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2. Materials & Methods For the purpose of this study, data of 140 arable farms from the Dutch Minerals Policy Monitoring Program (LMM) were used. Data were obtained from the Dutch Farm Accountancy Data Network (FADN) except the nitrate concentration which was measured by the National Institute for Public Health and the Environment (RIVM). The analysis of the N-soil surpluses and the economic results concerned 242 observations on sandy soils in the period 1991-2009 and 223 observations on clay soils in the period 1996-2009. The number of observations (years) per farm varied from 1 to 11, so the available dataset was an unbalanced panel. The N-soil surplus was calculated as the sum of the N surplus at the farm gate level and the N input from deposition and fixation minus gaseous N emission (Fraters et al., 2007). Various possible explanatory factors were selected based on literature review, with specific attention to recent changes in legislation (for instance the ban on the application of manure in autumn and winter). To determine the explanatory factors for N-soil surplus, gross margin and nitrate concentration linear regression analysis was used. Because of the unbalanced data, the Fixed Effects (FE) model was applied (Baltagi, 1998) The FE-model only uses the variation within the farms over years (and not the variation between farms), which is more useful to identify possibilities for farmers to adapt their management.
3. Results & Discussion Results for the sandy soils are presented in Table 1. This table does not show the complete model but only the explanatory factors where P0.05 for the N-soil surplus per ha, the gross margin per ha or the nitrate concentration are shown. R2 for N-soil surplus per ha is 0.76, for gross margin per ha
0.24 and for nitrate concentration 0.12. With crop yield level above average, arable farmers achieve both lower N-soil surpluses and higher gross margins. Lower levels of fertilizing result in lower Nsoil surpluses but do not affect gross margins, under the express condition that all other explanatory factors do not change.
In the case of the N-soil surplus in kg per ha on clay soils the results are similar to the sandy soils.
However this is not the case for the gross margin per ha as no significant (P0.05) explanatory factors were found, not even for the level of the crop yield. It is hypothesised that a higher crop yield on clay soils goes together with lower prices per unit or higher costs. Concerning the nitrate concentration in drain water only a higher level of artificial N-fertilizer slightly increases the nitrate concentration on clay soils, just as on sandy soils.
4. Conclusion This integrated approach of farm management, economics and environmental quality shows that Dutch arable farmers on both sandy and clay soils can reduce N-soil surpluses per ha by using less artificial fertilizer or organic manure without affecting the gross margin per ha. Important is the assumption of all other explanatory factors being equal which will often not be the case. Nitrate concentration can slightly decrease by less use of artificial N-fertilizer. For arable farms on clay soils that smaller use of artificial N-fertilizer can be enough to meet the EU-standards for nitrate concentration. For arable farms on sandy soils more stringent measures can be necessary because breaches of the EU-standards are higher than for arable farms on clay soils.
References Baltagi, B.H. 1998. Econometric analysis of panel data. 4th edition, Wiley Daatselaar, C.H.G., Doornewaard, G.J., Gardebroek, C., de Hoop, D.W. and Reijs, J.W. 2010. Bedrijfsvoering, economie en milieukwaliteit: hun onderlinge relaties bij melkveebedrijven (in Dutch with English summary). LEI, The Hague (NL), report 2010-053.
Nitrogen Workshop 2012 Replacing lime with gypsum as fertiliser filler in calcium ammonium nitrate (CAN): a strategy for minimising nitrogen losses to the environment Bailey, J.S.
Agri-Food and Biosciences Institute, 18A Newforge Lane, Belfast, BT9 5PX, Northern Ireland
1. Background & Objectives Calcium (Ca), when present in millimolar concentrations, has a stimulatory effect on a wide range of membrane-bound enzymes, including ATPase’s, (Marschner, 1995), and there is evidence that this type of stimulation may promote nitrogen (N) uptake by plants. Pot experiments have demonstrated that replacing calcium carbonate (CaCO3) with calcium sulphate (CaSO4) (a much more soluble Ca salt) as fertiliser filler, considerably enhanced (30%) the uptake of 15N-labelled NO3-N by perennial ryegrass within the first two weeks of regrowth. Thereafter, because losses of NO3-N from pots by denitrification or leaching had been minimal, plants supplied with N fertilisers containing CaCO3 or CaSO4 filler, eventually recovered equal amounts of N from the soil solution (Kirkpatrick and Bailey, 2006). In field situations, though, where the potential for denitrification loss is often high, any improvement in NO3- uptake as a result of Ca stimulation of N absorption, however transient, might help to improve fertiliser N efficiency and thus prevent significant losses of N to the environment. To test this hypothesis, field trials were conducted at Hillsborough to investigate whether replacing some or all of the CaCO3 filler in CAN with CaSO4, had the potential to significantly enhance N uptake and recovery by cut grassland swards.
