Christensen, CL

Hanly, JA

Hedley, MJ

Horne, DJ

English

Massey Research Online

1 THREE YEARS OF DURATION-CONTROLLED GRAZING: WHAT HAVE WE FOUND?  C.L. Christensen, M.J. Hedley, J.A. Hanly and D.J. Horne  Fertilizer and Lime Research Centre, Massey University   Abstract The practice of standing cows off pasture is used on dairy farms throughout New Zealand and globally to protect cows from adverse climatic conditions, increase production, reduce treading damage to pasture and soil, and minimise the loss of nutrients to waterways.  At Massey University’s No. 4 Dairy Farm, the effects of standing cows off pasture year-round is being investigated, using Duration-controlled (DC) grazing.  The effects of DC grazing on pasture accumulation, and the concentrations of nitrogen (N), phosphorus (P) and faecal microbes in mole and pipe drainage and surface runoff water have been measured from 14 pasture plots since June 2008.  Seven plots were managed under DC grazing (4 hour graze, day or night) and seven plots under ‘standard’ grazing (SG; 7 hour day graze, 12 hour night graze).  Slurry was returned to the DC plots in the first season with a nutrient loading equivalent to approximately the amount of nutrients produced in slurry from about 18 months of DC grazing.  Consequently, no slurry was applied during the second lactation season.  Four more dilute applications of slurry were applied to DC plots in the third season.  The average quantities of drainage over the three drainage seasons studied (2009, 2010 and 2011) were 373, 316 and 329 mm, respectively.  The quantities of nitrate (NO3-) lost in drainage from the SG plots during these seasons were 13.1, 8.0 and 20.9 kg NO3--N/ha, respectively.  Drainage NO3--N losses from the DC plots were 43, 65 and 53% lower, respectively, compared with the SG grazing plots for the three drainage seasons.     Pasture accumulation measured over the three lactation seasons (2008/09, 2009/10, and 2010/11) was 15212, 12778, and 14990 kg DM/ha per year, respectively, for the SG plots.  There was no significant difference seen in pasture accumulation on DC plots for the first season; however there was a 20% and 9% reduction seen for the second and third seasons respectively.  The smaller pasture accumulation achieved on the DC plots in the second season was likely due to less dung and urine deposited during grazing and the nil slurry return.  It is anticipated that emphasis on frequent slurry return to pasture (e.g. earlier spring applications) can be used to further minimise differences.  Over three seasons, DC reduced NO3- leaching by more than 50%, which supports the proposal that DC could play a very important role in mitigating nutrient losses from dairy farms in some parts of New Zealand.  However, slurry should be regularly applied throughout the lactation season if pasture growth is to be optimised under DC grazing management.  Introduction  Cattle urine spots are a major source of the nitrogen (N) leached from New Zealand dairy farms (Cameron et al. 2007; Wachendorf et al. 2005).  Restricting the time that cows spend grazing pastures is one way to decrease the deposition of urine spots in paddocks.  de Klein & 2 Ledgard (2001) found that, compared with a conventionally grazed system, restricting the grazing time of cows in the autumn in Southland led to a 35-50% reduction in nitrate (NO3-) leaching.  Duration-controlled grazing involves reducing the time cows spend grazing pasture with more time spent on feed pads or animal shelter facilities between grazings.  While the increased time spent on stand-off facilities results in greater quantities of excreta being collected as effluent or stored manure, this material can be returned to soils evenly and at relatively low N concentrations.      A three year field trial was established on Massey University’s No 4 dairy farm to assess the impacts of year-round, duration-controlled grazing on the quantities of N, phosphorus (P) and faecal microbes lost in drainage and runoff from a dairy farm with fine textured soils.  This paper discusses the nitrate leaching and pasture dry matter (DM) accumulation results. It builds on previous papers presented at FLRC Workshops, namely Lindsay et al. (2009), and Christensen et al. (2010; 2011).     Methods Trial site The experiment was conducted on Massey University’s No. 4 dairy farm near Palmerston North, Manawatu, New Zealand (NZMS 260, T24, 312867).  The trial site was located in a flat landscape (c. <3% slope) which received an average annual rainfall of approximately 1000 mm.  The site had a mixed pasture sward of predominantly perennial ryegrass (Lolium perenne) and white clover (Trifolium repens).  The trial was established on a mole-pipe drained, Tokomaru silt loam soil, which is classified as a Fragic Perch-gley Pallic Soil (Hewitt 1998).    The research area consisted of fourteen plots (~850 m2/plot), each with an isolated mole and pipe drain system.  Mole channels, ~ 40 m long, were installed at a depth of 0.45 m with an interval between moles of 2 m.  Drainage from the mole channels was intercepted by a collecting perforated pipe drain (0.11 m diameter) installed perpendicular to the moles at a depth of 0.60 m.  Further description of the topography and soil properties of the site can be found in Houlbrooke et al. (2004).   