Winter rotational cover crops effects on soil strength, aggregate stability and water conservation of a hardsetting cambisol in Eastern Cape Province, South Africa
- Authors: Mupambwa, Hupenyu Allan
- Date: 2012
- Subjects: Cover crops -- South Africa -- Eastern Cape , Soil mechanics , Crop rotation , Crops and soils , Soil penetration test
- Language: English
- Type: Thesis , Masters , MSc Agric (Crop Science)
- Identifier: vital:11868 , http://hdl.handle.net/10353/453 , Cover crops -- South Africa -- Eastern Cape , Soil mechanics , Crop rotation , Crops and soils , Soil penetration test
- Description: Winter rotational cover crops (WRCC) are often used to boost soil fertility and plant nutrition. However, selection and use of WRCC for soil physical improvement is usually overlooked. The objective of this study was to determine the effects of WRCC on soil strength, aggregate stability and water conservation of a hardsetting soil. The soil physical properties were determined after four rotations of growing monocultures of vetch (Vicia dasycarpa cv. Max), lupin (Lupinus angustifolius cv. Tanjil) and oats (Avena sativa cv. Sederberg) and after two rotations of growing bicultures of oats (Avena sativa cv. Pallinup) and vetch (Vicia dasycarpa cv. Max) across two soil layers, 0 to 15 cm and 15 to 30 cm. The individual WRCC and a weedy fallow constituted the treatments in the monoculture study whilst in the biculture study the various combinations of WRCC namely; 90% oat plus 10% vetch (O90V10); 70% oat plus 30% vetch (O70V30) and 50% oat plus 50% vetch (O50V50) and a weedy fallow constituted the treatments. After four rotations with cover crop monocultures, oats significantly (P ≤ 0.05) reduced penetration resistance (PR) whilst vetch increased PR in both soil layers compared to the weedy fallow control. The effect of the biculture treatments was only experienced within the 15 to 30 cm depth. The treatments O50V50 and O70V30 increased the PR compared to the control. The WRCC in monoculture significantly increased the soil aggregate stability relative to the control in both soil layers. Vetch, lupin and oats resulted in a 41.7%; 20.4% and 15.7% increase in MWD in the 0 to 15 cm soil layer and 47.2%; 44.2% and 39.7% in the 15 to 30 cm depth, respectively. An increase in aggregate stability was associated with increased macro-aggregation. Under the biculture, WRCC slightly increased, non- significantly, the aggregate stability. Both hot water and dilute acid extractable polysaccharides showed no significant correlation with aggregate stability in the two studies. Oats monoculture resulted in a significant difference (P ≤ 0.05) on cumulative infiltration compared to the control. However, after 2 h vetch and lupin showed no significant difference from the control on cumulative infiltration. Oats resulted in a 7.8% increase in final infiltration rate (FIR) whilst vetch and lupin reduced FIR by 9% and 16.7% respectively, compared to the control. Bicultures of oats and vetch significantly (P ≤ 0.05) increased cumulative infiltration compared to the weedy fallow control. A similar significant increase in FIR was also observed under bicultures. The treatments O50V50; O90V10 and O70V30 resulted in a 163.3%; 113.3% and 105.4% increase in FIR respectively, compared to the control. Cover crop monocultures significantly (P ≤ 0.05) increased plant available water (PAW) compared to the weedy fallow, with vetch, oats and lupin resulting in a 28.3%; 22% and 23.9% increase respectively, in PAW. However, no significant differences were observed on PAW after two rotations with bicultures. Compared with winter weedy fallow, WRCC improved most of the soil physical properties under study, with the most suitable results expected under bicultures compared to monocultures. Under CA, selection of WRCC like oats, vetch and lupin, one should therefore take into consideration their effects on soil physical properties as a selection criterion and not biomass and fertility alone.
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- Date Issued: 2012
'n Besluitnemings ondersteuningsmodel vir die bepaling van die mees geskikte wisselboustelsel-ritme vir gemengde graanboerderye in die Koeberg
- Authors: Potgieter, F J
- Date: 2001
- Subjects: Grain -- South Africa , Crop rotation
- Language: Afrikaans
- Type: Thesis , Masters , MTech
- Identifier: vital:10948 , http://hdl.handle.net/10948/43 , Grain -- South Africa , Crop rotation
- Description: Weens die unieke eiesoortigheid van die mens is sy behoeftes vanselfsprekend uiters divers. Wat vir die een persoon prioriteit is, mag vir sy buurman geensins belangrik wees nie. Dit is egter ook ’n gegewe, dat die mens heelwat gemeenskaplike ervarings, emosies en behoeftes deel. Een hiervan is die behoefte wat hy het om te weet dat die besluit wat hy gaan of wil neem die regte een binne die konteks van sy keuse mag wees. Die woord ‘behoefte’ kan waarskynlik in hierdie geval vervang word met die begrip ‘genade’. Sonder om 'n platvorm vir debat te skep, word die stelling gehandhaaf dat ‘genade’ slegs van die Skepper afkomstig is. Met hierdie stelling as agtergrond was dit 'n minder aangename ervaring om vir feitlik twintig jaar te moes toekyk hoe koringboere hul besluite, veral met betrekking tot die samestelling van wisselboustelsels, moes neem, klaarblyklik in totale gebrek aan die gawe van ‘genade’. Nodeloos om te sê, met gepaardgaande negatiewe gevolge. Die meer gemaklike verontskuldiging is om te redeneer dat ons Skepper relatief suinig is met die uitdeel van sy ‘genade’. Alvorens die begrip van Prediker 10:10 nog nie ten volle begryp is nie, kan so 'n stelling dalk makliker gemaak word. Hierdie gedeelte uit die Skrif sê in werklikheid die teenoorgestelde – dat God baie vrygewig is met Sy ‘genade’, maar dat die mens sy gesonde verstand moet gebruik om dit ten volle te benut. Die wens is dat hierdie studie, 'n deel sal uitmaak van die proses om die byl skerp te maak om sodoende die houtkap-proses effektief uit te voer.
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- Date Issued: 2001