Trials were conducted in nine commercial processing tomato fields in California from 1994 to 1995 to assess the effects of potassium fertilization on fruit yield and quality. Sites were selected to represent a range of ammonium acetate extractable soil K levels (91 to 284 mg·kg–1, top 30 cm) and K release rates (K at 1.8 to 8.5 mg·kg–1·d–1). Potassium was applied in furrow or drip irrigation during the fruit bulking stage at seasonal rates from 90 to 135 kg·ha–1. Significant yield increase (4% to 24%) was observed at three of the four sites with extractable soil K <125 mg·kg–1 (K released at <3.1 mg·kg–1·d–1); no yield response was observed at the five sites with greater soil K supply. Fruit color and soluble solids content was unaffected by K fertilization at any site. Additionally, red fruit of two cultivars (`Halley' and `Heinz 8892') were collected from 80 commercial fields in 1995 and evaluated for soluble solids content, color (of a comminuted sample as well as visual ranking of internal and external ripening disorders), and tissue K concentration. Fruit K concentration was poorly correlated with any quality characteristic. We conclude that yield response to K fertilization can be adequately predicted by either soil test method and that K supply plays a relatively minor role in tomato fruit quality under representative field conditions.
T.K. Hartz, R. Mullen, M. Cahn, and G. Miyao
This article examines the nutritional quality and human health benefits of melons, specifically, muskmelon or cantaloupe (Cucumis melo L. var. reticulatus Naud.) and honeydew melon (Cucumis melo L. var. inodorus Naud.) types. Melons are naturally low in fat and sodium, have no cholesterol, and provide many essential nutrients such as potassium, in addition to being a rich source of beta-carotene and vitamin C. Although melons are an excellent source of some nutrients, they are low in others, like vitamin E, folic acid, iron, and calcium. Since the U.S. diet is already high in fat and protein content, melons should be included in everyone's diet, along with five to eight servings per day of a variety of other fruit and vegetables, to ensure adequate nutrition, promote individual health, and reduce one's risk of cancer and certain other chronic diseases.
Donald J. Merhaut, Eugene K. Blythe, Julie P. Newman, and Joseph P. Albano
Release characteristics of four types of controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were studied during a 47-week simulated plant production cycle. The 2.4-L containers containing a low-fertility, acid-based substrate were placed in an unheated greenhouse and subjected to environmental conditions often used for production of azaleas and camellias. Leachate from containers was collected weekly and monitored for pH, electrical conductivity, and concentrations of NH4 + N, NO3 –N, total P and total K. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Differences were observed among fertilizer types, with Multicote often resulting in higher concentrations of N, P, and K in leachates compared to the leachates from the other fertilizer types during the first half of the study. Concentrations of NO3 – and P from all fertilizer types were often above permissible levels as cited in the federal Clean Water Act.
Ana Morales-Sillero, R. Jiménez, J.E. Fernández, A. Troncoso, and G. Beltrán
described in Regulation EEC/2568/91 ( European Union Commission, 1991 ). Free acidity, expressed as percentage of oleic acid, was determined with a potassium hydroxide titration. Peroxide value, expressed as meq O 2 kg −1 of oil, was analyzed by iodometry
Alvaro O. Pacheco, G.J. Hochmuth, D.N. Maynard, A.A. Csizinszky, and S.A. Sargent
Optimum economic yield is produced when nutrients in the proper amounts are supplied to the crop. Crop nutrient requirements (CNR) of essential elements have been determined for the major vegetables produced in Florida. However, for minor crops, such as muskmelon, little research has been conducted to determine the CNR, especially potassium. In many vegetables, yield has responded to increasing K rates when other elements were not limiting. Our objective was to determine the K fertility requirement for optimum yield of muskmelon and to evaluate the Mehlich-1 soil test calibration for soil testing low in K (<20 mg·kg–1). Experiments were conducted in the spring and fall seasons of 1995. Potassium at five rates (0, 56, 112, 168, and 224 kg·ha–1) was injected weekly, approximating the growth curve of `Galia' and `Mission'. There were significant yield responses to K fertilization for both cultivars during both seasons. During spring, average marketable yield was 14.5, 26.1, 31.9, 31.5, and 36.3 Mg·ha–1 and for fall, average marketable yield was 15.8, 32.9, 37.8, 37.2, and 36.4 Mg·ha–1 for the previously described K treatments, respectively. The cultivar response for both seasons was described by a linear-plateau model. In spring, yield was maximized with K at 116.8 and 76.3 kg·ha–1 for `Galia' and `Mission', respectively. In fall, K at 73.3 and 68.3 kg·ha–1 produced the peak response for the same cultivars. These results indicate that maximum yield of muskmelon in Florida can be obtained at considerably less K than the current recommendation of 140 kg·ha–1.
Brian K. Hogendorp and Raymond A. Cloyd
Cloyd, 2012 ). Potassium bicarbonate (MilStop ® ; BioWorks, Victor, NY) is a fungicide registered for use in agricultural and greenhouse cropping systems for the control of various foliar plant pathogens ( Abd-El-Kareem, 2007 ; Cushman et al., 2007
Kathryn M. Santos, Paul R. Fisher, and William R. Argo
), and potassium (K) in the tissue z . Table 5. Nitrogen, phosphorus, and potassium use efficiency for each location. Tissue uptake. Tissue uptake ranged from 0.9 to 4.5 g·m −2 N, 0.2 to 0.6 g·m −2 P, and 1.5 to 4.6 g·m −2 K ( Table 4 ), varying by a
Angela M. Madeiras, Thomas H. Boyle, and Wesley R. Autio
and metabolism ( Wang et al., 2003 ). A solution of 0.2% potassium nitrate has been found to enhance germination of Phlox drummondii ( Heit, 1957 ); however, Springer and Tyrl (1989) observed no significant enhancement of germination in seeds of P
Jun Yan, Jingbo Chen, Tingting Zhang, Jianxiu Liu, and Haibo Liu
others ( Foy and Murray, 1978 ) demonstrated that grasses in acidic soils suffered from P, potassium (K), Ca, and Mg deficiencies; inhibition of growth; and poor environmental stress tolerance. The negative effects of Al on plant growth and nutrient
T. K. Hartz
A 1993 survey of 50 commercial processing tomato fields in California revealed widespread potassium deficiency, as determined by tissue K levels below existing sufficiency standards and the occurrence of vine necrosis consistent with K deficiency. Soils from these fields were analyzed for exchangeable K by ammonium acetate extraction, and for K release rate by a 7 day incubation procedure (1:10 soil:. 01 M CaCl2 at 25°). Soil K release rate was more highly correlated with tissue K at midseason than was exchangeable K. These soils were further examined for K fixation capacity. Three g soil was blended with 3 ml 10 meq K as KNO3, allowed to dry, incubated for 7 days in a 1:10 soil: H2O solution, then extracted in 1 N NH4Cl; added K not recovered was considered fixed. Percent K fixation ranged from 0 to 82%. These data suggest that the inconsistent response of processing tomato to K application in numerous California trials may be related to a) the reliance on extractable K analysis to characterize soil K supply and b) no consideration of soil K fixation capacity in determining K application timing and method.