cost and stringent environmental regulation, these industries have a critical need to improve nitrogen (N) and phosphorous (P) fertilizer use efficiency to remain sustainable. Plant nutrient management is intensive when producing high
efficiency was calculated as the difference in total aboveground plant N content in a fertilized treatment from zero N control treatment divided by N fertilizer. Nitrogen uptake efficiency was aboveground plant N divided by mineral N in the soil at harvest
linear at Fillmore, whereas the pattern was less clear at Amherst. Table 1. Mean fraction of nitrogen derived from fertilizer (fNdff) and nitrogen uptake efficiency (NUE) in hybrid hazelnut tissues at Amherst and Fillmore in response to N application time
Improving sweet corn fertilizer-N efficiency promotes a more vigorous and healthy crop, rewards the grower with greater profits, and protects our water resources from nitrate-N pollution. Two areas of research that have the potential to improve the efficiency of fertilizer-N applications are the Minolta SPAD 502 chlorophyll meter and the presidedress soil N test. The SP meter is a rapid and nondestructive technique for assessing sweet corn leaf levels, and SP readings have been correlated to leaf N concentration. A presidedress soil N test measures the amount of soil N that will be available to the plant during the remainder of the growing season. SP meter readings combined with presidedress soil N analyses may be used to determine crop N needs and fertilizer-N sidedress application rates. Basing fertilizer-N sidedress application rates on actual crop N needs will reduce excess fertilizer-N applications and the resulting leaching of nitrates.
High levels of N are often used to produce a vigorous plant that is also aesthetically pleasing to the purchaser. Environmental concerns with the overuse of N raise the need to find the minimum N requirements necessary to produce a salable plant. Ilex opaca and Lagerstroemia indica plants growing in 1.5-gal containers were irrigated with nutrient solutions containing N concentrations of: 15, 30, 60, 120, 210, and 300 mg N/liter. After 4 months, data indicate that using solutions >60 mg N/liter for both plant species results in leachates with N concentrations higher than those in the applied solutions. Nitrogen leaching losses increased with applied N, ranging from ≈15% to 50% for the low and high treatments, respectively. Chlorophyll readings of leaf tissue were not significantly different for plants of both species receiving N solutions higher than 60 mg·liter–1. These results indicate that N levels lower than those typically used for production of these woody ornamentals will still produce salable plants while increasing N fertilizer-use efficiency.
Environmental conditions and incorporation of nutrients into the growing medium can affect the fertilizer needs of bedding plants. To evaluate the effects of photosynthetic photon flux (PPF) and starter fertilizer on the fertilizer requirements of subirrigated plants, we grew wax begonias (Begonia semperflorens-cultorum Hort.) under three PPF levels (averaging 4.4, 6.2, and 9.9 mol·m-2·d-1) and four fertilizer concentrations [electrical conductivity (EC) of 0.15, 0.33, 0.86, and 1.4 dS·m-1] in a normal (with starter fertilizer, EC = 2.1 dS·m-1) and heavily leached (with little starter fertilizer, EC = 0.9 dS·m-1) growing medium. Except for shoot dry mass, we did not find any significant interactions between PPF and fertilizer concentration on any of the growth parameters. There was an interactive effect of fertilizer concentration and starter fertilizer on all growth parameters (shoot dry mass, leaf area, plant height, and number of flowers). When the growing medium contained a starter fertilizer, fertilizer concentration had little effect on growth. When the growing medium was leached before transplanting, growth was best with a fertilizer EC of 0.86 or 1.4 dS·m-1. Water-use efficiency (WUE) was calculated from 24-hour carbon exchange and evapotranspiration measurements, and used to estimate the required [N] in the fertilizer solution to achieve a target tissue N concentration of 45 mg·g-1. Increasing PPF increased WUE and the required [N] (from 157 to 203 mg·L-1 at PPF levels of 4.4 and 9.9 mol·m-2·d-1, respectively). The PPF effect on the required [N] appeared to be too small to be of practical significance, since dry mass data did not confirm that plants grown at high light needed higher fertilizer concentrations. Thus, fertilizer concentrations need not be adjusted based on PPF.
