The fate of phosphorus under contrasting border-check irrigation regimes
R. W. McDowell A C and D. Rowley BA AgResearch Ltd. Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand.
B Department of Geography, University of Otago, PO Box 56, Dunedin, New Zealand.
C Corresponding author. Email: richard.mcdowell@agresearch.co.nz
Australian Journal of Soil Research 46(4) 309-314 https://doi.org/10.1071/SR07192
Submitted: 22 November 2007 Accepted: 10 April 2008 Published: 23 June 2008
Abstract
Flood-irrigation, to the extent that outwash (runoff from border-check bays) occurs, is a major cause of P loss from grazed pastures and has potential to harm surface water quality. We used a combination of rainfall simulation to produce runoff and field sampling of outwash to investigate processes of P loss from treatments receiving no irrigation and irrigation at 10%, 15%, and 20% soil moisture and every 21 days (3w). Intact soil blocks were removed from each treatment, dung removed, soils wetted to about 32% soil moisture, and runoff produced via rainfall simulation. This indicated that P losses were proportional to soil Olsen P concentrations (29.8–51.4 mg Olsen P/kg; 0.096–0.541 mg dissolved reactive P/L). Olsen P concentration was less in those treatments receiving a greater number of irrigations due to increased pasture production and, presumably, loss via outwash. When soil blocks were allowed to dry, concentrations in runoff more than doubled and were paralleled by a decrease in soil microbial biomass P. However, when outwash was sampled in the field, P loss was greater in more frequently irrigated treatments. This was attributed to increased stocking rates and P-release from dung masking any soil effect. However, differences in P loss in outwash from 2 treatments (without recent grazing) were attributed to different soil moisture before irrigation. Assuming 25% of irrigation is lost as outwash, annual loads were estimated to range from 0.7 kg P/ha in the 10% treatment, irrigated 2.6 times a year, to 12.6 kg P/ha in the 3w treatment, irrigated 6.5 times per year. This suggests that the frequency of irrigation and stocking rate dictate the majority of P lost in this system (not soil P concentration). Hence, mitigation practices should be promoted to minimise outwash in intensively sheep-grazed pastures and potential surface water quality impacts.
Additional keywords: dung, Olsen P, microbial biomass, fertiliser.
Austin NR,
Prendergast JB, Collins MD
(1996) Phosphorus losses in irrigation runoff from fertilized pasture. Journal of Environmental Quality 25, 63–68.
Bush BJ, Austin NR
(2001) Timing of phosphorus fertilizer application within an irrigation cycle for perennial pasture. Journal of Environmental Quality 30, 939–946.
| PubMed |
Carey PL,
Drewry JJ,
Muirhead RW, Monaghan RM
(2004) Potential for nutrient and faecal bacteria losses from a dairy pasture under border-dyke irrigation: a case study. Proceedings of the New Zealand Grassland Association 66, 141–149.
Close ME, Woods PH
(1986) Leaching losses from irrigated pasture: Waiau Irrigation Scheme, North Canterbury. New Zealand Journal of Agricultural Research 29, 339–349.
Condron LM,
Sinaj S,
McDowell RW,
Dudler-Guela J,
Scott JT, Metherell AK
(2006) Influence of long-term irrigation on the distribution and availability of soil phosphorus under permanent pasture. Australian Journal of Soil Research 44, 127–133.
| Crossref | GoogleScholarGoogle Scholar |
Eisenreich SJ,
Bannerman RT, Armstrong DE
(1975) A simplified phosphorus analytical technique. Environmental Letters 9, 45–53.
McBride SD
(1994) Pasture yield responses to irrigation in Canterbury. Proceedings of the New Zealand Grassland Association 56, 165–168.
McDowell RW
(2006) Contaminant losses in overland flow from cattle, deer and sheep dung. Water, Air, and Soil Pollution 174, 211–222.
| Crossref | GoogleScholarGoogle Scholar |
McDowell RW,
Monaghan RM, Carey PL
(2003) Potential phosphorus losses in overland flow from pastoral soils receiving long-term applications of either superphosphate or reactive phosphate rock. New Zealand Journal of Agricultural Research 46, 329–337.
McDowell RW,
Nash DM, Robertson F
(2007) Identifying the source of phosphorus lost from a grazed pasture soil. Journal of Environmental Quality (in press),
McDowell RW,
Sharpley A,
Brookes P, Poulton P
(2001) Relationship between soil test phosphorus and phosphorus release to solution. Soil Science 166, 137–149.
| Crossref | GoogleScholarGoogle Scholar |
McDowell RW, Sharpley AN
(2002) Effect of plot scale and an upslope phosphorus source on phosphorus loss in overland flow. Soil Use and Management 18, 112–118.
McDowell RW, Stewart I
(2005) Phosphorus in fresh and dry dung of grazing dairy cattle, deer and sheep: Sequential fractionation and 31P nuclear magnetic resonance. Journal of Environmental Quality 34, 598–607.
| PubMed |
McDowell RW, Trudgill ST
(2000) Variability of phosphorus loss from a small catchment in South Devon, U.K. Agriculture, Ecosystems & Environment 79, 143–157.
| Crossref | GoogleScholarGoogle Scholar |
Mundy GN,
Nexhip KJ,
Austin NR, Collins MD
(2003) The influence of cutting and grazing on phosphorus and nitrogen in irrigation runoff from perennial pasture. Australian Journal of Soil Research 41, 675–685.
| Crossref | GoogleScholarGoogle Scholar |
Nash D,
Hannah M,
Halliwell D,
Webb B, Chapman D
(2004) A field study of phosphorus mobilisation from commercial fertilisers. Australian Journal of Soil Research 42, 313–320.
| Crossref | GoogleScholarGoogle Scholar |
Parfitt RL,
Yeates GW,
Ross DJ,
Mackay AD, Budding PJ
(2005) Relationships between soil biota, nitrogen and phosphorus availability, and pasture growth under organic and conventional management. Applied Soil Ecology 28, 1–13.
| Crossref | GoogleScholarGoogle Scholar |
Saville DJ,
Moss RA,
Bray AR, Hannagan RB
(1997) Soil nutrient distribution in pastures flood-irrigated by the border strip method. New Zealand Journal of Agricultural Research 40, 99–110.
Turner BL,
Bristow AW, Haygarth PM
(2001) Rapid estimation of microbial biomass in grassland soils by ultra-violet absorbance. Soil Biology & Biochemistry 33, 913–919.
| Crossref | GoogleScholarGoogle Scholar |
Turner BL, Haygarth PM
(2001) Phosphorus solubilization in rewetted soils. Nature 411, 258.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Turner BL, Haygarth PM
(2003) Changes in bicarbonate-extractable inorganic and organic phosphorus by drying pasture soils. Soil Science Society of America Journal 67, 344–350.
Williams PH, Haynes RJ
(1992) Balance sheet of phosphorus, sulphur and potassium in a long-term grazed pasture supplied with superphosphate. Fertilizer Research 31, 51–60.
| Crossref | GoogleScholarGoogle Scholar |