Experimental design The trial consisted of two treatments. The Standard Grazing (SG) treatment involved a grazing duration of ~7 hours for day grazings and ~12 hours for night grazings.  The other treatment was Duration-controlled Grazing (DC) which involved a grazing duration of ~ 4 hours for both day and night grazings.  All plots were grazed on the same day with the same average stocking rate, which was set according to pasture cover (as estimated using a rising-plate pasture height meter).  Grazings alternated between ‘day’ and ‘night’ regimes to mimic standard farm practice.  There were 8-10 grazings per year.   The trial site was established during the summer of 2008.  For fertiliser applications and drainage dates for the years 2008 – 2010 refer to Christensen et al. (2011).   In the 2010/11 lactation season, ammonium sulphate was applied to all plots at 30 kg N/ha in September, and 25 kg N in October.  Cropmaster 20 was applied to all plots in March 2011at a rate of 150 kg/ha.  The 2011 drainage season began on 27th April and ended on 17th December 2011.   3 At each grazing during the lactation season, cows were offered 5-6 kg DM/cow as pasture on the plots and another 2-3 kg DM/cow from another source.  Prior to grazing the SG plots, cows were fed 2-3 kg DM/cow as supplementary feed on a feed pad.  The cows grazing the DC plots were removed from the plots after 4 hours and given the remainder of their feed requirements (either pasture or supplement).  Removal of the cows from the DC plots simulated their return from grazing to a standoff facility.    Estimated pasture dry matter accumulation, cow intakes and dung deposition  A rising-plate pasture height meter was used pre- and post-grazing to estimate the quantity of pasture on all plots.  Sixty measurements were made to generate an average pasture mass per plot.  These measurements were used to estimate pasture accumulation between grazings, the stocking rate required at each grazing and cow intakes at each grazing.    The dung pats deposited on each plot were counted to give an indication of the total amount of excreta returned to the plots (results not presented here).  The difference in average dung depositions between the two treatments was used to estimate the quantity of excreta collected on the feed pad and therefore the amount of slurry to be applied to the DC treatment.  The amount of slurry returned reflected an assumed N loss in storage of approximately 50%.  Slurry (5 to 10 mm) was first applied to the DC plots in mid-December 2008 (Lindsay et al., (2009)). This was the only application of slurry in the 2008/09 season. An amendment has been made to the amount of N in the slurry applied in December 2008 as reported in Lindsay et al. (2009). The corrected value, given in Table 1, corresponds to a nutrient loading equivalent to approximately 18 months of DC grazing.  Consequently, no slurry was applied during the second lactation season.  Four, dilute applications of slurry were applied to DC plots in the third season (Table 1).  Table 1: Amount of N returned (kg/ha) to DC plots in slurry applications Year Month  Amount of N applied to DC plots (kg/ha) 2008 December 212 2010 October 15  November 11 2011 February 68  April 21  Drainage water volume measurements and water analysis Drainage water from plots was channelled through drainage pipes into tipping-bucket flow meters located in sampling pits nearby.  Each tipping-bucket was calibrated dynamically to account for slightly larger tip volumes at greater flow rates.  All tipping buckets were instrumented with data loggers to provide continuous measurements of flow rate.  During each drainage event, a proportion (~0.1%) of the drainage water from every second tip of the tipping bucket flow meter was automatically collected to provide a volume-proportioned mixed sample for water quality analysis.   Drainage water samples were filtered through a 0.45 μm filter and the filtrate analysed for nitrate-N and ammonium-N using colorimetric methods on a Technicon Auto Analyser (Blakemore et al. 1987). 4 Results & Discussion  Pasture accumulation from September 2008 to September 2009 was similar for both treatments.  However, in the 2009/10 lactation season, average pasture accumulation was 20% less (P<0.05) on the DC plots (10204 kg DM/ha) than on the SG plots (12778 kg DM/ha) and this difference was increasing with time (Figure 1).   In the 2010/11 season, some accumulation periods between grazings were lower (P<0.05).  The overall accumulation on DC plots was 13619 kg DM/ha, and on the SG plots, 14990 kg DM/ha.       Figure 1: Pasture accumulation for DC and SG treatments over 3 lactation seasons   The smaller pasture growth accumulation measured on the DC plots in the 2009/10 season is predictable and underscores the importance of returning the nutrients excreted on the stand- off facility to paddocks.  The results presented here for the three seasons would also suggest 5 that the smaller and regular applications of slurry were more effective than large applications, which will be discussed in future publications.  The smaller, more regular applications in 2010/11 resulted in relatively better pasture accumulation on the DC plots.  