et al., 2005 ). In the past, MBr applications have effectively reduced nutsedge populations below damage thresholds. However, other fumigants do not have consistent efficacy against these weeds. Metam sodium and metam potassium (MK) are among the most
dynamic response of plant respiration to temperature Trends Plant Sci. 8 343 351 Broadley, M.R. White, P.J. 2010 Eats roots and leaves. Can edible horticultural crops address dietary calcium, magnesium and potassium deficiencies? Proc. Nutr. Soc. 69 601
potassium chloride (for K trial) (Kynoch, Pretoria, South Africa) applied 1 week after planting in the form of granules. The initial plant height was about 40 cm before the application of treatments. All plants received 1% magnesium sulfate (20% magnesium
control plants. Although the 1 m m N treatment produced the lowest response (no difference compared with controls), it produced a greater effect than any of the K treatments ( Table 1 ). Table 1. Effect of nitrogen (N) and potassium (K
alternate bearing. Potassium is essential for photosynthesis, carbohydrate and protein synthesis, and enzyme activation ( Marschner, 1995 ). Nonstructural carbohydrates and organically bound N must be transported from a source or storage site (net exporter
Soil applied potassium (K) may not alleviate K deficiency in fine textured California soils when high numbers of prunes per tree are produced leading to leaf necrosis and limb death. Because K demand is increased by fruit, K nitrate (KN) sprays appear to be a corrective option for growers in this situation. Our objectives were to determine best seasonal KN spray liming strategies to minimize K deficiency, quantify K uptake into leaves after spray and to evaluate spray effects on productivity. Results indicated that regardless of spray timing leaf K was increased by approximately 0.3% and three weeks later decreased 0.2%. Average leaf K in sprayed trees was 0.7% higher than untreated trees at harvest. Fruit fresh to dry weight ratios were lower (better) from summer sprayed trees than spring. Summer KN sprayed trees had yield efficiencies equal to those having soil applied K. Fruit size was similar regardless of K application method. Foliar KN sprays may be a viable K augmentation to soil application in heavy crop years on fine textured soils.
`Celebrity' tomatoes (Lycopersicon esculentum Mill.) were grown in peat-perlite under greenhouse conditions with five potassium (K) fertilization concentrations of 25, 50, 100, 200 and 300 (mg/liter) K in irrigation waters. Petiole sap K concentrations were monitored on a weekly basis with calorimetric paper test strips. Petiole sap K concentrations (ug/ml) were stable throughout crop development at each feed concentration. Total and marketable fruit yields increased linearly with increasing petiole sap K concentrations. However, the relationship between petiole sap K) concentrations and K levels in the irrigation waters was quadratic with a plataeu occuring at about 200 mg K/liter in the irrigation waters. Corresponding maximum sap K concentrations obtained were about 6200 ug K/ml. Yield responded quadratically to increasing K levels in the irrigation system, with maximum yields occuring at about 200 mg K/liter. Fruit yields appeared to decline as feed concentrations were increased beyond 200 mg K/liter. At optimum feed concentrations, maximum marketable yield of about 2.6 kg/plant were obtained on plants grown 21 weeks from seed.
years with large crops, “on-years,” that contributes to alternate bearing ( Goff et al., 2001 ; Kraimer et al., 2004 ; Wood, 2001b ). Potassium (K) could be limiting during on-years because developing fruit may deplete leaf K ( Diver and Smith, 1984
·ha −1 P as fused phosphate fertilizer. The K rates were 0, 67, 133, and 200 kg·ha −1 K as potassium sulfate. Every treatment also received decomposed commercial pig compost at 8.0 t·ha −1 . Compost, phosphate fertilizer (P), one-third of the urea (N
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