P. Domburg et al., A comparison of N and P inputs to the soil from fertilizers and manures summarized at farm and catchment scale, J AGR SCI, 134, 2000, pp. 147-158
Use of fertilizers and manures during 1994 were studied at the farm and cat
chment scale in the largely agricultural Ythan catchment, north-east Scotla
nd, using farm level census data supplemented by questionnaire data. Grassl
and accounted for 40% of the agricultural land, and seven farm types repres
ented 87% of the total land, having an average size of 90 ha. The average l
ivestock density of 1.2 livestock units/ha was high compared to Scotland as
a whole (0.5). Rates of inorganic fertilizer applied to individual crops i
n the area corresponded with the national average and current advisory reco
mmendations. At the catchment scale, most fertilizer N was applied to grass
land (47%), whereas spring crops received the greatest proportion of the fe
rtilizer P (35%). The annual manure production equated to an average over t
he catchment of 63 and 16 kg/ha of N and P, respectively. When calculated f
or farm types these figures ranged from 27 and 6 kg/ha on 'cereal' farms to
384 and 163 kg/ha on 'pig' farms. The ratio of applied fertilizer N and P
varied from 4:1 for 'general cropping' to 10:1 for 'cattle and sheer (lowgr
ound)' farms. There was no significant compensatory reduction in inorganic
fertilizer applications on crops, which also had received manures.