Sissel Hansen

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

Abstract 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.

Status of selenium and vitamin E on Norwegian organic sheep and dairy cattle farms

Herbage selenium (Se) concentration is generally low in Norway. It is unknown whether feeding practices on Norwegian organic farms fulfil the dietary needs of Se and vitamin E for sheep and dairy cattle. Therefore we analysed Se in soil and herbage, and Se and vitamin E in animal blood in the indoor feeding season at 14 organic dairy and 14 organic sheep farms. The herbage Se concentration was low. Approximately 50 and 35% of all samples in the first and second cut, respectively, had Se concentrations below the detection limit of 0.01 mg/kg dry matter (DM). The median (10th, 90th percentile) Se concentrations were <0.01 (<0.01, 0.03) and 0.02 (<0.01, 0.06) mg/kg DM in the first and second cuts, respectively. Whole blood Se concentrations were 0.10 (0.04, 0.15) μg/g in dairy cattle and 0.14 (0.03, 0.26) μg/g in sheep. Vitamin E concentrations were 4.2 (2.7, 8.4) mg/l in dairy cattle and 1.3 (0.9, 2.4) mg/l in sheep. None of the soil or plant variables explained the variation in herbage Se concentration, although Se in soil and plant tended to be correlated. Herbage Se concentration was inadequate to meet the dietary Se requirements. Vitamin E requirement was only met in dairy herds. We recommend Se and vitamin E supplementation to ruminants on organic farms.

Factors affecting the concentration of Zn, Fe and Mn in herbage from organic farms and in relation to dietary requirements of ruminants

To obtain a general picture of the herbage zinc, iron and manganese concentrations and their relation to dietary requirements of ruminants on organic farms, we analysed soil and herbage samples from four regions in Norway. The soil median Zn, Fe and Mn concentrations were 0.18, 13 and 0.84 mg/L, respectively. The herbage median (10th–90th percentile) Zn, Fe and Mn concentrations (mg/kg) in herbage in the first cut were 19 (14–34), 50 (36–88), 34 (22–86) and in the second cut 21 (16–37), 84 (52–171) and 66 (36–205), respectively. The results of mixed model analysis of herbage Zn, Fe and Mn indicate that soil pH, soil texture, soil mineral concentration and botanical composition are the most influencing factors. We conclude that Zn, Fe and Mn did not limit plant growth, and that the herbage concentrations, except for Zn, were sufficient to meet the dietary needs of ruminants on organic dairy farms.

Yield Responses and Nutrient Utilization with the Use of Chopped Grass and Clover Material as Surface Mulches in an Organic Vegetable Growing System

ABSTRACT Trials were performed with red beet and white cabbage in 1998–2001 to assess the effects on yields and nutrient utilization of surface mulch (chopped grass and/or red clover). No other nutrients were applied. Nitrogen (N), phosphorus (P) and potassium (K) contents were measured in mulch, saleable products and above-ground plant residues. A single mulch application of about 12 Mg DM ha−1 increased the yields of both crops significantly. Mean yields of saleable products were increased from 27 to 33, and from 44 to 56 Mg FW ha−1 of red beet and white cabbage, respectively. However, the average apparent recoveries of mulch derived nutrients in above-ground plant parts, calculated by subtraction of uptakes in the control treatment, were only 13, 14 and 18% of N, P and K, respectively. Some 3–10% of the N supplied in mulch was found as mineral N at 0–60 cm soil depth after harvest, and in late autumn approximately half of the P and all the K supplied was found as P-AL or K-AL (ammonium lactate and acetic acid) plus acid-soluble K in the topsoil. Mulch application also increased the yield level of spring cereals grown in the following year by on average 0.6 Mg ha−1, or 20%.

Copper, molybdenum and cobalt in herbage and ruminants from organic farms in Norway

To evaluate the animal nutritional status of copper, molybdenum and cobalt on Norwegian organic farms, soil, herbage and animal blood samples were collected from 27 dairy and sheep farms and analysed for Cu, Mo and Co. The herbage median (10th–90th percentile) Cu, Mo, and Co concentrations (mg/kg DM) and the Cu:Mo ratio in the first cut were 5.3 (3.9–6.8), 1.5 (0.6–4.8), <0.05 (<0.05–0.08) and 3.8 (1.1–8.3) and in the second cut 7.0 (5.7–9.3), 3.3 (1.6–10.1), 0.06 (<0.05–0.15) and 2.0 (0.8–5.2), respectively. The results of mixed model analyses of herbage Cu and Mo indicated that soil pH, soil organic matter content, herbage botanical composition, yield and phenological stage of timothy at harvest mostly influenced the herbage micronutrient concentration. We conclude that plant growth was not limited by the supply of Cu, Mo or Co, but the herbage mineral nutrient concentration alone was not balanced to meet the dietary needs of ruminants. Supplements of mineral nutrient mixtures and/or concentrates fortified with Cu and Co are required to ensure sufficient supply for ruminants.

Nitrogen fixation by red clover as related to the supply of Cobalt and Molybdenum from some Norwegian soils

A field trial, a pot experiment and a survey of organically farmed leys were undertaken to investigate whether N fixation in red clover pastures in Norway was limited by a low supply of cobalt and/or molybdenum. Fertilization with Mo did not result in any higher production or N fixation, whereas the N yield both from established clover leys and red clover grown in pots increased slightly after application of Co to many of the investigated soils. In the organically farmed leys there was a significant and positive correlation between Co content and the N content of the red clover. As many of the investigated clover-soil systems were of those previously known to be very low in Co and Mo, and the gain in N yield obtained by extra Co supply was marginal, it is unlikely that deficiency of these trace elements is a problem of great concern in legume based forage production systems in Norway.

N2O emissions from a cultivated mineral soil under different soil drainage conditions

In poorly drained (PD) soils, fertilizer N containing NO3 is easily denitrified. To determine emissions of N2O-N from PD, imperfectly drained (ID) and moderately well drained (MD) mineral soils, soil moisture and groundwater levels were monitored, and gas samples were collected from closed gas chambers during two crop growing seasons (i.e. April to August 2011 and 2012) in the South East of Norway. The gas samples were analyzed for N2O-N flux using gas chromatograph. In 2011, the depth to groundwater table ranged between 1 and 40 cm in PD, 50 and 89 cm in ID and 74 and 96 cm in MD soils during the growing seasons. In 2012, the depths were 11–51 cm in PD, 55–81 cm in ID and 46–78 cm in MD soil. Daily mean water filled pore space (WFPS) ranged between 51% and 70% in PD, 44% and 62% in ID and 38% and 72% in MD soils in 2011 and in 2012, the WFPS felled within this range. During the growing season, N2O flux rate (µg N m−2 h−1) varied from 20 to 635 (6–878) in PD, 22 to 112 (11–1607) in ID and 4 to 33 (8–92) in MD soils in 2011–2012 (mean of five chambers). Peak N2O-N fluxes in PD and ID soils were detected one week after fertilizer applications and immediately after rain events. Cumulative N2O-N emissions (kg N ha−1) from PD (6–10), from ID (4–12) and from MD soils (0.2–0.9) were emitted during (2011–2012) growing season. In general, PD soils emitted more N2O-N compared to MD soils mainly due to higher soil moisture and relatively shallow ground water table.