Comparison of nutrient use efficiencies in citrus under different fertilization and irrigation management practices

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dc.contributor.advisorHardie-Pieters, Ailsa G.en_ZA
dc.contributor.advisorRaath, Pieter J.en_ZA
dc.contributor.authorParker, Imaanen_ZA
dc.contributor.otherStellenbosch University. Faculty of Agrisciences. Dept. of Soil Science.en_ZA
dc.date.accessioned2024-02-20T07:34:19Z
dc.date.accessioned2024-04-26T13:36:39Z
dc.date.available2024-02-20T07:34:19Z
dc.date.available2024-04-26T13:36:39Z
dc.date.issued2024-03
dc.descriptionThesis (MScAgric)--Stellenbosch University, 2024. en_ZA
dc.description.abstractENGLISH ABSTRACT: Excessive applications of nitrogen and phosphorus can lead to soil acidification, runoff, leaching and groundwater contamination. Additionally, the production of synthetic nitrogen fertilisers is an energy- intensive process, while phosphorus fertilisers are derived from non-renewable sources. This underscores the need for the citrus industry to adopt more sustainable management practices, with focus on improving nutrient use efficiency (NUE). Despite extensive research on the NUE of annual crops such as cereal grains and maize in South Africa, little research has been conducted on perennial crops such as citrus. Additionally, there is a need for NUE benchmarks that producers can use to compare their own NUE values with to. The main aim of this study was therefore to gain an understanding of the factors affecting nutrient use efficiency (NUE) of citrus, and to quantitively compare the NUE of different production systems currently used within the citrus industry. Various NUE indices were evaluated over two production seasons, in four of the main citrus production regions of South Africa. Within each region, three to four different irrigation-fertiliser production systems were selected, namely, conventional drip [1.6 L h-1] with fertigation (Drip), low-flow continuous drip [< 1 L h-1] with fertigation (LowFlow), micro-sprinkler irrigation with fertigation (MicroFert) and micro-sprinkler irrigation with granular fertiliser (MicroGran). There were significant differences between production systems in terms of partial factor productivity (PFP), partial nutrient balance (PNB) and internal utilization efficiency (IE). The MicroGran treatment consistently had higher PFP in both seasons of the study. Furthermore, the results showed that production systems (treatments) that applied excessive fertiliser rates or had low yields, exhibited significantly lower PFP and PNB values, this was seen in the LowFlow production systems (treatments) during both seasons. In the 2021/22 season the MicroGran treatment exhibited the highest average yield (62 ton ha-1), while in the 2022/23 season the MicroFert treatment obtained the highest average yield (81 ton ha-1). No significant differences were found between PFP and PNB values among the Drip, MicroFert and MicroGran production systems (treatments), when looking at the main effects of production systems (treatments). When yields between 50-80 ton ha-1 are obtained, producers can expect to achieve PFPN of 406- 424 kg kg-1, and PNBN values 0.68-0.76 kg kg-1, when using Drip, MicroFert and MicroGran production systems. Whereas for LowFlow production systems (treatments) can expect PFPN and PNBN values of 178 and 0.30 kg kg-1. Additionally, the study calculated indices that make use of data from a control plot which received no fertiliser. These indices include agronomic efficiency (AE), crop recovery efficiency (RE) and physiological efficiency (PE). These indices showed the crop response specifically to the fertiliser applied. Results highlighted the significance of interpreting leaf analysis and NUE along with soil analysis, as there were some significant correlations between soil properties and these factors. Soil analysis is especially important for interpreting PNB values. Furthermore, the study showed that NUE is not only dependent on the fertiliser applied but also influenced by mineralizable nutrients in the soil and the remobilization of nutrients stored within the plant biomass. To achieve optimal NUE, it is important to consider all these factors.