Soluble Elements Released from Organic Wastes to Increase Available Nutrients for Soil and Crops

Member States of the European Union must ban burning arable stubble by 2023 and improve the recycling of organic waste into fertilizers and organic farming practices by 2030. The current lack of nutrients from soils and crops leads to food insecurity, human malnutrition and diseases. Consequently, innovative solutions are required, as technosols are constructed by waste. The objective of this paper is to educate on the nutrients that some pruning residues can provide. This work characterizes elemental composition, nutrients soluble fraction and physical and chemical properties of the following organic wastes: almond tree pruning, commercial peat substrate, olive tree pruning, pine needle, date palm leaf pruning, sewage sludge compost and vine pruning. The results show significant differences between macro (Na, K, Ca, Mg) and micronutrient (Fe, Mn, Cu, Zn) content and their solubility. Sewage sludge compost, olive pruning and pine needle are the three residues with the highest presence of nutrients in their elemental composition. Nevertheless, if a farmer applies pruning residues as a nutritional supplement for crops, it will be key to finding the short-term soluble nutrient rate and synchronizing the nutritional requirement curve of a plant's life cycle with its nutrient release. Consequently, organic waste (without composting treatment) obtains higher solubility rates, being date palm leaf residue the one with the greatest value. The solubility index of organic wastes can be significant in providing short-term nutrients to crops. Hence, our results can help in choosing the proper waste to enhance plant nutrient supply, mainly K, Ca, Mg and Na for crop nutrition, to ensure efficient biofertilization.

Automated summary

Member States of the European Union are required to ban burning arable stubble by 2023 and improve the recycling of organic waste into fertilizers and organic farming practices by 2030. This is because the current lack of nutrients from soils and crops leads to food insecurity, human malnutrition, and diseases. Therefore, innovative solutions using waste as technosols are needed. The objective of this paper is to educate on the potential nutrients provided by pruning residues. The study characterizes the elemental composition, solubility of nutrients, and physical and chemical properties of various organic wastes. Results show significant differences in nutrient content and solubility, with sewage sludge compost, olive pruning, and pine needle residue having the highest nutrient presence. However, it is important for farmers to consider the short-term soluble nutrient rate and synchronize it with a plant's nutrient requirement during its life cycle when applying pruning residues as a nutritional supplement. The study also highlights the significance of organic waste's solubility in providing short-term nutrients to crops, particularly K, Ca, Mg, and Na for efficient biofertilization.