Synthesis of the Apelsvoll Cropping System Experiment in Norway – Nutrient Balances, Use Efficiencies and Leaching

Abstract

In this overview, a synthesis of the first 10 years of the Apelsvoll cropping system experiment, located in southeast Norway, is given. All major flows of N, P and K in six different cropping systems, each covering 0.18 ha of separately tile-drained plots, were either measured or estimated. The effects of the cropping system on the soil nutrient pools (total-N, -P, and-K) were evaluated using mass balances, and the usefulness of such balances to predict nutrient losses via drainage (leaching) and surface water (runoff) was investigated. The cropping systems were further evaluated in terms of leaching, runoff and use efficiencies. The experiment included conventional arable cropping (CON-A), integrated arable cropping (INT-A), organic arable cropping (ORG-A), conventional forage cropping (CON-F), integrated forage cropping (INT-F), and organic forage cropping (ORG-F). All the arable systems had a calculated reduction in the soil N content. The soil N content of the forage system CON-F was sustained over 10 years, whereas that of INT-F showed a slight reduction. The greatest reductions were calculated for the organic systems ORG-A and ORG-F, amounting to approximately 3.3% of the initial soil N pool (to a depth of 1 m). The two arable systems CON-A and INT-A had increases in their calculated soil P contents, with up to 70kg P ha-1 (CON-A) over the 10 years. The other extreme was found in the two organic systems, ORG-A and ORG-F, in which there were accumulated net reductions of more than 120 kg soil P ha-1 over the same period. CON-F appeared to sustain its soil P content, whereas INT-F had a calculated reduction less than half that of ORG-F. Calculated net changes in soil K followed a similar pattern as for soil P. The calculated net changes in soil N were confirmed, at least partly, by soil measurements. Despite the calculated reductions in total soil P and K, a similar pattern was not found in either plant-available P (P-AL) or in acid-extractable K (K-HNO3). Nitrogen was mainly lost via drainage water runoff, P mainly via surface runoff, and K almost equally by these two pathways. On an annual basis, N losses via drainage water and surface runoff were in the range of 17.6-35.2 kg N ha-1 yr-1, and increased in the order ORG-A≈INT-F≈ORG-F<INT-A≈CON-F<CON-A. Annual P losses were in the range of 0.36–0.49 kg P ha-1 yr-1 and the annual K losses were in the range of 6.22–9.69 kg Kha-1 yr-1. There were fewer differences between the systems in terms of P and K losses, but INT-A appeared to have the lowest overall P and K losses. The balance between N supply and N removal (N applied in fertilizer, animal waste and symbiotic fixation minus N in harvested crops) averaged over the 10-year period explained up to 87% of the variation in total N leaching and N runoff. In contrast to N, mass balances of P and K were poorly correlated with leaching and runoff losses of these nutrients. The integrated systems had the largest production to loss ratios for N, P and K within each group of production (compared with systems having the same crop rotation).