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Quantifying the water use and water productivity of apple orchards under fixed and draped nets
Thesis (PhDAgric)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613760435257344 |
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| access_status_str | Open Access |
| author | Lulane, Edward Bongani |
| author2 | Midgley, Stephanie J. E. |
| author_browse | Lulane, Edward Bongani Midgley, Stephanie J. E. |
| author_facet | Midgley, Stephanie J. E. Lulane, Edward Bongani |
| author_sort | Lulane, Edward Bongani |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhDAgric)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131810 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:41:15.521Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131810 Quantifying the water use and water productivity of apple orchards under fixed and draped nets Lulane, Edward Bongani Midgley, Stephanie J. E. Volschenk, Theresa Dzikiti, Sebinasi Stellenbosch University. Faculty of AgriSciences. Dept. of Horticultural Science. Apples -- Breeding Apples -- Soils Orchards -- Management Apples -- Water requirements Plants -- Effect of water levels on Irrigation efficiency Mediterranean climate -- South Africa Plants -- Effect of shade on Apples -- Effect of temperature on UCTD Thesis (PhDAgric)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Apple (Malus domestica Borkh.) producers are increasingly using protective nets to address climate and fruit related challenges. There is insufficient quantitative information on the potential co-benefits of irrigation water savings in orchards under nets. This study firstly assessed the effects of two types of protective nets on microclimate variables. Secondly, the study aimed to establish if there are significant water savings and improvements in crop water productivity by using this technology. Lastly, the study investigated the effects of protective nets on apple tree physiology and water relations. White fixed net in the Koue Bokkeveld region (KBV) reduced daily total solar radiation by on average ~ 12%, wind speed by ~ 36%, and reference evapotranspiration by ~ 12%. Seasonal transpiration (T) was 11% lower under the net, while evapotranspiration (ET) was only 4% lower. The net reduced irrigation water requirement by about 4%. Peak mid-season basal crop coefficients (Kcb) were 0.54±0.02 and 0.59±0.02 with no differences in the single crop coefficients (Kc = 1.07±0.04 and 1.13±0.06) for the nets and control treatments, respectively. Transpiration based crop water productivity (WP) below the net was 20.7 kg m-3 compared to 18.2 kg m-3 in the open, with no differences in the ET-based WP values between the open and netted orchards. Black draped net tested in separate seasons in the KBV and Villiersdorp production regions reduced the daily total solar radiation by ~ 36% and ~ 31%, respectively. Wind speed was reduced by ~ 33% (KBV) and ~ 17% (Villiersdorp). Seasonal T was 8.5% and 8.3% lower under the net compared to the open in the two respective regions. Seasonal ET under the net declined by 7% in KBV and increased by 16% in Villiersdorp. Peak mid-season basal crop coefficients (Kcb) were 0.45±0.04 and 0.50±0.04 at KBV, and 0.74±0.18 and 0.77±0.19 at Villiersdorp for the draped net and control treatments, respectively. Transpiration-based crop water productivity (WP) was 25.5 kg m-3 under the net and 23.2 kg m-3 in the open at KBV, and 16.8 and 12.6 kg m-3 respectively, at Villiersdorp. The ET-based WP values were 19.3 and 14.8 kg m-3 for the net and control treatments, respectively, at KBV. At Villiersdorp, the values were 14.1 and 14.3 kg m-3 for the net and control treatments. Irrigation water productivity increased by 15% and 10.5% in the draped netted orchards in the two regions. Both pre-dawn and midday leaf water potential under the two net types were increased compared to the open. Net CO2 assimilation rate, transpiration rate and stomatal conductance were lower under the net, and the instantaneous leaf water use efficiency (WUEinst) was increased by the nets. Overall, the findings of the study show that the actual water saving benefits provided by fixed nets are smaller than expected possibly due to increased ET relating to a more active ground cover. However, a more substantial water saving benefit is possible in netted apple orchards if ET can be optimized through adapted management practices. AFRIKAANSE OPSOMMING: Appel (Malus domestica Borkh.) produsente gebruik toenemend beskermende nette om klimaat- en vrugteverwante