Nutrient supply to organic farms is a highly discussed topic in Europe, due to the restricted availability of external fertilizer resources and the use of contentious inputs. To optimize the flow of nutrients throughout the organic farming system, it is firstly necessary to obtain valid data on the nutrient status of organic farms. Nutrient budgets are a valid tool to investigate the nutrient demand or surplus of a system. However, there is currently no comprehensive overview of nutrient budgets of European organic farms. We therefore carried out a meta-analysis on 56 individual studies that reported either farm-gate or soil surface budgets. The analysis showed an imbalance between nutrients, a general surplus of nitrogen (45 kg N ha −1 year −1 [95% confidence interval (CI) 30, 61]), magnesium (16 kg Mg ha −1 year −1 [− 9, 40]) and sulfur (45 kg S ha −1 year −1 [− 29, 118]), a balanced phosphorus budget (0 kg P ha −1 year −1 [− 2, 2]), and a deficit for potassium (− 12 kg K ha −1 year −1 [− 21, − 3]). We observed large differences between farms that could be partly explained by farm type and budgeting method. Arable and mixed farms showed lower nitrogen, phosphor, magnesium, and sulfur budgets than dairy/beef farms or even vegetable farms, while all farm types besides dairy/beef farms showed deficits for K budgets. Further, farm-gate budget studies yielded higher budgets than soil surface budgets. Variations between studied countries could also be detected, but the coverage and comparability are low due to differences in studied farm types and budgeting method.

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.

Reducing soil tillage can lead to many benefits, but this practice often increases weed abundance and thus the need for herbicides, especially during the transition phase from inversion tillage to non-inversion tillage. We evaluated if subsidiary crops (SCs, e.g., cover crops) can mitigate the effects of non-inversion tillage on weed abundance. Two-year experiments studying SC use, tillage intensity, and nitrogen (N) fertilization level were carried out twice at six sites throughout northern and central Europe. SCs significantly reduced weed cover throughout the intercrop period (−55% to −1% depending on site), but only slightly during the main crops. Overall weed abundance and weed biomass were higher when using non-inversion tillage with SCs compared to inversion tillage without SCs. The effects differed due to site-specific weed pressure and management. With increasing weed pressure, the effect of SCs decreased, and the advantage of inversion over non-inversion tillage increased. N fertilization level did not affect weed abundance. The results suggest that SCs can contribute by controlling weeds but cannot fully compensate for reduced weed control of non-inversion tillage in the transition phase. Using non-inversion tillage together with SCs is primarily recommended in low weed pressure environments.

Ethyl 7-Chlorobutyrate.-Thirty-five grams (77%) of this product was obtained when 40 g. of y-ethoxybutyric acid, which boiled at 114-116°(7 mm.),20 and 54 g. of thionyl chloride were heated on a steam-bath for four hours. The ethyl -chlorobutyrate boiled at 70-71°( 10 mm.).21 When 30 g. of the ester was heated for six hours on a steam-bath with 18 cc. of coned, hydrochloric acid and the mixture extracted with ether, 8 g. of y-chlorobutyric acid, b. p. 104-109°( 6 mm.), and 18 g. of unchanged ester were obtained. Upon further fractionation, 4 g. of the acid was found to boil at 107-108°( 6 mm.); m. p. 13°.22 The following compounds were prepared in the manner described above. Ethyl iodobutyrate was obtained in 67% yield; b. p. 69-71°( 3 mm.).23Ethyl y-diethylaminobutyrate was prepared in 78% yield; b. p. 73-75°( 4 mm.).24 The hydrochloride, after recrystallization from a mixture of acetone and ether, melted at 113°.