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  • Author or Editor: J.C. Stark x
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Abstract

Field studies were conducted in 1985 and 1986 to compare the effects of banded ammonium polyphosphate (APP) and acid urea phosphate (AUP) on P nutrition and yield of potatoes (Solanum tuberosum L. cv. Russet Burbank). The studies were conducted on a Declo silt loam containing 9% CaCO3 equivalent. Soil NaHCO3-P values were 6.9 and 12.1 mg·kg-1 in 1985 and 1986, respectively. Ammonium polyphosphate and AUP were applied at planting in bands above the seedpiece at 0, 60, and 120 kg P/ha in 1985 and 0, 40, and 80 kg P/ha in 1986. Nitrogen fertilizer was applied at a uniform rate of 240 kg N/ha. In both years, petiole P concentrations for the APP treatments were higher than those for the AUP treatments during most of the tuber growth period and tuber yields were 9% to 15% higher with APP than with AUP.

Open Access
Authors: and

Abstract

Significant interactions between irrigation and N management for total yield and for incidence of brown center or hollow heart in potatoes (Solanum tuberosum L. cv Russet Burbank) were found in field studies conducted in southeastern Idaho during 1987 and 1988. When soil water content was maintained at 80% to 90% available, 30 kg N/ha applied weekly for 3 weeks, beginning shortly after tuber initiation, resulted in a higher incidence of brown center or hollow heart than when the same total amount of N was applied pre-plant or in smaller increments over a longer period of time.

Open Access

Abstract

Regression models of potato (Solanum tuberosum L. cv. Russet Burbank) leaf water potential (ψleaf) were developed for irrigated conditions using concurrent measurements of total solar irradiance (Rs), air vapor pressure deficit (VPD), air temperature (Ta) and windspeed. Estimates of potential evaporation (Ep) also were related to ψleaf. The data were collected over a 3-year period from two locations in southern Idaho. Of the variables tested, Rs had the highest simple correlation with ψleaf (r = 0.93), although a slightly higher correlation was obtained for log-transformed values of VPD (1n VPD). Potato ψleaf was best described by the equation ψleaf = -0.3672 - 0.1959 In VPD – 0.0005 Rs, where ψleaf, VPD, and Rs are expressed in units of MPa, kPa and W·m–2, respectively. The model accounted for 95% of the variation in ψleaf for well-watered ‘Russet Burbank’ potatoes. When the model was tested on an independent data set, it estimated diurnal changes in ψleaf for several different cultivars to within ±0.1 MPa of the measured values. The relationship between ψleaf and Ep was nonlinear and was described by an exponential function. Estimates for the Ep model were nearly identical to those for the VPD Rs model when ψleaf values were below -0.3 MPa.

Open Access

Abstract

Celery (Apium graveolens cv. Tall Utah 52-70R) was grown with only preplant N (100 kg/ha) or preplant plus 100, 200, or 300 kg/ha of additional N split into equal sidedress applications. Marketable yield and total N uptake significantly increased by the addition of sidedressed N, but there were no significant differences among sidedress treatments. However, increasing increments of N consistently increased early season crop and leaf growth rates and hastened maturity. With only preplant N, growth response was delayed but growth rates continued to increase after those of the side-dressed plants had begun to decrease.

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.

Free access

Abstract

Reference values were derived from field data for use in evaluating the N, P, K, Ca, and Mg status of ‘Valencia’ orange (Citrus sinensis [L.] Osbeck) trees by the Diagnosis and Recommendation Integrated System (DRIS). DRIS diagnoses generally agreed with diagnoses made by the sufficiency range method, with the advantage that DRIS reflects nutrient balance, and identifies the order in which nutrients are likely to become limiting. DRIS diagnoses were affected by the type and age of the tissue sampled. DRIS reflected changes in nutrient concentrations due to alternate bearing or crop load effects and agreed with the sufficiency range method when concentration changes were sufficient to affect the latter method.

Open Access