ABSTRACT
The three main sources of plant nutrients are the soil, organic manures (farmyard manure (FYM), animal slurries) and manufactured inorganic fertilizers. The soil has a basic fertility but there are well documented physical, chemical and biological means of improving its nutrient-supplying power. A wide range of manufactured fertilizers, which contain precise amounts of plant nutrients, are available for grassland farming. Similarly, organic manures are a source of plant nutrients (as is soil organic matter, which converts to humus), but their nutrient contents can vary considerably. Table 6.1 shows estimates of the N, P and K amounts supplied by animal slurries (Frame, 2000). Slurries and FYM also contain lesser amounts of Ca, Mg and S, the values of which are often overlooked. Estimates of readily available nitrogen (N), phosphorus (P) and potassium (K) in undiluted livestock slurry from 100 animals in 4 weeks https://www.niso.org/standards/z39-96/ns/oasis-exchange/table">
Livestock (liveweight)
Nutrients (kg)
N
P
K
Dairy cows (550 kg)
280
45
450
Young cattle (250 kg)
80
10
120
Fattening cattle (400 kg)
160
30
270
Fattening pigs (70 kg)
50
15
25
Source: Based on Frame, 2000.