Optimization of irrigation and fertilization regimes in greenhouses and other controlled environments requires accurate and frequent measurements of soil-water content. Recent studies on TDR use in gravely soils and in closed-container studies have indicated a potential use of this method in horticulture. In this study, TDR calibration curves were determined for tuff (granulated volcanic ash), vermiculite, perlite and a mix of two composted agricultural wastes (grape marc, separated cow manure). Widely used as horticultural substrates, mixes of these materials were tested as well. For all soil substitutes tested, measured calibration results are well described by linear equations throughout tested values of water content that cover the working range in horticulture. Ledieu's equation, widely used in soils, describes fairly well the measured results for perlite, but underestimates those obtained for organic media, vermiculite (because of the presence of bound water) and tuff (probably due to water in occluded pores). The differences obtained between the measured calibration equations and Ledieu's equation indicate that in order to avoid an erroneous irrigation management, calibration is necessary whenever a new soil substitute is used.
F.F. da Silva, R. Wallach, A. Polak, and Y. Chen
Keith A. Funnell, Errol W. Hewett, Ian J. Warrington, and Julie A. Plummer
Trust for providing funding for this project, and to the staff at the National Climate Laboratory for maintaining the controlled environment facilities used in this study. The cost of publishing this paper was defrayed in part by the payment of page
David R. Dreesen and Robert W. Langhans
Abbreviations: CEGR, controlled environment growth rooms; HI, high irradiante levels; LI, low irradiance levels; MHI, medium high irradiance levels; MLI, medium low irradiance levels 1 Former graduate research assistant, currently research associate
Peter R. Hicklenton, Suzie M. Newman, and Lindsay J. Davies
, New Zealand, for supporting this research and members of the Technical Services Group, National Climate Laboratory, HortResearch, for maintaining the controlled-environment rooms during this study. The cost of publishing this paper was defrayed in part
S. Al-Ghawas and K. Al-Mazeedi
Treated wastewater will play important role in the implementation of Kuwait National Agriculture Development Plan. As a substitute for brackish or fresh water in irrigation, treated municipal wastewater can be a practical solution. Nevertheless, special health and environmental considerations should be carefully assessed when using this water source. These considerations include potential infection with human pathogens, effects of heavy metals on the public health, and the ecological consequence on soil and water resources at large. These topics were investigated under controlled environment using a range of crops and two types of irrigation water: a tertiary treated wastewater source and fresh tap water as a control. Soil, water, and plant samples were collected at fixed intervals and were analyzed for total viable count; total Coliforms; faecal Coliforms; and faecal Streptococc, Salmonellae, Shigella, Ascaris imbricoides and pathogenic viruses. In addition, we measured for nine heavy metals (Cd, Zn, Fe, Mn, Cu, Ni, Co, Cr, and Pb). Soil salinity and build-up of sodicity in soil and ground water sources also were investigated for any changes that could indicate a potential long-term degradation effect. The results after 3 years of study indicate that the generated tertiary treated wastewater is of high quality. Its potential pathogenic content is below the guidelines recommended by WHO for using wastewater in mixed agriculture, and therefore, it had no accumulative effect on the irrigated soil or the different parts of plant tissues that were analyzed. However, treated effluent have occasionally exhibited pathogenic index higher than permitted levels reflecting the fluctuating nature of wastewater treatment. Heavy metals content of irrigation water and from the irrigated soils were negligible, and the plant tissues that were analyzed contained metallic contents below the established range in IPE. The treated water had low TDS but high sodium content with 25–35 SAR values; however, the effect on the irrigated soil was insignificant due to the calcareous nature of the soil used. This study used drip irrigation system and under similar conditions no health problems will be expected when using tertiary treated wastewater for irrigation. To minimize potential risk to the consumers, specific guidelines are recommended on the type of crops to grow and the horticulture practices to be used.
T.J.K. Radovich*, J.G. Streeter, P.P. Ling, and M.D. Kleinhenz
Clarifying the influence of abiotic environmental factors on the glucosinolate-myrosinase complex in vegetables of the Brassicaceae is an important step in understanding physiological processes that affect crop quality. Previous related work in this lab has shown that irrigation timing in the field may influence physical-, chemical- and sensory-based indicators of cabbage quality. The objective of this study was to record glucosinolate concentrations and myrosinase activity in crop tissues from plants subjected to varying soil moisture levels, employing radish as a model. Plants of cv. Belle Glade were grown in a controlled environment system designed at the Ohio Agricultural Research and Development Center in Wooster, Ohio for maintenance of target soil moisture levels. Pots were maintained at three soil moisture ranges, 40% to 60% (A), 20% to 30% (B) and 10% to 20% (C) volumetric soil moisture content at 30 °C. Preliminary observations revealed that treatments A, B and C corresponded to soil tensions which were not stressful, moderately stressful, and severely stressful to plants, respectively. Pot evapotranspiration, leaf stomatal conductance and plant size followed the order A>B>C, while canopy temperatures followed the order C>B>A. In leaves, glucosinolate concentrations and myrosinase activity were about 15% greater in treatments B and C than in A, while glucosinolate levels and myrosinase activity were 28 and 50% lower in hypocotyls and roots, respectively, in C than in A. It is hypothesized that changes in enzyme and substrate synthesis and translocation within the plant in response to sub-optimal soil moisture levels may explain the differential response of tissue glucosinolate concentrations and myrosinase activity to soil moisture treatments.
Robert Premier and Scott Ledger
Quality assurance (QA) in the horticultural industry has become well established in Australia; on-farm hazard analysis critical control point (HACCP)-based plans have been adopted due to pressures from supermarkets and other buyers, including fresh markets. Supermarkets' own systems and more general QA systems have been used by growers to meet these new requirements. Two QA systems, Freshcare and Safe Quality Food, have been introduced across the country with moderate success. A review of quality assurance parameters such as chemical residues and microbiological contaminants suggest that these QA systems have achieved some level of assurance. Local pressures, however, are not the only concern when it comes to QA. International demand for safe quality fruit and vegetables has meant that QA systems now need to be designed to satisfy export requirements. In addition to food safety, international demands must also address the environment and workers' health and safety. Many Southeast Asian governments have taken the initiative and developed country-specific QA systems to satisfy export markets and that are suitable for their farmers to use. Countries with schemes in place include Malaysia, Thailand, Indonesia, and Singapore, with other countries, such as the Philippines and Brunei Darussalam, in the process of introducing schemes. This presentation will discuss the status of QA systems in Australia and Southeast Asia, including the pressures behind their establishment, and the major differences between them. The presentation will also focus on the attempt by Southeast Asian governments to address a uniform standard through the development of the Association of Southeast Asian Nations (ASEAN) good agricultural practice (GAP), a GAP standard suitable for use by all 10 ASEAN member countries.
David R. Dreesen and Robert W. Langhans
Abbreviations: CEGR, controlled-environment growth room; HI, high irradiance levels; LAR; leaf area ratio; LI, low irradianee levels; MHI, medium-high irradiance levels; MLI, medium-low irradiance levels; MRGR, mean relative growth rate; NAR, net
Leslie S. Katzman, Alan G. Taylor, and Robert W. Langhans
1 Graduate Student. 2 Professor of Seed Science and Technology. To whom reprint requests should be addressed. E-mail address: email@example.com 3 Emeritus Professor of Controlled Environment Agriculture. This paper is a portion of a thesis
-timed publication. With the rising concerns about the extensive use of pesticides and their harmful effect on people and the environment, this book is a valuable resource for persons interested in natural alternatives to synthetic agrochemicals to control plant