Drought Damages Pecan

The effects of soil moisture deficits on pecan nut size and shape (Sparks, 1989; 1995) and fruit abortion (Gammon et al., 1955; Sparks, 1989) are documented. Nut size and shape are determined by soil moisture and degree of scab control. Drought effects on pecan nut size and shape were thought to be limited to the periods of rapid fruit elongation (June) and expansion (July to mid August). The prevailing belief in the Southeastern United State is that moisture stored in the soil profile from winter rains is sufficient to maintain the tree at least through early Spring. Fruit growth suppression (Fig. 1) from the widespread drought in Georgia (Table 1), clearly shows that drought affects the fruit very early, at least 3 weeks after ollination and before the period of rapid fruit elongation.

Table 1. Rainfall and departure from the normal in central Georgia.

Figure 1. Normally, except where drip irrigation is used to control nut size (Sparks, 1995), drip irrigation is operated 12 hours per day. The dramatic suppression of drought on fruit growth (Fig. 1) was compared with fruit from trees receiving no irrigation and 5 hours of drip irrigation per day. Had the irrigation system been operating 12 hours instead of only 5 hours per day, the effect would have been even more pronounced.

Figure 1 indicates that during drought in the Southeastern United States, managing irrigation for fruit growth should begin by pollination at least. However, suppression of shoot diameter from drought (Fig. 1) suggests that under drought conditions, irrigation for shoot growth should begin before or at budbreak depending on the severity of the drought.

Drought Damages Pecan During the Early Stage of Fruit Development

Drought Damages Pecan During the Early Stage
of Fruit Development