Decomposition and nutrient release patterns of Pueraria phaseoloides, Flemingia macrophylla and Chromolaena odorata leaf residues in tropical land use systems

The study determined the decomposition and nutrient release patterns of Pueraria phaseoloides, Flemingia macrophylla and Chromolaena odorata leaf residues in young secondary forest and bush land use systems atMfou, southern Cameroon. Residue mass loss after incubating fresh leaves for 120 days was C. odorata > P. phaseoloides > F. macrophylla. Mean weekly loss rates were 4.5, 3.9 and 2.8 per cent for C. odorata, P.phaseoloides and F. macrophylla, respectively. Across residue types, leaf mass loss was greater in the young secondary forest than in the bush land use. Soil texture and soil chemical properties were not correlated to leafmass loss. Except for N, releases of P, K, Ca and Mg were of the order C. odorata ³ P. phaseoloides > F. macrophylla. Proportions of K released from the leaf residues were greater than those for the other nutrients.Half of the K was released within the first 7 weeks after incubation for C. odorata and P. phaseoloides. Among the land uses, release of K in the forest was 1.8 times faster than in the bush. The slowest releases, irrespective of type of leaf residue, were in Ca and Mg. The study concluded that among the planted fallows, Pueraria phaseoloides had the greatest rate of nutrient release. It could, therefore, ensure greater nutrient availability to associated crops. The leaves of C. odorata are rich in all nutrients; hence, short-season crops could benefit from this source of nutrients if the weed is well managed

Nutrient concentrations and NH4+‐N mineralization under different soil types and fallow forms in southern Cameroon

To evaluate the soil‐fertility sustainability of the fallow systems, nutrient concentrations and NH4+‐N mineralization were determined in different soil and fallow types in the humid forest zone of southern Cameroon. Two experiments were conducted, the first comprised planted leguminous tree Calliandra calothyrsus, planted leguminous Pueraria phaseoloides, and regrowth mainly composed of Chromolaena odorata on the Typic Kandiudult. The second experiment made up of a fallow dominated by C. odorata, a fallow with C. odorata removed, and a P. phaseoloides fallow on the Rhodic Kandiudult, Typic Kandiudult, and Typic Kandiudox. In the first experiment, available P, Ca2+, K+ concentrations and effective CEC under C. calothyrsus were, respectively, 40%, 22%, 45%, and 15% lower when compared to P. phaseoloides but no differences were found between soils under P. phaseoloides and C. odorata. Mineralization of NH4+‐N was higher under C. calothyrsus than under C. odorata‐ and P. phaseoloides‐fallow types, indicating the impoverishment of organic material under the former. In the second experiment, the beneficial effect of P. phaseoloides was found in the Rhodic Kandiudult in the 0–10 cm layer throughout its low NH4+ release from mineralization. In the Typic Kandiudult, no differences in NH4+‐N mineralization were found between C. odorata and P. phaseoloides fallows. In the Typic Kandiudox, there was no difference in NH4+ mineralization between the three fallow types. According to the nutrient concentrations and NH4+ mineralization, the fertility sustainability of the different fallow types may be ranked as follow: P. phaseoloides ≥ C. odorata > C. calothyrsus > fallow without C. odorata

Decomposition and nutrient release patterns of Pueraria phaseoloides, Flemingia macrophylla dnd Chromolaena odorata leaf residues in tropical land use systems

