experiment was conducted to determine the impacts on tree and soil properties of varying rates of ACT. Treatment effects were examined for two tree species ( Acer saccharum and Quercus macrocarpa ) and three soil types (sand, uncompacted loam, and compacted
Tuan Anh Le, Zoltán Pék, Sándor Takács, András Neményi, Hussein G. Daood, and Lajos Helyes
of sand and sandy clay mixture sandy loam; its texture consisted of 69% sand, 22% silt, and 9% clay; it had a 1.57 g·cm −3 bulk density and 19% field capacity; and was neutral in pH, free from salinity (0.16 dS·m −1 ), and low in organic carbon: NO 3
Chun-hui Shi, Xiao-qing Wang, Xue-ying Zhang, Lian-ying Shen, Jun Luo, and Yu-xing Zhang
Fruit color is a commercially important quality for sand pear ( Pyrus pyrifolia Nakai). Sand pear can be divided into russet, semi-russet, and green types based on the color of the peel, which is typically composed of a cuticle layer, an epidermis
Larry J. Shoemake and Michael A. Arnold
Zea mays L. and Taxodium distichum L. seedlings were grown for 35 days in sand or 3:1 milled pine bark:sand media in 0.7 liter containers. Containers were painted on interior surfaces with 100 g Cu(OH)2/liter or 200 g Cu(OH)2/liter latex carrier (Spin Out™) or not. Five seedlings of each treatment combination were watered daily from 9.5 liter reservoirs with 100 ml of recycled fertilizer (20N-8.7P -16.6K. pH 6.0) solution initially containing 0.036 mg Cu/liter. Fertilizer solutions containing 0.036, 5, 10, 100, or 1000 mg Cu/liter were used to develop toxicity response curves with additional seedlings. Growth of both species in both media was increased by Spin Out treatments. Soluble Cu content of the recycled solution from Spin Out treated containers increased slightly (<1.2 mg/liter) during the experiment. Soluble Cu in leachate from Cu-treated containers ranged from 0.2 to 5 mg/liter with sand and from 0.30 to 1.2 mg/liter with bark. Soluble Cu in leachatc from non-treated containers ranged from 0.02 to 0.40 mg/liter with sand and 0.10 to 0.86 mg/liter for bark media.
Susan Sand and David R. Hershey
David R. Hershey and Susan Sand
A Venturi-type proportioner (VP), trade name Hozon, can be used for an inexpensive, hands-on laboratory exercise that demonstrates the effect of water pressure on dilution ratio and water flow. Using electrical conductivity (EC) meters to determine solution concentration allows students to discover that the dilution ratio increases with water pressure, from 1:10 at 15 psi to 1:15 at 55 psi. The greater dilution at higher pressure can be explained by measuring the water flow, which is 2.3 gal/min (8.7 litersžmin-1) at 15 psi but 3.5 gal/min (13.2 litersžmin-1) at 55 psi. Experiments relating water pressure to dilution ratio provide experience in use and calibration of VPs and EC meters, as well as graph preparation and interpretation.
C.A. Sanchez, R.L. Roth, and B.R. Gardner
Six field studies were conducted from 1980-88 to evaluate the response of cabbage (Brassica oleracea L., Capitata group) to sprinkler irrigation and sprinkler-applied N fertilizer on a coarse-textured soil. The plots were irrigated using a modified self-moving lateral sprinkler irrigation system that applied five levels of water and five levels of N (liquid NH4NO3) in specified combinations of central composite rotatable design. Cabbage yields were significantly increased by water and N applications in all experiments. The N rates predicted for maximum yield exceeded typical cabbage N fertilizer recommendations. However, the above-average plant populations used in these studies resulted in above-average yields and plant N accumulation. Deficit and excess irrigation produced negative results. Generally, cabbage production was optimized and N losses to the environment were minimized when crops were irrigated for evapotranspiration (ET) replacement. However, even when irrigated for ET replacement, these data demonstrate the potential for N leaching at high N rates, presumably as a result of rainfall.
Luther Waters Jr., Bonnie L. Blanchette, Rhoda L. Burrows, and David Bedford
High levels of sphagnum peat in the growing medium promoted growth of asparagus (Asparagus officinalis L. cv. Viking 2K) in a greenhouse study. Application of NH4NO3 > 1 g/pot (84 kg·ha-1 equivalent) was detrimental to root growth. High N rates and high organic matter levels decreased fibrous root development. Shoot dry weight was highly correlated with fleshy root number, root dry weight, and shoot vigor.
Nitrate pollution of surfacial aquifer is fairly widespread in deep sandy soil areas of Central Florida. Since citrus is a predominant crop in this area, despite lack of conclusive evidence suggesting citrus fertilization as the source of nitrate pollution, investigations are in progress to develop Best Management Practice (BMP) recommendations for N fertilization of citrus in an effort to improve N use by the trees and to minimize potential nitrate leaching. Our ongoing studies on both young and mature trees have demonstrated that the use of improved fertilizer formulations and programmed application schedules have facilitated to decrease the rate of N application considerably without any adverse impact on tree growth and/or fruit production while minimizing nitrate leaching below the rootzone. Our approach involves developing BMP recommendations on the basis of iudicious irrigation management and generating database on N removal by the fruits, annual N contribution to the trees by mineralization of organic N, and N losses including leaching, denitrification, etc.
A. A. Csizinszky
Two tomato (Lycopersicon esculentum Mill.) cvs. Agriset 761 and Equinox, were grown in spring and fall 1996 with two microirrigation rates 1x (HI) and 0.75x (LO) of the open pan evaporation and sprayed either weekly or biweekly with Anti-Stress 2000 (acrylic polymer) at 2.33 L·ha–1 in 280 to 561 L·ha–1 H2O during the first 10 weeks of the season. Tomato yields were similar with HI or LO irrigation rate and with antitranspirant sprays or water control. In both seasons, `Equinox' had a higher early but lower seasonal total marketable yield than `Agriset 761' (P ≤ 0.05). Residual soil concentrations of NO3-N and K were higher (P ≤ 0.05) with the LO, than with HI irrigation rate.