Does balanced phosphorus fertilisation sustain high herbage yields and phosphorus contents in alternately grazed and mown pastures?

Abstract

Many soils of agricultural land in affluent countries have been enriched with phosphorus (P), because P application via fertilisers and manures was larger than P withdrawal via harvested biomass. This practice threatens the long-term availability of P fertilisers derived from finite rock phosphates, as well as surface water quality because of P leaching and runoff losses. In response, restrictions on P fertilisation have been implemented in some countries. The objective of this study is to examine the effects of balanced P fertilisation in comparison to a surplus P fertilisation on dry matter (DM) grass yield, grass quality, and soil P status. A 15 years' lasting field experiment was conducted on four permanent grassland sites, on sand (two sites), peat and young marine clay in the Netherlands. Fertilisation levels, including cattle slurry, were aimed to implement P surpluses of 0, 9, and 18 kg P ha -1 year -1 , and N surpluses of 180 and 300 kg ha -1 year -1 . Grasslands were alternately grazed and mown, and grass yields and soil P levels were measured. Annual DM yield, P content, and P yield of grazed grassland were lower at balanced P fertilisation than at a surplus of 9 or 18 kg P ha -1 -year -1 on sand and peat. Differences between P treatments remained constant over time. On the recently reclaimed marine clay, DM yield did not differ between P treatments, but P content and P yield did respond to different P surpluses. Differences between sites in the response to P surpluses were related to differences in soil P status, according to P-AL (capacity indicator) and P-CaCl 2 (intensity indicator). At balanced P fertilisation, P-AL tended to decrease, while P-CaCl 2 tended to remain constant. At surplus P, P-AL tended to increase and P-CaCl 2 tended to remain constant. Herbage yield and P uptake also strongly responded to N treatments. In conclusion, there is a risk that balanced P fertilisation reduces herbage yield and P content relative to surplus P fertilisation, even at relatively high soil P status. The risk of yield reduction seems to be related to the ratio between the P intensity indicator and P capacity indicator.Electronic supplementary material The online version of this article

Crop yields and NPK use efficiency of a long-term experiment on a former sea bottom in the Netherlands

“…In such cases, the flows in Figure 5.2 move from labile to stable pools. Soil P increases, the more stable pools stronger than the more labile pools (Van Middelkoop et al, 2016). It takes considerable time to lower soil P ( Van der Salm et al, 2008), similar to the experience in this long-term experiment.…”

Intensification of Grassland-Based Dairy Production and Its Impacts on Land, Nitrogen and Phosphorus Use Efficiencies

“…These latter farms are required to lower the soil P status, so as to decrease the risk of soil P leaching and eutrophication of surface waters [62,63] . In the course of time, soil P status will likely decrease and the permissible P input will increase again, without much risk of crop yield losses [64] .…”

De enkelvoudige versus de gecombineerde indicator voor bepaling van de fosfaattoestand van de bodem : toetsing op data van veeljarige veldproeven op grasland en bouwland

“…De parameters a1 en a2 duiden respectievelijk de verandering in de fosfaatindicator bij evenwichtsbemesting (α1 * jaar) en bij overschotbemesting (α2 * jaar * P 2 O 5 overschot), waarbij het fosfaatoverschot is uitgedrukt als kg P 2 O 5 /ha/jaar. De gevonden trends zijn in overeenstemming met eerdere analyses welke zijn opgenomen in eerdere publicaties (Van der Salm et al, 2017;Middelkoop et al, 2016). Het model houdt rekening met de temporele variaties in de fosfaatindicatoren.…”

“…Op alle locaties is sprake van een statistisch significant effect van de fosfaatgift op het P-AL-getal bij gebruik van een statistisch model (REML-analyse) waarin rekening wordt gehouden met de temporele variatie en zodoende getoetst ten opzichte van de behandelingen met evenwichtsbemesting(Middelkoop et al, 2016). Echter, vanuit landbouwkundig oogpunt is een toename in het P-AL-getal pas relevant wanneer sprake is van een absolute en -in de tijd -consistente toename van het P-ALgetal.…”