Growth dynamics and productivity of an Eucalyptus grandis plantation under omission of N, P, K Ca and Mg over two crop rotation

Abstract

We conducted an experiment where Eucalyptus grandis was grown for two crop rotations (R1, planted in 2004; R2, clear felled and re-established in 2012) with and without N, P, K, and Lime application. The soil of the experimental site was an Oxisol. Our goal was to identify the magnitude and type of response to N, P, K, and lime applications over two crop rotations. We also aimed to identify the role of weather in tree growth dynamics and in the current responses of trees to fertilizer applications. For this, stem growth of fertilized and unfertilized trees was measured monthly, and wood volume and total biomass were measured every 12 months. In the absence of K, the wood volume decreased drastically (approximately 70%), and this effect was observed until the end of R1 and R2. On the other hand, in the absence of N, P, and Lime, the wood volume decreased from 20% to 50% at 2 years of age. This response decreased with age, disappearing at the end of both rotations for N and was approximately −10% for P and Lime. The trees fertilized with all nutrients were highly responsive to weather variation, showing a basal area increment of approximately 1.0 m2 ha−1 month−1 during the rainy season and values less than 0.2 m2 ha−1 month−1 during the dry season. The absence of K fertilization resulted in a slow but constant growth of approximately 0.2 m2 ha−1 month−1. During months with high water availability, a large current response of trees to fertilizer application was found. During months with low water availability, a low or no response to fertilizer application was found. These results show that a sequence of months with low water availability decreases the accumulated response of trees to fertilizer application, while the opposite is also true.