Key points are not available for this paper at this time.
K. Paustian, O. Andren, M. Clarholm, A.-C. Hansson, G. Johansson, J. Lagerlof, T. Lindberg, R. Pettersson, B. Sohlenius, Carbon and Nitrogen Budgets of Four Agro-Ecosystems With Annual and Perennial Crops, With and Without N Fertilization, Journal of Applied Ecology, Vol. 27, No. 1 (Apr., 1990), pp. 60-84
Paustian et al. (Sun,) studied this question.