Production of Biomass Crops Using Biowastes on Low-Fertility Soil: 2. Effect of Biowastes on Nitrogen Transformation Processes

Value-added products from wastewater reduce irrigation needs of Arundo donax energy crop

Irrigation restrictions due to drought periods related to climate change, would affect different crops, especially to non-food crops. In this regard the effect of irrigation reduction should be studied in energy crops in order to obtain a sustainable bioenergy cropping system. Arundo donax, has been considered a crop with high water requirements, it has nevertheless been proven to be drought tolerant. However, there is a lack of knowledge on the effect of reduced irrigation combined with the use of different fertilizers. This work studied the combined effect of value-added products (VAPs) from wastewater (treated sewage sludge) or traditional inorganic fertilizers, and irrigation reduction in Arundo donax crop in a 2-year pot experiment. Plant biometric characteristics, chemical properties and biomass yield were studied as well as the effect of treatment on soil properties. Results showed that under reduced irrigation conditions, biomass production was reduced, especially during the second year. Organic treatments from sewage sludge minimize the effect of irrigation reduction. In these treatments, biomass yield for reduced irrigation was similar to that of the control treatment with irrigation at field capacity. For this reason, it is recommended to use VAPs from wastewater as organic amendments enabling water restriction with lower effect on Arundo production.

Chemical Elements and the Quality of Mānuka (Leptospermum scoparium) Honey

Soil properties in the foraging range of honeybees influence honey composition. We aimed to determine relationships between the antimicrobial properties of New Zealand mānuka (Leptospermum scoparium) honey and elemental concentrations in the honey, plants, and soils. We analyzed soils, plants, and fresh mānuka honey samples from the Wairarapa region of New Zealand for the chemical elements and the antimicrobial activity of the honey as indicated by methylglyoxal (MGO) and dihydroxyacetone (DHA). There were significant negative correlations between honey MGO and the concentrations of Mn, Cu, Mg, S, Na, Ba, K, Zn, and Al. These elements may provide a low-cost means of assessing mānuka honey quality. For individual elements, except for K, there were no correlations between the honeys, plants, and soils. Soil nitrate concentrations were negatively correlated with concentrations of MGO and DHA in the honey, which implies that soil fertility may be a determiner of mānuka honey quality.

Energy Properties and Biomass Yield of Miscanthus x Giganteus Fertilized by Municipal Sewage Sludge

The application of municipal sewage sludge as fertilizer in the production of non-food energy crops is an environmentally and economically sustainable approach to sewage sludge management. In addition, the application of municipal sewage sludge to energy crops such as Miscanthus x giganteus is an alternative form of recycling nutrients and organic material from waste. Municipal sewage sludge is a potential source of heavy metals in the soil, some of which can be removed by growing energy crops that are also remediation agents. Therefore, the objective of the research was to investigate the effect of municipal sewage sludge applied at three different rates of 1.66, 3.22 and 6.44 t/ha on the production of Miscanthus. Based on the analyses conducted on the biomass of Miscanthus fertilized with sludge from the wastewater treatment plant in three fertilization treatments, it can be concluded that the biomass of Miscanthus is a good feedstock for the process of direct combustion. Moreover, the application of the largest amount of municipal sewage sludge during cultivation had no negative effect on the properties of Miscanthus biomass. Moreover, the cellulose and hemicellulose content of Miscanthus is ideal for the production of second-generation liquid biofuels. Fertilizer treatments had no effect on the content of cellulose and lignin, while a significant statistical difference was found for hemicellulose.

Biowastes to augment the essential oil production of Leptospermum scoparium and Kunzea robusta in low-fertility soil

Biowastes are unwanted materials of biological origin. They include biosolids, dairy shed effluent, and sawdust. When applied to soil, biowastes can provide plant nutrients, but also introduce heavy metals, pathogens, or xenobiotics. Biowastes could improve degraded or low-fertility soils and generate revenue through the production of non-food products such as essential oils. We grew New Zealand native plants, mānuka (Leptospermum scoparium J.R. Forst & G. Forst) and kānuka (Kunzea robusta de Lange & Toelken) in series of greenhouse experiments in low-to-medium-fertility soils (Bideford clay loam, Lismore stony silt loam, and Pawson silt loam) amended with either biosolids (up to 13500 kg N ha^-1 equiv.), biosolids + sawdust (1:0.5-1250 kg N ha^-1 equiv.) and dairy shed effluent (200 kg N ha^-1 equiv.). Two types of biosolids from Kaikoura (KB) and Christchurch City Council (CB) were used in the experiments. CB (1500 kg N ha^-1 equiv.) and dairy shed effluent (200 kg N ha^-1 equiv.) increased the biomass of L. scoparium by up to 120% and 31%, and K. robusta by up to 170% and 34%, respectively. Adding sawdust to KB increased the biomass of L. scoparium and K. robusta although it offset the L. scoparium growth increase in the KB-only treatment. The growth response of K. robusta to biowastes was greater than L. scoparium with oil production in K. robusta increasing by up to 211% when 1500 kg N ha^-1 equiv. of CB was applied to Lismore stony silt loam. Generally, the treatments had a negligible effect on oil concentration in all the soil types, except for the KB + sawdust treatment, which increased the oil concentration by 82%. Most of the EOs' major components were unaffected by biowaste addition in the soils, although some components increased in the Bideford clay loam following KB and KB + sawdust application. Biosolids increased foliar concentrations of Zn, Cu, and Cd, but these were below risk-threshold concentrations. Applying CB (up to 1500 kg N ha^-1 equiv.) to low-fertility soils is recommended to establish ecosystems dominated by L. scoparium and K. robusta that annually would produce ca. 100 kg ha^-1 of EOs worth US$ 26k and 24k, respectively. Adding sawdust to CB could have environmental benefits through reduction of N leaching. Field trials are warranted to elucidate critical ecological variables and production economics in biowaste management.