D. J. Horne

A review of literature on the land treatment of farm‐dairy effluent in New Zealand and its impact on water quality

Abstract 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 wash‐down 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.

Best management practices to mitigate faecal contamination by livestock of New Zealand waters

Abstract 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.

A study of water repellency and its amelioration in a yellow-brown sand. 1. Severity of water repellency and the effects of wetting and abrasion.

Water repellency of Himatangi sand was assessed by in situ water infiltration measurements and in the laboratory using the Molarity of an Ethanol Droplet (MED) technique. Infiltration rates on water repellent areas were an order of magnitude lower than rates on adjacent, less repellent areas. The surface (30mm) soil of cores removed from repellent areas was severely repellent(MED > 2.2), and soil to a depth of 150mm was moderately repellent. MED was strongly correlated with soil carbon content (R 2 =0.79). Attempts were made to overcome repellency by wetting the soil and by abrasion. The water repellency of Himatangi sand increased when the gravimetric soil water content, w, was increased from 0.03 to 0.05, and then declined rapidly with further increases in soil water content. Air-dry samples were agitated in an end-over-end shaker for a range of 1-48 h. Soil water repellency was significantly (P < 0.01)reduced by agitation for up to 8 h. Warter repellency of samples which had been shaken for 2,...

A study of water repellency and its amelioration in a yellow-brown sand. 2. Use of wetting agents and their interaction with some aspects of irrigation.

Abstract A range of soil wetting agents was evaluated in glasshouse experiments using the Himatangi sand. Comparisons of application rates required to overcome water repellency and enable ryegrass seedling emergence revealed significant differences (P 0.05) between plots. A blanket spray (20 litre/ha) of Wettasoil on a cultivated area (45 m2)of Himatangi sand increased the surface soil water content relative to untreated soil; however, this effect was not maintained over the following months. Glasshouse experiments were co...

Growth and chemical composition of legume‐based pasture irrigated with dairy farm effluent

Abstract Land treatment of farm effluent is becoming popular in many countries because this practice is considered less harmful to surface water and groundwater resources. However, the supply of large quantities of selective nutrients, such as nitrogen (N) and potassium (K), through effluent irrigation could affect the nutrient balance and the botanical composition of crops and pasture. The aim of the project was to investigate the influence of farm effluent irrigation on the growth and chemical composition of legume‐based pasture through a field experiment conducted at Massey University Dairy Unit, New Zealand. Three levels of effluent irrigation with N loading rates of 0,150, and 200 kg ha–1 were applied. Effluent irrigation at these rates also provided 0, 256, and 342 kg K ha–1. The effluent was irrigated either in the presence or absence of calcium (Ca—as gypsum), and magnesium (Mg—as epsom salt) addition. The effluent irrigation was applied once a month and the trial continued for 6 months. The dry matter (DM) yield, botanical composition, and nutrient concentration in the pasture were measured 1 month after each effluent irrigation. The pasture DM yield increased with increasing rate of effluent application. The DM response (kg DM kg–1 N applied) ranged from 4.1 to 7.2, slightly less than the values obtained for fertiliser N. The N and K concentrations in the pasture increased with increasing levels of effluent irrigation. Calcium and Mg fertiliser application had no effect on either pasture yield or the concentration of N or K in pasture. In the absence of Ca and Mg fertiliser application, the concentration of Ca and Mg in pasture decreased with increasing effluent irrigation. Application of Ca and Mg fertiliser increased the concentration of these elements in pasture at all levels of effluent application. Excessive uptake of K by pasture is likely to cause Ca and Mg deficiencies in grazing animals, leading to milk fever and grass staggers.

