Effects of biochar, urea and their co-application on the nitrogen mineralization in soil and growth of Chinese cabbage crop
Ruth
Baiga and Rajashekhar Rao BK*
Department of Agriculture
The Papua New Guinea University of Technology
Private Mail Bag, Lae 411
Morobe Province, Papua New Guinea
Tel: +675 4734464, Fax: +675 4734477
* Dr. Rajashekhar Rao B.K., E-mail: rsraobk@rediffmail.com
Abstract
Experiments
were conducted to study the influence of biochar material on N
mineralization pattern
from the soil applications of kunai grass (Imperata
cylindrica)
biochar (at 0 and 10 t ha-1)
and laboratory grade urea (0, 200 and 500 kg N ha-1)
and their co-application to an acid soil. The results of incubation
study showed that biochar only treatment and co-application with urea
at 200 kg N ha-1
could impede transformation of urea to NH4+-N.
Soil application of biochar together with urea 500 kg N ha-1
produced
the highest NO3--N
and mineral N concentrations in the soil over 90 days. In a parallel
study performed under greenhouse conditions, Chinese
cabbage (Brassica
rapa L.
ssp.
chinensis L.)
crop showed highest
marketable fresh weight, N uptake and N
use efficiency in soil treated with
biochar along with urea at 500 kg N ha-1.
However,
soil incorporation of biochar only or combined application with urea
did not offer any short-term agronomic advantages over mineral
fertilizer only at 200 or 500 kg N ha-1.
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