THE DEVELOPMENT OF MULCH-BASED AGRICULTURE AS A MULTI-FUNCTIONAL PRACTICE TO INCLUDE RESTRAINT OF UNWANTED ORGANISMS
Center for Agronomic Research, University of Costa Rica, San Pedro, Costa Rica and Agronomy Department, University of Wisconsin-Madison, 1575 Linden Drive, Madison, WI 53706, USA
Background and objectives
The objective of this 12-year study is to compare agro-ecological parameters (production, nodulation, mycorrhizae, diseases) of this traditional, low-input MBS with several other systems of bean (Phaseolus vulgaris) production: (i) fertilized MBS, 10N-30P-10K; (ii) alley-cropped MBS (four species of N-fixing trees, singly and in combination); and (iii) a newly-introduced, high-input soil-based system (SBS) without mulch.
Results and discussion
Mulch affected bean symbioses: nodulation was greater under the MBS in dry years and although percentage mycorrhizal fungus colonization was not affected by the system, colonization decreased more in the fertilized MBS than SBS. The mulch also prevented the sprouting of weed seeds. In alley-cropped plots, specific trees changed both the biomass and composition of weed species.
Under humid tropical conditions, beans are severely affected by the foliar diseases Thanatephorus cucumeris (sexual stage of Rhizoctonia solani) and Colletotrichum lindemuthianum, and farmers have developed methods of prevention: mulch and planting on east-facing slopes. In wet years, less foliar disease was found in the MBS than SBS. Root-knot nematode (Meloidogyne sp.) infection was significantly less in the MBS than SBS, and longer fallow reduced the nematode gall count.
Major advantages of the mulch in addition to disease prevention are: nutrients from mulch decomposition, efficiency of applied fertilizers, weed prevention and enhanced symbioses under some conditions, as well as increased soil organic matter, better soil aggregation and erosion control.