node decreased and flowering was delayed when no P was applied. Potassium at any level, including 0 mg·L −1 , was shown to have no effects on plants ( Miwa and Ozaki, 1975 ). The requirements for mineral nutrients, particularly N, P, and K, temperature
, 1980 ). Potassium also increases flux rates without diluting phloem sap content of organic solutes ( Mengel, 1980 ; Mengel and Haeder, 1977 ), thus transport rates are faster when adequate K is available. Thus, it appears that K may affect both phloem
) along with the Control (100%) where the total P concentration delivered during fertigation was 0.50 m m in the Control. Potassium was supplied at three lower rates (50%, 20%, and 0% of Control rate) along with the Control (100%), where total K
Twelve species of flowering potted plants were grown in a peat-based medium with water soluble fertilizer concentrations of 50, 100, or 200 mg·liter-1 N and K2O. Leaf blade or leaf petiole samples were collected six to eight weeks after planting. Sap was expressed using a hydraulic press and levels of nitrate nitrogen and potassium were determined using Cardy flat sensor ion meters. Petiole nitrate level ranged from 520 to 6300 mg·liter-1 and potassium levels ranged from 870 to 3600 mg·liter-1. The petiole nitrate concentration and change in petiole nitrate levels with changes in media nitrate levels was crop dependent. Leaf blade nitrate and potassium concentrations were lower than leaf petiole concentrations. The relationship of petiole nitrate to final plant fresh and dry mass and appearance at flowering will be presented.
blend of ammonium nitrate (NH 4 NO 3 ), superphosphate, and potassium sulfate (K 2 SO 4 )] was broadcast applied (60 cm wide) to the soil surface, at the rate of 17, 61, and 27 kg·ha −1 of N, P, and K, respectively. Then, 20-cm tall raised beds were
land was very stony and moderately rocky. The N was applied in the form of ammonium sulfate, except in the first production cycle (2000–01) where urea was used, P in the form of triple super phosphate, and K in the form of potassium chloride. The
Six years of previous research in a 12-year-old English walnut orchard, with a history of potassium deficiency, created a large number of trees with different potassium status. This provided the opportunity to study the long-term effects different potassium status has on English walnut trees growth, productivity, and nut quality. Walnut trees with a history of potassium deficiency, adequacy or luxury continued in this mode during this evaluation. Positive correlations existed between July leaf potassium levels and tree trunk sectional area (TCSA), visual potassium status, percent husk potassium, yield per tree, and tree yield per TCSA. These positive correlations suggest July leaf potassium levels of 1.4% to 1.5% as being adequate. This is higher than the 1.2% leaf potassium level currently recommended as being adequate for a July sample. Poor or no correlations existed between July leaf potassium levels and percent shell potassium, shell weight, shell breaking force, percent broken shell, nut size, nut weight, percent kernel potassium, percent light-colored kernels, percent edible kernel, percent kernel yield, or percent shriveled kernel. Trees with leaf potassium levels at or above 1.5% July leaf potassium produced 80 pounds per tree more yield than trees with leaf potassium levels at or below 1.0% July leaf potassium levels. These data indicate that good tree potassium status influences tree size and tree productivity. Also the walnut husk is an important sink for the accumulation of potassium. Currently recommended adequate potassium levels for walnut appear to be lower than what this study indicates.
The effects of potassium (K) status and water availability in the growth medium on growth, water content, water-use efficiency and stomatal conductance was studied in mist-rooted `Chemlali de Sfax' olive (Olea europaea L.) cuttings grown in a perlite substrate. Potassium starvation produced dehydration of all parts of the plant, reduced shoot growth and water-use efficiency. By contrast, K starvation enhanced stomatal conductance in well-irrigated plants and, even more, in water-stressed plants. These results suggest that moderate K deficiency in olives may impair the plant's ability to regulate stomatal closure; this may account for the dehydration observed in K-starved plants, particularly in situations of water stress. This result is of great importance for agricultural practices of this crop, because K status, which may not be considered deficient, can cause disorders in olive trees.
Five supersweet cultivars of corn (Zea mays L. var. rugosa) were planted in fields and growth chambers to compare potassium effects on seedling development at low temperatures. In fields, seeds were planted at Urbana, IL, in 1991 when soil temperatures were 15C(April) and 23C(June). Potassium chloride(KCl) was banded at 0, 45 or 90 kg KCl/ha. After 32 days `Illini Gold', `Florida Staysweet', and `Crisp'n`Sweet' were more developed than `Honey'n`Pearl' and `How Sweet It Is' as indicated by emergence, height, leaf area and number, and weight in April. However for June, cultivar differences were observed only for emergence. KCl had no effect on any cultivars. In chambers, seeds were planted in trays(6×22×30 cm) of vermiculite mixed with 0, 5 or 10 g KCl/tray at 17 and 26C. After 15 days, cultivar responses at both temperatures were similar to those at the April field planting except at 26C where none differed for emergence. KCl only affected seedlings at 26C when 10 g/tray slowed development. Thus more differences were found between cultivars at lower than higher temperatures, and potassium did not improve seedling development at low temperatures.
Yellow shoulder disorder (YSD) is a physiological disorder of processing tomato that affects both the appearance and nutritional quality of the fruit. This disorder reduces the suitability of fruit intended for the whole-peeled and diced product markets. The YSD involves an interaction between plant genotype and the environment. A number of soil factors have been related to the incidence of YSD, including organic matter, phosphorous, K/Mg ratios, and soil K. Varieties of tomatoes differ in their susceptibility to color disorders, thus variety selection offers growers one strategy to manage this color disorder. The use of supplemental K application at a time when plants are blooming and actively growing offers a second strategy for management of YSD. To this end, a field study was conducted at the Southwest Purdue Agricultural Program in southwestern Indiana to study the effects of different sources of K on the color and quality of tomato fruit. Potassium chloride, potassium nitrate, and potassium sulfate were applied at first flowering in a solid, broadcast application. Appropriate controls were used to balance the nutrients supplied in addition to K. Supplemental K, regardless of source, improved fruit hue, though the trend was not always statistically significant between treatments. Variety specific effects were observed. This is a complex disorder and its management will entail minimizing risk of incidence through careful selection of variety and field location.