This stage was determined by touching and pressing the heads. Endive was cut all at the same time because of a lack of a good way to determine differences in cutting time.

As soon as all plants had recovered from the transplanting shock they were counted in order to determine the success obtained by each treatment (see table II). The analysis of variance showed that there were no differences between treatments for both lettuce and endive. The growers opinion discussed before was not supported by these experiments.

Lettuce pruning showed a definite effect on earliness and uniformity at harvest time. Graph 1 and table III give a summary of data obtained. Control plots had better developed plants followed by the ones of the treatment 4 F. Their harvest finished within a period of 7 days while treatments 2 F and C needed 14 days. The heavier the pruning, the longer was the harvest period.

The average weight of the heads were about the same and the analysis of variance demonstrated no significant differences between treatments. The hand pressing of the heads proved to be good way to determine the cutting time (Table IV).

The total yield of the unpruned plants and those pruned to four leaves (4 F) were signilicantly higher than other pruning systems, up to the fifth harvest. The higher diiferences were obtained in the first and second harvest and decreased slowly up to the fifth harvest. In the sixth harvest, there was no significant difference between treatments. This result is understandable since the average plant weight was about the same and total yield turned out as a function of the number of plants harvested (Table IV).

The endive experiments showed about the same results but in a different way. The pruning systems did not show any effect on the number of plants that survived the transplant (Table I).

Endive seems to recover much better from heavier pruning than lettuce. The differences in growth were slightly different at harvest time and the F found in the analysis of variance was significant for treatment either for totai yield or average weight of the plants. Although the F was very close to the P = 0,05 value and Tukey method showed that there was no difference between average of treatments. Table V gives a summary of the data obtained.