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 />
This perfect symbiotic <str<strong>on</strong>g>system</str<strong>on</strong>g> is dependent <strong>on</strong> both<br />
the genetic determ<strong>in</strong>ant <str<strong>on</strong>g>of</str<strong>on</strong>g> the host plant and that <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
the Rhizobium stra<strong>in</strong>. Moreover, the bacteria <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />
genus Rhizobium found <strong>in</strong> Legume roots favor a<br />
perfect m<strong>in</strong>eral absorpti<strong>on</strong> to crops. By their<br />
presence, they block the acti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> other plantpathogenic<br />
microorganisms and allow the dissolv<strong>in</strong>g<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> certa<strong>in</strong> <strong>in</strong>soluble m<strong>in</strong>eral elements <strong>in</strong> the soil<br />
(Antoun et al., 1978; Bu<strong>on</strong>assisi et al., 1986;<br />
Ehteshamul-Haque and Gaffar, 1993 ; Chabot et al.,<br />
1996). They also play an important role <strong>in</strong> the<br />
decompositi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> plant residues by releas<strong>in</strong>g organic<br />
compounds that favor the formati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> organic matter<br />
<strong>in</strong> the soil.<br />
In rato<strong>on</strong> crop, <strong>on</strong> plots with Legumes as preced<strong>in</strong>g<br />
crops, the best <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> <strong>yield</strong>s were obta<strong>in</strong>ed thanks<br />
to the supply <str<strong>on</strong>g>of</str<strong>on</strong>g> the half-dose <str<strong>on</strong>g>of</str<strong>on</strong>g> urea as <strong>in</strong> the works<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> K<strong>on</strong>até et al., 2012. Through these results, it is<br />
obvious that the Legume cultivati<strong>on</strong> reduces the use<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> m<strong>in</strong>eral fertilizers <strong>in</strong> <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> cultivati<strong>on</strong>. It also<br />
shows that <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> productivity can be improved at<br />
lower cost thanks to the <str<strong>on</strong>g>rotati<strong>on</strong></str<strong>on</strong>g> <str<strong>on</strong>g>system</str<strong>on</strong>g> with<br />
Legumes. These results c<strong>on</strong>firm the works <str<strong>on</strong>g>of</str<strong>on</strong>g> PRC<br />
(2011) showed a reducti<strong>on</strong> <strong>in</strong> <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> producti<strong>on</strong><br />
costs by 18%. Indeed, Legume cultivati<strong>on</strong> as<br />
preced<strong>in</strong>g crop provides a large amount <str<strong>on</strong>g>of</str<strong>on</strong>g> plant<br />
residues, c<strong>on</strong>stitut<strong>in</strong>g an important source <str<strong>on</strong>g>of</str<strong>on</strong>g> organic<br />
matter. This helps to restore the natural fertility <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
soils and thus enrich them with essential m<strong>in</strong>eral<br />
elements (Becker et al., 1996). The exudates <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
Legumes buried <strong>in</strong> the soil are equally resp<strong>on</strong>sible for<br />
the solubilizati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> many major m<strong>in</strong>eral elements<br />
such as Phosphorus, Potassium, Calcium, etc. This<br />
<strong>in</strong>creases their availability <strong>in</strong> the soil and therefore<br />
their absorpti<strong>on</strong> by plants as shown by Alvey et al.<br />
(2001) <strong>in</strong> their studies.<br />
The fallow improved with Soybean and Lablab has<br />
helped improve soil fertility by prevent<strong>in</strong>g nutrient<br />
leach<strong>in</strong>g due to run<str<strong>on</strong>g>of</str<strong>on</strong>g>f or seepage. This <str<strong>on</strong>g>cropp<strong>in</strong>g</str<strong>on</strong>g><br />
<str<strong>on</strong>g>system</str<strong>on</strong>g> tends to restore soil fertility, but also to<br />
protect them from destructi<strong>on</strong> due to erosi<strong>on</strong> (Yost<br />
and Evans, 1988). Moreover, Legumes such as Lablab<br />
not <strong>on</strong>ly fight aga<strong>in</strong>st erosi<strong>on</strong>, but also favors water<br />
retenti<strong>on</strong> <strong>in</strong> the soil.<br />
In c<strong>on</strong>trast, <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g>s result<strong>in</strong>g from the<br />
