Abstract
When plant nutrition problems are observed in the field, one is faced with the question “What is the best and most economical way to solve this problem?” Traditionally, workers in both agronomy and horticulture have used soil amendments to correct deficiencies of macro- and micronutrients, and to correct soil pH to avoid Al or Mn toxicity. Horticulturists have had few economic limitations in solving plant nutrition problems because they work with crops with higher production costs and potential profit. Philosophically, we must recognize that some nutrients are removed from soils by cropping, and these must be replaced eventually. We can remove stored nutrients from the soil, but this reduces soil fertility. For elements such as Zn, Cu, Mn, B, and Co, addition of elemental fertilizers is both effective and inexpensive in nearly all cases. Boron, Cu, and Zn fertilization are normal horticultural management practices. Soil testing or plant analysis can identify potential microelement fertility problems and deficiencies can be avoided by timely fertilizer application. Similarly, the pH of the surface soil can be economically raised by limestone to reduce the availability of some toxic ions such as Al and Mn. This approach has been called “Change the soil”.
Sweetpotato [Ipomœa batatas (L.) Lam.] is a major subsistence crop in southern Africa, where iron and zinc deficiency in humans is an important health problem. A cultivar of sweetpotato that is suited for subsistence farming in this region and that is high in iron and zinc could be an important means of combatting these deficiencies. As part of a program of the HarvestPlus program, under the auspices of the International Potato Center (CIP) to develop such a cultivar, we are working to identify the high and low range of iron and zinc in sweetpotato cultivars grown throughout the world by testing a number of cultivars for these nutrients. Subsidiary objects include determining the heritability of iron and zinc levels and surveying the variability in the levels of these nutrients from root to root on the same plant, from plant to plant of the same cultivar, from the proximal to the distal end of a given root, and from cambium to cortex. For the roughly 80 cultivars in the genotypic variability study, results showed a three-fold difference between the high- and low-yielding cultivars on a fresh weight basis and a two-fold difference on a dry weight basis, for both iron and zinc.
Upper leaf necrosis (ULN) on Lilium `Star Gazer' has been recently demonstrated to be a calcium (Ca) deficiency disorder. In the current studies, we confirmed this by using a Ca-free nutrient regime to reproduce ULN symptoms. The ability of a bulbous storage organ to supply calcium to a growing shoot is poorly understood. Therefore, we conducted experiments to determine Ca partitioning during early growth stages, and under suboptimal Ca levels to determine how the bulb affects the symptomatology. The results indicated that ULN is originally caused by an insufficient Ca supply from the bulb. In the most susceptible period, bulb dry matter decreased dramatically and Ca concentrations in immature folded leaves dropped to very low levels. Consequently, necrosis began to appear on the upper, young leaves. The bulb was able to supply Ca to other organs, but only to a limited extent since Ca concentration in bulbs was low (0.04% w/w). To confirm this result, we cultivated lilies with low-Ca or Ca-free nutrient solution and obtained bulbs with extremely low internal Ca concentrations. Upon forcing these low-Ca bulbs, we found, as expected, prominent necrosis symptoms on the lower and middle leaves. Data suggested the lower and middle leaves relied more on Ca supplied from the bulb, while upper leaves and flowers relied more on Ca uptake from the roots. Different organs have different Ca requirements, and tissue sensitivity to Ca deficiency varies according to the growth stage.
Osmotic compounds, such as polyethylene glycol 8000 (PEG-8000), reduce plant elongation by imposing controlled drought. However, the effects of PEG-8000 on nutrient uptake are unknown. Impatiens `Dazzler Pink' (Impatiens walleriana Hook. F.) were grown hydroponically in modified Hoagland solutions containing 0, 10, 17.5, 25, 32.5, 40, 47.5, 55, or 62.5 g·L–1 PEG-8000. Impatiens were up to 68% shorter than control plants when grown with PEG-8000 in the nutrient solution. Plants treated with PEG-8000 rates above 25 g·L–1 were either damaged or similar in size to seedlings treated with 25 g·L–1 of PEG-8000. Impatiens leaf water potentials (Ψw) were positively correlated with plant height. PEG-8000 reduced the electrical conductivity of Hoagland solutions as much as 40% compared to nontreated Hoagland solutions, suggesting that PEG-8000 may bind some of the nutrient ions in solution. Foliar tissue of PEG-treated impatiens contained significantly less nitrogen, calcium, zinc, and copper, but significantly more phosphorus and nickel than tissue from nontreated impatiens. However, no nutrient deficiency symptoms were induced.