The study determined the decomposition and nutrient release patterns of Pueraria phaseoloides, Flemingiamacrophylla and Chromolaena odorata leaf residues in young secondary forest and bush land use systems at Mfou, southern Cameroon. Residue mass loss after incubating fresh leaves for 120 days was C. odorata>P.phaseoloides > F. macrophylla. Mean weekly loss rates were 4.5, 3.9 and 2.8 per cent for C. odorata, P. phaseoloides and F. macrophylla, respectively. Across residue types, leaf mass loss was greater in the young secondary forest than in the bush land use. Soil texture and soil chemical properties were not correlated to leaf mass loss. Except for N, releases of P, K, Ca and Mg were of the order C. odorata≥ P. phaseoloides > F. macrophylla. Proportions of K released from the leafresidues were greater than those for the other nutrients.Half of the K was released within the first 7 weeks afterincubation for C. odorata and P. phaseoloides. Among the land uses, release of K in the forest was 1.8 times faster than in the bush. The slowest releases, irrespective of type of leaf residue, were in Ca and Mg. The study concluded that among the planted fallows, Puerariaphaseoloides had the greatest rate of nutrient release. It could, therefore, ensure greater nutrient availability to associated crops. The leaves of C. odorata are rich in all nutrients; hence, short-season crops could benefit from this source of nutrients if the weed is well managed.Décomposition et les schémas de dégagement de nutriment du résidu foliaire de Pueraria phaseoloides,Flemingia macrophylla et Chromolaena odorata dans lessystèmes d’utilisation de terre tropicale. Nous avons déterminé la décomposition et les schémas de dégagement de nutriment du résidu foliaire de Pueraria phaseoloides,Flemingia macrophylla et Chromolaena odorata dans les systèmes d’utilisation de forêt de jeunes arbres et de terre arbustive à Mfou, au sud du Cameroun. La perte de masse résiduaire après l’incubation de feuilles fraîches pour 120 jours était C. odorata > P. phaseoloides > F.macrophylla. Les taux de perte moyen par semaine étaient 4.5, 3.9 et 2.8% respectivement pour C. odorata, P.phaseoloides et F. macrophylla. En travers de types deresidu, la perte de masse foliaire était plus élevée dans l’utilisation de forêt de jeunes arbres que dans la terrearbustive. La texture de sol et les propriétés chimiques de sol ne corrélaient pas à la perte de masse foliaire. Excepté A, les dégagements de P, K, Ca et Mg suivaient l’ordre C.odorata ≥ P. phaseoloides > F. macrophylla. Lesproportions de K dégagées de résidu foliaire étaient plusélevées que celles des autres nutriments. La moitié de Kétait dégagée dans les 7 premières semaines aprèsincubation pour C. odorata et P. phaseoloides. Parmi les utilisations de terre, le dégagement de K dans la forêt était1.8 fois plus rapide que dans la terre arbustive. Les dégagements les plus lents, indépendamment de type de résidu foliaire, étaient en Ca et Mg. L’étude a tiré la conclusion que parmi les jachères plantées, Pueraria phaseoloides, avaient les taux de dégagement de nutrimentles plus levés. Elle pourra donc assurer la disponibilité de nutriment plus élevée aux cultures associées. Les feuilles de C. odorata sont riches en tous les nutriments donc les cultures de courte période pourraient tirer des bienfaits de cette source de nutriments si la mauvaise herbe est bien maîtrisée

Decomposition and Nutrient Release Patterns of Pueraria phaseoloides and Flemingia macrophylla Under Two Rainfall Regimes

We report on a study to determine the decomposition and nutrient release patterns of Pueraria phaseoloides and Flemingia macrophylla leaf residues under two rainfall regimes in southern Cameroon. Fresh leaf material of the two legume species were put in litter bags and placed on the soil surface for 120 days at Ngoumou (high rainfall) and Nkometou (low rainfall). Mass loss of the leaf residue was faster in P. phaseoloides than F. macrophylla such that half-lives ranged from 9.0 - 9.5 weeks for P. phaseoloides and 14.6 - 20.2 weeks for F. macrophylla. Per cent leaf mass remaining was greater (p < 0.05) at Ngoumou than at Nkometou with mean half-lives being 14.6 and 12.1 weeks, respectively. The release of nutrients (N, P, K, Ca and Mg) was faster and in greater quantities in P. phaseoloides than F. macrophylla. More than half of the constituent N in P. phaseoloides was released in 9 weeks. Generally, half of K released from either legume species was within the first 5 weeks. The rate of release of each constituent nutrient was faster at Ngoumou than at Nkometou. The study concluded that P. phaseoloides had the largest amounts and rates of nutrient releases and therefore could ensure greater nutrient availability to associated crops. Banful, B., Hauser, S., Kumaga, F., Ofori, K. & Ndango, R. Les Modèles de la Décomposition et le Transfert des Nutriments dans le Cas de Pueraria Phaseoloides et Flemingia Macrophylla sous deux Régimes Pluvieux. Nous faisons notre réportage sur une étude pour déterminer les modèles de la décomposition et le transfert des nutriments dans le cas de Pueraria Phaseoloides et flemingia macrophylla sous deux régimes pluvieux au sud du Caméroon. Frais matériau de feuille des espèces légumineuses étaient mis dans des boîtes litières et placés sur la superficie du sol pour 120 jours à Ngoumou (pluie intenses) et Nkometou (pluies non intenses). La perte en masse des feuilles était plus rapide en P. phaseoloides que F. macrophylla tel que “démi vies” ont rangé entre 9.0 et 9.5 semaines dans le cas de P. phageoloides et 14.6 et 12.1 semaines dans le cas de F. macrophylla. Le pourcentage de feuille qui reste était plus grand à Nkometou avec un moyen “démi-vies” de 14.6 et 12.1 semaines respectivement. Le transfert des nutriments (N,P,K, Ca et Mg) était plus rapide et en grande qualité dans le cas de p. phaseoloides que F. macrophylla. Plus de la moitié des composants N dans P. phaseoloides étaient transférés en 9 semaines. Généralement, la moitié de K transféré de chaque espèce légumineuses était dans la première 5 semaines. Parmi les villages, le niveau de transfert de chaque composant nutrif était plus rapide à Ngoumou qu\' à Nkometou. L\'étude a conclu que pueraria phaseoloides possèdait un niveau plus élevé de transfert des nutriments et donc capable d\'assurer la disponibilité des nutriments aux cultures associeées en grande quantité. Keywords: Rainfall, mass loss, nutrient loss, planted fallows. Agricultural and Food Science Journal of Ghana Vol. 6 2007 pp. 485-50