This was evident when comparing daily pasture growth rates (kg DM/ha/day) between plots (Figure 2).  In the 2010/11 season, there was a sharp decline in growth rates when no slurry was applied.  This showed the high reliance of pasture growth through these periods on rapidly recycling nutrients via dung and urine, or effluent application.     Figure 2: Daily pasture growth rates (kg DM/ha) for DC and SG treatments over 3 lactation seasons   6 The cumulative drainage from the SG plots was slightly less than that from the DC plots in all years (Figure 3).  The average amount of drainage from all the plots was 373, 316 and 329 mm for 2009, 2010 and 2011, respectively.    Figure 3: Cumulative drainage (mm) for DC and SG treatments over 3 years   The nitrate-N (NO3--N) concentrations in 2011 were consistently lower from the DC plots than the SG plots.  Also, the concentrations from all plots were very low (<2 ppm) by August.  The majority of NO3--N leaching occurred in the first few months of winter drainage (Figure 4). This pattern of NO3--N leaching has been consistent for all years of the current study Christensen et al. (2011) and is a common observation for climates similar to the Manawatu. In 2009, the total NO3--N lost from the DC treatment plots was 7.5 kg N/ha, which was 43% less than the 13.1 kg N/ha lost from the SG plots (Figure 4).   7   Figure 4: Cumulative nitrate-N leached (kg/ha) in drainage water for DC and SG treatments over 3 years   The cumulative NO3--N (kg N/ha) losses in drainage were smaller in 2010 (Figure 4) than in previous years (Christensen et al. 2010).  Overall however, the percentage difference in cumulative NO3--N lost between treatments was larger, with a 65% reduction from the DC plots (2.8 kg/ha), compared with the SG plots (8.0 kg/ha).    In the final drainage season (2011), 53% less NO3--N was lost in drainage from the DC plots (9.9 kg/ha) compared with the SG plots (20.9 kg/ha).    Over all 3 years of this trial, DC has resulted in a reduction in NO3--N leaching of more than 50%, which exceeds the dairy industry’s strategy/target.  NO3--N leaching from DC plots has been consistently lower, regardless of the length or timing of the drainage season.   8 Conclusion Duration-controlled grazing has shown to reduce NO3--N leaching by ~50% on dairy farms.  Therefore, it has the potential to be an important mitigation strategy, particularly in nitrogen-sensitive areas.  However, small, regular applications of slurry are required to maintain or even increase pasture growth rates.  If this can be achieved, then DC grazing could be adopted by many farmers around New Zealand.  References Blakemore LC, Searle PL, Daly BK (1987) Methods for chemical analysis of soils. New Zealand Soil Bureau Scientific Report 80. Cameron KC, Di HJ, Moir JL, Roberts AHC (2007) Reducing nitrate leaching losses from a Taupo pumice soil using a nitrification inhibitor eco-n. Proceedings of the New Zealand Grassland Association 69, 131-135. Christensen CL, Hedley MJ, Hanly JA, Horne DJ (2010) Using duration-controlled grazing to reduce nitrate leaching from dairy farms. In 'Farming's Future: Minimising Footprints and Maximising Margins'. (Eds LD Currie, CL Christensen) pp. 46-52. (Fertilizer and Lime Research Centre, Massey University: Palmerston North). Christensen CL, Hedley MJ, Hanly JA, Horne DJ (2011) Nitrate leaching and pasture production from two years of Duration-Controlled grazing. In 'Adding to the knowledge base for the nutrient manager'. (Eds LD Currie, CL Christensen). (Fertilizer & Lime Research Centre: Palmerston North). de Klein CAM, Ledgard SF (2001) An analysis of environmental and economic implications of nil and restricted grazing systems designed to reduce nitrate leaching from New Zealand dairy farms. I. Nitrogen losses. New Zealand Journal of Agricultural Research 44, 201-215. Hewitt AE (Ed.) (1998) 'NZ Soil Classification.' (Manaaki Whenua - Landcare Research New Zealand Ltd Press: Lincoln). Houlbrooke DJ, Horne DJ, Hedley MJ, Hanly JA, Scotter DR, Snow VO (2004) Minimising surface water pollution resulting from farm-dairy effluent application to mole-pipe drained soils. I. An evaluation of the deferred irrigation system for sustainable land treatment in the Manawatu. New Zealand Journal of Agricultural Research 47, 405-415. Lindsay CL, Hanly JA, Hedley MJ, Horne DJ (2009) Controlling nitrogen and phosphorus loss from dairy farms using restricted grazing practices. In 'Nutrient Management in a rapidly changing world'. Palmerston North. (Eds LD Currie, CL Lindsay) pp. 295-302. (Fertilizer and Lime Research Centre, Massey University). Wachendorf C, Taube F, Wachendorf M (2005) Nitrogen leaching from 15N labelled cow urine and dung applied to grassland on a sandy soil. Nutrient Cycling in Agrosystems 73, 89-100.  MASSEY UNIVERSITYMASSEY RESEARCH ONLINE http://mro.massey.ac.nz/Massey Documents by Type Conference PapersThree years of duration-controlled grazing:What have we found?Christensen, CL2012-02http://hdl.handle.net/10179/1413520/01/2020 - Downloaded from MASSEY RESEARCH ONLINE

Three years of duration-controlled grazing: What have we found?

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Three years of duration-controlled grazing: What have we found?

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