Long term changes in soil properties and enzyme activities after almond shell mulching in avocado organic production

Abstract

The recycling of almond shell as mulch would allow avocado orchards to be managed organically, maintaining plant yield and improving soil conditions simultaneously. This study aims to analyze the long term effects of successive applications of almond shell as mulching for organically grown avocado. Effects on soil properties, enzyme activities and soil carbon storage as well as avocado yield and growth were studied in comparison to no-tillage conventionally managed (using mineral fertilizers and herbicides) avocado. In 2002, 2007 and 2012 almond shells were applied in a 7 cm thick layer (26.0 kg dry matter m-2) covering 4 x 8 m per tree. After a 10 year period a new soil organic horizon was established in the organic treatment, and the upper mineral soil layer (0-25 cm) enhanced its C content from 43 g kg-1 in F to 91 in g kg-1 , and proportionally P and N contents. The high lignin content of almond shells, 362 g kg-1 , led to low organic matter degradation, 37% for the 10-year period. Nevertheless, this reduced rate of organic matter mineralization was sufficient to supply the needed nutrients and to maintain or even increase fruit yield in the organic treatment. Urease, β-glucosidase, dehydrogenase, protease and phophomonoesterase showed high microbiological activity in the organic layer decreasing in mineral layers. Enzyme activities were significantly correlated to soil OC (organic C) content and site specific soil moisture. Reduced mineralization and high surface microbiological activity make almond shell an ideal mulch for avocado trees combining increased soil organic C content and agricultural benefits.

Effects of Straw Incorporation on Soil Nutrients, Enzymes, and Aggregate Stability in Tobacco Fields of China

“…Catalase activity had no significant correlations with any tested soil nutrients except for EK (Table 5). Increased soil enzyme activities might be due to increased SOC and C and N immobilization during straw decomposition after application, as several studies have shown that soil enzyme activities can be affected by SOC [53][54][55]. Soil pH did not show significant effects on soil enzymes, except for alkaline phosphatase, in this study.…”

Evaluation of different mulch materials for reducing soil surface evaporation in semi‐arid region

“…In addition to macroaggregates formation, organic matter can also stabilize and increase the size of soil aggregates (Chenu et al ., ). On the other hand, unlike synthetic mulches, that need to be removed after a period of time, organic mulches decompose and they need to be re‐applied, increasing water holding capacity, releasing nutrients and promoting favourable soil biotic activities, such as soil respiration and microbial biomass (López et al ., ).…”

Use of organic mulch to enhance water-use efficiency and peach production under limiting soil conditions in a three-year-old orchard

“…Mulching techniques have emerged in recent years to address these soil constraints yielding positive results in a variety of scenarios. An early study by Kumar et al (1985) and other more recent studies (Kar & Kumar, 2007;Mubarak et al, 2009;Okonkwo et al, 2011;García-Moreno, 2013;López et al, 2014;Zribi et al, 2015) reported the positive effects of mulches and organic amendments on soil physical properties, such as increased water retention and decreased soil evaporation.…”