Browsing by Author "Mahadeo, Leeshan"

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    Understanding the system and supply chain effects of two residue management treatments in pine and eucalyptus plantations
    (Stellenbosch : Stellenbosch University, 2022-03) Mahadeo, Leeshan; Talbot, Bruce; Ackerman, Simon; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: There is an increased interest in understanding the effect of different residue management practices on forestry in South Africa. In addition to clearly established environmental benefits of residue mulching, as opposed to burning residues in-situ, as mulching or mastication offers the alternative of comminuting these residues almost immediately after harvesting. The aim of this study was to investigate the cost of mulching and determine whether this cost is justified through potential savings from increased pitting and planting productivity in the forestry value chain. Relevant data was collected from sites in Zululand and Bulwer in KwaZulu-Natal and Jessievale on the Mpumalanga Highveld. The study was limited to Eucalyptus grandis x urophylla pulpwood and Pinus patula pulpwood and sawtimber regimes. The study included estimating residual biomass and remaining stump volumes using a Zigzag and Line-Intercept methods respectively. Time studies quantified time consumption and the productivities of the various mulching machines, mechanised pitters, semi-mechanised planters, manual pitters, and manual planters, between treatments. An attempt to classify mulch quality was investigated. The costs of each operation per residue treatment were calculated to determine cost effectiveness. Initial plant growth response to mulched and burnt residues were evaluated. Mulching results for pulpwood residues showed no significant difference between Eucalyptus sites (0.35 ha) and pine sites (0.36 ha PMH-1) and were also not affected by residual biomass volume. Significant differences were found in Eucalyptus mechanised pitting productivity between mulched (0.26 ha PMH-1) and burnt (0.25 ha PMH-1) treatments. Mechanised pitting on sawtimber pine stands differed significantly with a 24% increase in productivity after mulching. Productivities of 0.57 ha PMH-1 and 0.46 ha PMH-1 on mulched and burnt pine sawtimber residues respectively were seen. Manual pitting was more productive for burnt sites (0.06 ha PPH-1) than mulched sites (0.05 ha PMH-1). Semi-mechanised planting was 27% faster on mulched sites (1.70 ha·PMH-1) than on burnt sites (1.33 ha PMH-1). Manual pine planting after mulching was 33% faster compared to planting on burnt sites. This resulted in a manual planting productivity on mulched sites of 0.08 ha PPTH-1 being greater than on sites where residues were burnt (0.06 ha PPTH-1). In both pine and eucalypts, increases in productivities in mechanised pitting, semi-mechanised planting, and manual planting (except manual pitting) after mulching were evident. The total cost of mulching was approximately R 5 450 ha-1 for eucalyptus sites and R 6 170 ha-1 in pine pulpwood sites. The increase in pitting and planting productivity after mulching approximately offsets the mulching cost by R 220 ha-1 on eucalyptus and R 290 ha-1 in pine pulpwood. These saving in increase productivity after mulching are however not enough to justify the expense of mulching generally. When considering mulching foresters should holistic approach the undertaking by considering the biological advantages of mulching in general including soil nutrients benefit as well as long term growth and yield gains, in addition to the increase in productivity of pitting and planting after mulching.