Recycled by-products can make positive contributions to the yield and nutritional composition of grass-clover leys

Abstract

Four selected by-products (bioga s digestate, pot ale, wood ash and rockdust) were tested for their fertiliser value to a mi xed perennial ryegrass–red cl over crop in terms of crop performance (yield and botanical composition) and mineral quality. To render the results relevant to production systems on marginal land, tw o inherently low-fertility soils were used for the 14 months pot experiment . A number of nutrients of in terest in high-yielding dairy production were determined in plants and soils: N, P, K, Ca, Mg, Na, Co, Cu, Mn, Mo, Ni and Zn. All tested by-products increased overall yiel d and affected nutrient concentrations of the individual plant species. The effects differed between the grass and clover, though, which lead to changes in botanical compos ition indirectly affecting the nut rient concentrations of the mixed crop. Individual by-products increased concentrations of Cu, Mg, Na and/or Zn to close to or over the recommended minimum concen trations. There is thus potential to enhance agricultural productivity on margin al land through improved fora ge production and quality by matching of by-products, soils a nd forage species/mixtures. Howe ver, to secure sustainable use of by-products as fertilisers or soil ame ndments, soil quality must be considered and monitored in addition to crop quality, e.g. by using element balances