The role of tactical and operational grassland management in achieving agronomic and environmental objectives; ‘De Marke’, a case study

Abstract

Reduction of N losses, especially nitrate leaching, is an important objective for dairy farms in the Netherlands. So far, many strategies have focused on changes in strategic and tactical management. Little attention has been paid to operational grassland management. So a conceptual model of operational grassland management was defined, with strong interactions between N rates, realized dry matter (DM) yields, herbage N content, growing days and utilization per cut. Analysis of data from 'De Marke' and from monitoring projects shows that grassland production and utilization can be improved by changes in operational grassland management. DM yields for grazing and cutting need to be increased, grazing per paddock must be shorter and slurry must be applied as early as possible. This improved grassland management is able to partly compensate the decrease in DM production resulting from a lower N input.

Operational nitrogen fertilizer management in dairy farming systems: identification of criteria and derivation of fertilizer application rates

“…The use of a fixed growth period of 30 d leads to relatively high N fertilizer application rates in the first half of the growing season and to strongly diminishing N applications in the second half of the growing season, except when the amount of unrecovered N is used as an additional criterion (Figure 2). Inventories indicate that many dairy farmers in the Netherlands do not aim at a target DM yield of herbage but at a target growth period of 15–21 d during the whole season, while N‐fertilizer application rates are based on target DM yields of herbage of about 2000 kg DM ha −1 when used for grazing (Holshof, 1997; Vellinga and Hilhorst, 2001). Farmers often use a fixed growth period per cut, as this fits within a rotational grazing system.…”

“…, 1991; Van Den Brandt and Smit, 1997; Vertès et al. , 1997; Vellinga and Hilhorst, 2001; Ondersteijn et al. , 2002).…”

“…The approach presented allows farms to select their preferred criteria but at the same time provides them with the consequences of their choice. The approach can be extended to include constraints of nitrate leaching, ammonia volatilization, legislation and farm economics explicitly (Anonymous, 1991;Scholefield et al, 1991;Van Den Brandt and Smit, 1997;Vertè s et al, 1997;Vellinga and Hilhorst, 2001;Ondersteijn et al, 2002).…”

“…Soil mineral nitrogen (SMN) at the end of the growing season has been suggested as a good indicator of N loss via leaching and denitrification (Barraclough et al. , 1992; Cuttle and Bourne, 1993), although the amount of unrecovered N fertilizer is to a limited extent found as SMN (Vellinga and Hilhorst, 2001). Another complicating factor is grazing.…”

“…In this study, target DM yields of herbage for grazing and cutting are set at 2000 and 3000 kg DM ha )1 respectively (Anonymous, 1998). Growth periods per cut were set at 20 and 30 d (Vellinga and Hilhorst, 2001). When target DM yield of herbage is used as criterion, growth period is the result and vice versa.…”