Fertilisation schemes based on organic amendments; decomposition and nutrient contribution of traditionally used species in an indigenous region of southern Mexico

ABSTRACT The use of organic soil amendments to sustain crop production provides a feasible option for low-income farmers. In La Montaña, in southern Mexico, farmers grow organic hibiscus (Hibiscus sabdariffa) as their main source of income, but yields are low. The aim of this study was to evaluate the decomposition and nutrient release of different species traditionally used by farmers and to make recommendations for their use as soil amendments. The decomposition of Mucuna pruriens, Calliandra houstoniana and stover of hibiscus (separately and as 1:1 mixtures) was evaluated using litterbags in the field, analysing dry weight and chemical components of the remaining litter at monthly intervals. Mucuna on its own and mixtures containing this species, decomposed on average 50% faster than the other amendments. Mucuna on its own released the highest amount of nitrogen (155 kg ha−1 year−1), which was in excess of that required by the hibiscus crop (45 kg nitrogen ha−1 year−1). To complement crop nutrition whilst minimising nitrogen losses and improving soil quality, the calliandra-mucuna mixture was proposed as the most promising amendment, because: (i) the nitrogen demand of the hibiscus crop was met (75.7 kg ha−1 year−1), (ii) the asynchrony of available nutrients was minimised as half of the mass of the amendment had decomposed by the time of the flowering stage of the hibiscus, and (iii) it contributed carbon and nutrients to the soil organic matter. This information can be used to promote agroforestry systems that include mucuna and calliandra trees in hibiscus plantations.