2. Materials & Methods Five CAN-based granulated N fertilisers were prepared by Kemira Agriculture UK. Each fertiliser contained 27% N as NH4NO3, had fillers containing CaCO3 and CaSO4 in the following ratios (F1 F2 - 75:25), (F3 - 50:50), (F4 - 25:75) and (F5 - 0:100), and contained between 0 and 12% SO3. Established forage grassland sites were selected at Terry’s hill, for a two-year field trial in 2001 and 2002, and at Pantridge’s, for a one year trial in 2003. The trial at Terry’s Hill had a 5 x 3 factorial design with 5 fertilisers (F1-F5), three rates of N application: 50, 75 and 100 kg N ha-1 cutand 5 replicates. The trial at Pantridge’s, had a 3 x 2 design with just 3 fertilisers (F1, F3 and F5) and two rates of N application (75 and 100 kg N ha-1 cut-1), and 12 replicates. Plots, 6m x 2m in size, were laid out in fully randomized blocks on both sites. Fertiliser treatments were applied in early April for 1st cut crops (except at Terry’s hill in 2001, when Foot and Mouth prevented access to the site), after 1st cut in May, and after 2nd cut in July. Basal dressings of potassium (K) and sulphur (S) were applied to provide annual rates of application of 95 kg K ha-1 and 37.5 kg S ha-1 at Terry’s Hill (soil K index 3), and 135 kg K ha-1 and 37.5 kg S ha-1 at Pantridge’s (soil K index 2).
Phosphorus was not applied at either site as soil P indices were ≥ 3. Plots were harvested using a plot harvester, and fresh yields determined. Sub-samples of herbage were collected, oven-dried, milled and chemically analysed to provide DM and nutrient yield data. All data were subjected to analyses of variance (ANOVA), and trends and interactions between treatments were tested using student’s t test and with pooled standard errors from the ANOVA.
3. Results & Discussion Overall, the results of the trials showed that replacing CaCO3 with CaSO4 as fertiliser filler never proved detrimental to N uptake or sward DM production and at various harvests significantly enhanced one or other or both of these yield parameters, thus demonstrating its potential as a strategy for improving fertiliser N efficiency and minimising N losses to the environment. Rather
The absence of N (and DM) yield responses to increased CaSO4 concentrations in filler at other cuts is not unexpected, since such responses are only likely when conditions are conducive for N loss.
4. Conclusion Replacement of all or most of the CaCO3 in CAN with CaSO4 can significantly improve fertiliser N efficiency and minimise N losses to the environment. CaSO4-modified CAN also provides a valuable supply of S for early and mid-season silage crops, which can be prone to S deficiency.
References Kirkpatrick, T. and Bailey, J.S. 2006. Calcium sulphate versus lime as fertiliser filler: effects on ammonium and nitrate uptake by perennial ryegrass. Communications in Soil Science and Plant Analysis, 37, 733-750.
Marschner, H. 1995. Mineral Nutrition of Higher Plants (2nd Edition), Academic Press, Ltd, London, pp 484-498.
Nitrogen Workshop 2012
Response of a range of forage swards to slurry nitrogen Dale, A.J.a, Laidlaw, A.S.b, Bailey, J.S c Agri Food and Biosciences Institute (AFBI) aHillsborough, Co Down, Northern Ireland BT26 6DR, bCrossnacreevy, Houston Road, Crossnacrevy, Co Down, Northern Ireland BT6 9SH, cNewforge, Belfast, Northern Ireland, BT9 5PX
1. Background & Objectives Grass species vary in their response to nitrogen (N) fertiliser (Frame, 1991), but less is known about the responsiveness of different species to slurry N. In a study in the United States, the dry matter (DM) yield response to dairy slurry application was greater for tall fescue than for cocksfoot albeit N off take was highest for cocksfoot and so apparent N recovery was similar for both species (Cherney et al., 2002). Grass/legume swards tend to be less responsive to slurry N than grass swards (Lambe et al., 2005), largely because growth stimulation of grasses by slurry N leads to competition with the legumes and so the net effect on total forage production is lower than for non-legume forages or mixtures. Consequently, the type of grass or legume-based forage to which slurry is applied may have an impact on the efficiency of utilisation of nutrients applied. From a management perspective, such differences between forage types as regards their responsiveness to slurry, could affect the choice of grassland to which slurry is applied. The following experiment was therefore undertaken to determine the effect of forage type on slurry N off take and efficiency of utilisation in a simulated silage cutting regime over four years.
