The buffer zones seem to be effective to stop erosion and trap particle bound P in surface runoff from the autumn ploughed clay soil. On pastures, the buffers are not so important, if P fertiliser is not surface applied and the grazing intensity is not too high. However, the high DRP loss to surface runoff may be a real problem on grass fields in spring. The buffers are not able to uptake nutrients in early spring when the runoff is highest

Uusi-Kämppä, Jaana

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www.njf.nuNJF seminar 401 Phosphorus managementin Nordic-Baltic agriculture –reconciling productivityand environmental protectionUppsala, Sweden - 22-23 September 2008NJF Report Volume 4, No 4 • 2008pp _ pNJF Report • Vol 4 • Nr 4 • Year 2008               NJF Seminar 401  Phosphorus management in Nordic-Baltic agriculture – reconciling productivity and environmental protection  Book of abstracts Uppsala, Sweden – 22-23 September 2008     Editor: Gitte H Rubæk   Gitte H. Rubæk, Aarhus University, Faculty of Agricultural Sciences, Department of Agroecology and Environment, Blichers Allé 20, P.O. BOX 50, DK-8830 Tjele          Layout of frontpage: Tommy Nilsen, Follotrykk, Norway   Front page photos:  Tractor applying manure with trail hoses: Torkild S. Birkmose, Danish Agricultural Advisory Service, Denmark Algal bloom in Lake Årungen: Gunnhild Riise, Department of Plant and Environmental Sciences, Norwegian University of Life Sciences Buffer strip along an open ditch in central Sweden: Faruk Djodjic, Department of Water and Environment, SLU, Uppsala, Sweden    ISSN 1653-215 NJF Report • Vol 4 • Nr 4 • Year 2008 Evaluating vegetated buffer zones for phosphorus retention in cereal and grass production  Jaana Uusi-Kämppä Plant Production Research, MTT Agrifood Research Finland, FI-31600 Jokioinen Jaana.Uusi-Kamppa@mtt.fi    Introduction Agriculture is estimated to be the main cause of eutrophication and blue-green algae blooms in shallow freshwater lakes and coastal waters. One way to mitigate phosphorus (P) losses from agricultural soils is to establish buffer zones (BZs) between field areas and waterways. The BZs mitigate significantly erosion and the losses of particle phosphorus (PP) and total P (TP) in surface runoff (e.g. Dillaha et al., 1989; Uusi-Kämppä et al., 2000). Instead, retention of dissolved reactive P (DRP) may be poor on the BZs. This paper aims to evaluate the P removal efficacy of BZs when the field above is either conventionally tilled with autumn ploughing (1992–2002), pastured (May 2003–Apr. 2006) or direct drilled (May 2006– Apr. 2008).  Materials and methods The effects of 10-metre wide grass buffer zones (GBZs) and buffer zones under natural vegetation (VBZs) on the losses of total solids (eroded material), TP, PP and DRP in surface runoff on a 6-plot clay soil (Vertic Cambisol) were studied for 16 years at Jokioinen, SW Finland (Figure 1). The grass was cut and residue removed annually on the GBZs, whereas scrubs and herbs were not harvested on the VBZs. The results of field plots with GBZ and VBZ were compared with those of 70-m-long and 18-m-wide plots without a buffer zone (NBZs). The field area above the BZs was fairly even, whereas the BZs were on a steep slope (12–18%). The field above the BZs and the slope on the NBZs were ploughed in autumn and barley or oats were sown in spring 1992–2002 (Uusi-Kämppä, 2005). The annually used fertilizer amounts on the cereal field were typical on Finnish farms. The area was grazed by cattle (72, 234 and 128 cow grazing days ha-1 yr-1 in summer 2003, 2004 and 2005 respectively). The grass was killed off with Roundup in Aug. 2005, and barley was direct drilled into grass stubble the following spring. The fertilizer N and P amounts on the field were 150 kg N ha-1, 190 kg N ha-1 and 6 kg P ha-1, 130 kg N ha-1, and 68 100 kg N ha-1 in 2003, 2004, 2005 and 2006 respectively. After the harvesting of the barley in Aug. 2006, 20 t cattle slurry ha-1 (40 kg N ha-1, 6 kg P ha-1) was surface applied to the field area and to the slope of the NBZs, and after that winter wheat was direct sown.   