Bedding plant petunia (Petunia ×hybrida) is often produced with high nutrient concentrations as a cool-season crop. How a plant uses the nutrients supplied will depend in large part on the environmental factors influencing growth rate, such as light and CO2. Since more growers are considering using supplemental CO2 to improve energy efficiency for plant production, it is important to understand light and fertilizer levels needed for efficient production of high-quality plants. Using a multi-chamber controlled environment system, petunia plants were grown from seed for 6–8 weeks after transplanting into different light and CO2 environments and fed with either a low (7.1 mM N) or high (21.3 mM N) fertilizer regime. Plants were evaluated for appearance, harvested periodically, and separated into flower, stem, and leaf biomass. Biomass was then dried and analyzed with ICP-OES for essential macro- and micronutrients. Low-fertilizer-grown plants had consistently earlier and more flowers, but showed symptoms of nutrient deficiencies in the final few weeks of production at all light and CO2 levels. There were significant interactions between light and fertilizer treatments for different nutrients. Calcium uptake was greatly influenced by light level, Fe, P, and K were influenced by the fertilizer supply, and Mg and B were inversely influenced by fertilizer supply at high light. These data suggest new management strategies are needed to improve fertilizer use efficiency in different environments.
Application of nutrients to correct nutrient deficiencies in turfgrasses are often based on tissue analysis. Previous research has indicated that near infrared reflectance spectroscopy (NIRS) may be useful in tissue nutrient concentration determination since it requires minimum sample preparation and has been a reliable predictor of N concentration. The objective of this study was to evaluate the reliability of NIRS in determining P, K, Ca, and Mg concentrations in bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy]. Tissue samples were collected from Florida golf courses, representing different cultivars grown under various conditions and fertilizer regimes. Tissue samples were analyzed using NIRS and traditional wet chemistry (Mehlich-1 extracts analyzed using inductively coupled argon spectrophotometer) before results were statistically compared. Results from wet chemistry analysis averaged 15% lower than those obtained from NIRS. Although results for certain cultivars and elements were positively correlated (`Tifdwarf' Ca, r 2 = 0.72; P < 0.01), precision across all cultivars and nutrients was not sufficient (accounted for only 26% of variability) to indicate that NIRS would be an effective management tool for the elements evaluated in this study.
Wastewaters from farm and composting operations are often rich in certain nutrients that can be reutilized in crop production. Liners of silverleaf dogwood (CornusalbaL. `Argenteo-marginata'), common ninebark [Physocarpusopulifolius(L.) Maxim.], and `Anthony Waterer' spirea (Spiraea×bumaldaBurvenich) were grown in 6-L containers filled with a medium consisting of 73% bark, 22% peat, and 5% pea gravel, by volume. Plants were fertigated daily via a computer-controlled multi-fertilizer injector with three recirculated fertilizer treatments: 1) a stock solution with macro- and micronutrients, electrical conductivity (EC) 2.2 dS·m-1; 2) wastewater from a mushroom farm; and 3) process wastewater from anaerobic digestion of municipal solid waste. The wastewaters used in both treatments 2 and 3 were diluted with tap water, and the computer was programmed to amend, dispense, and recirculate nutrients, based on the same target EC as in treatment 1. For comparison, there was a traditional controlled-release fertilizer treatment [Nutryon 17–5–12 (17N–2P–10K) plus micronutrients incorporated into the medium at a rate of 6.5 kg·m-1, nutrients not recirculated]. All three species responded similarly to the three recirculated fertilizer treatments. Growth in the recirculated treatments was similar and significantly higher than that obtained with controlled-release fertilizer. A similar trend in EC was observed in the media near harvest. Throughout the study, there was no sign of nutrient toxicity or deficiency with any of the species or treatment.
