This paper summarises findings from the Pathogen Transmission Routes Research Program, describing pathogen pathways from farm animals to water bodies and measures that can reduce or prevent this transfer. Significant faecal contamination arises through the deposition of faeces by grazing animals directly into waterways in New Zealand. Bridging of streams intersected by farm raceways is an appropriate mitigation measure to prevent direct deposition during herd crossings, whilst fencing stream banks will prevent access from pasture into waterways by cattle that are characteristically attracted to water. Riparian buffer strips not only prevent cattle access to waterways, they also entrap microbes from cattle and other animals being washed down-slope towards the stream in surface runoff. Microbial water quality improvements can be realised by fencing stock from ephemeral streams, wetlands, seeps, and riparian paddocks that are prone to saturation. Soil type is a key factor in the transfer of faecal microbes to waterways. The avoidance of, or a reduction in, grazing and irrigation upon poorly drained soils characterised by high bypass flow and/or the generation of surface runoff, are expected to improve microbial water quality. Dairyshed wastewater should be irrigated onto land only when the water storage capacity of the soil will not be exceeded. This "deferred irrigation" can markedly reduce pollutant transfer to waterways, particularly that via subsurface drains and groundwater. Advanced pond systems provide excellent effluent quality and have particular application where soil type and/or climate are unfavourable for irrigation. Research needs are indicated to reduce faecal contamination of waters by livestock.
There is little information available on the magnitude of nutrient losses to surface water from the two-pond and daily irrigation treatment systems for farm-dairy effluent (FDE). A research site has been established on a mole-pipe drained Tokomaru silt loam at Massey University's No. 4 Dairy Farm (475 cows) to investigate some of these issues. The site consists of four plots (40 × 40 m) that have been instrumented to allow the continuous monitoring of drainage and surface runoff. The research was conducted over three lactation seasons (2000/01-2002/03). Based on data collected at the study farm it was calculated that in the past 1500 kg N yr -1 and 250 kg P yr -1 were potentially discharged from the two-pond system directly to a stream. A simulation exercise suggests that approximately 108 kg N yr -1 and 18 kg P yr -1 would be lost to surface waters if daily irrigation was practised at the farm. The problems of daily irrigation, particularly A04050; those related to surface runoff, were further quantified in an experiment in which a single 25-mm FDE irrigation was applied to a soil near field capacity. Approximately 40% of the applied effluent left the soil profile as mole and pipe drainage and 30% as surface runoff. These losses equated to 12 kg N ha -1 and 2 kg P ha -1 . To minimise nutrient losses from land application of FDE, a system called "deferred irrigation" was designed. Deferred irrigation involves storing effluent in a two-pond treatment system and then applying it strategically when there is a suitable soil water deficit, i.e., the irrigation volume does not exceed the potential soil-water storage. The evaluation of deferred irrigation over three lactation seasons showed that direct losses of nutrients to surface waters were almost eliminated and resulted in the drainage of only approximately 1% of the total effluent nutrients applied. The successful adoption of the deferred irrigation system would require only the capability to store effluent and model or measure soil moisture status within the active root zone.
Dairy farming is the largest agricultural industry in New Zealand, contributing 20% of export earnings but providing a challenge for the environmentally acceptable treatment of wastes from dairy farms. Nutrient-rich farm-dairy effluent (FDE), which consists of cattle excreta diluted with washdown water, is a by-product of dairy cattle spending time in yards, feed-pads, and the farm dairy. Traditionally, FDE has been treated in standard two-pond systems and then discharged into a receiving fresh water stream. Changes brought about primarily due to the Resource Management Act 1991 have meant that most regional councils now prefer dairy farms to land treat their FDE. This allows the water and nutrients applied to land in FDE to be utilised by the soil-plant system.Research on the effects of land-treating FDE, and its affects on water quality, has shown that between 2 and 20% of the nitrogen (N) and phosphorus (P) applied in FDE is leached through the soil profile.In all studies, the measured concentration of N and P in drainage water was higher than the ecological limits considered likely to stimulate unwanted aquatic weed growth. Gaps in the current research have been identified with respect to the application of FDE to artificially drained soils, and the lack of research that has taken place with long term application of FDE to land and at appropriate farm scale with realistic rates of application. Whilst the land treatment of FDE represents a huge improvement on the loss of nutrients discharged to fresh water compared with standard two-pond systems, there is room for improvement in the management of FDE land-treatment systems. In particular, it is necessary to prevent the direct discharge of partially treated FDE by taking into account soil physical properties and soil moisture status. Scheduling effluent irrigations based on soil moisture deficits results in a considerable decrease in nutrient loss and may result in a zero loss of raw or partially treated effluent due to direct drainage.
Surface-activated biochars not only represent a useful carbon sink, but can also act as useful filtering materials to extract plant nutrients (e.g. NH4+) from wastes (e.g. animal or municipal waste streams) and added thereafter to soils. Biochars produced by low-temperature pyrolysis of fibrous debarking waste from pine (PI) and eucalyptus (EU) were pre-treated with either diluted (L) or undiluted (S) alkaline tannery waste (L-PI, S-PI, L-EU, S-EU). Biochars produced from untreated feedstock were used as controls. Samples were characterised by FT-IR, solid-state CP MAS 13C NMR, XPS, SEM microphotographs, and BET specific surface area. Elemental composition, carbon recovery, yield, surface charge, and NH4+ sorption/desorption properties were also studied. Carbon recovery was lower in biochars prepared from L-EU and S-EU (43 and 42%, respectively) than in control EU (45%) but these biochars showed greater changes in their chemical characteristics than those made from L-PI and S-PI, which showed minimal decrease in recovered carbon. The specific surface area of the biochars decreased with treatments, although acidic surface groups increased. In subsequent sorption experiments, treated biochars retained more NH4+ from a 40 mg N/L waste stream (e.g. 61% retention in control EU and 83% in S-EU). Desorption was low, especially in treated biochars relative to untreated biochars (0.1–2% v. 14–27%). The results suggest that surface activated biochars can be obtained with negligible impairment to the carbon recovered.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.