Effect of Green-Manuring and Fallowing on Soil Nitrogen and Organic Carbon and on the Succeeding Crop in the Central Clay Plain of the Sudan

Under green-manure and bare fallow the soil organic nitrogen increased. The increase in organic nitrogen under leguminous green-manure crops was more than the increase under sorghum, green-manure or bare fallow. There was no significant effect of green-manuring and bare fallowing on the soil organic carbon content. The C/N ratio of the soil tended to narrow down under the treatments and this was more due to an increase in the organic nitrogen content rather to decrease in the organic carbon content.

Green-manure crops sown early in July and disced under after a period of 7 weeks of growth were the best.

Application of nitrogen at the rate of 20 kg per feddan had no effect on sesame crop grown following green-manure by leguminous crops and bare fallow. Cotton yield increased after green-manure over that of bare fallow. Removal of aerial parts of sorghum green-manure just before discing under was beneficial over where it was disced under.