Abstract
Typical values of plant available nitrogen (N) from animal manures are provided in fertilizer recommendation schemes. However, only a few attempts have been made thus far to study the variation in these values among contrasting soil types. The objective of this study was to examine the interactions between animal manure and soil types on N mineralization and total plant N recovery (shoots + roots) during one growing season.
A pot experiment was conducted in a greenhouse during a growth period of 180 days. Experimental treatments included solid cattle manure (SCM), cattle slurry (CS) and poultry manure (PM), all applied to sandy, clay and peat soils sown with perennial ryegrass. Total N application rate was 120 kg ha(-1).
There were clear interactions (P < 0.05) between the manure and soil types on N mineralization and total plant N recovery. For each manure type, both parameters followed the pattern (P < 0.01): peat > sandy > clay. In case of the peat soil, net mineralization of the applied organic N was on average 90 % from PM, 39 % from SCM and 26 % from CS. However, in the clay soil a positive net N mineralization occurred only from PM (42 %). Besides, significant proportions of the applied mineral N from SCM (17 %) and CS (35 %) were immobilized in this soil type. Consequently, apparent total plant N recovery was highest in the peat soil with values of 80, 57 and 50 % from PM, CS and SCM, respectively. In contrast, these values were only 57, 28 and 15 % for the clay soil.
It is concluded that wide variations do exist in the extent of net N mineralization and plant N recovery from a given animal manure type when applied to diverging soil types. This indicates the need for more soil-specific manure fertilizer recommendations.