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Oormatige toedienings van stikstof en fosfor kan lei tot grondversuring, afloop, loging en grondwaterbesoedeling. Die vervaardiging van sintetiese stikstofkunsmis is ʼn energie-intensiewe proses, terwyl fosforkunsmis van nie-hernubare bronne verkry word. Dit beklemtoon die behoefte vir die sitrusbedryf om meer volhoubare bestuurspraktyke aan te neem, met die fokus op die verbetering van voedingstof gebruiks effektiwiteit (VGE). Verskeie VGE-indekse is geëvalueer oor twee produksieseisoene, in vier van die belangrikste sitrusproduksiestreke van Suid-Afrika. Binne elke streek is drie tot vier verskillende besproeiing- kunsmisproduksiestelsels gekies, naamlik konvensionele drup [1.6 L h-1] met bemesting (Drup), laevloei aaneenlopende drup [< 1 L h-1] met bemesting (Laevloei) ), mikro-sprinkelbesproeiing met bemesting (MicroFert ) en mikro-sprinkelbesproeiing met korrelkunsmis (MicroGran). Daar was betekenisvolle verskille tussen produksiestelsels in terme van gedeeltelike faktorproduktiwiteit (GFP), gedeeltelike voedingstofbalans (GVB) en interne benuttingsdoeltreffendheid (ID). In beide seisoene van die studie het die MicroGran-behandeling ‘n hoër GFP gehad. Verder het die resultate getoon dat behandelings wat buitensporige kunsmishoeveelhede toegedien het, of lae opbrengs gehad het, aansienlik laer GFP en GVB waardes vertoon het. Dit word gesien in die lae vloei behandelings gedurende beide seisoene. In die 2021/22-seisoen het die MicroGran-behandeling die hoogste gemiddelde opbrengs (62 ton ha-1) getoon, terwyl die MicroFert- behandeling in die 2022/23-seisoen die hoogste gemiddelde opbrengs (81 ton ha-1) behaal het. Geen betekenisvolle verskille is gevind tussen GFP- en GVB-waardes tussen die Drup-, MicroFert- en MicroGran-behandelings deur aanlyding van die hoofeffekte van die behandelings nie. Wanneer opbrengste tussen 50-80 ton ha-1 is, kan produsente wie Drup-, Microfert-, en MicroGran- produksiestelsels gebruik verwag om ‘n PFPN van 406- 424 kg kg-1 te behaal, en PNBN-waardes van 0.68-0.76 kg kg-1. Laevloei-behandelings kan PFPN- en PNBN-waardes van 178 en 0.30 kg kg-1 verwag. Die studie het indekse bereken wat gebruik maak van data van 'n kontroleperseel wat geen kunsmis ontvang het nie. Hierdie indekse sluit in agronomiese doeltreffendheid (AD), gewas herwinningsdoeltreffendheid (HD) en fisiologiese doeltreffendheid (PD). Hierdie indekse het die gewasreaksie spesifiek op die toegediende kunsmis getoon. Resultate het die waarde van die interpretasie van blaaranalise en VGD saam met grondontleding beklemtoon, aangesien daar 'n paar beduidende korrelasies tussen grondeienskappe en hierdie faktore was. Grondontleding is veral belangrik vir die interpretasie van GVB-waardes. Verder het die studie getoon dat VGD nie net afhanklik is van die kunsmis wat toegedien word nie, maar ook beïnvloed word deur mineraliseerbare voedingstowwe in die grond en die hermobilisering van voedingstowwe wat in die plantbiomassa gestoor word. Dit is belangrik om al hierdie faktore in ag te neem om ʼn optimale NUE te bereik.af_ZA
dc.description.versionMastersen_ZA
dc.format.extent110 pages : graphs (color)en_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130328
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshCitrus -- Breedingen_ZA
dc.subject.lcshNitrogen fertilizersen_ZA
dc.subject.lcshPhosphatesen_ZA
dc.subject.lcshFruit trees -- Nutrition -- South Africaen_ZA
dc.subject.lcshFruit trees -- Irrigationen_ZA
dc.subject.lcshNitrogen in agricultureen_ZA
dc.subject.lcshSoils and nutrition -- Managementen_ZA
dc.subject.lcshSoil fertility -- South Africaen_ZA
dc.subject.nameUCTDen_ZA
dc.titleComparison of nutrient use efficiencies in citrus under different fertilization and irrigation management practicesen_ZA
dc.typeThesisen_ZA
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