Response of Improved Rainfed Rice Varieties to Low Soil Nitrogen | Chapter 12 | New Perspectives in International Plant and Soil Research Vol. 1
Nitrogen is one of the major essential
plant nutrients and a key input required for better crop yields and therefore
scarcity of nitrogen fertilizer has been a major constraint to rice production
particularly in developing countries. Low soil fertility prevalent in farmer’s
fields has led to low rice yields and the ever escalating fertilizer prices
have made this important input unaffordable to most smallholder farmers who
have limited resources for purchasing the required inputs. There has been
concerted efforts to identify rice varieties that are tolerant to low soil
nitrogen since varieties differ in their ability to impact productivity and
some varieties can perform well under low nitrogen input.The Mwea Upland rice
(MWUR) varieties have been bred under low fertilizer input environment while
other authors have indicated that the New Rice for Africa (NERICA) gives high
yields under low input conditions. There is therefore need to identify the
superior rice varieties that are adaptable to low soil nitrogen levels. Thus,
the objective of this study was to investigate the effects of different rates
of nitrogen fertilizer on improved upland rice varieties and to identify the
low input adaptable varieties. Field studies were conducted at Alupe in Western
Kenya under rainfed upland conditions between August 2012 and April 2013. The
experimental layout was split plot factorial in a Randomized Complete Block
Design with three replicates. The main plot treatments were four rates of
nitrogen fertilizer levels which were; 0 (control), 40, 80 and 120 kg ha-1
applied as calcium ammonium nitrate (26% N) in two equal splits; 21 days after
sowing (DAS) and at panicle initiation (46 DAS). Sub-plots consisted of four
MWUR varieties namely MWUR 1, MWUR 2, MWUR 3, MWUR 4; and four NERICA varieties
namely NERICA 1, NERICA 4, NERICA 10 and NERICA 11. The parameters measured
included plant height, tiller number, filled grain ratio percentage and yield
components. In the study, nitrogen treatment showed significant effect on plant
growth and the measured parameters increased significantly with increase in
nitrogen level. MWUR varieties studied were more adaptable to low nitrogen
conditions as compared to NERICA varieties. The NERICA varieties recorded
higher yield at high nitrogen levels as compared to MWUR varieties. However,
NERICA 4 gave higher yield as compared to other NERICA varieties regardless of
the nitrogen level. Results from our study suggest that MWUR 1 and 2 and NERICA
4 were more tolerant to low nitrogen as compared to MWUR 3 and 4 and NERICA 1,
10 and 11, because of higher height, more tiller number, higher filled grain ratio
percentage and higher yield component as compared to the other studied
varieties and may be suitable for soils low in nitrogen.
Author(s) Details
Dr. P. A. Sikuku
Department of Botany, Maseno
University, P.O.Box 333 Maseno, Kenya.
Dr. J. M. Kimani
Kenya Agricultural Research
Institute-Mwea-Tebere, P.O.Box 298-10300, Kerugoya, Kenya.
Dr. J. W. Kamau
EAAPP PCU, P.O.Box 30028 –
00100, Nairobi, Kenya.
S. Njinju
Kenya Agricultural Research
Institute-Mwea-Tebere, P.O.Box 298-10300, Kerugoya, Kenya.
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