Effects of high and normal frequency deficit irrigation on crop development and yield of kidney bean (Phaseolus vulgaris L.). PDF Download

Author: M. Resende
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Languages : pt-BR
Pages : 94

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Book Description
The effect of normal and high frequency irrigation on plant water status, leaf growth, dry matter accumulation and yield of Dark Red Kidney been in the field was studied by using line-source sprinkler irrigation on a deep Yolo soil in Davis, California in 1977 and 1978. The treatments involved two frequencies or regimes with high frequency (HF) irrigated every other day normal frequency (NF) irrigated every seven days (1977) and twelve days (1978); within each frequency the amount of water applied was varied as percentage of the maximum evapotranspiration (ET) as follows in 1977: NF - 100, 88, 84, 70 and 62% of the maximum ET HF - 100, 81, 74, 64 and 53% of the maximum ET. And in 1978, the percentages were: NF - 100, 81, 74, 62 and 52% of the maximum ET HF - 100, 80, 74, 64 and 53% of the maximum ET. More water was applied to HF plots, up to full ground cover on a 100% level treatment, to compensate for higher soil evaporation on these plots as compared to NF ones, based on lysimeter and class A pan evaporation data. No difference was found in midday leaf water potential (W) between NF and HF treatments at the 100% ET level. But leaf W was about 2 bars lower in more stressed plots, with the lowest W values around -12 bars. The W value in all treatments recovered to about the same poit (-4 bars) around 4 am. Leaf resistance and photosynthetic rate were not affected by irrigation regime nor by the degree of stress. On the other hand, source size as indicated by percentage of ground cover, LAI and leaf dry weight were reduced about the same proportion as the reduction in ET, independent of the frequency. Leaf enlargement was considered to be the main factor responsible for this difference in source size, and the pattern of leaf elongation rate was studied. Diurnally there were two elongation rate peaks, one in late afternoon and another before dawn. This change in leaf elongation rate at night (also common to four other varieties) did not correlate with leaf water, solute or pressure potential or leaf resistance but correlated reasonably well with changes in leaf angle at night. Total dry matter accumulation decreased in about the same proportion as the reduction in ET and presented a linear relationship when plotted against the integrated value of ground cover, independent of the irrigation frequency, indicating the importance of source size as affected by the degree of stress in determining the total dry matter. The Harvest Index was not affected by any treatment (1978), indicating no influence on dry-weight partitioning. Pods/ plant decreased with increase in the degree of stress in both irrigation regimes and seed/pod tended to increase. The effect of source size on total dry matter was considered the main factor in explaining the linear decrease in seed yield with decrease in seasonal ET in both irrigation regimes. At the same seasonal ET level, the seed yield was significantly lower at 1% level in HF treatments, than in NF, due to high soil evaporation. The lines of relative yield as a function of relative ET for HF treatments were significantly different at 1% level between 1977 and 1978. No difference was found between the lines for NF treatments. The general conclusion is that the important factor in determining yield response to water stress was seasonal transpiration and irrigation frequency had no major effect other than increasing evaporation in the high frequency treatments.