Chapter 5
General conclusions and recommendations
Compost and residues from biogas plant as raw materials are good potting substrates for salt-tolerant plants (grass, rape and sunflower). Compost derived from garden wastes supplied abundant available N and K content while anaerobic digested residues originated from pig manure and maize offered rich available P and K for plants.
As negative results of leaching of compost, the yield and total nutrient uptake of salt-tolerant plants were decreased. Therefore the leaching of compost before using as a potting substrate is not recommended.
The influence of leaching of residues from biogas plant was not distinct. While yield formation of grass, rape and sunflower was not significantly influenced, the uptake of K, N and S was slightly reduced. Therefore leaching of residues from biogas plant is not recommended in term of nutrient uptake by salt-tolerant plants. To make a final decision further investigations are necessary.
Regarding the additives supplemented into the raw materials (20% by volume), the incorporation of additives such as Perlite, Hygromull, Lecaton, Peat, Cocofiber into compost materials had positive effects on yield formation and nutrient uptake of salt-tolerant plants, especially of younger plants at the first stage of cultivation. However, to give a specific suggestion of an additive to compost, further investigations are necessary.
Different from compost, the supplement of additives to residues from biogas plant resulted in an indistinct influence. Only Hygromull or Peat may be recommended as an additive to anaerobically digested residues because of their favor for plant growth and nutrient uptake.
Because of the high salt content, 100% compost is improper to grow salt-sensitive plants. Even less compost with the application rate of 80% or 50% by volume and combination with an additive (Hygromull or Cocofiber) resulted in a low yield formation and total nutrient uptake of Pelargonium and Salvia. The replacement of more than 50% compost by SPS is favorable for salt-sensitive plants and resulted in the highest yield and total nutrient uptake among compost mixtures. Consequently, compost-based substrates with more than 50% by volume are not recommended as potting substrates for salt-sensitive plants.
Chapter 5: General conclusions and recommendations T.C Van Do
Changes of the compost proportion (25%-14%) added into peat-based substrates remarkably increased yield formation and nutrient uptake of Pelargonium and Salvia as compared to the results of compost-based substrates and reached marketable values in term of ornamental production. Therefore, the incorporation of less than 25% volume of compost into Peat was recommended to create reasonable peat-based potting media for salt-sensitive plants like Pelargonium and Salvia.
The presence of typical artificial additives such as Hygromull, Cocofiber, Styromull or Perlite had insignificant effects on both plant growth and nutrient uptake, thus they were not recommended for the partial supplement into Peat and compost mixtures. However, in concerns of Peat substitution these additives might be suggested.
Regarding the results with antibiotics an uptake of Chlortetracyline and Sulfomethazine by cabbage could not be detected even with the highest application rate.
Appendices
1stHarvest_Comp & Comp-S 1stHarvest_BioR & BioR-S
2ndHarvest_Comp & Comp-S 2ndHarvest_BioR & BioR-S
TKS1 100%C-S Per Sty Hy Le Peat Coco
100%C Per Sty Hy Le Peat Coco
TKS1 100%C Per Sty Hy Le Peat Coco
100%C-S Per Sty Hy Le Peat Coco
TKS1 100%B-S Per Sty Hy Le Peat Coco
100%B Per Sty Hy Le Peat Coco
TKS1 100%B Per Sty Hy Le Peat Coco
100%B-S Per Sty Hy Le Peat Coco
3rd Harvest_Comp & Comp-S
4thHarvest_BioR & BioR-S
3rdHarvest_BioR & BioR-S
4thHarvest_Comp & Comp-S TKS1 100%C Per Sty Hy Le Peat Coco
100%C-S Per Sty Hy Le Peat Coco
TKS1 100%B Per Sty Hy Le Peat Coco
100%B-S Per Sty Hy Le Peat Coco
TKS1 100%B Per Sty Hy Le Peat Coco
100%B-S Per Sty Hy Le Peat Coco TKS1 100%C Per Sty Hy Le Peat Coco
100%C-S Per Sty Hy Le Peat Coco
Comp & Comp-S_after 51 days BioR & BioR-S_after 58 days
TKS1 100%C-S Per Sty Hy Le Peat Coco 100%C Per Sty Hy Le Peat Coco
TKS1 100%B-S Per Sty Hy Le Peat Coco 100%B Per Sty Hy Le Peat Coco
TKS1 100%C-S Per Sty Hy Le Peat Coco
Appendix 2. Rape planted in the substrates based on compost and residues from biogas plant before harvest
BioR & BioR-S_after 40 days Comp & Comp-S_after 40 days
TKS1 100%C Per Sty Hy Le Peat Coco
100%C-S Per Sty Hy Le Peat Coco TKS1 100%B Per Sty Hy Le Peat Coco 100%B-S Per Sty Hy Le Peat Coco
Appendix 3. Sunflower planted in the substrates based on compost and residues from biogas plant before harvest
2.5g sample suspended in 20mL of Citric acid extraction solution Ultrasound and centrifuged for 20 min at 2500xg (twice), supernatant collected OASIS HLB 200mg cartridge (preconditioned with 6 mL of methanol and 6 mL of milipore water)
Eluted with 6 mL methanol and condensed by rotovap (flow rate at 200 ± 35 mbar and 40oC) Liquid sample passed through cadtridge HPLC MS analysis
Appendix 4. Extraction procedure of antibiotics from plant material