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Petiole NO3-N concentrations (PNCs) of seven potato (Solanum tuberosum L.) genotypes grown under four N treatments were studied. In 1986-88, the cultigens were planted in plots with a gradient of available N created by adding 0,140,280, or 420 kg N/ha ammonium nitrate split between preplant and periodic seasonal applications. PNCs were significantly (P ≤ 0.05) affected by year, sampling time (four times per season), N rate, and cultigen. All first- and second-order interactions were also significant (P <0.05). The relative PNC ranking among cultigens remained nearly constant across years when averaged across sampling dates and N rates. Regression-equation distinctiveness for each cultigen relating PNC to sampling time demonstrated a genotypic influence on seasonal PNC and allowed separation into four response classes. Using a data subset consisting of the 1988 trial, an optimal N rate was determined and regression equations were computed relating PNC to sampling date for each cultigen at the applied N rate nearest to the optimum. Tests for distinction separated the equations of the seven cultigens into six unique classes; `Frontier Russet' and `Ranger Russet' equations were coincident.

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The effects of six applied N treatments differing by rates and frequencies of application on the yield and quality of pepper (Capsicum annuum var. annuum L. `Anaheim Chili') grown for seed was studied. The timing of N applications was based on crop phenology, leaf petiole nitrate-nitrogen concentrations (NO3-N) minimum thresholds, and scheduled calendar applications of fixed amounts of N. Solubilized NH4NO3 was applied through a trickle-irrigation system to ensure uniform and timely applications of N. Rate of mature (green and red) fruit production was unaffected by any treatment except weekly applications of 28 kg·ha-1 of N, which stopped production of mature fruit before all other treatments. Early season floral bud and flower production increased with increasing amounts of N. The two highest total N treatments produced more floral buds and flowers late in the season than the other treatments. Total fruit production was maximized at 240 kg N/ha. Differences in total fruit production due to frequency of N application resulted at the highest total N level. Red fruit production tended to be maximized with total seasonal applied N levels of 240 kg·ha-1 and below, although weekly applications of N reduced production. Total seed yield was a function of red fruit production. Pure-1ive seed (PLS) production was a function of total seed production. Nitrogen use efficiency (NUE) for red fruit production also decreased with N rates >240 kg·ha-1, but PLS yield and NUE decreased in a near-linear fashion as the amount of total seasonal applied N increased, regardless of application frequency. Season average NO3-N (AVE NO3-N) values >4500 mg·kg-1 had total seed and PLS yields less than those treatments <4000 mg·kg-1. Six-day germination percentage was reduced with weekly N applications of 14 kg·ha-1. Seed mass was reduced with weekly N applications of 28 kg·ha-1. Final germination percent, seedling root length and weight, and field emergence were unaffected by any of the N treatments. These findings indicate that different N management strategies are needed to maximize seed yield compared to fruit yield and, therefore, there may be an advantage to growing `Anaheim Chili' pepper specifically for seed.

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. Concentration of leaf blade nitrogen (N), phosphorus (P), and potassium (K) and petiole nitrate-nitrogen (NO 3 -N), phosphate-phosphorus (PO 4 -P), and K in 53 California strawberry fields across the production season. Sampling stage 1 = early flowering, 2

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Soil 246 201 209 Kubota, A. Thompson, T.L. Doerge, T.A. Godin, R.E. 1997 A petiole sap nitrate test for broccoli J. Plant Nutr. 20 669 682 Lewis, R.J. Love, S.L. 1994 Potato genotypes differ in petiole nitrate-nitrogen concentrations over time

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