3.6. Aboveground biomass production
No-till maize produced significantly more biomass than
cassava, sweet potato, bean, and pigeonpea in CAR and CTR in
2011/12 and 2012/13 (Table 5). In 2011/12, intercropping pigeon-
pea added 656 kg ha1 and 184 kg ha1 of biomass in Nkhotakota
and Dowa, respectively. No-till maize and intercropping cowpea
(731 kg ha1) with second year pigeonpea (2609 kg ha1) significantly
increased biomass production compared to soybean in CTR.
Conventional tillage rotation produced the greatest maize biomass
in 2013/14 in both districts, significantly greater than NTM. Maize
residue had the highest C:N ratio (75:1), while all other crops
grown in this study had C:N ratios ranging from 21:1 to 32:1 (data
not shown).
In Nkhotakota, 607 kg ha1 and 937 kg ha1 of biomass was
removed from CAR as fuel and planting material in 2011/12 and
2012/13, respectively. In Dowa in 2011/12, no pigeonpea biomass
and only 23 kg ha1 of sweet potato vines were removed from CAR
as fuel or planting materials. In both districts, no aboveground
biomass was retained in the
field in CTR as all biomass was
removed prior to planting every year. Biomass retained in the
field
from the previous season was positively correlated with soil
moisture content at 20 cm, total soil water, infiltration, and
final
infiltration rate in Nkhotakota in 2013/14 (Table 6). Additionally,
the amount of residue retained in the
field was negatively correlated with soil temperature in Dowa in 2012/13 and sediment
runoff in both districts in 2013/14.