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  • Author or Editor: Martin Makgose Maboko x
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Direct seeding or transplanting younger seedlings should reduce costs in hydroponic systems. A 2-year study (2011–12 and 2012–13) was conducted to determine yield of two hydroponically grown tomato cultivars using transplanted seedlings at different growth stages vs. direct seeding. An open bag, using 10-L plastic bags filled with sawdust, was used for direct seeding and transplanting of seedlings at two-, four- or six-leaf stages. Data were collected on early marketable, early total, total, total marketable and cull yield as well as plant fresh and dry mass. In 2011–12, there was increased early marketable and total yields from direct-seeded plants or plants transplanted at the two- or four-leaf stage. Cultivar FA593 produced a higher early marketable yield and total yield compared with ‘Linares’. In 2012–13, the highest early marketable and total yields were for plants developed from those transplanted at the two-leaf stage or from those developed from direct seeding. There was no difference between cultivars on marketable and total yield. Cultivar Linares produced the highest plant fresh and dry mass. Early yield can be induced by direct seeding or transplanting seedlings at the two-true leaf stage with no significant effect on total yield and marketable yield. Direct-seeded plants, or transplanting seedlings at the two-leaf stage, will benefit growers by producing tomatoes earlier for the market while eliminating or reducing transplant shock.

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A 2-year study (2012–13 and 2013–14) was conducted to evaluate the effect of plant growth regulator’s (PGRs) on plant growth, yield, and quality of hydroponically grown sweet peppers. In 2012–13, sweet pepper plants were subjected to two levels of gibberellic acid (GA3) (10 and 15 mg·L−1), two levels of naphthalene acetic acid (NAA) (15 and 30 mg·L−1), and four combinations of NAA and GA3 (10 mg·L−1 GA3 + 15 mg·L−1 NAA, 10 mg·L−1 GA3 + 30 mg·L−1 NAA, 15 mg·L−1 GA3 + 15 mg·L−1 NAA, and 15 mg·L−1 GA3 + 30 mg·L−1 NAA) applied to plants at flower initiation in a non-temperature-controlled tunnel. This PGR application was repeated 60 days after transplanting (DAT). In 2013–14, in addition to previously mentioned treatments, two levels of 4-chlorophenoxyacetic acid (4-CPA), at 30 and 45 mg·L−1, were applied at flower initiation followed by three additional applications of the latter treatments at 20-day intervals in a temperature-controlled tunnel. Marketable and total yield were markedly reduced by application of 4-CPA at 30 and 45 mg·L−1. Plant height was increased by application of GA3, and GA3 in combination with NAA, compared with application of 4-CPA, 30 mg·L−1 NAA, and the control. Results also showed that application of GA3 at 10 and 15 mg·L−1 or in combination with NAA increased plant fresh and dry mass as well; however, this had no beneficial effect on the yield of sweet pepper fruit. The application methods and concentrations of various PGRs needs further investigation under different growing conditions on sweet pepper cultivars.

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Mycorrhizal inoculation improves nutrient uptake in a range of host plants. Insufficient nutrient uptake by plants grown hydroponically is of major environmental and economic concern. Tomato seedlings, therefore, were treated with a mycorrhizal inoculant (Mycoroot™) at transplanting to potentially enhance nutrient uptake by the plant. Then seedlings were transferred to either a temperature-controlled (TC) or a non-temperature-controlled (NTC) tunnel and maintained using the recommended (100%) or a reduced (75% and 50%) nutrient concentration. Plants grown in the NTC tunnel had significantly poorer plant growth, lower fruit mineral concentration, and lower yield compared with fruit from plants in the TC tunnel. Leaves from plants in the NTC tunnel had higher microelement concentrations than those in the TC tunnel. Highest yields were obtained from plants fertigated with 75% of the recommended nutrient concentration, and not from the 100% nutrient concentration. Application of arbuscular mycorrhizal fungi (AMF) neither enhanced plant growth, nor yield, nor fruit mineral nutrient concentrations. However, temperature control positively affected the fruit Mn and Zn concentration in the TC tunnel following AMF application.

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Rapid leaching of soluble nitrogen (N) sources in soil poses a significant challenge in agricultural practices. Therefore, gaining a comprehensive understanding of crop responses to slow-release N application rates has become crucial to contributing valuable insights to optimize N management strategies in agriculture. A field study was conducted to investigate the influence of preplant calcium cyanamide fertilizer on the growth, yield, quality, and shelf life of short-day onion. Six levels of calcium cyanamide (CaCN2, 19.8% N), 0, 90, 120, 200, 400, and 600 kg⋅ha−1 CaCN2, which are equivalent to 0, 17.82, 23.76, 39.6, 79.2, and 118.8 kg⋅ha−1 N, respectively, replicated four times were broadcasted and incorporated into the top 5 to 10 cm of soil. Using 400 kg⋅ha−1 of CaCN2 yielded noteworthy improvements in various parameters of onion growth, such as plant height, leaf count, bulb weight per plant, bulb diameter, bulb length, and overall plant weight, as indicated by the study results. The application of different levels of CaCN2 as an N source exerted a significant influence on these growth factors. Moreover, the study revealed a direct correlation between CaCN2 application levels and the storage life of onions. Specifically, the findings demonstrated that the application of 400 kg⋅ha−1 CaCN2 resulted in enhanced yield and overall onion plant growth. However, the application of 600 kg⋅ha−1 CaCN2 increased the incidences of bulb weight loss, rots, and sprouting during the 8-week storage period at room temperature. These findings provide valuable insights for onion investors and farmers in the region and offer practical recommendations for optimizing fertilizer use and storage practices to improve onion production and minimize postharvest losses.

Open Access