Effect of a sugarcane-legume cropping rotation system on cane yield under irrigated conditions in Côte d'Ivoire
To find an alternative to the use of nitrogenous fertilizers in sugarcane cultivation, this study was initiated in order to improve soil fertility and sugarcane yield by growing legumes. The trials were carried out on-farm according to split-splot design in ferké 1 sugar bowl northern Côte d’Ivoire. The main factor was the cropping system (4 levels) and the subsidiary factor was the treatment with urea (3 levels). On the experimental plot, two legumes fallows (Soybean and Lablab) were grown in rotation with sugarcane. The sugarcane yields obtained were compared with those of the conventional system and those obtained after natural fallow using only nitrogenous fertilizers. In main crop as well as ratoon crop, sugarcane yields were statistically identical for all four cropping systems. Nevertheless in ratoon crop, the effect of treatment with urea was significant. Thus, the input of half-dose of urea was the best treatment with urea. During the two years of cultivation, sugarcane yields were statistically different; the effect of years being significant on sugarcane yield, with the first ratoon as the best crop year with an average yield of 58.4 Tc/ha. Legume cultivation as a preceding crop has enabled subsequent canes to provide yields that are statistically identical to those of other cropping systems that use only nitrogenous fertilizer. It has also helped to halve the use of urea in ratoon crop and finally to obtain higher sugarcane yields in ratoon crop.
To find an alternative to the use of nitrogenous fertilizers in sugarcane cultivation, this study was initiated in order to improve soil fertility and sugarcane yield by growing legumes. The trials were carried out on-farm according to split-splot design in ferké 1 sugar bowl northern Côte d’Ivoire. The main factor was the cropping system (4 levels)
and the subsidiary factor was the treatment with urea (3 levels). On the experimental plot, two legumes fallows (Soybean and Lablab) were grown in rotation with sugarcane. The sugarcane yields obtained were compared with those of the conventional system and those obtained after natural fallow using only nitrogenous fertilizers. In main
crop as well as ratoon crop, sugarcane yields were statistically identical for all four cropping systems. Nevertheless in ratoon crop, the effect of treatment with urea was significant. Thus, the input of half-dose of urea was the best treatment with urea. During the two years of cultivation, sugarcane yields were statistically different; the effect of years being significant on sugarcane yield, with the first ratoon as the best crop year with an average yield of 58.4 Tc/ha. Legume cultivation as a preceding crop has enabled subsequent canes to provide yields that are statistically identical to those of other cropping systems that use only nitrogenous fertilizer. It has also helped to halve the use of urea in ratoon crop and finally to obtain higher sugarcane yields in ratoon crop.
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Int. J. Agr<strong>on</strong>. Agri. R.<br />
The design used was a split-splot whose ma<strong>in</strong> factor<br />
was the four-level <str<strong>on</strong>g>cropp<strong>in</strong>g</str<strong>on</strong>g> <str<strong>on</strong>g>system</str<strong>on</strong>g>s that are<br />
c<strong>on</strong>venti<strong>on</strong>al <str<strong>on</strong>g>system</str<strong>on</strong>g> (CS1), natural fallow (CS2),<br />
<str<strong>on</strong>g>rotati<strong>on</strong></str<strong>on</strong>g> with soybean (SC3) and <str<strong>on</strong>g>rotati<strong>on</strong></str<strong>on</strong>g> with Lablab<br />
(CS4). As a sec<strong>on</strong>dary factor, we had treatments with<br />
urea, <strong>in</strong>clud<strong>in</strong>g three applicati<strong>on</strong> doses: dose T0 (0kg<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> urea, that is, 0kg <str<strong>on</strong>g>of</str<strong>on</strong>g> N); dose T1 (1.8kg <str<strong>on</strong>g>of</str<strong>on</strong>g> urea, that<br />
is, 69kg <str<strong>on</strong>g>of</str<strong>on</strong>g> N) and dose T2 (3.6kg <str<strong>on</strong>g>of</str<strong>on</strong>g> urea, that is,<br />
138kg <str<strong>on</strong>g>of</str<strong>on</strong>g> N). T0 corresp<strong>on</strong>ds to the treatment without<br />
urea (0%), T1 to the half-dose <str<strong>on</strong>g>of</str<strong>on</strong>g> urea (50%) and T2 to<br />
the total dose <str<strong>on</strong>g>of</str<strong>on</strong>g> urea (100%) applied <strong>on</strong> the<br />
elementary plots. This split-splot design c<strong>on</strong>sisted <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
three blocks, thus three repetiti<strong>on</strong>s, was made <strong>on</strong> a<br />
plot with a surface area <str<strong>on</strong>g>of</str<strong>on</strong>g> 4320m². Each block<br />
c<strong>on</strong>ta<strong>in</strong>ed 12 elementary plots, mak<strong>in</strong>g a total <str<strong>on</strong>g>of</str<strong>on</strong>g> 36<br />
elementary plots <str<strong>on</strong>g>of</str<strong>on</strong>g> 120m² each (12m × 10m) as<br />
shown <strong>in</strong> Fig. 2.<br />
Inoculati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>legume</str<strong>on</strong>g> seeds<br />
Soybean and Lablab seeds were <strong>in</strong>oculated with the<br />
bacterium Rhizobium jap<strong>on</strong>icum from the method<br />
used by Kouamé et al., 2007. First <str<strong>on</strong>g>of</str<strong>on</strong>g> all, 25 pieces <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
