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  • Author or Editor: Jeffrey C. Stark x
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Abstract

Seed yield and quality of four spring pea cultivars (Pisum sativum L.) were evaluated when subjected to deficient, optimal, and excessive irrigation levels. Irrigation at 100% of the estimated optimal irrigation amount (IR) resulted in the greatest seed yields, whereas irrigation at 60% or 140% IR reduced yields by 468 and 222 kg·ha−1, respectively. Yield reductions for individual cultivars were as large as 694 and 350 kg·ha−1 for deficient and excessive irrigation, respectively. Increased yields for the 100% IR treatment resulted from increases in pods per plant and seeds per pod. Irrigation at 140% IR reduced germination of pea seed by 5% to 13%. Deficient irrigation reduced seed yield more than did excessive irrigation, whereas excessive irrigation caused the greatest reduction of seed quality.

Open Access

Field studies were conducted in 1986 and 1987 to evaluate the potential of using canopy temperature measurements to evaluate the relative drought tolerance of potato genotypes. In both years, 14 potato genotypes representing a relatively wide range of Solarium tuberosum L. germplasm were grown under well-watered [irrigation ≈100% potential evapotranspiration (ET) and stressed (irrigation ≈40% to 50% potential ET) coditions. Irrigation differences were imposed with a line source irrigation system. Canopy temperatures of the 14 genotypes were measured between 0900 and 1430 hr on 7 clear days during tuber bulking. A general linear relationship between canopy minus air temperature (ΔT) and air vapor pressure deficit (VPD) was determined for each year by regressing all ΔT data onto corresponding VPD values. The relative sensitivity of each genotype to changes in VPD was determined by regressing observed ΔT values onto the estimated ΔT from the general equation for that year. Genotypes with higher than average temperatures under well-watered conditions were generally less sensitive to changes in VPD than those with lower than average temperatures. Warmer genotypes under well-watered conditions were also generally less susceptible to drought than cooler genotypes. Thus, ΔT measurements from well-watered plots can be effectively used to assess the relative drought tolerance of potato genotypes.

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Abstract

Field studies were conducted in 1985 and 1986 to evaluate the effects of final irrigation timing on spring pea (Pisum sativum L. cv. Mars) seed yield, percent germination, and distribution of yield within the canopy. Final irrigations were applied on 10 dates during the period from 10% bloom to early senescence. Total seed yield did not increase with irrigations applied past 237 degree-days (base 4.5°C) after bloom (DDAB) in 1985 or 366 DDAB in 1986. However, the highest germination percentages and viable seed yields in 1985 and 1986 were obtained when final irrigations were applied at 487 and 450 DDAB, respectively. In 1986, total seed yield, percent germination, and viable seed yield throughout the canopy increased when the final irrigation was applied at 366 or 588 DDAB compared to earlier final irrigations. Viable seed yield reductions for the early irrigation cut-off dates resulted primarily from reduced numbers of pods per plant, and seeds per pod in the upper canopy (nodes 14 to 17) and decreased germination of seed produced throughout the canopy. We conclude that application of the final irrigation at ≈450 to 500 DDAB (usually 2 weeks after final pod set) should produce viable seed yields similar to those obtained with continued irrigation through early senescence.

Open Access

Cane growth, leaf blade area, blade and petiole fresh and dry weights and mineral nutrients of six grape (Vitis vinifera) cultivars were evaluated in 2000 and 2001 under climatic conditions of southwestern Idaho. The cultivars were: `Barbera 02', `Cabernet Sauvignon 02', `Cabernet Sauvignon 04', `Chardonnay 29', `Merlot 01', and `Sangiovese 04'. No differences were found in cane growth of different cultivars. `Sangiovese 04' and `Merlot 01' had larger leaf area and heavier leaves (both blades and petioles) and higher concentrations of blade nitrogen (N), while `Merlot 01' and `Chardonnay 29' had higher petiole nitrate-N than all other cultivars. `Merlot 01' had relatively the highest potassium (K) concentrations in both blade and petiole tissues. `Chardonnay 29' had lower concentration of calcium (Ca) and `Sangiovese 04' had lower concentrations of magnesium (Mg) in both blade and petiole tissues than other cultivars although differences were not always significant. `Barbera 02' had higher blade iron (Fe) and tended to have higher blade copper (Cu) than other cultivars. However, `Chardonnay 29' had higher petiole Fe than `Barbera 02', `Cabernet Sauvignon 04', and `Sangiovese 04'. `Merlot 01' had higher blade manganese (Mn) than `Sangiovese 04'.

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