Human activity has greatly perturbed the nitrogen cycle through increased fixation by legumes, by energy and fertilizer production, and by the mobilization of N from long-term storage pools. This extra reactive N is readily transported through the environment, and there is increasing evidence that it is changing ecosystems through eutrophication and acidification. Rothamsted Experimental Station, UK has been involved in research on N cycling in ecosystems since its inception in 1843. Measurements of precipitation composition at Rothamsted, made since 1853, show an increase of nitrate and ammonium N in precipitation from 1 and 3 kg N ha −" yr −" , respectively, in 1855 to a maximum of 8 and 10 kg N ha −" yr −" in 1980, decreasing to 4 and 5 kg N ha −" yr −" today. Nitrogen inputs via dry deposition do, however, remain high. Recent measurements with diffusion tubes and filter packs show large concentrations of nitrogen dioxide of c. 20 µg m −$ in winter and c. 10 µg m −$ in summer ; the difference is linked to the use of central heating, and with variations in wind direction and pollutant source. Concentrations of nitric acid and particulate N exhibit maxima of 1n5 and 2 µg m −$ in summer and winter, respectively. Concentrations of ammonia are small, barely rising above 1 µg m −$ .Taking deposition velocities from the literature gives a total deposition of all measured N species to winter cereals of 43n3 kg N ha −" yr −" , 84 % as oxidized species, 79 % dry deposited. The fate of this N deposited to the very long-term Broadbalk Continuous Wheat Experiment at Rothamsted has been simulated using the SUNDIAL N-cycling model : at equilibrium, after 154 yr of the experiment and with N deposition increasing from c. 10 kg ha −" yr −" in 1843 to 45 kg ha −" yr −" today, c. 5 % is leached, 12 % is denitrified, 30 % immobilized in the soil organic matter and 53 % taken off in the crop. The ' efficiency of use ' of the deposited N decreases, and losses and immobilization increase as the amount of fertilizer N increases. The deposited N itself, and the acidification that is associated with it (from the nitric acid, ammonia and ammonium), has reduced the number of plant species on the 140-yr-old Park Grass hay meadow. It has also reduced methane oxidation rates in soil by c. 15 % under arable land and 30 % under woodland, and has caused N saturation of local woodland ecosystems : nitrous oxide emission rates of up to 1n4 kg ha −" yr −" are equivalent to those from arable land receiving 200 kg N ha −" yr −" , and in proportion to the excess N deposited ; measurements of N cycling processes and pools using "&N pool dilution techniques show a large nitrate pool and enhanced rates of nitrification relative to immobilization. Ratios of gross nitrification : gross immobilization might prove to be good indices of N saturation.

The accumulation of carbon (C) and nitrogen (N) was measured on two sites on Rothamsted Farm that had been fenced off some 120 years ago and allowed to revert naturally to woodland. The sites had previously been arable for centuries. One had been chalked and was still calcareous; the other had never been chalked and the pH fell from 7.1 in 1883 to 4.4 in 1999. The acidic site (Geescroft wilderness) is now a deciduous wood, dominated by oak (Quercus robor); the calcareous site (Broadbalk wilderness) is now dominated by ash (Fraxinus excelsior), with sycamore (Acer pseudoplatanus) and hawthorn (Craetagus monogyna) as major contributors. The acidic site gained 2.00 t C ha−1 yr−1 over the 118‐year period (0.38 t in litter and soil to a depth of 69 cm, plus an estimated 1.62 t in trees and their roots); the corresponding gains of N were 22.2 kg N ha−1 year−1 (15.2 kg in the soil, plus 6.9 kg in trees and their roots). The calcareous site gained 3.39 t C ha−1 year−1 over the 120‐year period (0.54 t in the soil, plus an estimated 2.85 t in trees and roots); for N the gains were 49.6 kg ha−1 yr−1 (36.8 kg in the soil, plus 12.8 kg in trees and roots). Trees have not been allowed to grow on an adjacent part of the calcareous site. There is now a little more C and N in the soil from this part than in the corresponding soil under woodland. We argue from our results that N was the primary factor limiting plant growth and hence accumulation of C during the early stages of regeneration in these woodlands. As soil organic N accumulates and the sites move towards N saturation, other factors become limiting. Per unit area of woodland, narrow strips; that is, wide hedges with trees, are the most efficient way of sequestering C – provided that they are not short of N.

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Globally soil quality and food security continue to decrease indicating that agriculture and the food system need to adapt. Improving connection to the soil by knowledge exchange can help achieve this. We propose a framework of three types of connections that allow the targeting of appropriate messages to different groups of people. Direct connection by, for example, handling soil develops soil awareness for management that can be fostered by farmers joining groups on soil-focused farming such as organic farming or no-till. Indirect connections between soil, food and ecosystem services can inform food choices and environmental awareness in the public and can be promoted by, for example, gardening, education and art. Temporal connection revealed from past usage of soil helps to bring awareness to policy workers of the need for the long-term preservation of soil quality for environmental conservation. The understanding of indirect and temporal connections can be helped by comparing them with the operations of the networks of soil organisms and porosity that sustain soil fertility and soil functions.

Several in vitro fermentation studies had demonstrated the efficacy of Mootral, a patent-pending natural feed supplement, in reducing methane gas production. In order to test the supplement's application in a commercial farm, Jersey (n = 121) and Holstein-Friesian (HF, n = 275) lactating cows received 500 g of pellets containing 3% Mootral powder for 12 weeks. Their enteric methane gas production was monitored using a hand-held laser methane detector. During 7 weeks of pre-Mootral supplementation period, dry matter intake (DMI), milk yield and milk quality (fat, protein, urea, pH, bulk tank somatic cell count (BTSCC)) were monitored for both herds and continued during 12 weeks of Mootral supplementation (Mootral period), and 4 weeks after withdrawal of Mootral (post-Mootral period). Feed samples were analysed during each period, and feed efficiencies (FE) for each herd were calculated. Compared to the baseline, the methane gas produced by the Jersey and HF cows during the Mootral period were lower by 38.3% and 20.7% (p < 0.05), respectively. DMI for Jerseys were greatest during the pre-Mootral period (p < 0.05), while no difference was recorded for the HF cows. Milk yield increased significantly (p < 0.05) for both herds during Mootral supplementation. FE increased significantly for the Jersey herd during the Mootral and post-Mootral periods (p < 0.05). Statistically significant changes were detected for urea in both herds, and BTSCC for HF cows, but these did not adversely affect milk quality. Results demonstrated Mootral reduces enteric methane production in lactating cows while increasing milk yield without affecting milk quality.