94
inorganic N by ranges of 9.0–11.4% and 10.2–13.1% for Lilongwe and Dowa sites,
respectively. From this study, it is noted that the novel legume-legume cropping
system involving pigeon pea and cowpea is amongst technologies that improve
NUE, yields and quality of the subsequent maize crop and play a great role in sustainable agricultural intensification.
1 Introduction
Declining soil fertility continues to be one of the main challenges for sub-Saharan
Africa crop production systems (Zingore et al. 2015). Continuous soil erosion and
nutrient depletion are some of the most pressing challenges in managing agricultural soils in most parts of the region (Tamene and Le 2015). Earlier studies listed
Burundi, Malawi, Kenya, Ethiopia, Lesotho and Rwanda as countries with very
high nutrient depletion rates (Stoorvogel and Smailing 1990). The rising costs of
inorganic fertilizers and growing human populations are exacerbating the challenges in managing soil fertility and increasing crop production (AGRA 2014).
For the case of Malawi, where agricultural production is dominated by smallholder maize production, affordability of inorganic fertilizers is one of the crucial
challenges (African Development Bank 2011), with nitrogen being the most limiting element in maize production (Makumba 2003; Tamene et al. 2015). Over the
years, the Malawi government has shown a political will to improve the situation by
implementing a farm input subsidy policy, which reasonably improved yields in
some years but with unproven sustainability (Dorward and Chirwa 2011; RickerGilbert et al. 2014). Similar to many other countries, research and implementation
of various soil management interventions, including use of various types of manures,
agroforestry technologies and inclusions of legumes in the cropping systems, are
promoted. Inclusion of food legumes seems to be the most popular in Malawi due
to a number of factors including food diversity and security, increased income and
soil fertility improvement (Kerr et al. 2007; Kamanga et al. 2010; Snapp et al. 2014).
Legumes such as common beans (Phaseolus vulgaris), groundnuts (Arachis
hypogaea), pigeon pea (Cajanus cajan), soybean (Glycine max) and cowpea (Vigna
unguiculata) are grown by many farmers in Malawi, both as food and cash crops
(Kamanga et al. 2010). They are grown in various cropping systems, including sole
or monocropping, legume-cereal intercrops and legume-legume intercrops, commonly referred to as “doubled-up” legume technology (ICRISAT/MAI 2000).
Soil fertility benefits from legume interventions evaluated through their effects
on maize in short rotations have been reported from studies done in Malawi and
elsewhere (Sakala et al. 2003; Mhango 2011). However, very few studies have
reported soil fertility benefits from legumes that are grown as legume-legume intercrops. Soil fertility benefits on maize yields from doubled-ups of pigeon
pea- groundnuts or pigeon pea-soybean were reported to be comparable to those of
sole crops (Mhango 2011; Njira et al. 2013; Phiri et al. 2014).
K. O. W. Njira et al.
inorganic N by ranges of 9.0–11.4% and 10.2–13.1% for Lilongwe and Dowa sites,
respectively. From this study, it is noted that the novel legume-legume cropping
system involving pigeon pea and cowpea is amongst technologies that improve
NUE, yields and quality of the subsequent maize crop and play a great role in sustainable agricultural intensification.
1 Introduction
Declining soil fertility continues to be one of the main challenges for sub-Saharan
Africa crop production systems (Zingore et al. 2015). Continuous soil erosion and
nutrient depletion are some of the most pressing challenges in managing agricultural soils in most parts of the region (Tamene and Le 2015). Earlier studies listed
Burundi, Malawi, Kenya, Ethiopia, Lesotho and Rwanda as countries with very
high nutrient depletion rates (Stoorvogel and Smailing 1990). The rising costs of
inorganic fertilizers and growing human populations are exacerbating the challenges in managing soil fertility and increasing crop production (AGRA 2014).
For the case of Malawi, where agricultural production is dominated by smallholder maize production, affordability of inorganic fertilizers is one of the crucial
challenges (African Development Bank 2011), with nitrogen being the most limiting element in maize production (Makumba 2003; Tamene et al. 2015). Over the
years, the Malawi government has shown a political will to improve the situation by
implementing a farm input subsidy policy, which reasonably improved yields in
some years but with unproven sustainability (Dorward and Chirwa 2011; RickerGilbert et al. 2014). Similar to many other countries, research and implementation
of various soil management interventions, including use of various types of manures,
agroforestry technologies and inclusions of legumes in the cropping systems, are
promoted. Inclusion of food legumes seems to be the most popular in Malawi due
to a number of factors including food diversity and security, increased income and
soil fertility improvement (Kerr et al. 2007; Kamanga et al. 2010; Snapp et al. 2014).
Legumes such as common beans (Phaseolus vulgaris), groundnuts (Arachis
hypogaea), pigeon pea (Cajanus cajan), soybean (Glycine max) and cowpea (Vigna
unguiculata) are grown by many farmers in Malawi, both as food and cash crops
(Kamanga et al. 2010). They are grown in various cropping systems, including sole
or monocropping, legume-cereal intercrops and legume-legume intercrops, commonly referred to as “doubled-up” legume technology (ICRISAT/MAI 2000).
Soil fertility benefits from legume interventions evaluated through their effects
on maize in short rotations have been reported from studies done in Malawi and
elsewhere (Sakala et al. 2003; Mhango 2011). However, very few studies have
reported soil fertility benefits from legumes that are grown as legume-legume intercrops. Soil fertility benefits on maize yields from doubled-ups of pigeon
pea- groundnuts or pigeon pea-soybean were reported to be comparable to those of
sole crops (Mhango 2011; Njira et al. 2013; Phiri et al. 2014).
K. O. W. Njira et al.