sugar were dissolved <strong>in</strong> a quarter glass <str<strong>on</strong>g>of</str<strong>on</strong>g> water, then<br />
the bacterial <strong>in</strong>oculum was added to the sugar soluti<strong>on</strong>.<br />
After mix<strong>in</strong>g, the whole <strong>in</strong>oculum and sugar soluti<strong>on</strong><br />
was spilled <strong>in</strong>to a c<strong>on</strong>ta<strong>in</strong>er c<strong>on</strong>ta<strong>in</strong><strong>in</strong>g Legume seeds.<br />
After mix<strong>in</strong>g, <strong>in</strong> order to let the <strong>in</strong>oculum adhere to all<br />
the seeds, the c<strong>on</strong>ta<strong>in</strong>er c<strong>on</strong>ta<strong>in</strong><strong>in</strong>g the <str<strong>on</strong>g>legume</str<strong>on</strong>g> seeds<br />
was sheltered from the sun.<br />
Establishment <str<strong>on</strong>g>of</str<strong>on</strong>g> trials<br />
C<strong>on</strong>venti<strong>on</strong>al <str<strong>on</strong>g>cropp<strong>in</strong>g</str<strong>on</strong>g> <str<strong>on</strong>g>system</str<strong>on</strong>g><br />
After harvest<strong>in</strong>g the previous <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g>s, persistent<br />
rato<strong>on</strong>s were elim<strong>in</strong>ated and soil preparati<strong>on</strong> was<br />
d<strong>on</strong>e (plow<strong>in</strong>g and furrow<strong>in</strong>g). As a result <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />
plow<strong>in</strong>g, the cutt<strong>in</strong>gs (three <strong>in</strong>ternodes) were spread<br />
<strong>in</strong>to each furrow, <strong>on</strong>e after the other so that there<br />
would be no spac<strong>in</strong>g dur<strong>in</strong>g emergence. Thus, <strong>in</strong> each<br />
elementary plot, eight rows <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> were planted<br />
over 10 m l<strong>on</strong>g with a c<strong>on</strong>venti<strong>on</strong>al spac<strong>in</strong>g <str<strong>on</strong>g>of</str<strong>on</strong>g> 1.5m<br />
between each row.<br />
Fig. 2. Plot plan <str<strong>on</strong>g>of</str<strong>on</strong>g> treatments accord<strong>in</strong>g to a splitsplot<br />
design.<br />
Soil preparati<strong>on</strong><br />
It c<strong>on</strong>sisted <strong>in</strong> the destructi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> persistent rato<strong>on</strong>s<br />
and weeds with a total herbicide c<strong>on</strong>ta<strong>in</strong><strong>in</strong>g<br />
glyphosate at 360 EC, then us<strong>in</strong>g a reversible plow<br />
with notched discs, the soil was plowed <strong>in</strong> order to<br />
turn the organic matter over. The cutt<strong>in</strong>gs were then<br />
planted <strong>in</strong> the furrows made thanks to the furrow<br />
openers hang<strong>in</strong>g <strong>on</strong> a tractor.<br />
Fertilizer spread<strong>in</strong>g<br />
Spread<strong>in</strong>g <str<strong>on</strong>g>of</str<strong>on</strong>g> the m<strong>in</strong>eral fertilizer preceded the<br />
plant<strong>in</strong>g <str<strong>on</strong>g>of</str<strong>on</strong>g> cutt<strong>in</strong>gs. Urea (46% N), KCl (60% K) and<br />
PCa3 (33.5% P) was used. In each elementary plot, a<br />
particular dose <str<strong>on</strong>g>of</str<strong>on</strong>g> urea (0; 1.8 or 3.6kg) and standard<br />
doses <str<strong>on</strong>g>of</str<strong>on</strong>g> KCl (4.2kg) and PCa3 (2.1kg) were applied.<br />
Natural fallow <str<strong>on</strong>g>system</str<strong>on</strong>g><br />
Follow<strong>in</strong>g <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> harvest<strong>in</strong>g, Persistent rato<strong>on</strong>s<br />
were elim<strong>in</strong>ated and the elementary plot left fallow.<br />
After two and a half m<strong>on</strong>ths, the land was plowed and<br />
furrowed, and the new <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> cutt<strong>in</strong>gs were<br />
planted over eight rows, each spaced 1.5 m apart.<br />
Cane <str<strong>on</strong>g>rotati<strong>on</strong></str<strong>on</strong>g> with Glyc<strong>in</strong>e max L. and Lablab<br />
purpureus L.<br />
Follow<strong>in</strong>g <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> rato<strong>on</strong>s, the seeds <str<strong>on</strong>g>of</str<strong>on</strong>g> each<br />
<str<strong>on</strong>g>legume</str<strong>on</strong>g> species were randomly planted <strong>in</strong> the<br />
elementary plots. After the first emergence <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />
different <str<strong>on</strong>g>legume</str<strong>on</strong>g> species, manual weed<strong>in</strong>g was carried<br />
out to elim<strong>in</strong>ate weeds. Then, after two and a half<br />
m<strong>on</strong>ths <str<strong>on</strong>g>of</str<strong>on</strong>g> cultivati<strong>on</strong>, Legumes were elim<strong>in</strong>ated with<br />
RoundUp (glyphosate, 360 EC) and their biomass<br />
was buried <strong>in</strong>to the soil. F<strong>in</strong>ally, the plant<strong>in</strong>g <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />
new <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> cutt<strong>in</strong>gs was carried out <strong>on</strong> the<br />
different elementary plots.<br />
Harvest<strong>in</strong>g and <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> masse determ<strong>in</strong>ati<strong>on</strong><br />
Once at the end <str<strong>on</strong>g>of</str<strong>on</strong>g> the cycle, the plots were totally<br />
burned. First, a mechanical harvest was carried out<br />
us<strong>in</strong>g machetes.<br />
Kouamé et al. Page 4