Nitrogen balance and seasonal fluctuations in soil nitrogen contents in a corn (Zea mays L)‐rye (Secale cereale L) rotation field

Abstract

AbstractIn a corn (Zea mays L)‐rye (Secale cereale L) rotation field, the N output (plant uptake) and N input (crop residue and fertilizer applied) were measured for two years in order to evaluate the N balance in a forage production field. The soil was Low‐humic Andosol (mesic Typic Hapludand). The disappearance of crop residues on both a dry matter and N basis, and the seasonal fluctuations of total, inorganic, and available soil N content in the field were investigated. The interaction between the nitrogen balance and the soil N contents are discussed. The total plant N uptake of the corn and rye exceeded the sum of the N input of the fertilizer applied and the N from crop residues, so the N balance of the corn‐rye rotation had a negative value (two year average: −8.4 gN m−2). After the gradual disappearance of crop residue on the dry matter basis, rapid disappearance on the N basis was observed. At the same time, the C/N ratio decreased to less than 20. The soil available (38.4–55.3 mg kg−1) and inorganic (21.5–45.2 mg kg−1) N had their lowest values in spring. After they increased in early summer, they decreased in late summer and increased in autumn. The total N (0.5–0.7%) gradually decreased during the experimental period. The results indicated that the soil‐available N and inorganic N in the present study were highly dependent on the fertilizer‐applied N. The relation among management practices, N input and soil available N contents are discussed. It is suggested that the negative N balance is one of the causes for a decrease in soil total N.