The mineral nutrition requirements and fertilizer application methods for container-grown shade tree whips are not well understood. This experiment was conducted to determine the effects of fertility method (water soluble vs. controlled release) on growth, water, and N use efficiency of four taxa [(Acer ×freemanii `Jeffersred' (Autumn Blaze® maple), Cercis canadensis L. (Eastern redbud), Malus (Mill.), `Prairifire' (Prairifire crabapple), and Quercus rubra L. (red oak)] in two production environments [outdoor gravel pad vs. a retractable roof structure (RRS)]. No single fertilizer method consistently resulted in the greatest growth. In the RRS, maple and crabapple heights, and crabapple and redbud caliper were larger when whips were fertilized with controlled-release fertilizer (CRF); outdoors, CRF resulted in taller maples and larger caliper crabapples. However, in the RRS, maple whips fertilized with water-soluble fertilizer had higher production water use efficiency than those fertilized with CRF, whereas crabapple whips had higher N use efficiency when fertilized with CRF. Nitrogen use efficiency was higher for redbud and crabapple whips fertilized with CRF than with CRF. Outside, crabapple whips fertilized with CRF had higher production water use efficiency than those fertilized with water-soluble fertilizer. There were no differences in N use efficiency attributed to fertilizer method. When averaged over fertilizer application methods, height, caliper, water, and N use efficiency were greater when whips were grown in RRS than outdoors. There were two exceptions: Maple caliper and production water use efficiency were marginally higher when whips were grown outdoors. The greater growth for whips produced in the RRS was attributed to reduced ambient and substrate temperature stress.
Many agronomic and horticultural studies on nutrient uptake and use-efficiency have indicated, in general, that agricultural crops are poor competitors for nitrogen (N) and phosphorus (P) in soil-based systems, with estimates of overall nutrient efficiency being less than 50% for N and 10% for P. Low efficiencies are due to losses from leaching, runoff, gaseous emissions and soil fixation, but uptake efficiency is also affected by rate and timing (i.e. seasonal effects) of applications. Controlled-release fertilizers (CRF's) have been promoted as a technology that can slowly release nutrients; the release rate is most often a function of prill coating and temperature. There are few data in the ornamental literature that have directly compared the total uptake efficiency of CRF's to soluble fertilizer sources. From 1999-2002, we collected three annual N and P budgetary datasets, comparing two species (Rhododendron cv. azalea and Ilex cornuta cv.`China Girl') with different growth rates and hence nutrient requirements. Plant N and P uptake efficiencies were usually less than 20% of the total applied, but all datasets included a significant soluble fertilization component. In 2003, a new study with Ilex cornuta cv.`China Girl' was initiated, where nutrients were supplied only from two CRF sources, as we want to determine whether this technology can significantly increase nutrient uptake efficiency at similar rates. A preliminary analysis of the data indicate that total N and P uptake efficiencies between different CRF sources were similar, but leaching losses between sources varied during the growing season. It appears that the primary determinant of uptake efficiency is not source material or timing, but the overall rate of nutrient application.
Chili pepper (Capsicumannuum cv. Delicacy) was grown in single- and double-bed rainshelters and irrigated using furrow and drip irrigation to determine effect on yield and efficiency of water and nutrient application in the lowland tropics of southern Taiwan during the hot wet season. The experiment was laid out using a split-plot design with four replications. The main plots were rainshelters (single, double, open field) and the two irrigation methods (furrow and drip) were the subplots. Grafted chili seedlings were transplanted in double rows on raised beds at row spacing of 80 cm and plant spacing of 50 cm. The furrow-irrigated crop was applied with basal N-P2O5-K2O at the rate of 180–180–180 kg·ha-1 and 240–150–180 kg·ha-1 of N-P2O5-K2O as sidedressing. The drip-irrigated crop received half of the total rate applied for the furrow-irrigated crop. Significant differences (P < 0.05) in marketable yield were observed between rainshelter treatments. Highest yield (42.2 t·ha-1) was produced from the single-bed rainshelter, and crops grown under double-bed rainshelters produced the lowest marketable yield. Irrigation method did not significantly influence marketable yield, but crops grown under drip irrigation produced a higher yield than furrow-irrigated crops. Nutrient uptake by plants grown under drip irrigation was also higher (P < 0.05) than for furrow-irrigated crops. Water use efficiency was 60.7% higher in drip-irrigated plots. Results indicate that in high rainfall vegetable production areas, drip irrigation minimizes nutrient loss through leaching and maximizes efficiency of fertilizer use.
Timing nutrient application to periods of high nutrient demand could increase nutrient use efficiency and reduce the potential for fertilizer leaching or runoff. However, current recommendations for field nursery and landscape ornamentals (extension publications) suggest fertilizing in late fall and early spring despite research with perennial fruit crops that demonstrates low uptake potential during those times. Research is needed to resolve this apparent conflict. Application rates for woody ornamentals, established in the 1960s and 1970s, also need reexamination in the light of environmental concerns.