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Firstfruits

Tag: Citrus

25 Aug 2024
Leaf Analysis
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Evaluation of the usefulness of early leaf analysis to improve nutrition management of citrus

The response of Citrus sinensis ‘Midknight’ (Nelspruit, Mpumalanga, South Africa) and Citrus paradisi ‘Orri’ (De Wet, Western Cape, South Africa) to excessive fertilisation (double the normal rate) with nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg) was investigated. The goal was to determine whether early-season leaf mineral compositions respond to fertilisation rates so that in-season adjustments of the fertilisation programme can be made.

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25 Jun 2024
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Short-term effects of cover crops on soil properties and the abundance of N-cycling genes in citrus agroecosystems

Limited information is available on the influence of cover crops (CCs) on soil nutrient cycling and the abundance of bacterial and archaeal communities, nitrogen (N)-fixers, nitrifiers, and denitrifiers in tree crops. We examined the effect of replacing the traditional weedy inter-row middle of a commercial citrus orchard in Florida with two different mixtures of CCs: legumes and non-legumes (LG + NL) and non-legumes only (NL). A no-treatment/grower standard was used as a control (GSC). After one year of CCs, the use of NL and LG + NL CCs significantly increased soil carbon (C) availability in the row middles compared to GSC as shown by increases in permanganate oxidizable C, and to a lesser extent, soil organic matter. Treatment with LG + NL significantly increased soil ammonium content compared to the NL and GSC treatments. Improved C cycling in soils treated with CCs was related to increased abundance of bacteria and archaea. Changes in the size of the soil N pool were accompanied by increases in the abundance of N-fixation (nifH) and nitrification (amoA) genes in soils treated with LG + NL, likely due to greater N-mineralization and N-fixation by legumes.

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24 May 2024
Citrus flower
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Demonstration of a Change in Nitrogen Metabolism Influencing Flower Initiation in Citrus

Changes in the leaf NH3-NH4 + content were monitored during floral induction in Citrus. Five-year-old rooted cuttings of ‘Washington’ navel orange (Citrus sinensis) were induced to flower by subjecting the trees to 8 weeks of low temperature, 8-h day (500 μE m−2 s−1) at 15–18°C/16-h night at 10–13°C and by transferring them afterwards to 12-h day (500 μE m−2 s−1) at 24°C/12-h night at 19°C. Maximum bloom occurred 4 weeks after the transfer to the warmer temperature. The number of flowers and the NH3–NH4 + content of leaves increased significantly (p < 0.05 and P < 0.01, respectively) with the length of the low temperature treatment. Sixteen-year-old ‘Frost Lisbon’ lemon trees (Citrus limon) on ‘Troyer’ citrange rootstocks (C. sinensis × Poncirus trifoliata) under commercial production were subjected to water-deficit stress of increasing severity.

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25 Jan 2024
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A Cost-Benefit Analysis for Crop Load

Generating profits in difficult conditions is one of the key drivers for sustainability in agriculture.

In recent years, some citrus producers have struggled to realise good returns as the industry faced a plethora of challenges. These challenges include, but are not limited to the cost of fertiliser, chemical, and fuel that rose rapidly because of the invasion of Ukraine, record freight rates and a decline in market prices.

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24 Jul 2023
Clemgold
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ClemenGold International shares its citrus

Around 1,000 tonnes of citrus is to be distributed to disadvantaged communities this year Leading South African citrus company ClemenGold International has said that it is teaming up with a relief organisation to deliver some 1,000 tonnes of citrus to help alleviate the plight of people in some of the country’s poorer communities. “Caring for the communities surrounding our partner farms and packhouses has been a value upon which we’ve acted since the establishment of our business,” explained Adéle Ackermann, marketing manager for ClemenGold International.

“Fruit is our business and donating Vitamin C-rich citrus is a logical way of contributing towards helping communities to thrive.” The company has announced a partnership with SA Harvest, a registered non-profit and leading food rescue and hunger relief organisation, whereby 1,000 tonnes of citrus will be donated during the 2023 season.

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24 Jul 2023
Orange Tree
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Winter storms affect Cape growers

With the latest of a series of winter storms sweeping over the South African Western Cape region, citrus and other fruit growers are facing a difficult period of recovery. For the last ten days all citrus harvesting in the Oliphant’s River Valley, the most important region supplying summer citrus to the US, has been suspended. Infrastructure in the Valley and in other parts of the Western Cape has been damaged, with key roads washed away and communities in rural regions flooded.

The winter storms in these regions have been described as the worst since 2008 when floods rose to record levels in places. It comes when significant volumes of South African citrus are due to be discharged in the US later this week, marking the real start of the marketing season. Significant volumes have also been shipped by containers since April. Industry leaders said that before the storms started enough fruit had been packed for the first three vessels, but that their departure could be delayed.

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24 Jul 2023
Brown Rot
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Postharvest Strategies for Managing Phytophthora Brown Rot of Citrus using Potassium Phosphite in Combination with Heat Treatments

Phytophthora brown rot, caused by several species of Phytophthora, is an economically important disease of citrus in areas with rainfall during the late stages of fruit development. Recent export restrictions of California orange fruit to China due to the presence of brown rot caused by the quarantine pathogen Phytophthora syringae have mandated more rigorous disease management. We evaluated postharvest applications with the phosphonate fungicide potassium phosphite in combination with heat treatments. In timing studies, potassium phosphite at 1,500 mg/ml was most effective when applied within 18 h after inoculation of orange fruit with P. citrophthora, reducing the incidence of decay by >96% as compared with the control. Potassium phosphite was also highly effective in inoculations with P. syringae. Heated water treatments at 60°C were consistently and highly effective in reducing the incidence of brown rot after inoculation with P. citrophthora, whereas treatments at 55 or 50°C were more variable and generally less effective.

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