Introduction and evaluation of improved varieties of Dioscorea rotundata, and D. cayenensis with high micronutrient content in Cameroon

Yam (Dioscorea sp.) is an extremely important delicacy in Cameroon, with some estimated 45,215 hectares devoted to it, and corresponding annual production of 275,101 metric tons. Production is constrained by several factors including the limited availability and cost of planting material, as well as susceptibility to a range of pests and diseases that cause considerable pre- and post- harvest losses, translated into low yields and poor quality of tubers during storage. With the development of new genotypes of yams through seed hybridization by the International Institute of Tropical Agriculture (IITA), new materials are being made available both in seed and tissue culture form for evaluation. In 2004, this scheme was extended to Cameroon, whereby fifteen D. rotundata and two D. cayenensis varieties were introduced for evaluation and selection at Mbalmayo (3o 25N latitude, 11o 28E longitude and 640 masl). They were planted in two blocks of equal number of seeds per variety spaced 1 x 1m, 1 x 0.5m and 1 x 0.25m for ware yams, seed yams and seeds for seed yams respectively. Data collected included reaction to anthracnose, yam virus, yield and tuber characteristics and micronutrient content. One D. cayenensis variety (TDc 98-136) and nine D. rotundata varieties (TDr Dente, TDr Muchumundu, TDr 95/19156, TDr 95/18531, TDr 95/18988, TDr 95/19127, TDr 93-83, TDr 89/02565, TDr 95/19177) were selected with farmers for further evaluation. Thus, uniform yield trials consisting of replicated large plots of each of the selected varieties were established at Mbalmayo and in farmers’ fields at Nkometou, Ombessa and Bamenda in collaboration with NGOs. Five varieties TDc 98-136, TDr Dente, TDr 95/18531, TDr 95/19158 and TDr 95/19156 were reported as best with high yield and post-harvest qualities. These varieties are currently under fast-track multiplication and distribution to farmers in seven provinces. In same vein, new varieties are introduced annually for on-station and on-farm participatory trials

Evaluation and delivery of disease resistant cassava varieties with comparable micronutrient density to farmers in Cameroon

Cassava (Manihot esculenta Crantz) is one of the most important staple food crops of the people in Cameroon, with some estimated 204,548 hectares devoted to it and corresponding annual production of 1,998,819 metric tons. It plays a major role in efforts to alleviate food crisis due to its efficient production of food energy, year-round availability, tolerance to extreme stress conditions, and suitability to present farming and food systems. Traditionally, cassava roots are processed by various methods into numerous products and utilized in various ways according to local customs and preferences while the leaves are consumed as vegetables. However, traditional varieties have become relative unproductive, due to a combination of biotic and abiotic constraints, thus justifying the necessity to cultivate improved varieties. In recent years, the International Institute of Tropical Agriculture (IITA) has used conventional breeding methods to achieve important breakthrough in developing pest and disease resistant varieties with low cyanide content, short crop cycle, high-yield and micronutrient content. However, these varieties still require further testing, validation and possibly adaptation to local conditions, before farmers will adopt them. Thus from 2001, over 500 new varieties introduced from Nigeria have undergone advanced yield trials at Mbalmayo (3o 25N latitude, 11o 28E longitude and 640masl) resulting in further selection for uniform yield and multilocational trials with significant contribution from farmers. In 2004 ten varieties (BBulk P6, 8085, 880447-2, 880713, 92/0057, 92/0326, 95/0109, 96/0023, 96/1414 and 96/1762) with excellent resistance to pest and diseases, high root yield (>20 tons ha-1), high dry matter content (>35%), high iron content (>5ug/g), high zinc content (>7 ug/g) and high total carotenoid content (>0.7 ug/g) were selected and are being tested in seven provinces of Cameroon. Results indicate good performance of improved varieties. Due to restrictions on across border movement of planting materials resulting from quarantine regulations, availability of sufficient improved varieties to meet farmers’ needs is limited by IITA’s capability to respond to requests. Hence the adoption of evaluation, multiplication and delivery hubs serving as focal points to satellite centers that will provide planting material of improved varieties to farmers. Adoption of these varieties in Cameroon may make significant contribution to food security and poverty alleviation