increased , and the levels of P increased after 4.5 years . ... For example , in a traditional shifting cultivation system in the lowlands of Papua New Guinea , the cropping cycle is usually 18 months , consisting on mixed food crop ...

Two years after planting , the total ecosystem levels of Mg and Ca declined , while total N and K increased ... For example , in a traditional shifting cultivation system in the lowlands of Papua New Guinea , the cropping cycle is ...