c<strong>on</strong>venti<strong>on</strong>al <str<strong>on</strong>g>system</str<strong>on</strong>g> and natural fallow, have <strong>on</strong>ly<br />
benefited from the little nitrogen present <strong>in</strong> the soil<br />
due to fallow and m<strong>in</strong>eral nitrogen (amm<strong>on</strong>iacal<br />
nitrogen or nitrate nitrogen) made available to them<br />
by the urea provided <strong>in</strong> sufficient quantity. S<strong>in</strong>ce<br />
m<strong>in</strong>eral nitrogen is not the equivalent <str<strong>on</strong>g>of</str<strong>on</strong>g> natural<br />
nitrogen associated with other microelements<br />
produced by bacteria, it could not allow biological<br />
fertilizati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> soils favored by the activity <str<strong>on</strong>g>of</str<strong>on</strong>g> soil<br />
micr<str<strong>on</strong>g>of</str<strong>on</strong>g>lora. This expla<strong>in</strong>s why the <strong>yield</strong>s obta<strong>in</strong>ed<br />
were not significantly different from those <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />
other <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.<br />
Furthermore, Legume cultivati<strong>on</strong> between two<br />
<str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> crop cycles is also an important <str<strong>on</strong>g>system</str<strong>on</strong>g> that<br />
helps overcome <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> m<strong>on</strong>oculture that has been<br />
practiced for more than thirty years <strong>in</strong> the SUCAF-CI<br />
(Ferké 1 and 2) sugar complex accord<strong>in</strong>g to<br />
Maubouss<strong>in</strong>, 1988 and Mari<strong>on</strong>, 2000. The ANOVA<br />
analyses <str<strong>on</strong>g>of</str<strong>on</strong>g> variance showed no significant difference<br />
(p˃ 0.05) between <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> <strong>yield</strong>s for An*CS and<br />
An*CS*T <strong>in</strong>teracti<strong>on</strong>s. This is due to the great ability<br />
<str<strong>on</strong>g>of</str<strong>on</strong>g> Legumes to fix huge amounts <str<strong>on</strong>g>of</str<strong>on</strong>g> atmospheric<br />
nitrogen that they store <strong>in</strong> the soil for the benefit <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
subsequent <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g>s. This release <str<strong>on</strong>g>of</str<strong>on</strong>g> natural<br />
nitrogen makes it possible to rec<strong>on</strong>stitute the<br />
physicochemical properties <str<strong>on</strong>g>of</str<strong>on</strong>g> soils favorable to the<br />
good development <str<strong>on</strong>g>of</str<strong>on</strong>g> subsequent <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g>s. This is<br />
why, <strong>in</strong> rato<strong>on</strong> crop, <strong>on</strong> plots that hosted <str<strong>on</strong>g>legume</str<strong>on</strong>g>s as<br />
ma<strong>in</strong> crop, <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g>s grown without urea had their<br />
<strong>yield</strong>s equal to those <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>s <strong>in</strong> the<br />
c<strong>on</strong>venti<strong>on</strong>al <str<strong>on</strong>g>system</str<strong>on</strong>g> and after natural fallow. These<br />
results c<strong>on</strong>firm the works <str<strong>on</strong>g>of</str<strong>on</strong>g> K<strong>on</strong>até et al., 2012. This<br />
shows that Legume cultivati<strong>on</strong>, <strong>in</strong> ma<strong>in</strong> crop, has<br />
favored the fertility <str<strong>on</strong>g>of</str<strong>on</strong>g> soils <strong>under</strong> <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g><br />
cultivati<strong>on</strong>, allow<strong>in</strong>g rato<strong>on</strong> crop <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g>s to have<br />
higher <strong>yield</strong>s.<br />
C<strong>on</strong>clusi<strong>on</strong><br />
This study, carried out at the Ferké 1 sugar complex,<br />
which was about <str<strong>on</strong>g>sugar<strong>cane</strong></str<strong>on</strong>g> cultivati<strong>on</strong> <strong>in</strong> <str<strong>on</strong>g>rotati<strong>on</strong></str<strong>on</strong>g><br />
with Legumes fallows, gave important results. This<br />
<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> helped obta<strong>in</strong> <strong>yield</strong>s statistically<br />
identical to those <str<strong>on</strong>g>of</str<strong>on</strong>g> the c<strong>on</strong>venti<strong>on</strong>al <str<strong>on</strong>g>system</str<strong>on</strong>g> and the<br />
natural fallow us<strong>in</strong>g nitrogen fertilizers.<br />
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