Effects Of Pig Manure Application On Transfer And Transformation Of Cu In Fluvio-aquic Soil-Crop System And Of Amendments On In-situ Inactivation Of Cu In The Soil

Intensive confined livestock and poultry production systems generate large quantities of manure by-products, which have the potential for being recycled on land. Protecting the quality of the environment is a major consideration when developing management practices to effectively use manure by-products as a nutrient resource and soil conditioner in agricultural production system. To date, most of the environmental problems associated with land application of manure by-products have centered on the contamination of groundwater and/or surface water with two major nutrients, nitrogen (N) and phosphorus (P). With increasing use of trace elements such as Cu as nutritional supplement in the form of feed additive in intensive animal production industries, manure application has emerged as an important source of certain metals (e.g., Cu, Zn,and As) input in soils. At present, regulations governing livestock and poultry manure by-products are generally based on total N and/or P loading. Manure by-products are applied on land to primarily benefit from their N and/or P content, without regarding to their heavy metals contents. The danger lies in accumulation of manure-borne metals since they virtually don't degrade with the potential of eventually becoming phytotoxic and thus resulting in problem of food security. In order to reduce the risk of offsite contamination, it is prudent to propose that land application guidelines for manure by-products be developed that consider their total composition rather than just only specific component (i.e., N and/or P). There are little informations on the effect of manure-induced Cu on farmland ecosystem, and the measures to control Cu pollution caused by applying animal manure. Therefore, the present research aims to examine the effects of pig manure application on transfer and transformation of Cu in a fluvio-aquic soil-crop system, and to understand the efficiency of three amendments (bentonite, apatite, and fly ash) to in-situ inactivation of Cu of the soil. The effects of pig manure-induced Cu contamination on accumulation of Cu and amount of available Cu in the soil, and Cu accumulations in different organs of both paddy and wheat were characterized. The effects of pig manure application and Cu pollution on the growth of paddy and wheat were investigated. The inactivation effeciency of the three amendments on Cu in a fluvio-aquic soil-crop system were also studied.The results obtained in the study are summarized as follows:(1)Availability of Cu in the soils decreased with increasing rate of pig manure application and increasing incubation time of added Cu with the soils. In fluvio-aquic soil contaminated with Cu, application of pig manure could reduce Cu contamination-induced negative effect on the chlorophyll content of paddy plant. However, application of pig manure had no significant effects on the tillers and grain weight. The concentrations of Cu in grain, stem and root of paddy plant decreased with increasing application rate of pig manure. The concentration of Cu in different organs of paddy plant decreased in the sequence of root>stem> grain.(2)Inactive effects of amendments on soil Cu decreased with increasing level of Cu contamination in the fluvio-aquic soil-wheat system. All of three amendments decreased the contents of soil available Cu, and fly ash and apatite decreased the water soluble Cu when 200 mg/kg of Cu was added to incubated soil. However, the effects of three amendments on decrease of soil available Cu were not significant when 400 mg/kg of Cu was added to incubated siul. Any of three amendments could reduce toxic hazard of Cu to wheat root in certain extern, promote the growth and root development of wheat and improve the root weight and tillers of wheat. The application of bentonite and apatite have no significant effect on Cu accumulation in grain.(3)In fluvio-aquic soil-paddy system, alleviation effects of the amendments on soil available Cu is more evident at earlier stage of the experiment than at later stage of the experiment. The effects were also more evident in soils contaminated with low level of Cu than those contaminated with high level of Cu. Application of any of three amendments increased Cu accumulation in grain of paddy growing in incubated soils with Cu treatment of 200mg/kg. However, it decreased Cu accumulation in grain of paddy growing in the soils with Cu treatment of 400mg/kg. Application of amendments has no significant effects on height, chlorophyll content and grain weight of paddy plant. In generally, the effects of three amendments on modification of soil physic-chemical property, reducing of Cu toxicity to wheat and paddy, and improvement of crop's yield decreased in sequence of bentonite> apatite >fly ash. The effect of apatite on increase of root weight and grain weight of paddy was better than those of fly ash and bentonite.(4)At lower than 800 mg/kg of Cu was added in incubated soils under the study, whether applying pig manure and amendments or not, contents of Cu in the grains of paddy and wheat growing in all incubated soil were lower than 10 mg/kg, a food safety standards of China (GB14935-1994).