Effects of nitrogen and phosphorus micro-dosing on maize-pigeon pea intercrops grown under different soil moisture management practices
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Date
2018
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture.
Abstract
Declining soil fertility and moisture stress arc among the serious constraints facing
agriculture in most developing countries in the world. Tanzania inclusive.
Continuous farming with none or low use of fertilizer accelerates nutrient mining
in the soil. Average fertilizer use under smallholder farming systems is 16 - 19
kg/ha in sub Saharan Africa. Low fertilizer adoption by smallholder farmers arc
mainly due to inadequate knowledge on fertilizer usage, untimely availability of
inorganic fertilizers and low affordability. Declining soil fertility may cause yield
reduction of up to 50% when not addressed resulting into low food availability and
poor income generation. Inadequate rainfall and uneven distribution results into
prolonged dry spells. Low rainwater and poor runoff management practices under
the flat cultivation increases water loss, moisture stress and soil erosion that affects
plant nutrient availability and uptake. In both semi-arid and sub-humid areas.
maize production is also limited by inadequate soil moisture due to fluctuation of
rainfall regimes. A prolonged dry spell and change in rainfall pattern results into
low crop yield and shrinkage of grazing land which increase conflicts between crop
producers and pastoralist. Recommended N and P fertilizer rates have been
developed in maize as the most limiting in different agro-ccological zones.
However, only 12% of smallholder farmers use inorganic fertilizers due to poor
capital and unavailability of fertilizer in their areas. Use of a fertilizer micro-dosing
technology which is about 25% of the rate recommended, would enable farmers to
start with the lowest-cost effective technology and gradually move to higher
capital-intensive technologies as their resources increase. Il is an entry point for
resource poor farmers to use fertilizers. Intcr-row rainwater harvesting practicesii
have been reported to increase crop yield in rain-fed farming and minimizes risks
of crop failure in drought prone areas. The influence of micro-dosing fertilizer and
soil moisture conservation through inter-row rainwater harvesting on maize and
pigeon-pea cropping systems would increase crop productivity, maximize land use
efficiency, increase financial return and nutritional quality. Most recommendations
of technologies arc from agronomic analysis with emphasis on maximum yield
without economic analysis. As farmers do the economic analysis at farm level.
profitability analysis is therefore important in recommending fertilizer micro
dosing rate along with rainwater harvesting practices and cropping system.
Therefore, the objectives of this study were: i) To determine micro-dose rates of
phosphorus and nitrogen for maize crop, ii) To evaluate the effect of nitrogen and
phosphorus fertilizer micro-dosing on yields, resource utilization and nutritional
quality of maize and pigeonpea cropping systems as influenced by soil moisture
management through rainwater harvesting technique, and iii) To determine the
profitability of the micro-dose rates in maize production, as well as profitability of
inter-row rainwater harvesting and fertilizer use on maize and pigeonpea cropping
systems.
To achieve the objectives of this study, two field experiments were conducted in
Ilakala and Changarawc villages of Kilosa District in Morogoro Region Tanzania.
The first experiment was laid out in split-plot involving three phosphate fertilizer
types (Diammonium phosphate, Minjingu mazao and triple super phosphate), and
micro-dose rates (12.5, 25, 50 and 75% of recommended N and P) with control and
recommended rate (80 kg N and 40 kg P/ha). The second experiment was laid outiii
in split-split plot design. It involved rainwater harvesting practices (tic ridge, open
ridge and flat cultivation), cropping systems (maize sole, pigeonpea sole and 1:1
maizc-pigconpea intercrop), and fertilizer use (control,
micro-dosing and
recommended rate).
Results indicated that Minjingu mazao fertilizer had significantly higher maize
yield than DAP by 6.63% and TSP by 9.55%. Fertilizer micro dose rates at 12.5%
(10 kg N and 5 kg P/ha) and 25% (20 kg N and 10 kg P/ha) increased the yield
from 1012 kg/ha in control to 1928 kg/ha (90.5%) and 2394 kg/ha (137%).
respectively. Tied ridges conserved soil moisture by 13.33% more than flat
cultivation at 30 cm depth after ten days of rainfall. Ridges increased maize yield
by 8 - 15% than Hat cultivation, but decreased pigeon pea yield by 23% than Hat
cultivation. Fertilizer use increased maize yield by 93% at micro-dosing rates and
132% at recommended rate compared to control plot, l ie ridges and fertilizer use
increased maize yield by 90% and pigeon pea yield by 20% than flat cultivation
without fertilizer.
Land use efficiency was ranging from 28 to 100% higher in intercropping than sole
crop. Financial return was high ranging from 2 to 4 million shillings from maize
pigeonpea intercrop applied with micro-dose and recommended fertilizer in both
tied ridges and fiat cultivation. Maize sole had more energy than pigeonpea under
tied ridges, however the highest energy was between 60.000 and 70.000 kJ/ha from
intercrops and recommended fertilizer. The highest protein ranging between 400
and 500 kg/ha was from intercropping applied with micro-dose and recommended
fertilizer in both tied ridges and flat. Micro-dosing rale at 12.5% was more
profitable than no fertilizer application and the profitability increased towards 25%iv
and 50% of recommended fertilizer rates and thereafter, decreased at recommended
rate. Tied ridges and fertilizer micro-dose had higher gross margin than open ridges
and flat cultivation in maize sole cropping. Pigeonpea sole cropping had higher
gross margin in flat cultivation than tie and open ridges. Maize and pigeonpea
intercropping under fertilizer micro-dosing had the highest gross margin above 4.5
million Tanzanian shillings. Intercropping maize and pigeonpea had high B/C ratio
ranging from 6.1 to 15.6 in commercial farming and from 12 to 32 in subsistence
farming. Adoption of micro-dosing fertilizer at 12.5% could be an entry point to
fertilizer use and later on advance to 25% and 50% micro-dosing rates which arc
more profitable with better yield under smallholder farming systems in sub-humid
tropics. Inter-row rainwater harvesting and fertilizer micro-dosing would increase
food and nutritional security and optimize profit in both sole and intercropping
systems of sub-humid tropical farming.
Description
Keywords
Maize crop, Soil moisture management, Maize production, Pigeon-pea cropping systems, Phosphorus fetilizer, Nitrogen fertilizer