Mulching as an alternative technique for weed management in mandarin orchard tree rows

Moving towards sustainable agriculture implies exploring the interconnections between farming and the environment, and soil is a key component of sustainability. Mulching is one of the methods to protect and enhance the productivity of the soil. We studied here the effect of mulching applied to mandarin tree rows for weed control in two localities near Tortosa, Spain, to compare its performance with the present chemical weed control system using the herbicide glyphosate. Three mulches were tested in each citrus orchard: rice straw, almond husk and black geotextile. Five plots per treatment, that is, three mulches, glyphosate application and control, were arranged following a randomized block design. Each plot was five trees long and its width was the distance between the two drip-lines. Just before mulch installation, bags containing non-dormant seeds of Amaranthus retroflexus and Diplotaxis erucoides were buried at three depths, and were exhumed one year later. After exhumation, sets of 250 seeds were placed in incubators and cumulative germination was obtained. Moreover, the weed flora was monitored at the two localities on four dates over one year and its total cover was evaluated. Seeds of A. retroflexus and D. erucoides showed the highest germination below almond husk, 90.9% and 96.2%, respectively. In total 74 species were recorded covering the mandarin tree rows. Our results indicated that black geotextile and almond husk controlled the presence of weeds as well as or better than the applications of glyphosate at least during the first year after their introduction. No significant differences were found between the mean weed cover of black geotextile (0.88%), almond husk (4.04%) and herbicide plots (2.04%). Altogether, our results show that mulching is one weed control strategy in mandarin orchards that also provides other benefits in terms of sustainable agriculture, such as soil protection or avoiding herbicide pollution.