uitdagings aan te spreek. Daar is onvoldoende kwantitatiewe inligting oor die potensiële byvoordele van besproeiingswaterbesparing in boorde onder nette. Hierdie studie het eerstens die uitwerking van twee tipes beskermende nette op mikroklimaatveranderlikes beoordeel. Tweedens was die studie daarop gemik om vas te stel of daar beduidende waterbesparings en verbeterings in gewaswaterproduktiwiteit is deur hierdie tegnologie te gebruik. Laastens het die studie die uitwerking van beskermende nette op appelboomfisiologie en waterverhoudings ondersoek. Wit vaste net in die Koue Bokkeveld-streek (KBV) het daaglikse totale sonbestraling met gemiddeld ~ 12% verminder, windspoed met ~ 36%, en verwysingsevapotranspirasie met ~ 12%. Seisoenale transpirasie (T) was 11% laer onder die net, terwyl evapotranspirasie (ET) slegs 4% laer was. Die net het besproeiingswaterbehoefte met sowat 4% verminder. Piek mid-seisoen basale gewaskoëffisiënte (Kcb) was 0.54±0.02 en 0.59±0.02 met geen verskille in die enkel gewaskoëffisiënte (Kc = 1.07±0.04 en 1.13±0.06) vir die nette en kontrole behandelings, onderskeidelik. Transpirasie gebaseerde gewaswaterproduktiwiteit (WP) onder die net was 20.7 kg m⁻³ vergeleke met 18.2 kg m⁻³ sonder net, met geen verskille in die ET-gebaseerde WP-waardes tussen die oop en bedekte boorde nie. Swart gedrapeerde net wat in afsonderlike seisoene in die KBV- en Villiersdorp- produksiestreke getoets is, het die daaglikse totale sonbestraling met onderskeidelik ~36% en ~31% verminder. Windspoed is verminder met ~ 33% (KBV) en ~ 17% (Villiersdorp). Seisoenale T was 8.5% en 8.3% laer onder die netto in vergelyking met die oop in die twee onderskeie streke. Seisoenale ET onder die net het met 7% in KBV gedaal en in Villiersdorp met 16% toegeneem. Piek mid-seisoen basale gewaskoëffisiënte (Kcb) was 0.45±0.04 en 0.50±0.04 in KBV, en 0.74±0.18 en 0.77±0.19 in Villiersdorp vir die gedrapeerde net en kontrole behandelings, onderskeidelik. Transpirasie-gebaseerde gewaswaterproduktiwiteit (WP) was 25.5 kg m⁻³ onder die net en 23.2 kg m⁻³ sonder net in KBV, en 16.8 en 12.6 kg m⁻³ onderskeidelik, in Villiersdorp. Die ET-gebaseerde WP waardes was 19.3 en 14.8 kg m⁻³ vir die net en kontrole behandelings, onderskeidelik, in KBV. In Villiersdorp was die waardes 14.1 en 14.3 kg m⁻³ vir die net- en kontrolebehandelings. Besproeiingswaterproduktiwiteit het met 15% en 10.5% in die gedrapeerde net boorde in die twee streke toegeneem. Beide voor sonsopkoms - en mid-dag blaarwaterpotensiaal is verhoog onder die twee nettipes in vergelyking met geen net. Netto CO2 assimilasietempo, transpirasietempo en stomatale geleiding was laer onder die net, en die oombliklike blaarwatergebruiksdoeltreffendheid (WUEinst) is deur die nette verhoog. Oor die algemeen toon die bevindinge van die studie dat die werklike waterbesparingsvoordele wat deur vaste nette verskaf word, kleiner is as wat verwag is, moontlik as gevolg van verhoogde ET wat verband hou met 'n meer aktiewe grondbedekking. 'n Meer aansienlike waterbesparingsvoordeel is egter moontlik in netbedekte appelboorde as ET geoptimaliseer kan word deur aangepaste bestuurspraktyke. Doctoral 2025-03-28T12:50:55Z 2025-03-28T12:50:55Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131810 Stellenbosch University xiii, (8) 229 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Apples -- Breeding Apples -- Soils Orchards -- Management Apples -- Water requirements Plants -- Effect of water levels on Irrigation efficiency Mediterranean climate -- South Africa Plants -- Effect of shade on Apples -- Effect of temperature on UCTD Lulane, Edward Bongani Quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| title | Quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| title_full | Quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| title_fullStr | Quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| title_full_unstemmed | Quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| title_short | Quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| title_sort | quantifying the water use and water productivity of apple orchards under fixed and draped nets |
| topic | Apples -- Breeding Apples -- Soils Orchards -- Management Apples -- Water requirements Plants -- Effect of water levels on Irrigation efficiency Mediterranean climate -- South Africa Plants -- Effect of shade on Apples -- Effect of temperature on UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131810 |
| work_keys_str_mv | AT lulaneedwardbongani quantifyingthewateruseandwaterproductivityofappleorchardsunderfixedanddrapednets |