Contaminationof soil, surface water and groundwater with biogenic compounds(nutrients, macroelements), most notably nitrogen and phosphorus, is themajor environmental threat posed by large-scale livestock farming.Concentrated livestock production and intensified agriculturalproduction are major sources of pollution from agriculture. Thecirculation of matter in agroecosystems can be seriously compromised,especially when livestock waste (organic fertilisers) are not includedin the agricultural production, which can be considered the distinctivefeature between agricultural holdings and farm enterprises. In cropproduction, only around 30% of nitrogen is released to the environment,as opposed to 75% nitrogen losses in livestock production.
Thiscan be explained by the fact that some farms are focused exclusively onlivestock production, and tend to be located at a large spatial andtechnological distance from farms which cultivate land. The increasinggap between industrial livestock production and crop production meansthat large livestock farms produce excess livestock waste which is nolonger a fertiliser (high-value by-product) but a troublesome wasteproduct.
90%of crop production in Poland is consumed by livestock, and the share ofmanure in total fertiliser consumption is only 15%, which illustratesthe real scale of imbalance in the circulation of biogenic compounds inagroecosystems. For comparison, around 38% of all fertilisers used areartificial fertilisers (GUS, 2009). Estimated overproduction of biogeniccompounds in agricultural holdings is as follows: N - 56 kg/ha/year, P -20 kg/ha/year, K - 22 kg/ha/year.
Itis assumed that the volume of biogenic compounds excreted by cattle isthe same as the volume produced by 16.4 humans, 1.9 pigs, 0.3 minks, and0.14 of poultry. If a cow produces 74.2 kg N and 14.4 kg P per year,then the daily production is around 203 g of nitrogen and around 40 g ofphosphorus. For daily waste production of 150 L per cow, the meanconcentrations of nitrogen and phosphorus compounds are around 1350 mg/Land 263 mg/L, respectively. These values exceed the maximum permittedconcentrations of nitrogen and phosphorus in municipal waste by dozen orhundred times (a mean of 20-85 mg/L of total nitrogen and 6-20 mg/L oftotal phosphorus). What follows, the maximum cattle livestock whichwould guarantee full utilization of natural fertilisers (produced fromlivestock waste) is 1-2 animals per 1 ha.
Onaverage, around 50% of nitrogen, 80% of phosphorus and around 95% ofpotassium contained in feed is excreted. 55% of nitrogen and 99% ofphosphorus is excreted with faeces. As much as 80% of potassium isexcreted with urine. There values are to a large extent influenced bythe animal rearing system, for example, in intensive livestockproduction, nitrogen content in urine exceeds 70% of total nitrogencompounds excreted.
Thehighest quantities of biogenic compounds from livestock waste(equivalent to emissions to the natural environment) are lost inlivestock farming, fertiliser storage and landspreading. Around 10-25%of nitrogen is lost in non-litter livestock buildings, and around 30% -80% in straw-bedded livestock buildings, around 25% in swine housings,and around 70% in deep litter poultry housings. 20-50% of nitrogen islost from manure slabs. 10% (manure) to 65% (slurry) is lost fromlandspreading; around 50-70% is leached from soil.Medium uptake ofnutrients in Polish agricultural holdings is around 20-30% for N, around25-40% for P and slightly above 10-30% for K.
Over-fertilisationand nutrient runoff from fields to groundwater are the sources ofsurface water pollution, and the resulting pollution of the Baltic Sea.It is estimated that around 75% of all nitrogen compounds and over 95%of phosphorus compounds which pollute the Baltic Sea are carried withwater. Total nitrogen and phosphorus runoff to the Baltic Sea in 2006amounted to around 638,000 and 28,400 tons, respectively (HELCOM, 2010).Poland (24% N; 36% P), Sweden (19% N; 13% P) and Russia (17% N and 14%P) are the major contributors (HELCOM, 2010). Per capita nitrogen andphosphorus runoff in Estonia ? around 22 kg and 1.2 kg, respectively, isthe highest (in Poland, per capita nitrogen and phosphorus runoff isaround 3.5 kg and 0.2 kg). Agriculture in general is the biggest sourceof highest nitrogen and phosphorus supply to the Baltic Sea.
Thereare diffuse sources and point sources (such as large-scale livestockproduction) of agricultural pollution distinguished. Point sources arespecific discharge sites (factories, municipal waste collectors), asopposed to diffuse sources which include surface runoff from largeareas, related mainly to crop production as well as small and mediumlivestock farms. It is estimated that 60% of nitrogen and 40% ofphosphorus (from agriculture) is discharged to the Baltic Sea fromlarge-scale livestock farming.
Large-scalelivestock farms should be classified as point sources of pollution dueto the nature of nutrient runoff (clearly defined and restricted to asmall area, as is the case with industrial facilities), and thedischarge volume. The concentration and extent of contributions fromintensive livestock production as point sources of the Baltic Seapollution with nutrients can be illustrated by comparing a city with25,000 inhabitants and a large-scale non-litter livestock farm with25,000 dairy cows. In consideration of the living conditions, body massand physiology of compared organisms, this comparison is based on highlygeneralized points of reference; however, it illustrates the scale ofenvironmental impact of large-scale livestock farming.
Poortechnical condition or even absence of fertiliser storage installationsincreases nitrogen and phosphorus runoff to soil and water. In a studyconducted in Miedwie Lake catchment area in Zachodniopomorskie Province,Poland, only nearly 53% of livestock farms had proper livestock housingfacilities. Moreover, enclosed natural fertiliser tanks were present inonly slightly more than 26% of these holdings. It is estimated thatonly 35-45% of all agricultural holdings in Poland are equipped withproper manure storage slabs, and only 20-30% of all agriculturalholdings in Poland have suitable tanks for fermented urine.
Whatis also important, coastal regions are considered most exposed to waterpollution by nitrogen and phosphorus compounds from agriculture. Therisk of contamination with potassium compounds is also the highest incoastal regions.
Waterpollution, water eutrophication, soil degradation, and increasedcontent of nutrients in crops are the most serious consequences ofnutrient overload. Another consequence, which is often underestimated,is the accumulation of nitrates, which are toxic to animals(decomposition of Vitamin A and beta-carotene, growth and developmentinhibition, haemoglobin conversion into methaemoglobin), and ofpotassium, which is antagonistic to many macro-and microelements(including phosphorus, magnesium, sodium, copper, cobalt) in some crops(oat, barley, corn, lucerne, sugar beets, fodder beet) and weeds (milkthistle, common nettle, goosefoot, common amaranth). High nitrate levelscan create conditions favourable to the development of toxic andcarcinogenic nitrosamines. Contamination of plants can result in toxintransfer to livestock feed, human food, and wild animals.
Accordingto the Regulation of the Minister of the Environment of 23 December2002 on criteria for classifying water exposed to pollution by nitrogencompounds from agricultural sources (Polish Journal of Laws Dz.U.2002.241.2093), waters with nitrate content of 50 mg N-NO3/lor with signs of eutrophication should be classified waters pollutedfrom agricultural sources.Waters with nitrate content of 40 - 50 mgN-NO3/L and rising are classified as waters at risk ofpollution. It is estimated that nitrate content in as many as half ofall water wells in agricultural holdings in Poland is higher than thelimit values established for potable water (10 mg/l N-NO3).