Groundwater quality on dairy farms in central South Africa

Leana Esterhuizen,Annabel Fossey,Elsa Potgieter

doi:10.4314/wsa.v41i2.04

Abstract

Dairy farms in central South Africa depend mostly on groundwater for domestic needs and dairy activities. Groundwater samples were collected from 37 dairy farms during 2009 and 2013. Sixteen water quality parameters were tested and compared to the standard. Four parameters in 2009 and six in 2013 exhibited 100% compliance with the standard. Nitrate, Escherichia coli and total coliforms showed relatively low compliance across farms and years. Almost all farms were noncompliant for hardness in both sampling years. T-tests revealed significant changes from 2009 to 2013 for pH (t = 2.580; p = 0.006), hardness (t = 2.197; p = 0.016) and potassium (K) (t = 1.699; p = 0.0468). For hardness, approximately 45% of the farms in 2009, and 57% in 2013, posed a health risk to sensitive consumers. More than 50% of the farms in both years demonstrated levels of nitrates that could pose a health risk, particularly for babies. High levels of coliforms and E. coli were found, indicating a health risk for clinical infections in consumers. The number of farms presenting 3 or more parameters with a health risk more than doubled from 13.5% in 2009 to 27.0% in 2013.

Highlights

Dairy farming is the fourth largest agricultural industry in South Africa, representing 6% of the gross value of overall agricultural production (Mkhabela et al, 2010)
On some of the farms the nitrate levels were exceptionally high, up to 7 times greater than the South African specified health limit of 11 mg/l (SABS, 2011), which is more stringent than the 50 mg/l specified for nitrates by the World Health Organisation (WHO, 2011)
A groundwater study conducted in the rural areas of South Africa indicated that increasing nitrate levels in groundwater are hazardous to bottle-fed infants as well as to livestock (Tredoux et al, 2000)

Summary

Introduction

Dairy farming is the fourth largest agricultural industry in South Africa, representing 6% of the gross value of overall agricultural production (Mkhabela et al, 2010). The dairy industry is a major contributor to the South African economy through employment, with about 60 000 farm workers employed by more than 4 000 milk producers (DAFF, 2012). The total number of milk producers, as recorded in January 2008, was 3 665, of which 919 were situated in the Free State Province (Mkhabela et al, 2010). Dairy farm effluent, which refers to manure and urine deposited throughout the milking process, is diluted while washing the milking shed floor (Williamson et al, 1998; Hooda et al, 2000). Animal waste in dairy effluent is a major source of pollution through nutrient enrichment of streams and groundwater which may, in turn, have a significant impact on the environment (Wilcock et al, 1999; Ali et al, 2006; Atalay et al, 2008; Kay et al, 2008; Van der Schans et al, 2009)

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Conclusion