High Nitrogen Costs of Dairy Production in Europe: Worsened by Intensification

Intensification of agriculture has been proposed as one way of minimizing emissions per unit of product, apparently legitimizing the ongoing structural changes in agriculture. We have investigated the relationship between the farming intensity and the nitrogen (N) dissipation by calculating the overall N emission factor (E: total N surplus per unit of N in the produce) from several studies of dairy farms, covering a wide range of environments and production intensities. Fundamental steps were 1) the distinction between trophic levels, mineral, plant and animal N; and 2) the inclusion of N losses related to bought feed. The results show that E increases significantly with the production intensity of the dairy farm. The tradition for separate optimization of the animal and crop sectors may be a reason. We suggest that the N pollution can be mitigated by more extensive farming, both by re-coupling crop and animal production side by side, and by keeping land under cultivation when production is reduced

Lite nitrogentap fra mjølkegarder som baserer seg på egen fôrprodukjson

Tap av nitrogen (N) er et stort problem i landbruket, og i Europeiske direktiver blir det krevd forandring i landbrukspraksis for å redusere avrenningen. Ekstensiv mjølkeproduksjonen basert på heimeprodusert fôr er den mest effektive måten å bedre N-effektiviteten på. N-effektiviteten på gardsnivå reduseres dersom innkjøpet av fôr er høgt i forhold til planteproduksjonspotensialet på garden

Large variation in nitrogen efficiency among organic and non-organic farms

Agricultural production is requested to be environmental friendly and resource efficient. A literature review of farm surveys and prototype farm studies found that increasing use of N fertilizer and imported feed increased the yields and the productivity of dairy farms, but also increased the N-surplus. We studied the N-efficiency and cause of variation in organic and non-organic commercial dairy farms. Increased amount of purchased-N per ha farmland increased the farm N-surplus per ha on organic and non-organic farms. Increased amount of purchased-N tended to decrease N-efficiency, but not on non-organic farms. The correlation between the N-surplus per unit of produce and N-purchase was weak. The organic farms had lower N-surplus per ha than the conventional farms, had higher efficiency of imported nitrogen and lower N-surplus per unit of produce, leading to an overall better utilization of available N. Within organic and non-organic farm management, the variation in estimated N-efficiencies is larger than the differences between the averages of these two groups

High N relative to C mineralization of clover leaves at low temperatures in two contrasting soils

Predicting N mineralization from green manure in different soil types during the cold season is instrumental for improving crop management with higher N use efficiency and reduced risks of N losses in a cool and humid climate. The objective of our work was to study the effects of low temperatures and soil type on the net nitrogen (N) mineralization and the relationship between N and carbon (C) mineralization from N-rich plant material. A silty clay loam and a sandy loam were incubated with or without clover leaves for 80 days at 0, 4, 8.5 or 15 ◦C. The results showed a substantial mineralization of N in clover leaves (7% of N added), unaffected by temper- ature, already on 3rd day. This was followed by net N immobilization for about 4 weeks in the clay soil, with similar tendencies in the sandy soil, and more severely at the higher than the lower temperatures. After 80 days of incubation, net N mineralization was only 13–22% of total N in clover leaves. The ratio of net mineralized N to C was higher at lower temperatures, and higher in the sandy than in the clay soil. After the immobilization period, the N mineralization increased, positively related to temperature, and the ratio of net mineralized N to C became constant. In conclusion, low temperature during the initial phase of mineralization altered the ratio between net N and C mineralization from easily decomposable plant material, and the net N mineralization occurred more rapidly in the sandy soil. The change in stoichiometry at low temperatures, as well as the modifying effect of soil type, should be considered when predicting N mineralization of N-rich plant material

Species interactions in a grassland mixture under low nitrogen fertilization and two cutting frequencies II:Nutritional quality

Mixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in a three-cut and a five-cut system in southern Norway, at a low fertilization rate (100 kg N ha−1 year−1). The nutritional quality (annual weighted averages) of the dried forage from the two-first harvesting years was analysed. There was no significant effect of species diversity on crude protein (CP) concentration. In the three-cut system, we found a significant species diversity effect leading to 10% higher concentrations of acid detergent fibre (ADF), 20–22% lower concentrations of water-soluble carbohydrate (WSC) and 4% lower net energy for lactation (NEL) concentrations in mixtures compared with pure stands (averaged across the two-first years). In the five-cut system, similar effects were seen in the first year only. This diversity effect was associated with a reduction in WSC and NEL concentrations and an increase in ADF, NDF and CP concentrations in the grass species, and not in red clover, when grown in mixtures. This is thought to be a combined result of better N availability and more shading in the mixtures. Species diversity reduced the intra-annual variability in nutritional quality in both cutting systems.acceptedVersio

Karbon til bondens beste

This report summarizes our observations from the project “Carbon for benefit of the farmer” on carbon storage, biological activity, soil structure and other physical soil conditions on commercial farms in Surnadal and Sør-Østerdal and Solør. In the last 20 years, these farms have had either solely arable farming or crop rotations with grassland included. We do also present simple methods for assessment of soil quality for agricultural advisors and farmers. More carbon storage in soil is wanted to both remove CO2 from the atmosphere and enhance organic matter content, which improves the agronomic characteristics of the soil when it is low in organic matter. Crop rotations with grassland and fertilization, particularly with manure has been seen upon as measures to enhance the content of organic matter and thus carbon storage in soil. However, there have been done few investigations on this in silty and sandy soils. We have chosen Surnadal and Sør-Østerdal and Solør areas because there are farms with silty sand in both those areas and because they are placed in two different climatic zones (coast and domestic climate). Both places have farms with solely arable farming and farms with grasslands in the crop rotation. We selected eight farms in each of two areaes. In Surnadal there were four arable farms and four farms with also grasslands in the crop rotation. In Sør-Østerdal and Solør there were less differences in the crop rotations between farms with solely arable land and crop rotations with grassland included. The farms were fertilized with mineral fertilizer and animal manure, mainly slurry from cattle or pig. On the farms with grassland included in crop rotation there were none that only used mineral fertilizer. On each farm two fields with cereals 2020 were chosen. On each of these fields two sample areas were selected where we investigated soil physical, biological, and chemical parameters. The period of sample collection lasted from August until October 2020, and it was in all farms done shortly after the cereal was threshed. We observed a clear trend with more organic carbon, better soil aggregate formation and aggregate stability, more rapid transformation of organic matter and more earthworms with grasslands included than by solely arable farming. Isolated, many of these factors are not significantly different, but together they showed a pattern with better soil conditions when grassland is included in crop rotations. For the factors root depth, penetration depth, soil infiltration, soil pore volume, POXC-carbon and soil respiration, the difference between solely arable farming and when grassland is included, is not so clear. One could assume that a part of the differences between farms with and without grassland in crop rotation could be explained by more manure used in farms with grassland, but that is not the case. Contradictory, on some of the arable farms larger quantities of animal manure was used than on the farms with grasslands included. However, we observed that fertilization with animal manure increased carbon storage, improved aggregate stability, and enhanced soil respiration on arable farms. We recommend the spade as the best tool to judge soil structure, dense layers, root growth, content of earthworms and degradation of plant material from last year. This can be supplemented with various simple methods like digging down a piece of cotton cloth, or a tea bag and then examining how much is left a few months later. Penetrometers and infiltration measurements can provide valuable information, but moisture conditions and soil type must be considered in the assessments. Bouncing tails and other small insects can be caught in a trap and counted. There are several simple microbiological tests under development such as Pasco CO2 sensor, Solvita basal CO2 and Microbiometer. We will gather more experience before we make recommendations on them

Improving N efficiency in barley through green manure management and biogas slurry

