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Firstfruits

Category: Articles

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 Aug 2024
Orange on soil
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Nutrient management zones for citrus based on variation in soil properties and tree performance

Site-specific soil management can improve profitability and environmental protection of citrus groves having large spatial variation in soil and tree characteristics. The objectives of this study were to identify soil factors causing tree performance decline in a variable citrus grove, and to develop soil-specific management zones based on easily measured soil/tree parameters for variable rate applications of appropriate soil amendments. Selected soil properties at six profile depths (0–1.5 m), water table depth, ground conductivity, leaf chlorophyll index, leaf nutrients and normalized difference vegetation index were compared at 50 control points in a highly variable 45-ha citrus grove.

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25 Aug 2024
Managing Salinity in Citrus
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Salinity resistance of citrus seedlings in relation to hydraulic conductance, plasma membrane ATPase and anatomy of the roots

The evaluation of the response of three rootstocks to conditions of high salinity (NaCl 90 mmollL) and the relationship with different parameters was the objective of this study. The three rootstocks were Cleopatra Mandarin, considered to be tolerant to salinity, Citrange Carrizo and Citrus Macrophylla, considered to be sensitive to salinity. We related the differences in salinity resistance to water and nutrient uptake, ATPase and anatomy of roots. For this, root hydraulic conductivity, ion concentrations in the xylem obtained under transpiration flow, root plasma membrane ATPase activity and anatomy of the root tips were determined in seedlings grown in a controlled environment.

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25 Jul 2024
Pre-blossom sprays
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Yield benefits associated with pre-blossom low biuret urea sprays on Citrus spp

This study evaluated the potential yield benefits of pre-blossom urea sprays on various Citrus spp. and to ascertain whether these yield benefits are as a result of altering the blossom composition or of supplying readily utilizable N during the critical flowering/fruit set period. Pre-blossom low-biuret urea sprays, 6–8 weeks before anthesis, at 1% concentration, one or two sprays 10–14 d apart, have resulted in significant (P<0.05) yield benefits in certain orchards. Experiments were conducted over a period of 2–4 years. Cultivars evaluated included ‘Shamouti’ oranges, ‘Ellendale’ tangor and ‘Minneola’ tángelo.

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25 Jul 2024
Preventing postharvest fungal rotting
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Non-chemical treatments for preventing the postharvest fungal rotting of citrus caused by Penicillium digitatum and Penicillium italicum

Citrus is one of the most economically important horticultural crops in the world. Citrus are vulnerable to the postharvest decay caused by Penicillium digitatum and P. italicum, which are both wound pathogens. To date, several non-chemical postharvest treatments have been investigated for the control of both pathogens, trying to provide an alternative solution to the synthetic fungicides (imazalil, thiabendazole, pyrimethanil, and fludioxonil), which are mainly employed and may have harmful effects on human health and environment. Scope and approach: The current study emphasizes the non-chemical postharvest treatments, such as irradiations, biocontrol agents, natural compounds, hot water treatment (HWT), and salts, on the prevention of decay caused by P. digitatum and P. italicum, also known as green and blue molds, respectively. The mode of action of each technique is presented and comprehensively discussed.

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25 Jul 2024
Citrus Rot
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Effect of storage temperature on rind pitting and fruit rot in Satsuma ‘Okitsu’

Rind disorders on satsuma mandarin have caused serious crop losses in Uruguay. The causes of these disorders are not well understood and their incidence is erratic, showing high variability from year to year and among orchards. Satsuma fruit suffers chilling injury during cold storage, and rind pitting is a common symptom. The objective of this study was to analyze fruit response to different storage temperatures evaluating pitting development and the incidence of different drench treatments on fruit rot and pitting development. Satsuma ‘Okitsu’ fruits were harvested from two different farms, one with high pitting history (Q102) and the other with low pitting history (Q100).

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25 Jun 2024
Citrus Fruit Drop
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PGR For Controlling Pre-Harvest Fruit Drop And Improving Quality of Kinnow

A field trial was conducted to evaluate the effect of PGR (2, 4-D, NAA and GA3) at different concentrations on fruit drop and enhancement in fruit quality of Kinnow. Three sprays of PGR viz. 2, 4-D, NAA and GA3 were given to the Kinnow plants as per the treatment concentrations from initiation of flowering to before harvesting. The results revealed that among all the PGR’s tried at different concentrations, spray of 2, 4-D @ 30 ppm was the most promising in reducing the fruit drop in Kinnow as fruit physical and chemical characters were found to be superior as compared to all other treatments. There was an enhancement in the fruit size with the application of 2, 4-D @ 30 ppm, which led to an overall increase in the yield of Kinnow.

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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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