95
However, information on effects of the combinations of crops, specifically
pigeon pea-cowpea doubled-up on maize yields, and yield components such as
quality is scanty. Furthermore, information on the mineralization patterns of legume
residues in various combinations of either legume-legume or legume-cereal is
scanty. Therefore, the objective of this study was to evaluate and compare the effects
of the pigeon pea-cowpea “doubled-up”, in comparison with sole and legume-cereal
intercrops, on N mineralization patterns and their implications on N uptake, nitrogen use efficiency, yields and grain protein content of maize in short rotation when
integrated with inorganic fertilizers.
2 Materials and Methods
2.1 Site Description and Characterization
The study was conducted as a continuation of the 2013/2014 legume-based study at
Lilongwe and Dowa districts of central region of Malawi (Sect. 2.4). Assessment of
the effects of legume-based treatments on subsequent maize was conducted in the
2014/2015 growing season. For the Lilongwe site, the experiment was conducted at
the Lilongwe University of Agriculture and Natural Resources (LUANAR) research
farm (14° 11′ S, 33° 46′ E) within the Mkwinda Extension Planning Area (EPA),
specifically at Bunda Campus; and in Dowa district, the experiment was conducted
at Nachisaka EPA (13° 37′ S, 33° 56′ E). Both Lilongwe and Dowa districts fall
within the medium-altitude agro-ecological zone of Malawi. Lilongwe (Bunda
Campus) is at 1157 m above sea level, whereas Dowa (Nachisaka EPA) is at 1190 m
above sea level. Overall the medium-altitude areas receive an average rainfall of
about 875 per annum. Soils of the two sites are deep well-drained Chromic Luvisols
(WRB classification) or Alfisols (Typic Hapludalfs in the USDA Soil Taxonomy)
(Chilimba et al. 2011; Mutegi et al. 2015).
2.2 Initial Soil Fertility Status at the Start of the Experiment
Soil analysis at the beginning of the 2013/2014 cropping season at the 0–20 cm
depth indicated that the soils have sand-clay-loam texture, moderate acidity (pH of
6.0), low soil organic matter (1.1%), low total N (0.05%), high available Mehlich-3
P (57 mg kg
−1
) and high amounts of basic cations showing 1.24, 4.24 and 0.35 cmol c
kg
−1
soil for Mg, Ca and K, respectively, for the Dowa site. On the other hand, the
Lilongwe site soil have sand-clay-loam texture, slight acidity (pH of 6.2), medium
soil organic matter (2.8), medium total N (0.14%), high available Mehlich-3 P
(41 mg kg
−1
) and adequate amounts of basic cations showing 0.99. 4.78 and 0.23
cmol c kg
−1
soil for Mg, Ca and K, respectively.
Integrated Soil Fertility Management Based on Pigeon Pea and Cowpea Cropping…
However, information on effects of the combinations of crops, specifically
pigeon pea-cowpea doubled-up on maize yields, and yield components such as
quality is scanty. Furthermore, information on the mineralization patterns of legume
residues in various combinations of either legume-legume or legume-cereal is
scanty. Therefore, the objective of this study was to evaluate and compare the effects
of the pigeon pea-cowpea “doubled-up”, in comparison with sole and legume-cereal
intercrops, on N mineralization patterns and their implications on N uptake, nitrogen use efficiency, yields and grain protein content of maize in short rotation when
integrated with inorganic fertilizers.
2 Materials and Methods
2.1 Site Description and Characterization
The study was conducted as a continuation of the 2013/2014 legume-based study at
Lilongwe and Dowa districts of central region of Malawi (Sect. 2.4). Assessment of
the effects of legume-based treatments on subsequent maize was conducted in the
2014/2015 growing season. For the Lilongwe site, the experiment was conducted at
the Lilongwe University of Agriculture and Natural Resources (LUANAR) research
farm (14° 11′ S, 33° 46′ E) within the Mkwinda Extension Planning Area (EPA),
specifically at Bunda Campus; and in Dowa district, the experiment was conducted
at Nachisaka EPA (13° 37′ S, 33° 56′ E). Both Lilongwe and Dowa districts fall
within the medium-altitude agro-ecological zone of Malawi. Lilongwe (Bunda
Campus) is at 1157 m above sea level, whereas Dowa (Nachisaka EPA) is at 1190 m
above sea level. Overall the medium-altitude areas receive an average rainfall of
about 875 per annum. Soils of the two sites are deep well-drained Chromic Luvisols
(WRB classification) or Alfisols (Typic Hapludalfs in the USDA Soil Taxonomy)
(Chilimba et al. 2011; Mutegi et al. 2015).
2.2 Initial Soil Fertility Status at the Start of the Experiment
Soil analysis at the beginning of the 2013/2014 cropping season at the 0–20 cm
depth indicated that the soils have sand-clay-loam texture, moderate acidity (pH of
6.0), low soil organic matter (1.1%), low total N (0.05%), high available Mehlich-3
P (57 mg kg
−1
) and high amounts of basic cations showing 1.24, 4.24 and 0.35 cmol c
kg
−1
soil for Mg, Ca and K, respectively, for the Dowa site. On the other hand, the
Lilongwe site soil have sand-clay-loam texture, slight acidity (pH of 6.2), medium
soil organic matter (2.8), medium total N (0.14%), high available Mehlich-3 P
(41 mg kg
−1
) and adequate amounts of basic cations showing 0.99. 4.78 and 0.23
cmol c kg
−1
soil for Mg, Ca and K, respectively.
Integrated Soil Fertility Management Based on Pigeon Pea and Cowpea Cropping…