Soilless cultivation for high-quality vegetables with biogas manure in China: Feasibility and benefit analysis

Abstract

Vegetables, the indispensable staple produce providing humans with many beneficial substances, are readily contaminated by nitrate, heavy metals and pesticides during conventional cultivation. In particular, off-season vegetables grown in protected systems with low light intensity do tend to accumulate more nitrate in tissues due to excess N fertilization driven by farmers' desire for high yields. Over-the-limit accumulation of the harmful substances in vegetables constitutes a serious hazard to human health globally. Soilless cultivation, currently a fraction of vegetable cultivation in China, is a promising cultivation method to decrease the accumulation of harmful substances through nutrient solution regulation and environmental factor control. However, conventional inorganic nutrient solutions present few quality benefits besides plant nutrition for the widely acknowledged formulations. Currently, high-quality vegetables are urgently desired by humans globally, but they are difficult to grow for lack of an effective and practical cultivation method to lower the accumulation of harmful substances and to improve nutritional quality simultaneously. Although some attempts have been made, few commercial formulations have been applied in practice. Biogas manure (biogas slurry and biogas dregs) is a by-product of biogas production. It has been shown to be a good fertilizer with abundant nutrients, amino acids and bioactive substances. In China, as a product of the recycling process of agricultural wastes, biogas manure is an ever-growing resource due to the rapid development of biogas projects. Therefore, the need to utilize biogas manure is an urgent issue that relates both to environment protection and nutrient resources utilization. In this paper, the updated research results on yield and the quality effects of vegetables cultivated with biogas dregs and the solutions modified from biogas slurry in China are summarized, highlighting the feasibility and benefits of biogas manure in high-quality vegetable production. It is concluded that biogas manure is an effective nutrient source for high-quality vegetable production based on its synergistic effects and effectiveness in yield and quality improvement (particularly depression effects on nitrate accumulation), and stress resistance. However, deliberate component regulations need to be developed for better yield and quality of vegetables under soilless cultivation due to the large variability of components of biogas manure caused by various combinations of fermentative materials.

Effects of Pig Slurry as Basal and Panicle Fertilizer on Trace Element Content and Grain Quality in Direct-Seeding Rice

“…Liu et al [39] reported that biogas manure is an effective nutrient source for high-quality vegetable production, based on synergistic effects and its ability to enhance yield and improve quality, and to suppress nitrate accumulation. In the present study, application of PS combined with nitrogen fertilizer decreased the processing quality of direct-seeding rice only slightly, but in our previous study, Gao et al [28] found that application of PS to machine-transplanted rice enhanced brown, milled and head milled rice.…”

Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review

“…Under soilless conditions, digestates from animal slurries are an effective nutrient source in vegetable production. Undiluted digestates with high electrical conductivity are not suitable . The key problems obstructing their application in soilless culture are the variability of components and the imbalance in the elemental composition .…”

“…Under soilless conditions, digestates from animal slurries are an effective nutrient source in vegetable production. Undiluted digestates with high electrical conductivity are not suitable [29].…”

“…The reduction in nitrate content has been related to differences in N composition. In contrast to nutrient solutions supplying nitrate, biogas digestates supply NH 4 + -N and as organic components mainly aminoand amide-N [29,107]. In one study, no effects were found under field conditions [101].…”

Light Environmental Management for Artificial Protected Horticulture

“…High-quality vegetables can be produced in protected facilities. Liu et al [6] defined high-quality vegetables as vegetables not containing over-the-limit harmful substances (nitrate, nitrite, heavy metals and pesticides), and not having negative effects on human health after ingestion. Health-beneficial phytochemicals of vegetables are referred to some substances, such as ascorbic acid, carotenoids, phenolics, flavoids, which are influential beneficially to human health.…”