Surface runoff to a depth of 0.3 m was collected in a modified collector trench designed by Puustinen (1994) at the lower end of each plot. The water volume was measured with a tipping bucket, and representative samples were taken for nutrient analyses (Uusi-Kämppä, 2005). The DRP was determined by a molybdate blue method, using ascorbic acid as the reducing agent (Murphy & Riley, 1962) after filtration (pore size 0.45 µm before 1995, and 0.2 µm since 1995). Surface soil was sampled on the BZs to analyse the concentration of easily soluble phosphorus (PAc) by the method used in Finland (0.5 M NH4–acetate–0.5 M acetic acid, pH 4.65; Vuorinen & Mäkitie, 1955).  Field60 mBuffer10 mN=Collector  (9 m)18 mPasture & Cut grass bufferPasture &  Grazedgrass bufferPasture & Non-cut scrub bufferPasture & Cut grass bufferPasture & Grazedgrass bufferPasture & Non-cut scrub buffer   GBZ VBZ NBZ VBZ NBZ  GBZ  Figure 1. Schematic diagram of the experimental field in 2003–2005.  Results and Discussion Surface runoff losses The losses of eroded material and PP declined by half, and the decrease of TP loss was ca 40% in the surface runoff on the GBZs and VBZs compared with those on NBZs in 1992–2002 (Table 1). Instead, the DRP loss was 60% higher on the plots   69with the VBZ than on the other treatments. The high DRP loss from the VBZs was most likely due to P leaching from the soil surface and high mass of decaying grass residue on the VBZ during spring runoff (Uusi-Kämppä, 2005; 2006). Also in laboratory experiments, the extraction of TP in plant leachates from the grass of the BZs was high (1.6–3.1 kg ha-1) after three freeze-thaw-cycles, over 90% being as DRP (Uusi-Kämppä, 2007). Thus, at least a part of the high surface runoff DRP losses in spring might have been from the frozen and thawed plants on the VBZ.  On the pasture, the mean annual losses of eroded material and PP to surface runoff were significantly smaller than those on the conventionally tilled field (Table 1). The mean DRP loss was, however, the highest on the pasture. Extremely high DRP losses (0.4–0.9 kg ha-1) were measured in spring runoff in 2003, after a warm and dry autumn. The mean concentrations of DRP were also rather high, over 1 mg L-1, in spring runoff 2003 (Uusi-Kämppä, 2006). After killing the grass in Aug. 2005, high DRP loss (0.6 kg ha-1) was measured the following spring. According to the first results from the direct drilling, there were no clear differences in erosion and nutrient losses among the treatments. The annual surface runoff losses in direct   Table 1. Mean (± difference of mean and minimum) annual precipitation, surface runoff, erosion and losses of total P, particle bound P and dissolved reactive P (DRP) on the conventionally tilled field, pasture and direct drilled field. Treatment Runoff  Erosion  Total P  Particle P  DRP (n)‡ mm  yr-1 t  ha-1 yr-1 kg  ha-1 yr-1 Conventional tillage with autumn ploughing, 1992–2002 (precipitation 660 mm yr-1) NBZ (245)  160 ± 20  1.3 ± 0.5  1.3 ± 0.5  1.2 ± 0.5  0.16 ± 0.02  GBZ (245)  130 ± 20  0.6 ± 0.09  0.8 ± 0.1  0.6 ± 0.1  0.16 ± 0.03 VBZ (245)  140 ± 20  0.5 ± 0.1  0.8 ± 0.08  0.5 ± 0.07  0.26 ± 0.02 Pasture, 13 May 2003–8 May 2006 (precipitation 653 mm yr-1)    NBZ (71)  130 ± 20  0.26 ± 0.06  0.9 ± 0.1  0.3 ± 0.07  0.59 ± 0.08 GBZ (72)  120 ± 20  0.24 ± 0.03  0.8 ± 0.03  0.3 ± 0.03  0.51 ± 0.01 VBZ (72)  110 ± 4  0.23 ± 0.003  0.7 ± 0.05  0.3 ± 0.06  0.41 ± 0.01 Direct drilling, 9 May 2006–17 Apr. 2008 (precipitation 674 mm yr-1)   NBZ (28)  100 ± 20  0.40 ± 0.08  0.7 ± 0.1  0.5 ± 0.09  0.20 ± 0.05 GBZ (28)  100 ± 10  0.34 ± 0.02  0.6 ± 0.02  0.4 ± 0.01  0.20 ± 0.01 VBZ (28)  70 ± 20  0.30 ± 0.06  0.5 ± 0.09  0.4 ± 0.06  0.16 ± 0.03 ‡ Number of sampling dates in parenthesis.    70drilling were as small as the losses on the plots with GBZ and VBZ in conventional tillage in 1992–2002 (Table 1). The study of direct drilling continues on the field.  