Search

Nitrogen (N) budgets at farm level are influenced by N fertilisation recommendations. In this study, we reviewed and analysed the underlying principles and methods of N fertilisation recommendations in 10 West European countries, to identify similarities and differences, and develop suggestions for reconsideration and improvement. An analysis of national official documents on N fertilisation recommendations revealed that there were three main categories of calculation methods: (i) 'N mass balances' (France, Italy, Spain), (ii) 'Corrected standards' (Germany, Netherlands, Switzerland, Luxembourg), and (iii) 'Pre‐parameterised calculations', which rely on a soil N supply typology (United Kingdom, Ireland, Belgium). In total 16 variables were identified in the calculation methods. The more complex methods use 10 (Italy, France), while the simplest only rely on 3 (Luxembourg). The most common variables include the availability of N in manure, the N uptake by a crop, and the N released by crop residues. Few countries explicitly consider N losses to ground and surface waters or to the atmosphere in the calculation methods. In some countries, the N fertilisation recommendation has a voluntary status, and in other countries, a legal one (caps on maximum allowable N rates). We compared the N fertiliser recommendations for a wheat crop grown on a farm with livestock, and for a farm with a diverse arable crop rotation without livestock. Across the 10 countries, large differences in the N fertilisation calculation methods and resulting N recommendations existed for the two management scenarios, ranging from almost no fertilisation to 135 kg N ha−1, and from 111 to 210 kg N ha−1, respectively. The differences were not accounted for by the complexity of the equations used, but rather resulted from contrasting reference values for N availability in manure, N uptake by crop and N leaching. However, the study concluded that standardisation of the method to calculate N fertilisation recommendations is likely to be counterproductive as there are no objective reasons to favour one method more than the others. Nonetheless, improvements in N use efficiency are necessary. Farm scale mass balance, combined with parameters such as minimum residual soil mineral N test at harvest, was suggested as being an important consideration. [ABSTRACT FROM AUTHOR]

The article challenges the notion that cover crops are effective in increasing soil organic carbon (SOC) stocks. The authors argue that the study's validity is questionable due to the exclusion of relevant published experimental data that show clear positive effects of cover crops on SOC stocks. They also criticize the authors for not following international standards for systematic reviews and meta-analyses. The article concludes that doubts about the positive effects of cover crops on SOC are unjustified and criticizes the authors' opinions on the relevance of policies and public subsidies. [Extracted from the article]

Cover crops (CC) promote the accumulation of soil organic carbon (SOC), which provides multiple benefits to agro‐ecosystems. However, additional nitrogen (N) inputs into the soil could offset the CO2 mitigation potential due to increasing N2O emissions. Integrated management approaches use organic and synthetic fertilizers to maximize yields while minimizing impacts by crop sequencing adapted to local conditions. The goal of this work was to test whether integrated management, centered on CC adoption, has the potential to maximize SOC stocks without increasing the soil greenhouse gas (GHG) net flux and other agro‐environmental impacts such as nitrate leaching. To this purpose, we ran the DayCent bio‐geochemistry model on 8,554 soil sampling locations across the European Union. We found that soil N2O emissions could be limited with simple crop sequencing rules, such as switching from leguminous to grass CC when the GHG flux was positive (source). Additional reductions of synthetic fertilizers applications are possible through better accounting for N available in green manures and from mineralization of soil reservoirs while maintaining cash crop yields. Therefore, our results suggest that a CC integrated management approach can maximize the agro‐environmental performance of cropping systems while reducing environmental trade‐offs. [ABSTRACT FROM AUTHOR]

