Istjalo sitlhoga ukuthola umtjhiso kanye namakhaza ukobana sikhule. Iinkhathi zomtjhiso namakhazezi zibizwa bona ma-heat units kanye nama-chill units.
Ama-Crop Heat Units Kwentjalo
I-Crop heat units (CHU) itlhadlhula umthelela olethwa mazinga womtjhiso ekukhuleni kwentjalo kanye nekuthuthukeni kwazo. Ukukhula kwentjalo kuya ngenani elipheleleko lomtjhiso iintjalo eziwutholako lokha nazitjaliweko, ekubizwa bona ma-degree. Amazinga aphasi womtjhiso enza bona isitjalo sikhule kabuthuka atjhisa khulu enze bona sikhule msinya.
ESewula Africa amazinga womtjhiso siwasebenzisa ngokuebenzisa i-10°C, esetjenziswa esphileni kanye nezinye iintjalo, amazinga womtjhiso la, mazinga womtjhiso angaphasi angabanga umonakalo eentjalweni, enze bona istjalo singarhoni ukukhula nanyana singakhiqizi amazinga womtjhiso ayahlukahluka hlangana nentjalo. Ukwenza isibonelo amazinga womtjhiso alungele ukungakhulisa kuhle ama-peas ekusitjalo esifuna amazinga womtjhiso apholileko ngayi-4°C, wesphila kube yi-10°C ekusitjalo sehlobo, kube yi-13°C wamalamula kanye newomoba abe yi-18ºC wama-date palms.
Ezinye izinto ezinomthelela ekukhuleni kwentjalo bubude belanga, ukuvunda kwehlabathi kanye namanzi asehlabathini. Ukuvuthwa kwestjalo kungabambezeleka (nange kunamanzi amanengi) nanyana amanzi amancani estjalweni.
Iintjalo, Iintjhabalalisi Kanye Namazinga Wokutjhisa
Iintjhabalalisi zentjalo zibangwa mtjhiso kanye nemiphumela womtjhiso. Njeke ukobana kutjhisa kangangani qobe lilanga kungasetjenziselwa ukufunisela kobana iinunwana zizoba ngangani kwenziwe amano wokuthola iprogamu yesimpreyi setjhabalalisi.
Ukwenza isibonelo amazinga womtjhiso abanga ubulwelwe bamalamula bamapiyeri, njalo njalo obubizwa bona yi-ecodling moth, bubakhona lokha amazinga womtjhiso ahlangana kwe-11ºC. Amazinga womtjhiso abanga ubulwelwe be-cotton bollworm kulokha amazinga womtjhiso ahlangana kwe-14ºC. Iinunwana zentjalo ezifana nama-peas,amabhontjisi, amabele, igadoni, isphila, amalamula, i-cucurbits, amazambani, itamati kanye ne-lurcene. Lokha ubulwelwe be-oriental fruit moth, busitjhabalalisi esikhulu samaperegisi esibakhona lokha amazinga womtjhiso ayi-7ºC.
Yini Ama-Chill Units?
Ama-chill unit kuvamise kobana abizwe bona ma-positive chill units’ (PCUs). Ama-PCUs akafani nama-heat unit. Kusetjenziswa iimbalo ukuhlola inani elipheleleko lama iri asetjenziswa ngaphasi kwamazinga athize ukwenza Isibonelo i-4°C. Enarheni ye-USA, amazing womtjhiso ayi-4.4°C kanye ne-7.2°C asetjenziswa njengamazinga amahle wokubona i-chilling hour.
Iintjalo zitlhoga amazinga womtjhiso apholileko ngamabanga ahlukeneko. Ezinye iinthelo ziyaphumula ekupheleni kwehlobo. Azisakhuli zize zithole izinga elithize lamakhaza ebusika. Ukwenza Isibonelo, amaperegii atlhoga amazing womtjhiso ahlangana kwe-2.5°C kanye ne-9°C ukobana ziphumule ziqede.
Nange zingatholi amakhaza aneleko, kungarholela emirarweni etwasahlobo, efana ngokobana iinhlumela zingavuleki msinya (amaperegisi – nokobana kuvunwe lada.) Nanyana azibi namathuthumbo eenhlumayeleni (ukwenza Isibonelo, ama-apula – athele iinthelo ezincani ezimbalwa njalonjalo.) Lokhu kubanga ukuphunguka komkhiqizo.
Eentjalweni ezinjalo ezifana namaperegisi kanye nama apula amakhemikhali kwesinye isikhathi asetjenziselwa ukwenza bona iinhlumela zivuleke lokha i-PCUs engakaneli ukuqiniseka kobana iinhlumela ziyavuleka.
Eenthelweni ezikhiqizwa eendaweni ubujamo bezulu obuya nge-PCUs bungasetjenziswa ukuhlola kobana iinhlumela zizokuvuleka nini, kanye nobungozi bokobana iinthelo ezithuthumbako zibanjwe lirhwaba kanye namalanga iinthelo ezizokuvunwa ngawo. Ingasetjenziselwa ukubambezela iskhathi sokuthuthumba kwentjalo, ukukhandela bona zingoniwa ambethe, nanyana ukuhlola bona inarha ekutjalwe kiyo iyafaneleka na kobana kungatjalwa kiyo iintjalo ezithize.
Amabele atlhoga ukutlhogonyelwa ngamakhaza ekubizwa bona yi-vernalization. Vernalization ekungilokha amazinga aphasi womtjhiso atlhogeka ukobana amathuthumba athome ukuthuthumba kanye nalokha nakukhiqizwa isphila.
Translated by Busisiwe Skhosana