Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: O. A. Lorenz x
Clear All Modify Search

Abstract

No records exist of the first instance of crop fertilization by Neolithic man. For that matter, most of the repeated events leading to horticultural practice in the first 250 years following colonization of the U.S. remain unrecorded. Of course one such incident, the lessons of Squanto in corn fertilization, is familiar to all.

Open Access
Authors: and

Abstract

Determinant cultivars ‘VF 145B-7879’ and ‘VF 109’ of processing tomato (Lycopersicon esculentum Mill.) develop smaller root systems under field conditions with less root proliferation particularly below 60 cm than semideterminant fresh market cultivars, ‘Early Pak’ and ‘Pearson’. Following fruit set, K concentration in shoots of ‘VF 145’ and ‘VF 109’ decreased from about 4% to below 2% resulting in K deficiency symptoms, whereas no deficiency symptoms were observed in ‘Early Pak’ and ‘Pearson’. The data suggest that the K deficiency condition is due to the inability of the relatively small root systems of the determinant tomato cultivars to absorb K at a rate sufficient to meet the demands of the concentrated fruit set. ‘VF 145’ and ‘VF 109’ compensate for the stress condition by translocating K out of leaves and stems and into fruit as evidenced by a negative rate of accumulation of K in the shoots. They also partition a higher percentage of absorbed K into fruit rather than into continued vegetative growth than ‘Early Pak’ and ‘Pearson’.

Open Access

Abstract

The new mechanical-harvest varieties of tomatoes ‘VF-145’ and ‘VF-13L’ exhibited symptoms of K deficiency under both greenhouse and field conditions, while the older hand-harvested varieties remained free of symptoms. In the field the K-deficient varieties showed deficiency symptoms regardless of the amount of K applied to the soil. In late season the K concentrations in the petioles of the K-deficient varieties were much lower than in the other varieties. There were no differences between varieties in the rate or amount of K absorption from nutrient solutions. Root grafts indicated that there were no differences in the ability of the different rootstocks to absorb K.

Open Access

Abstract

Solution and sand culture experiments were conducted with ‘Early Pak’, ‘VF 145’, and ‘UC 82’ tomatoes (Lycopersicon esculentum Mill.) to study the propensity for K stress shown by ‘VF 145’ plants. The measured parameters that may contribute to the expression of K stress in ‘VF 145’ are low root weight and K content, high shoot:root ratios, high fruit K content, and a low K efficiency ratio.

Open Access

Abstract

Growth of radish (Raphanus sativus L.) was inhibited by NH4 as the source of N at concentrations from 1 to 240 ppm N. Higher levels of free NH4 accumulated in the plants as a result of NH4 nutrition. Nitrate equivalent to 10% or more of the NH4 concentration alleviated the inhibitor effects of NH4 on growth and also decreased the NH4 content of the plants. Five cultivars of radish responded similarly. Ammonium was also harmful for growth of etiolated seedlings, but NO3 did not reverse the inhibitory effects of NH4.

Open Access

Abstract

The effects of NH4 + on several physiological and biochemical parameters of radish (Raphanus sativus L.) were determined. Photosynthetic CO2 fixation rates of radish plants cultured with NH4 + as the source of N were about 50% of those with NO3 but dark respiration rates were the same. Plants grown with NO3 fixed at least twice as much, 14CO2 in vitro into acid stable products using ribulose-1, 5-bisphosphate, ribose 5-phosphate, 3-phosphoglyceric acid and phosphoenolpyruvic acid as substrates. This suggests that CO2 fixation both in light and darkness was decreased by NH4 + nutrition. Chlorophyll and total soluble protein concentration of plants, cultured with NH4 + as the source of N, were about 33% and 70%, respectively, of those cultured with NO3 . In vitro activities of glutamate dehydrogenase and isocitrate dehydrogenase were higher and lower, respectively, in plants cultured with NH4 + over those with NO3. Results indicate that NH4 + toxicity in radish plants is closely related to inhibition of photosynthesis. Evidence is presented suggesting that NO3 facilitated NH4 + assimilation in radish plants.

Open Access

Abstract

In field studies with potatoes, cantaloupes, and tomatoes, using N sources banded in the soil, highest yields were obtained with (NH4)2SO4. Yields with urea-formaldehyde and sulfur-coated urea were similar to each other, and less than those from urea. Nitrogen absorption, as determined by NO3 - concn in the petiolar tissue or total N absorption by the entire plant, was in the same sequence as yields. Controlled-release fertilizers did not increase N absorption during late growth. About 90% of the N from (NH4)2SO4 and urea had nitrified and leached from the fertilizer band within 40 days after application. In contrast, about half of the N from urea-formaldehyde remained in the fertilizer band 120 days after application.

Open Access