effects of agricultural buffer strips on the ecological quality of adjacent surface waters
DESCRIPTION
Poster presentation at INTECOL 2013, LondonTRANSCRIPT
Dutch national policy
● Reduction of nutrient and herbicide emission to surface waters
Testing for effects of agricultural buffer strips
on the ecological quality of adjacent surface waters
Jan H. Wanink, Ronald Bijkerk, Marian van Dongen, Jetty Noordam
Koeman en Bijkerk bv, Ecological Research and Consultancy, P.O. Box 111, 9750 AC Haren, The Netherlands
Water Board Hunze en Aa's, P.O. Box 195, 9640 AD Veendam, The Netherlands
www.koemanenbijkerk.nl
www.hunzeenaas.nl
[email protected] [email protected]
Variable H1 t n p
Total P A < B 1.08 41 0.8573
Total N A < B - 2.42 50 0.0095
Ammonia A < B - 2.21 37 0.0169
Nitrate A < B - 2.18 40 0.0175
Variable (2009) H1 t n p
EQR
macrophytes A > B 0.31 16 0.3796
EQR species
composition A > B 1.76 16 0.0497
N characteristic
species A > B 1.40 16 0.0908
Variable H1 t n p
Chloride A < B - 2.47 48 0.0085
Conductivity A < B - 2.33 46 0.0122
Measures
● Application of buffer strips between farmland and adjacent watercourses
● Fertilization and spraying of the strips prohibited
Research questions
● Are buffer strips effectively reducing phosphorus and nitrogen loads?
● Is buffer strip management effectively improving ecological water quality?
Disadvantage of monitoring and trend analysis
● Large seasonal fluctuations in nutrient loads inhibit trend detection
Our solution
● One-time sampling of many paired stations; using paired Student’s t-test
● Northeastern Netherlands: 35 farmers constructed 160 km buffer strips in 2006
● We sampled 52 paired stations A (buffer strip) and B (control) in 2008/2009
● Strips were 3 m wide, sewed with a mixture of grain, grasses and weeds
● Stations A (next to buffer strip) located at the downstream end of the strip
● A and B at opposite sides of same arable plot (identical management) EQR = Ecological Quality Ratio (Water Framework Directive)
Tested water parameters ● Temperature, transparency, conductivity, acidity, dissolved oxygen
● Nitrogen / phosphorus compounds; chloride ● Aquatic vegetation
Results
● A-stations: lower concentrations of total nitrogen, nitrate and ammonium
● A-stations: lower concentrations of chloride
● A-stations: lower conductivity
● A-stations: higher EQR macrophyte species composition (in 2009)
● No significant differences between A and B for the other parameters
Conclusions
● Pairwise testing is an effective method to determine intervention effects
● Absence of differences for P, attributed to internal fluxes from sediment
● For other parameters, attributed to spatial variation / small sample sizes
● A-stations: lower conductivity attributed to lower chloride concentrations
● Aquatic vegetation: response time longer than for chemical parameters