Green manure in coffee systems in the region of Zona da Mata, Minas Gerais: characteristics and kinetics of carbon and nitrogen mineralization.

The use of green manure may contribute to reduce soil erosion and increase the soil organic matter content and N availability in coffee plantations in the Zona da Mata, State of Minas Gerais, in Southeastern Brazil. The potential of four legumes (A. pintoi, C. mucunoides, S. aterrimum and S. guianensis)to produce above-ground biomass, accumulate nutrients and mineralize N was studied in two coffee plantations of subsistence farmers under different climate conditions. The biomass production of C. mucunoides was influenced by the shade of the coffee plantation.C. mucunoides tended to mineralize more N than the other legumes due to the low polyphenol content and polyphenol/N ratio. In the first year, the crop establishment of A. pintoi in the area took longer than of the other legumes, resulting in lower biomass production and N2 fixation. In the long term, cellulose was the main factor controlling N mineralization. The biochemical characteristics, nutrient accumulation and biomass production of the legumes were greatly influenced by the altitude and position of the area relative to the sun

System performance analysis of an alley-cropping system in Western Kenya and its explanation by nutrient balances and uptake processes

Alley-cropping has successively been overestimated and despised, due to unrealistic expectations of this ¿more natural¿ type of agriculture and the disappointment thereafter, when the negative effects of trees on crops became evident over time. In this paper we examine the performance and underlying mechanisms of a Calliandra (Calliandra calothyrsus Meissn.)¿maize (Zea mays L.) alley-cropping system on a phosphorus (P) limiting Ferralsol in Western Kenya. The system performance analysis methods of [The `dark side¿ of intercropping: manipulation of soil resources. In: Sinoquet, H., Cruz, P. (Eds.), Proceedings of the International Conference on Ecophysiology of Intercropping. INRA, Paris, France, pp. 45¿66] and [Agric. Ecosyst. Environ. 80 (2000) 87] were used as well as mechanistic research into availability, uptake and balances of below ground resources. The Calliandra¿maize system performed worse than sole maize (I=¿66%, according to Ong¿s method) Calliandra affected the less limiting resource nitrogen (N) positively, but the negative effect of Calliandra on P-availability, the main limitation of the environment outweighed the positive or fertility effect, according to Kho¿s performance analysis method. However, after P application, when the main limiting resource for maize in our environment shifted to N, the Calliandra had still only a marginal positive effect on maize yields (insignificant 5% increase of alley-cropping compared to sole maize). This was explained by a negative total N balance in the soil of ¿30 kg ha¿1, and a negative inorganic N balance in the soil of ¿277 kg ha¿1 over the seven seasons. The difference between total and inorganic N balance was due to a mineralisation of only 20% of the N in all the Calliandra mulch applied over the seven seasons. Net negative nutrient balances also explain the general trend of decreasing yields of 40¿90% over the seven seasons. We conclude that the combination of Ong¿s simple method, Kho¿s resource-base explanation and further investigation of long-term supply and availability of the resources that are the main limitation(s) of an environment can give an understanding needed to create productive and sustainable alley-cropping systems