In cereal production on stockless organic farms, green manure (GM) is commonly used to improve soil fertility. The clover-grass swards are mown frequently and the herbage is commonly mulched. The purpose of this study was to increase knowledge of the N-dynamics in such rotations, in order to suggest methods for improving N efficiency and thus organic cereal yields. The hypothesis was that spring application of biogas residue from anaerobic digestion of GM herbage increases the N uptake and yield of a subsequent barley crop, compared with repeatedly in situ mulching of the same GM herbage in the preceding season. The effect of various GM treatments on spring barley yields and nitrogen dynamics was investigated, at four sites differing in soil and climatic conditions. The results suggest that, under the Norwegian climate, mulching of GM herbage can increase cereal yields compared to its removal, depending on soil type and rotation history. However, the use of GM herbage for biogas production appears to be much more N-efficient on farm level. We applied about half of the N available in GM herbage, and the surplus residue makes it possible to manure other fields

Variations in nitrogen utilisation on conventional and organic dairy farms in Norway

Reduced N-surpluses in dairy farming is a strategy to reduce the environmental pollution from this production. This study was designed to analyse the important variables influencing nitrogen (N) surplus per hectare and per unit of N in produce for dairy farms and dairy systems across 10 certified organic and 10 conventional commercial dairy farms in Møre og Romsdal County, Norway, between 2010 and 2012. The N-surplus per hectare was calculated as N-input (net N-purchase and inputs from biological N-fixation, atmospheric deposition and free rangeland) minus N in produce (sold milk and meat gain), and the N-surplus per unit of N-produce as net Ninput divided by N in produce. On average, the organic farms produced milk and meat with lower N-surplus per hectare (88 ± 25 kg N·ha−1) than did conventional farms (220 ± 56 kg N·ha−1). Also, the N-surplus per unit of N-produce was on average lower on organic than on conventional farms, 4.2 ± 1.2 kg N·kg N−1 and 6.3 ± 0.9 kg N·kg N−1, respectively. All farms included both fully-cultivated land and native grassland. Nsurplus was found to be higher on the fully cultivated land than on native grassland. N-fertilizers (43%) and concentrates (30%) accounted for most of the N input on conventional farms. On organic farms, biological Nfixation and concentrates contributed to 32% and 36% of the N-input (43 ± 18 N·kg N−1 and 48 ± 11 N·kg N−1), respectively. An increase in N-input per hectare increased the amount of N-produce in milk and meat per hectare, but, on average for all farms, only 11% of the N-input was utilised as N-output; however, the N-surplus per unit of N in produce (delivered milk and meat gain) was not correlated to total N-input. This surplus was calculated for the dairy system, which also included the N-surplus on the off-farm area. Only 16% and 18% of this surplus on conventional and organic farms, respectively, was attributed to surplus derived from off-farm production of purchased feed and animals. Since the dairy farm area of conventional and organic farms comprised 52% and 60% of the dairy system area, respectively, it is crucial to relate production not only to dairy farm area but also to the dairy system area. On conventional dairy farms, the N-surplus per unit of N in produce decreased with increasing milk yield per cow. Organic farms tended to have lower N-surpluses than conventional farms with no correlation between the milk yield and the N-surplus. For both dairy farm and dairy system area, N-surpluses increased with increasing use of fertilizer N per hectare, biological N-fixation, imported concentrates and roughages and decreased with higher production per area. This highlights the importance of good agronomy that well utilize available nitrogen.acceptedVersio

Nitrogen mineralization from clover leaves: Effect of soil type and low temperature

The period following the incorporation of N-rich leys into soil is crucial both for the N supply to the following crop and for the risk of N leaching. Soil-crop models used for exploring the possibility of improving the nitrogen recovery, generally assume that there is a stoichiometric relationship between carbon and nitrogen mineralization. Our aim was to study how temperature and soil type affect the net N mineralization relative to C mineralization of plant litter incorporated in soil. This knowledge is instrumental for improving the modelling of nitrogen dynamics after ploughing. The experiment confirmed that N mineralization of N-rich plant material occurs even at 0 °C, and that the ratio of net mineralized N to mineralized C is larger at lower than at higher temperature