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Three species of woody plants, Ilex crenata 'Helleri', Juniperus chinensis procumbens 'Nana', and Ligustrum lucidum, were grown in one-liter containers filled with pine bark to determine Fe and Mn requirements with regard to rate and ratio. FeEDTA and MnEDTA were applied at either a 2:1 or 1:2 ratio of Fe:Mn at 5 concentrations each, 3 times per week with each irrigation. Medium solutions were collected every 21 days on one species and analyzed for Fe and Mn levels. Dry weight and tissue Fe and Mn levels were determined for all three species. Neither rate nor ratio of applied Fe and Mn had an effect on shoot dry weights. Control treatments, in general, had the lowest medium solution and tissue levels of Fe and Mn, however, there was no difference in dry weights between control and treatment plants. These results suggest that pine bark supplies adequate levels of Fe and Mn for growth under the conditions of this study. In a second study, three sources of Fe and Mn were applied to Tagetes erecta 'Inca' growing in 500 cc plastic pots containing sieved pine bark at 3 lime rates: 0, 3, and 6 kg m⁻³. Sources of Fe and Mn were pre-plant Micromax, liquid sulfate salts, and liquid chelates applied in the irrigation water. No difference in growth between micronutrient sources was detected, however, growth was greater at the 3 and 6 kg m⁻³ lime rates. Levels of Fe and Mn in medium solution and tissue decreased with increasing lime rate, with availability of Fe and Mn greatest with chelate as the source, regardless of lime rate. A similar study was conducted with a control and liquid sulfate treatment. There was no difference in dry weight between the sulfate treatment and the control, except at 0 kg m⁻³ lime where the control plants were larger. Again, lime additions increased growth, and Fe and Mn availability in medium solution and tissue levels decreased. These results suggest that if Fe and Mn additions are needed, all sources provide adequate Fe and Mn for growth. / M.S.

The effects of high medium temperatures on the growth and mineral nutrition of selected woody plants and on the composition of the medium solution were studied. Medium temperature profiles were established for 3.8-liter black polyethylene containers exposed to solar radiation under Virginia nursery conditions. On clear days in mid-summer, maximum recorded medium temperatures on the southwest side of containers were as high as 45°C and could exceed 40°C for 4 to 5 hours. The high medium temperatures in exposed containers reduced the shoot relative growth rate and the specific rate of nitrogen uptake for Ilex crenata ‘Convexa’ in comparison to that of plants grown in containers insulated from solar radiation. Shoot dry weights of J. crenata ‘Helleri’ , Juniperus chinensis, Buxus microphylla, and Nandina domestica were at least 20% lower in exposed containers than in insulated containers. In a pine bark medium, growth response of J. crenata, J. horizontalis, or N. domestica to increased N application rate was similar when root-zones were at 40°C for 6 hrs/day or more optimal growth temperature. In unlimed pine bark, root-zone temperature of 40°C for 6 hrs/day resulted in higher medium solution pH and NH₄- N:NO₃-N ratio than at lower temperature. Limestone addition to the medium negated these effects and alleviated growth reductions due to high root-zone temperature for N. domestica and J. horizontalis. The higher medium solution pH associated with heated root-zones resulted in lower medium solution and shoot tissue Mn concentrations for I. crenata. A limed pine bark medium periodically fertilized with ammonium N was heated to temperatures of 28°, 34°, 40°, 46°, or 52°C for daily exposure duration of 1, 2, 4, 6, or 24 hours for 20 days. Treatment temperature of at least 40°C with a daily exposure duration of 24 hours resulted in an increase in medium solution NH₄-N concentration. Similar increase in NH₄-N was found for 2 hr/day exposure to 46°C, with further increases in NH₄-N at longer exposure times. The maximum level of NH₄- N occurred after 1 hr/day exposure to 52°C or 24 hr/day exposure to 46°C. Decreases in medium solution NO₃-N concentration generally coincided with the increases in NH₄- N. Results indicate that high container temperature may increase the ratio of NH₄- N:NO₃-N in the medium solution of plants fertilized with predominately ammoniacal N. / Ph. D.

Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / The influence of cultural practices can be modified by environmental conditions such as container-type or positioning. The objective of the study was to determine whether container-type and positioning would have an influence on the growth of tomato plants and suppression of Meloidogyne javanica exposed to biomuti (Trial 1) and Afrikelp (Trial 2). Different container-types were filled with approximately 10.4 L growing mixture comprising steam-pasteurised sandy loam soil and Hygromix-T at 3:1 (v/v) ratio. The containers were established in microplots at 0.6 m × 0.6 m spacing, with treatments being brown pot-below; brown pot-above, black pot-below, black pot-above, plastic bag-above and plastic bag-below. Tomato (Solanum lycopersicum L.) cv. 'Floradade' seedlings were each transplanted and irrigated with 500 ml chlorine-free tapwater every other day. Seven days after transplanting, each plant was inoculated with 2000 eggs and second-stage juveniles (J2) of M. javanica. Biomuti and Afrikelp, obtained from the Agricultural Research Council (ARC) Vegetable, Ornamentals and Plants (VOP), were applied in separate trials weekly at 2.5%. At 56 days after inoculation, plant growth including selected nutrient elements and nematode variables were measured. Data were subjected to analysis of variance, with separation of means achieved using Fisher’s Least Significant Difference test at the probability level of 5%. In the biomuti trial, container-type and positioning had a significant effect on plant height, fruit number, dry root mass, dry shoot mass and fruit mass, contributing 82, 48, 44, 85 and 89% in total treatment variation (TTV) of the respective variables. Relative to brown pot-below; black pot above, plastic bag-above and brown pot-above reduced plant variables, whereas treatment effects were not significant on nematode variables. In the Afrikelp trial, trends where similar to those in biomuti, treatments had highly significant effects on xvi plant height, dry root mass, dry shoot mass and gall rating, contributing 91, 88, 66 and 60% in TTV of the respective variables. Relative to brown pot-below; black pot above, plastic bag-above and brown pot-above reduced the plant variables, but had no significant effects on nematode variables. Generally, plastic bags and polyethylene pots below-ground improved most plant growth variables when compared to those in containers positioned above-ground.

As ornamental container nurseries face diminishing water allocations, many are looking to automated irrigation solutions to increase their water application efficiency. This thesis presents the findings of a study conducted at a commercial container nursery to determine 1) whether a capacitance or load cell sensor was better suited for monitoring volumetric water content in the substrate; 2) if the actual irrigation distribution conformed to the expected pattern, how uniform were the weights of plants, and how these combined with plant canopy affected the leaching fraction; and 3) the reliability of the wireless network used to transmit the data to a central database. It was found that 1) the load cells outperformed the capacitance-based sensors because the load cells took an integrated measure; 2) the actual irrigation pattern followed the expected pattern, the variation of irrigation sections were low (C.V. = 0.06) and similar (C.V. ranging from 0.029 to 0.12), and unpruned plant canopies produced greater leaching fraction than pruned canopies (P < 0.18); and 3) wireless network transmission reliability was low (75.2%), suggesting that the system was not suitable for real-time irrigation control, but was sufficient for calculating irrigation length and monitoring net effective irrigation application and evapotranspirative consumption. / Graduation date: 2012