Home gardening is a popular year-round recreational activity in Hawaii that helps to increase community food security in suburban and rural communities where high levels of poverty and unemployment exist. Updated fertilizer recommendations and accurate information about the latest products allows home gardeners to improve crop growth, and to minimize nutrient imbalances in the soil, pest problems, and environmental risks from nutrient runoff or leaching. Two field experiments were conducted in Oahu, Hawaii, to evaluate several new products in the market for the production of two home-garden Chinese cabbage varieties. The treatments included Miracle Grow, a new Miracle Grow Plus formulation, Plant Power 2003 nutrient solution, a Maui Liquid Compost product, and a standard fertilizer control (150 kg·ha-1 N rate). Each treatment consisted of a 6-m long row with 30-cm plant spacing in the row. Each treatment was replicated four times in a completely randomized block design, for a total of 40 plots (two varieties × five treatments × four replications). Data collected included soil fertility before initiation and after experiment completion, tissue nutrient analysis, plant height collected twice during the growing cycle, and head weight and length measured at harvest time. The variety Pagoda was more responsive to fertilizer applications, showing an average of 30% yield increases between the best and poorest treatment, compared to 20% for `China Express'. Overall, the Miracle Grow formulations outperformed the other products. The tissue nutrient data showed tissue nutrient levels above those recommended by the Extension Service. The treatments with highest yield response also showed greater symptoms of “black heart” from possible boron deficiency.
Growers tend to over fertilize their plants as a way to minimize the likelihood of encountering nutrient deficiencies that would reduce the quality of their plants. Much of the nutrition literature focuses on the nutritional extremes namely of toxicity and deficiency. Once plants get to this stage, little can be done to correct the problem. Characteristics of plant performance in super-optimal conditions, yet below toxic levels, is less well known, and needs to be developed to help growers identify problems in their production practices before they impact sales. New Guinea Impatiens were grown over a wide range of N, K, and B levels, from 15% to 400% full strength Hoagland's solution for each nutrient after establishing transplanted rooted cuttings in a peat: perlite soilless media. Plants were grown for four weeks during treatment, during which time the flowers were pinched. After only 2 weeks of treatment, plants with 200% and 400% N were significantly shorter than control plants and plants with 15% N. Reflectance measurements and photographs were made twice a week. At the end of the four weeks, plant tissue was analyzed for form of N, root development and structure, and leaf area. Tissue samples were also analyzed with SEM and energy dispersive X-ray analysis to determine changes in nutrient location and tissue structure. This data provides insight into the nutrition economy of plants in general, tests the use of reflectance spectrometry as a method of detecting super-optimal fertilizer concentrations, and will help growers optimize their fertilization requirements to reduce production costs yet maintain high plant quality.
Coniferous forest trees showing chlorosis and dieback appear to be deficient in Ca and Mg. These deficiencies may be induced by nitrogenous nutrients borne in the atmosphere. This study assessed the roles of nitrogen nutrition and soil on nutrient accumulation by red spruce (Picea rubens, Sarg.) and radishes (Raphanus sativus, L.). Plants were grown in the greenhouse in acid O or A horizons (Typic Haplorthod) collected from a red spruce forest. Plants were grown with a complete nutrient solution with 15 mM N of which NH4 was 0, 3.75, 7.5, 11.25, or 15 mM with the remainder being NO3 -. After 120 days, the spruce needles became chlorotic with 11.25 or 15 mM NH4. Radishes exhibited NH4-toxicity after 28 days. Radishes were larger in the O horizon than in the A horizon. As NH4 was increased, radishes had lesser dry weights and accumulated less foliar Ca. Foliar Ca also was lower in spruce with the higher NH4. Magnesium concentrations in leaves of red spruce and radishes were not affected significantly by increasing NH4 supply. Radishes are suitable indicator plants to study the effect of nitrogen form on mineral nutrition of spruce because each species responded similarly to the treatments.