Cover crops (CCs) provide ecosystem services to agricultural systems by soil health enhancement. However, the long‐term legacy of CCs on arbuscular mycorrhizal fungi (AMF) and subsequent main crop performance is unclear. The main objective of this work was to assess the 8‐year legacy of CCs on AMF activity and several soil and plant parameters during a subsequent maize (Zea mays L.) crop. The study was conducted in a field experiment established in 2006 under Mediterranean climate. Winter treatments were fallow and two CCs, barley (Hordeum vulgare L.) and vetch (Vicia sativa L.). We chose four sampling dates during maize development to evaluate the effect of CCs on AMF over time. Compared with fallow treatment, barley CC increased mycorrhizal colonization by 7%, the hyphae length by 39–124%, and AMF spores by 48–87%. However, contrary to expectations, vetch CC did not have any effect on AMF. Overall, earlier sampling dates better displayed treatment differences. Mycorrhizal colonization percentage demonstrated time‐sensitive values, whereas other AMF parameters (hyphae length, AMF spores) better maintained treatment differences over time. Mycorrhizal stimulation after barley increased maize shoot P concentration but shoot N was not increased despite the N deficit. Soil water stable aggregates were enhanced by barley CC (25–51% higher than fallow), notably related to the length of hyphae, AMF spores and glomalin content. Promotion of soil aggregation, nutritional state and plant height by CCs did not translate into maize yield increments. The main benefits of introducing CCs were related to the enhancement of soil quality and nutrient supply rather than to an increased yield of the following maize crop. [ABSTRACT FROM AUTHOR]

In the northeast of Spain, the production of large amounts of pig slurry that exceed the fertilization requirements of local field crops is contributing to the deterioration of the soil environment. In recent years, the construction of six treatment facilities has allowed the exportation of nutrient surplus as thermally dried pig slurry (TDPS). Even though it is already used as an amendment, however, little is known about its effect on soil N availability. A long-term aerobic incubation test was used to monitor organic C and apparent N mineralization. After 34 wk, the untreated soil cumulative apparent N mineralization value was 145 mg kg-1 and the potentially mincralizable N (θN*) was 196.6 mg kg-1. In soil treated with 1.6g kg-1 TDPS, the θN* increased by 14% in relation to untreated soil. In soil treated with 4.8 g kg-1of TDPS, the ϑN* increased by 24%. The similar patterns of the emitted CO2-C and the recovered NO3-N in the untreated soil and TDPS-treated soil show that it is unlikely that significant losses of N occur as gaseous N. It was found that when a low N dose was used, the ϑN* was 66% of that added, but only 37% was detected when a higher dose was used. This suggests that, in relative terms, at higher doses there is less microbiological activity than at lower doses. Adding 62.8 mg N kg-1 as (NH 4)2HPO4 and (NH2)2CO, however, enhanced the mineralization of the soil organic N, providing 20% more N in relation to the untreated soil. [ABSTRACT FROM AUTHOR]

Capacitance probes (CP) based on responses to electromagnetic properties in soil are widely used for monitoring soil volumetric water content (θv), but proper calibration is necessary to obtain reliable results. The objectives of this study were to: (i) compare errors in evaluating θv when using soil-specific equations as opposed to the manufacturer's default equation; (ii) compare the CP calibration equations obtained in the laboratory and in the field; and (iii) evaluate the accuracy of CP under field conditions using soil-specific equations as opposed to the manufacturer's default equation. Laboratory and field calibrations were conducted by fitting statistical relationships between readings from CP and θv measured from soil cores. The accuracies of the obtained calibration equations were evaluated under field conditions during two irrigation cycles. In both calibration studies, the manufacturer's default equation consistently overcalculated θv (RMSE > 0.044 m3 m-3), whereas custom CP calibration equations provided accurate θv determinations (RMSE < 0.028 m3 m-3). Even when θv was overestimated, the manufacturer's default equation was able to reproduce θv dynamics during irrigation. Therefore, if users are interested in relative differences in θv, they may use the manufacturer's default equation. If absolute values are needed, however, soil-specific calibration is required. The accuracy of CP in monitoring θv under field conditions was slightly better using the laboratory calibration equation (RMSE = 0.0 19 m3 m-3) rather than the field calibration equation (RMSE = 0.023 m3 m-3). The use of a laboratory calibration is recommended given that it is easily reproducible, facilitates work planning, and minimizes uncertainties. [ABSTRACT FROM AUTHOR]