Die moontlike rol van Oumansoutbos (Atriplex Nummularia Lindl.) as weigewas in hoë reënvalgebiede (Afrikaans)

Abstract

OMSB het gunstig op bemesting in die saailingfase, waar die groeimedium ‘n swak voedingstatus gehad het gereageer. ‘n Swak reaksie op bemesting na verplanting is verkry, waarskynlik omdat die voedingstatus van die grand waarin plante gevestig is, gunstig was. Die invloed van suurheidsgraad op OMSB, veral op saailinge, word moontlik oorskat. Aangesien die reaksie van OMSB op kaliumlnatriumsout-bemesting beperk was, is dit moontlik dat die gewas soute in plantweefsel stoor, en dus ‘n luukse voeder van elemente soos kalium en natrium is. Terrasorb verbeter die waterhouvermoë van gronde beduidend. Op swaar grande kan hierdie verhoging in waterhouvermoë egter ‘n negatiewe invloed op die groeikragtigheid van plante hê. Die effektiwiteit van Terrasorb hang grootliks van die voghuishouding af. Indien vog beperkend is, kan Terrasorb die groei van OMSB in beide ligte en swaarder gronde bevorder, terwyl dit die groei van OMSB in kleigrond kan inhibeer indien vog vrylik beskikbaar is. Gedurende die tydperk Oktober 1990 tot Februarie 1991, het OMSB plante in Pretoria gemiddeld 20g nat materiaal/dag en 6.8g droë materiaal (DM) per dag geproduseer. Dit is ongeveer nege ton nat materiaal/ha en drie ton DM/ha, oor ‘n periode van 150 dae. Die produksiepotensiaal en groeitempo van OMSB vergelyk besonder gunstig met die van ander weidingsgewasse. Die graad van terugsnoei voor verplanting, het binne redelike perke, nie ‘n beduidende negatiewe effek op saailingontwikkeling gehad nie. Vog was egter vrylik beskikbaar en onder meer stremmende toestande kan groei waarskynlik gestrem word. Die graad van ontblaring na verplanting het 'n beduidende invloed op die herstelvermoë van OMSB gehad. Verskille in groeitempo is tussen plante wat tot op verskillende hoogtes gesnoei is, gemeet. Die gemiddelde groeitempo van plante onderworpe aan die somer snoeibehandeling, was effens laer as dié van plante onderworpe aan 'n lente behandeling. Hierdie plante het egter 'n korter aktiewe groeiperiode as plante wat in die lente gesnoei is, gehad. 121 GVE (Grootvee eenheid) weidae/ha en 253 GVE weidae/ha is met onderskeidelik die matige en swaar benuttings verkry, wat aandui dat 'n relatief hoë weidingskapasiteit dus met OMSB verkry kan word. Die herstelvermoë van OMSB, soos gemeet in terme van DM opbrengs en met behulp van oppervlakte projeksies, was selfs na 'n totale benutting, relatief goed. Plante wat totaal benut was, was egter tot 'n baie groter mate aan afsterwing onderworpe. Hierdie tendense is met die herfs-, winter- en lente benutting gevind. OMSB is waarskynlik beter aangepas by matige benutting. Plante wat straf ontblaar word, is waarskynlik meer gevoelig vir stremming. OMSB kan meer as een maal per jaar effektief benut word, mits ontblaring nie oormatig is nie. Die weidingskapasiteit van die gewas kan moontlik met effektiewe bestuur aansienlik verhoog word. Diereprestasie mag ook, wanneer 'n matige weidruk toegepas word, as gevolg van die seleksie van 'n hoër kwaliteit dieet toeneem. ENGLISH: The aim of this study was to determine the value of Oldman Saltbush (OMS) as an alternative fodder in areas with a relatively high rainfall. Aspects that were studied were establishment. reaction to fertilization. production and reaction to utilization. OMS reacted positively to fertiliser in the seedling phase. where the growing medium had a poor nutrient status. a Poor reaction to fertilisation was obtained after transplanting. probably because of the favourable nutrient status of the particular soil. The influence of soil acidity. on OMS. particularly on seedlings. is probably overrated. As OMS showed a limited reaction to sodium/potassium fertilisation. it is argued that OMS stores salts in plant tissue and probably is a luxury feeder of elements such as potassium and sodium. Terrasorb improves the water holding capacity of soil significantly. On heavier soil this increase in water holding capacity could have a negative effect. The effectivity of Terrasorb depends greatly on the current moisture situation. Terrasorb could enhance growth in both light and heavy soil if moisture is a limiting factor. Where moisture is not limiting. growth in heavy soil could be inhibited. During the period October 1990 until February 1991. OMS plants in Pretoria produced 20g wet material and 6.8g dry material (OM) per day on average. This amounts to approximately nine tons of wet material/ha and three tons of DM/ha. in 150 days. The production of OMS compares favourably with that of other fodder crops. The degree of defoliation before transplanting did not. within limits. had a significant negative influence on seedling development. Moisture. however. was not a limiting factor and growth probably could be inhibited under stress. The degree of defoliation after transplanting, had a significant effect on the recovery of OMS. Differences in growth rate were found between plants defoliated to different heights. The mean growth rate of plants defoliated during summer, was somewhat lower as the growth rate found for plants defoliated during spring, probably because the recovery period was shorter. A total of 121 Large stock unit (LSU) grazing days/ha and 253 LSU grazing days/ha were obtained with the moderate and severe utilizations respectively, which shows that a relatively high grazing capacity can be obtained with OMS. The recovery potential of OMS as measured in terms of DM yield and with area projections was, even after severe utilization, relatively good. The survival rate of OMS was, however, significantly higher when plants were moderately utilized. This was found with autumn-, winter- and spring utilization. OMS is probably better adapted to moderate utilization. Plants that are severely utilized, are probably more susceptible to stress. OMS can be utilized effectively more than once a year, if defoliation is moderate. The grazing capacity of this crop could possibly be increased with effective management, while animal production might increase with the selection of a higher quality diet, when moderate grazing pressures are applied.