24 Aug 2021

The influence of nitrogen concentration and ammonium/nitrate ratio on N-uptake, mineral composition and yield of citrus

In  short-term   water  culture  experiments  with  different  15N  labeled  ammonium  or  nitrate  concen trations,  citrus seedlings absorbed  NH; at  a higher  rate  than  No;. Maximum NO; uptake  by the whole plant  occurred  at 120 mg L – 1  NO;-N, whereas NH; absorption  was saturated  at 240 mg L –  1 NH;-N. 15NH; accumulated in roots and to a lesser degree in both leaves and stems. However,  15NO; was mostly partitioned  between leaves and roots.

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24 Aug 2021

Relationship between chloride and nitrate and its effect on growth and mineral composition of avocado and citrus plants

Two rootstocks of avocado (Persea americana Mill.), the salt-tolerant ‘Degania-113’ and the salt-sensitive ‘Smith’, and two rootstocks of citrus, the salt-tolerant ‘Cleopatra’ mandarin (Citrus reshni Hort. ex Tan) and the salt-sensitive ‘Troyer’ citrange (Poncirus trifoliata x Citrus sinensis [L.] Osbeck), were grown in a sandy soil and irrigated daily with nutrient solutions containing various chloride concentrations. Increasing the concentration of chloride resulted in elevated chloride levels in all avocado plant parts, and toxic symptoms that were more pronounced in the ‘Smith’ than in the ‘Degania-113’ avocado rootstock. When leaves of both rootstocks had accumulated similar chloride levels and showed scorching damage, the leaves of ‘Degania-113’ abscised, while those of ‘Smith’ did not. High chloride reduced the total dry matter yield of the root more than that of the shoot, decreasing the “root: shoot” dry weight ratio in both rootstocks. Addition of nitrate to the irrigation water reduced chloride accumulation in the plant and alleviated its adverse effects. Accumulation of nitrogen in the plant exceeded that of chloride in all cases.

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24 Aug 2021
Soil

A Review of the Use of the Basic Cation Saturation Ratio and the “Ideal” Soil

The use of “balanced” Ca, Mg, and K ratios, as prescribed by the basic cation saturation ratio (BCSR) concept, is still used by some private soil-testing laboratories for the interpretation of soil analytical data. This review examines the suitability of the BCSR concept as a method for the interpretation of soil analytical data. According to the BCSR concept, maximum plant growth will be achieved only when the soil’s exchangeable Ca, Mg, and K concentrations are approximately 65% Ca, 10% Mg, and 5% K (termed the ideal soil). This “ideal soil” was originally proposed by Firman Bear and coworkers in New Jersey during the 1940s as a method of reducing luxury K uptake by alfalfa (Medicago sativa L.).

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24 Aug 2021
Horticultural planning

Horticultural practices

Grove management starts with planning of the planting site, and by comprehending every operation until harvesting time in order to achieve the best marketable fruit yield and quality. It includes horticultural practices such as grove establishment, irrigation, nutrition, canopy management, and grove protection. Importantly, fruit quality starts in the grove. In this chapter we are focusing on grove planning with special focus on tree spacing, canopy management, and tree size control, and crop load management from a horticultural point of view.

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22 Jul 2021

Signing of South Africa-Chinese lemon protocol will attract R325 million in new export revenue

The Citrus Growers’ Association of South Africa welcomes the recent signing of a revised citrus protocol between South Africa and China by Minister of Agriculture, Land Affairs and Rural Development Thoko Didiza.

With local lemon production expected to grow by 175 000 metric tons by 2024, the finalisation of the revised protocol means China will now become a critical new market for this growth and will secure R325 million in new export revenue and secure 800 jobs in the industry.

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19 Jul 2021

Citrus industry rolls out recovery plan

The citrus industry is rolling out a recovery plan to continue exports.

In a statement, Justin Chadwick, CEO of the The Citrus Grower Association of Southern Africa (CGA), said that while the citrus value chain has been impacted by the closure of the Durban port, the industry has and will continue to ensure that citrus is exported to key markets.

Growers in the northern provinces of Limpopo and Mpumalanga have been diverting their fruit to other ports across the country, with citrus from other regions continuing to be exported from Cape Town and Coega ports.

“Last week saw little impact on volumes of citrus being exported to markets including the European Union, Middle East, China and the United States.

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01 Jul 2021
Olifants River

Cold in the Cape boosts citrus colour development

In the Western Cape where citrus producers are packing late navels, soft citrus like Fairchild and Valley Gold, with a bit of lemons, harvesting has ceased as the southwestern part of the province experiences a winter as it’s supposed to be: icy and very wet.

Citrusdal has recorded 35mm over the past 24 hours, while it has been raining more or less continuously since the end of last week (right: Citrusdal orchard after recent rains).

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01 Jul 2021
Citrus Seedlings

Effects of Low pH on Photosynthesis, Related Physiological Parameters, and Nutrient Profiles of Citrus

Seedlings of “Xuegan” (Citrus sinensis) and “Sour pummelo” (Citrus grandis) were irrigated daily with a nutrient solution at a pH of 2.5, 3, 4, 5, or 6 for 9 months. Thereafter, the following responses were investigated: seedling growth; root, stem, and leaf concentrations of nutrient elements; leaf gas exchange, pigment concentration, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and chlorophyll a fluorescence; relative water content, total soluble protein level, H2O2 production and electrolyte leakage in roots and leaves.

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01 Jul 2021

Citrus Fertilizer Management on Calcareous Soils

Soils in the south Florida flatwoods are underlain by calcium carbonate (CaCO3) that has accumulated through marine deposition over thousands of years. In most flatwoods, the CaCO3 lies below the profile and the overlying surface soil is usually acidic. However, CaCO3 also can occur at the surface, either naturally or as a result of earth-moving operations that have mixed the soil. The resultant soil is called calcareous. Soils also can become calcareous through long-term irrigation with water from the Floridan aquifer. This water contains small amounts of dissolved CaCO3 that can accumulate with time.

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29 Jun 2021

Citrus exports to Philippines may reach R205 million

The new Philippine market potentially offers the opportunity for South African producers to export 20 000 tons of citrus fruit a year. After twelve years of negotiations between South Africa and Philippines the landmark export plan was at the end of last year. The South African citrus industry is expected to grow with approximately 500 000 tons over the next few years. Thus, expanding to new markets is of upmost importance to ensure that an oversupply does not occur in existing markets. The area used for soft citrus production is expected to grow with approximately 29 %, of which 42 % of the growth is expected to be mandarins.

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