Phosphorus in soil In the beginning of the study (April 1992), the mean PAc was 6.8–8.8 mg L-1 at a depth of 0–10 cm on the slope area of the experimental field (Figure 2). Later the PAc was measured from the surface soil (0–2 cm), and it was on the VBZ two times as high as on the NBZ and GBZ. On the VBZ, some DRP might also have leached from the surface soil. According to Sharpley et al. (1986) there is a significant linear relationship between the soil P content of the top 1-cm of surface soil and DRP concentrations in surface runoff from cropped and grassy watersheds. On the NBZ, the soil was fertilized in spring and ploughed in autumn. Due to ploughing the PAc in surface soil changed seasonally on the NBZ in 1992–2002 (Fig. 2).  0481216June 19928.5.199528.9.19959.5.19968.5.199821.10.199828.4.199912.10.200216.5.20031.9.20033.5.200413.10.200426.4.200510.10.200525.4.200623.8.2006PAc, mg L-1NBZ GBZ VBZPasture Conventional tillage DD Figure 2. Mean (± difference of mean and minimum) concentration of easily available P (PAc) in the surface soil (0–2 cm) on the slope areas without a buffer zone (NBZ), and with a grass buffer zone (GBZ) and with a vegetated buffer zone (VBZ). The above source area and the slope of the NBZ were conventionally tilled, pastured, and direct drilled (DD) in 1992–2002, 2003–2005, and 2006 respectively. In June 1992, the soil was sampled from a depth of 0–10 cm.   71Conclusions The buffer zones seem to be effective to stop erosion and trap particle bound P in surface runoff from the autumn ploughed clay soil. On pastures, the buffers are not so important, if P fertiliser is not surface applied and the grazing intensity is not too high. However, the high DRP loss to surface runoff may be a real problem on grass fields in spring. The buffers are not able to uptake nutrients in early spring when the runoff is highest. Moreover, part of DRP probably leached from the surface soil and from frozen and thawed grass residue on the BZs. Therefore, innovations are needed for trapping DRP from surface runoff in spring. According to the first results in the direct drilling, the buffer zones are not as important as in the conventional tillage where the fields are normally bare in the winter season. Further results are needed to give recommendations for buffer zones on direct drilled fields.  References Dillaha, T.A., Reneau, R.B, Mostaghimi, S., Lee, D., 1989. Vegatative filter strips for agricultural nonpoint source pollution control. Trans. ASAE 32, 513–519. Murphy, J., Riley, J.P., 1962. A modified single solution method for the determination of phosphate in natural waters. Anal. Chim. Acta. 27, 31–36.  Puustinen, M., 1994. Effect of soil tillage on soil erosion and nutrient transport in plough layer runoff. Publ. Water Res. Inst. 17, 71–90. Nat. Board of Waters and Environ., Helsinki. Sharpley, A.N., Smith, S.J., Menzel, R.G., 1986. Phosphorus criteria and water quality management for agricultural watersheds. Lake Reserv. Manage. 2, 177–182. Uusi-Kämppä, J., 2005. Phosphorus purification in buffer zones in cold climates. Ecol. Eng. 24, 491-502. Uusi-Kämppä, J., 2006. Vegatated buffer zones for agricultural non-point source pollution control. In: Horn, R., Fleige, H., Peth, S., Peng, X. (Eds.). Soil Management for Sustainability. Adv. in Geoegology 38, 337–343. Uusi-Kämppä, J., 2007. Effects of freezing and thawing on DRP losses from buffer zones. In: Heckrath, G., Rubæk, G.H., Kronvang, B. (Eds.). Diffuse phosphorus loss, Risk assessment, Mitigation Options and Ecological Effects in River Basins. The 5th International Phosphorus Workshop (IPW5), 3–7 September 2007, Silkeborg, Denmark. DJF Plant Science No. 130. Faculty of Agricultural Sciences, Aarhus Universitet, Denmark, pp. 169–172.   72Uusi-Kämppä, J., Braskerud, B., Jansson, H., Syversen, N., Uusitalo, R., 2000. Buffer zones and constructed wetlands as filters for agricultural phosphorus. J. Environ. Qual. 29, 151–158. Vuorinen, J., Mäkitie, O., 1955. The method of soil testing in use in Finland. Agrogeol. Publ. 63, 1–44.    73

Evaluating vegetated buffer zones for phosphorus retention in cereal and grass production

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