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Kwame Nkrumah University of Science and Technology (2005)

Tilage and cropping systems effects on soil moisture, nitrogen fixation and yield of cowpea intercropped with maize in Northern Ghana

Kombiok, James Mantent

Titre : Tilage and cropping systems effects on soil moisture, nitrogen fixation and yield of cowpea intercropped with maize in Northern Ghana

Auteur : Kombiok, James Mantent

Université de soutenance : Kwame Nkrumah University of Science and Technology

Grade : Doctor of Philosophy in Agronomy, 2005

Résumé partiel
Results from research work on tillage systems conducted mostly in the rainforest and coastal Savanna zones under monocultural crop production systems have been conflicting. Against this background, experiments were conducted at Nyankpala within the northern savanna ecology to assess the influence of different tillage systems on soil properties, water storage, nitrogen fixation and crop yield. The experiments were laid in split-plot design with four replications. Tillage systems which consisted of Conventional (CON), Bullock Plough (BP), Hand hoe (RH) and Zero-tillage (ZT) were the main treatments. The sub-treatments were sole maize, sole cowpea, maize/cowpea inter-row cropping system and bare fallow in 2000 which was replaced in 2001 with maize/cowpea intra-row cropping system. The results showed that tillage loosened the soil and thus reduced soil bulk density, increased porosity and enhanced surface roughness. Bulk density and surface roughness were in decreasing order of ZT>HH>BP>CON and CON>BP>HH>ZT respectively. The ZT, which had a sparse vegetative cover due to bush tires in the preceding dry season, recorded the lowest surface roughness among the tillage treatments. The reduction in soil bulk density and the increase in surface roughness due to tillage reduced runoff and more water were stored in the deeper tilled than the shallow and the non-tilled treatments. The average reduction in estimated runoff over the two years experimentation was 54% in cowpea and 43% in maize under CON. More than 50% of the water in the 105 cm deep profile was stored at the 0-30 cm depth in all the treatments. Among the tillage treatments, CON and BP with greater working depths of not less than 12 cm stored more water than HH and ZT treatments. There was also a mean reduction of 50% by CON and BP in weed infestation compared to RH and ZT treatments. The ZT treatment significantly (P<0.05) reduced plant height and LAI of crops, which in turn reduced the amount of light intercepted, and the subsequent low dry matter yield produced by the crops on it. Calculated water use (ET) was higher for maize than cowpea. Water use efficiency (WUE) of maize for dry matter production at 8 WAP was significantly (P<0.05) higher under CON and BP than under HH and ZT treatments. A similar trend was observed for cowpea in 2000 but in 2001 ZT significantly (P<0.05) recorded a greater reduction of 42.8% in WUE. Grain yields of maize and cowpea did not differ between CON and BP but were significantly higher (P<0.05) than the grain yields of the RH and ZT treatments. The differences in land equivalent ratios (LER) among tillage treatments were not significant but each was more than 1 (>1) implying a substantial agronomic advantage over sole cropping system. Generally, there were no consistent increases of both nodule weight and nodule number per cowpea plant due to tillage at the 4 and 6 WAP but each of them declined at 8 WAP. Nodule weight was not affected by tillage but nodule number per plant was significantly lower (P<0.05) on ZT than CON, BP and HH treatments at 8 WAP. The percent nitrogen fixed by cowpea under each of the tillage treatments was higher than 50% but the differences among the treatments were not significant. Cropping systems had no significant influence on soil bulk density and water storage but bare fallow in 2000 significantly reduced (P

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Page publiée le 22 février 2018, mise à jour le 17 février 2020