Nutrient Management Under Grazing

Abstract

Abstract. This chapter reviews nutrient management of intensively managed grasslands used for dairy farming in The Netherlands, with emphasis on research but with linkages to practice. Firstly, it provides an overview of the changes that have taken place in nutrient management research and practice during the 20th century. Secondly, it presents the current concept of nutrient management with application to grazed grassland. Finally, it discusses nitrogen (N) management of pastures and the tools to improve N management at operational level.Nutrient management under grazing has evolved from merely optimizing manure and fertilizer applications for high herbage yield towards improving nutrient use efficiency at farm level whilst maintaining productivity. Nutrient management under grazing is highly complex, because of the uneven distributions of nutrients in pastures, the difference in nutrient element requirements for herbage growth and dairy production, and the difference in mobility between nutrients and the tendency of especially N to escape from the system. Furthermore, boundary conditions of nutrient management in practice change frequently due to changes in manure policy.The economic costs of nutrients in dairy farms have decreased during the 20th century, but the time and costs associated with nutrient management in practice have increased, mainly because of the manure policy. Nutrient balance sheets have greatly contributed to increased understanding of nutrient cycling and nutrient management in dairy farming, as they provide guidance to improving nutrient use efficiency. Emphasis in nutrient management under grazing has been on N and to a much lesser extent on P, K and Mg. The emphasis on N follows from its impact on productivity and the environment. In the near future, there will be increasing attention also for P and micro-nutrients like copper and zinc as they tend to accumulate in intensively managed grassland soils to levels critical for the environment and animal and human health.

Assessing bioenergy potential in rural areas – A NEG-EROEI approach

“…Dairy manure is the biomass source with the highest single NEG, its efficiency (EROEI) can however be optimized by co-digestion with other types of manure and biomass since co-digested biomass is known to produce more energy than mono-digested ones [41]. The co-digestion of pig manure with other types of biomass will not conflict with phosphate recovery from pig manure, because resulting digestate can be further processed for the recovery of phosphate and many other valuable minerals [37,57]. The biomass yield and energy efficiency of cattle manure (dairy and beef cattle) for bioenergy production can also be improved by making cattle stay longer in barns and on hard surfaces.…”

“…Natural grassland management policy of the Netherlands requires that grasslands be mown two or three times annually for nature conservation purposes (reduction of nutrients in the ecosystem and restoration of ecological diversity) [36,37]. About 50% of silage grass from natural grasslands is usually used to supplement the grass in the feed-mix; however 50% of that can be made available for bioenergy production [38].…”

“…Although the late harvest scheme is about 72.6% more energy efficient than the intermediate harvest scheme and about 233% more energy efficient than the early harvest scheme, it may however not be feasible because of the natural grassland management policy of the Netherlands. It prescribes that nutrient-rich grasslands should be mowed two or three times annually; while nutrient-poor grasslands should be mowed once annually [36,37,56]. Consequently, the next most energy efficient and most feasible harvest scheme, which also gives the highest net energy gain on the natural grassland is the intermediate harvest scheme.…”