Method and timing of grassland renovation affects herbage yield, nitrate leaching, and nitrous oxide emission in intensively managed grasslands

• Published in: Nutrient cycling in agroecosystems 2010-04, Vol.86 (3), p.401-412
• Main Authors: Velthof, G. L, Hoving, I. E, Dolfing, J, Smit, A, Kuikman, P. J, Oenema, O
• Format: Article
• Language: English
• Subjects: Agriculture; Agronomy; application timing; Biomedical and Life Sciences; botanical composition; Clay minerals; Clay soils; clover; crop yield; cultivation; decision making; dissolved organic nitrogen; Dry matter; dry matter accumulation; Emission; Emissions; fertilizer; Fertilizer application; field experimentation; Field tests; gas emissions; Grassland management; Grasslands; herbicides; intensive farming; Leaching; Life Sciences; losses from soil; Mineralization; netherlands; nitrate nitrogen; Nitrates; Nitrogen; nitrogen fertilizers; Nitrous oxide; Organic chemistry; Organic nitrogen; Organic soils; pasture; Plant growth; plowing; range management; Research Article; Sandy soils; seasonal variation; soil; soil organic matter; Sward; swards
• ISSN: 1385-1314; 1573-0867
• DOI: 10.1007/s10705-009-9302-7

Managed grasslands are occasionally ploughed up and reseeded in order to maintain or increase the sward productivity. It has been reported that this renovation of grassland is associated with a flush of soil organic nitrogen (N) mineralization and with a temporary increase in soil mineral N contents. Here, we report on the effects of method and time of grassland renovation on herbage yield, nitrate (NO₃ ⁻) leaching and nitrous oxide (N₂O) emission. Field experiments were carried out at three sites (two sandy soils and a clay soil) in the Netherlands for three years. Renovation of grassland increased the percentage of Perennial ryegrass from 48-70% up to more than 90%. However, averaged over three years, dry matter yields were higher for the reference (not reseeded) swards (on average 13.6 Mg ha⁻¹ for the highest N application rate) than for the renovated grasslands (12.2-13.1 Mg ha⁻¹ dry matter). Grassland renovation in April did not increase N leaching in comparison to the reference. However, renovation in September increased the risk of leaching, because mineral N contents in the 0-90 cm were in November on average 46-77 kg N ha⁻¹ higher than in the reference. Contents of dissolved organic N (DON) in the soil were not affected by renovation. Renovation increased N₂O emissions by a factor of 1.8-3.0 relative to the reference grassland. Emissions of N₂O were on average higher after renovation in April (8.2 kg N₂O-N ha⁻¹) than in September (5.8 kg N₂O-N ha⁻¹). Renovation without ploughing (i.e. only chemically destruction of the sward) resulted in a lower percentage of perennial ryegrass (60-84%) than with ploughing (>90%). Moreover, N₂O emissions were higher after renovation without ploughing than with ploughing. Clearly, farmers need better recommendations and tools for determining when grassland renovation has beneficial agronomic effects. Losses of N via leaching and N₂O emission after renovation can probably not be avoided, but renovation in spring in stead of autumn in combination with ploughing and proper timing of fertilizer application can minimize N losses.