Maize is the third most important grain crop in the Savannah zone of Nigeria, following sorghum and rice, respectively. However, its yield is drastically limited by deficiency of N and P in the soils, low cation exchange capacity and soil acidity. Hence, responses of maize to N and P fertilizers have often been recorded in the guinea Savannah zones of Nigeria (Odiete et al., 2005). However, the high cost of chemical fertilizers and its scarcity has limited its use by farmers. Also the N fertilizers tend to aggravate soil acidity problem (Uyovbisere and Elemo, 2000). These problems necessitate study into locally sourced cheap agro-wastes that could add nutrients such as P, K, Ca and Mg and even act as a lining material when used along with N fertilizer (urea). Sawdust ash (SDA) is waste generated from wood and sawmilling industries. Used alone, it has been found to increase yield of tomato and okra significantly in South-West Nigeria and it also increased okra pod and leaf P, K, Ca and Mg content (Owolabi et al., 2003). It was also found that Sawdust ash increased soil pH, organic matter, P, K, Ca and Mg and fruit yield of pepper (Odedina et al., 2003). In the present study, the effect of SDA and its combined use with urea (U) on performance of maize and leaf nutrient status is studied in the guinea savannah zone of Nigeria. It is expected that the ash would supply cations and other nutrients not supplied by urea thus ensuring reduced use of chemical fertilizer and more balanced plant nutrition in an integrated form (Louise, 2003).
MATERIALS AND METHODS
Two experiments were conducted between March and December 2004 on two sites
(Benin Road and Kabba Road) at Ohiana in Southern Guinea Savannah zone of Nigeria,
10 km from Okene. The soils are clay loam and sandy loam soils. The soil is
derived from sandstones and classified as oxisols (Akintunde et al.,
2000). The sites were planted to maize and cassava in previous two years. Land
was manually cleared. There were six treatments applied to soil grown to maize.
The treatments were:
(a) untreated control-no urea, no sawdust ash,
(b) 1 t ha-1 sawdust ash + 187.5 kg urea ha-1,
(c) 2 t ha-1 sawdust ash + 125 kg urea ha-1,
(d) 3 t ha-1 sawdust ash + 62.5 kg urea ha-1,
(e) 4 t ha-1 sawdust ash and
(f) 250 kg ha-1 urea.
Treatments were replicated three times using a randomized complete block design. Each plot (5 m2) was planted with maize at 60x60 cm (28000 plant h-1). Three weedings were done manually at 3, 6 and 9 weeks after planting.
Five plants were selected per plot for determination of growth parameters at 100% silking. Plant growth at 120 cm level and height were taken. At harvest, the ear and cob weight were air-dried gram weight were taken.
At 9 weeks after treatment application, ear leaf samples collected from
plots were air-dried and ground. Total N was determined by kjeldahl method.
For P, K, Ca and Mg samples were digested using nitric-perchloric-sulphuric
acid mixture and determined as described for soil.
The SPSS for window 10 was used for analysis of variance. Means were compared
using the least significant difference at 95% level of probability.
RESULTS AND DISCUSSION
At 4, 6 and 7 weeks after treatment application (WAT), sawdust ash (SDA), urea fertilizer (U) and combined application of reduced levels of SDA and urea (U) increased maize height (Table 1).
The increased were not significant at site 1 (Benin Road) at 4 WAT. Aside from
the latter, the 1 t ha-1 SDA + 287.5 kg ha-1 U increased
height consistently at both sites (Benin Road and Kabba Road, Site 2). The two
other combinations: 2 t ha-1 SDA + 125 kg ha-1 U and 3
t ha-1 SDA + 62.5 kg ha-1 U increased plant height at
site 2, 6 and 7 WAT. At site 2 at 6 and 7 WAT, combined application of SDA and
urea of reduced levels increased plant height compared with SDA and urea and
SDA gave least values. The overall values of mean plant height gave similar
impression. Therefore, the presence of urea alone or combined with SDA enhanced
maize growth and urea had better effect in combination with SDA. This could
be due to immobilization of Nitrogen and its gradual release by microorganisms
acting on the carbonaceous sawdust ash.
|| Effect of sawdust ash (SDA) and urea (U) on height of maize
|WAT = No. of Weeks After Treatment application; NS = Non Significant
Sawdust is known to have very high C:N ratio of 300 to 500 (Olayinka and Adebayo,
1989). The integrated use of urea and sawdust ash is also expected to enhance
release of nutrients from SDA due to enhanced microbial action and reduce the
C:N ratio of the soil environment (Olayinka and Adebayo, 1989). While combined
use of SDA and urea could temporarily immobilize N for longer effect, use of
urea alone would have exposed it to leaching and volatile loss thereby reducing
Table 2 shows that compared with the untreated control, SDA, urea and the combinations of other reduced levels increased maize cob and grain weight. The yield parameters tended to increase in the order: control<SDA<3 t ha-1 SDA + 62.5 kg ha-1 U, 2 t ha-1 SDA + 125 kg ha-1 U< 250 kg ha-1 U< 1 t ha-1 SDA + 187.5 kg ha-1 U. Therefore the latter treatment gave the highest maize cob and grain yields which were significantly higher than those for the control and it was followed by 250 kg ha-1 U. The two treatments however gave similar yields. It is also shown that the three combinations of SDA and urea gave similar yield compared to urea alone and could therefore substitute for urea fertilizer.
The untreated control and SDA, respectively had least values of leaf nutrient contents especially with regard to N and P (Table 3). The observation that the untreated control had least values of leaf N, P, K, Ca and Mg suggests that SDA, urea and their combinations increased nutrient availability to maize. However, only the increases in leaf N and K were significant (p<0.05). Compared with the untreated control, 1 t ha-1 SDA + 187.5 kg ha-1 U increased leaf N significantly, while urea and 2 t ha-1 SDA+ 125 kg ha-1 U increased leaf K significantly. As in case of yield, the three combinations of SDA and urea gave similar leaf N, P, K Ca and Mg concentrations. It is suggested that availability of these nutrients to maize, especially in case of N dictated maize yield. Hence 1 t ha-1 SDA + 187.5 kg ha-1 U which gave highest leaf N had highest maize yield and mean value of plant height. Maize is known to have a high N requirement on savanna soils (Akintunde et al., 2000).
The finding that SDA used alone or combined with urea enhanced nutrient availability
to maize and its growth and yield is consistent with data on analysis of SDA
as given by Odedina et al. (2003). The data were 0.27% N, 0.01% P, 5.8%
K, 1.5% Ca and 4.08 Mg. Owolabi et al. (2003) gave values of 1.16% N,
0.04% available P, 2.8% K, 0.07% Mg and 0.35% Ca. Composition of sawdust ash
would vary depending on type of wood and burning intensity. It is ascertained
that SDA is a source of nutrients.
||Effect of sawdust ash (SDA) and urea (U) on maize yield
|| Effect of sawdust ash (SDA) and urea (U) on nutrients at
|* Mean data for the two sites; NS = Non Significant
Sawdust ash combined with urea could be utilized as source of nutrients especially N and K in maize production. Its use would enhance growth and yield. The effect of the combined application of the ash with urea on soil chemical properties would be studied for some time. Meanwhile it is recommend for use at 1 t ha-1 combined with reduced level of urea (187.5 kg ha-1).