2. Materials & Methods The trial was a slit plot design with slurry rate as the main plot factor and sward type as the sub-plot factor, with plots (112) 6.0 m x 1.5 m in size laid out in 4 replicate blocks in the autumn of 2004.
The trial was conducted over the subsequent 4 years, 2005-2008. Slurry was applied by the trailingshoe technique at an average annual rate of 0, 33.8 (Low), 60.0 (Medium) and 89.2 (High) m3 ha-1.
Across all slurry rates, 50% of the total annual application was applied in spring, and 25% applied after each of the first and second harvests. No other nutrients were applied during the four years of the trial. The seven sward types included two perennial ryegrass mixtures (diploid, PRG Dip, and tetraploid, PRG Tet), hybrid ryegrasses (Hyb RG), Italian ryegrass (Ital RG), low input mixture (LIM, comprising cocksfoot, perennial ryegrass, timothy and meadow fescue), perennial ryegrass/white clover (PRG WC) and red clover (RC).
Plots were harvested three times per annum, except in 2007, when four harvests were taken. The N content of herbage samples was determined using the Kjeldahl method, except in 2008, when the determinations were made by direct combustion using a Leco CN-2000 elemental analyzer. Annual DM response to slurry N was calculated from the difference between annual DM yield per slurrytreated plot and that of the corresponding forage receiving no slurry in that replicate, divided by the rate of slurry N applied. Apparent slurry N recovery was calculated similarly except difference in harvested N rather than in harvested DM was divided by the appropriate rate of slurry N applied.
Data were analysed by analysis of variance on a split plot model using Genstat (Release 12.1)
3. Results & Discussion Annual DM response to slurry N was significantly higher at the low slurry rate than at the two higher rates of application (Table 1a). The differences in response between sward types (P0.001) were due to the two legume-containing swards (PRG WC, RC) having a lower DM response to slurry application than the remaining grass-only swards (Table 1b).
Nitrogen Workshop 2012
Table 1. Annual response (kg DM harvested/kg slurry N applied), and apparent N recovery (kg N uptake in harvested herbage due to slurry/kg slurry N applied) per annum and for each application, all averaged over 4 years at: a) for three slurry rates, and b) for each sward type (no interactions were significant).
Apparent slurry N recovery declined significantly (P=0.06) with increasing slurry rate (Table 1a).
The legume-containing swards had a lower (P0.001) apparent N recovery than all the grass swards, with PRG-WC having a higher N recovery than RC. Among the all-grass swards, the apparent N recovery by Ital RG was the lowest, and that by LIM, the highest. Nitrogen recovery from the 1st spring slurry application was significantly higher at the lowest rate of slurry than at the other two rates, and over all rates, was significantly greater than that at the 2nd slurry application.
On average over all three slurry application rates, N recovery from the 2nd application was only about 40% of that from the other two applications (Table 1a). Except at the 1st application, apparent recovery of N was lowest for slurry applied to legume-containing swards (Table 1b). At the first application in spring, the recovery of slurry N by PRG WC was as high as the recovery by Ital RG.
The poorer DM response to slurry N and the lower N recovery by legume swards compared to grass-only swards was due to both a reduction in legume content and a lower apparent N fixation per unit weight of harvested herbage when slurry was applied. The poor apparent N recoveries from 2nd slurry applications, was partly due to weather conditions favouring ammonia loss (Lalor and Schulte, 2008), but mainly to slow regrowth and low N uptake following a heavy first harvest.
4. Conclusion To maximise use of slurry N, application to swards with high legume content and/or following heavy silage crops in early summer, should be avoided, unless other slurry nutrients are needed.
References Cherney, D.J.R., Cherney, J.H. and Mikhailova, E.A. 2002. Orchardgrass and tall fescue utilization of nitrogen from dairy manure and commercial fertilizer. Agronomy Journal, 94, 405-412.