Browsing by Person "Oelofse, Myles"

Now showing 1 - 2 of 2

Reliance on biological nitrogen fixation depletes soil phosphorus and potassium reserves
(2020) Reimer, Marie; Hartmann, Tobias Edward; Oelofse, Myles; Magid, Jakob; Bünemann, Else K.; Möller, Kurt
Limited nutrient availability is one of the major challenges in organic farming. Little is known about nutrient budgets of organic farms, the underlying factors or effects on soil fertility. We therefore assessed farm gate nutrient budgets for nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and sulfur (S) of 20 organic farms in Germany and analyzed their soil nutri-ent status. In average, the budgets showed a surplus of N (19 kg ha−1), K (5 kg ha−1), S (12 kg ha−1), and Mg (7 kg ha−1), and a deficit of P (−3 kg ha−1). There was, however, high variability between farms (e.g. standard deviation up to ± 36 kg N ha−1), which was mainly explained by different degrees of reliance on biological N fixation (BNF) as N source. When farms obtained more than 60% of their N input through BNF, they had deficits of P (mean −8 kg P ha−1) and K (mean −18 kg K ha−1). Nutrient status of most soils was within the ad-vised corridor, but for P, K and Mg, 10–15% of fields were lower and 45–63% were higher than advised. Extractable soil nutrient contents did not correlate with the nutrient budgets, inputs or outputs. Only extractable soil P increased with increasing P inputs and outputs. Fur-thermore, a decrease in extractable soil P was detected with a prolonged history of organic farming, indicating a risk of soil P mining in organic farming systems. In conclusion, the study revealed nutrient imbalances in organic farming and pointed to P and K scarcity as a major challenge for organic farms with high reliance on BNF in the long term.
Sustainable growth of organic farming in the EU requires a rethink of nutrient supply
(2024) Reimer, Marie; Oelofse, Myles; Müller-Stöver, Dorette; Möller, Kurt; Bünemann, Else K.; Bianchi, Silvia; Vetemaa, Airi; Drexler, Dóra; Trugly, Bence; Raskin, Ben; Blogg, Hugh; Rasmussen, Anton; Verrastro, Vincenzo; Magid, Jakob
The European Commission recently set a target of increasing the area of organic agriculture to 25% by 2030. To achieve this, it is imperative to understand current nutrient use patterns and identify sustainable nutrient supply opportunities. To that end, this study assessed the sustainability of the current nutrient origin and supply of 71 arable organic farms in 8 European regions. Deficient nutrient supply was found on 24%, 66%, and 56% of farms for nitrogen, phosphorus, and potassium, respectively. On average, we show a moderate surplus for nitrogen (28 kg ha −1 ), while phosphorus and potassium balances were close to zero (− 1 and 2 kg ha −1 , respectively). Large variation between countries and farm types shows a divide between more intensive systems relying on external inputs, and less intensive systems facing nutrient deficits and lower outputs. We show, for the first time, the extent of current use of external input types, where conventional manures supplied 17–26% of external nutrients and inputs from non-agricultural origin supplied 31–41%. A large proportion of nutrient sources within the last group are materials derived from urban wastes. The sustainable expansion of the organic sector will require increased use of locally available recycled fertilizers from urban wastes, and acceptance of such sources by organic farmers is shown to be high, provided they are considered safe.