The performance of travelling effluent irrigators: Assessment, modification, and implications for nutrient loss in drainage water

Abstract and application of farm‐dairy effluent (FDE), the treatment option preferred by most regional councils, is commonly practised with the use of small travelling irrigators. Field observations indicate that FDE application by rotating irrigators to artificially drained soils can generate drainage contaminated with partially treated FDE, even when the set application depth is less than soil water deficit. The uniformity of FDE application from rotating, modified‐rotating, and oscillating travelling irrigators was determined for a range of application depths and wind conditions. The rotating irrigator produced a bimodal application profile with a two‐ to threefold difference between the highest and lowest application depths. These high application depths are likely to result in drainage of partially treated FDE in late winter and spring when soil moisture deficits are often small. A rotating irrigator was modified with splash plates or an irrigation bar that diverted more FDE to the centre of the application profile. Neither modification improved the uniformity of application. The most uniform application profiles were obtained using a new technology oscillating irrigator. The measured application profiles and a soil water balance were used to simulate the drainage and nutrient loss under each irrigator type. In early spring and late autumn, when soil water deficits were low, the more uniform application profile of the oscillating irrigator, set at its lowest application depth of 10 mm, created less risk of partially treated FDE reaching pipe drains. The simulation model estimated that when operating at a set average application depth of 25 mm the rotating irrigator and oscillating irrigator required soil water deficits of 44 and 32 mm, respectively, to avoid generating drainage. When FDE was applied at 25 mm depth with a deficit of only 18 mm, substantial quantities (30%) of partially treated effluent were estimated to have been drained from the soil no matter which irrigator was used. When application depth equalled the moisture deficit, the more uniform oscillating irrigator had a lower drainage loss (7%) compared with the rotating irrigator (14%). With only a small buffer of 7 mm between soil moisture deficit and application depth it was estimated that the oscillating irrigator achieved zero drainage. When set at their fastest travel speeds, the peak application depths of the rotating and the oscillating irrigators were similar (13 mm) and therefore these irrigators have the same number of operational irrigation days at times when soil water deficits are low.

Potential Uses of Fluidised Bed Boiler Ash (FBA) as a Liming Material, Soil Conditioner and Sulfur Fertilizer

To meet the Clean Air standard, many North American and European power plants have adopted fluidized bed combustion techniques. These systems require lower capital investment, to reduce the sulfur-dioxide (SO2) emissions in flue gases, than the wet flue gas desulfurization process. In the former system, limestone chip mixed with the fine coal is burnt in a bed suspended by compressed air. Sulfur dioxide released as the coal is burnt, reacts with CaO generated in the furnace therefore minimizing SO2 emissions from the stack. The resulting ash from the boiler bed and trapped fly ash, known as fluidized bed boiler ash (FBA), contains CaSO4 and unreacted CaO. Mixing this ash with water, to overcome dust problems, subsequently converts CaO to Ca(OH)2. The chemical composition of FBA is highly dependent on the efficiency of the boilers and the nature of the fuel and limestone sources.

The pugometer: an evaluation of a new tool for assessing treading damage of pasture soils and comparisons with other methods

Treading damage inflicted by grazing animals degrades soil physical quality, increases sediment and nutrient loss to water, and reduces pasture yield. The extent or severity of treading damage can be assessed using several methods such as roller chain, depth of pug, and visual scoring. However, the ability of these methods to assess treading damage, and their relative merits, have not previously been compared. Four methods of measuring treading damage are compared in this study including the three methods mentioned and a new tool called the pugometer, which was developed to measure treading damage in a spatially explicit manner. These comparisons were conducted on three paddocks at Massey University’s Dairy 4 farm near Palmerston North, Manawatu, New Zealand which had sustained treading damage of varying levels during grazing in wet conditions. All four methods were able to identify varying degrees of treading damage competently with strong correlations between them (R2 = 0.72–0.87). Therefore, the selection of the most appropriate method to assess treading damage will depend on the circumstances. Visual scoring was the quickest and simplest method to use over a large area, and so could be employed easily by a farmer. The pugometer provides a quantitative measure of the spatial variability of treading damage and so would be a useful research tool. The depth of pug and roller chain methods are reliable but much more time consuming and therefore are only practicable as research tools for small plot studies. Following a treading event, the pugometer was able to monitor the recovery of surface roughness in a spatially explicit and rapid manner. Additional keywords: depth of pug, quantifying pugging, roller chain, visual assessment.