Alternatives to polyethylene mulch film - a field assessment of transported materials in capsicum (Capsicum annuum L.)

Materials used as mulches may be either transported to the farm then laid o n the soil surface or grown in situ. To assess biodegradable alternatives t o non-degradable polyethylene film, the response of capsicum (Capsicum annu um L. cv. Target) grown in soil beds covered with hessian (burlap), hardwoo d sawdust, sugarcane (Saccharum spy.) trash, paper film, black biodegradabl e polymer film, white polyethylene film, or left uncovered was investigated in a field trial during the autumn-winter growing season in subtropical Au stralia. Use of a split-plot design (mulch whole plots with weeded or unwee ded subplots) permitted both weed growth and the effect of weed competition on fruit yield to be measured. The presence of substances within the mater ials that were possibly detrimental to plant growth was assessed in a separ ate experiment. The weight of marketable fruit was highest for capsicum pla nts grown in the weeded subplots of biodegradable polymer and polyethylene, although the yields from these subplots were not different from those for plants grown in the weeded subplots of the paper and sawdust or the unweede d subplots of the biodegradable polymer and paper. The reduction in weight of marketable capsicum fruit from weed competition was ranked for the vario us mulch treatments as follows: paper < biodegradable polymer < cane trash < polyethylene < hessian < sawdust < bare soil. Mon hours at optimum soil t emperature for root growth (18.9-30 degreesC) before canopy closure probabl y accounted for the variation in marketable yield of the capsicum crop. Res ults from the mulch toxicity experiment indicated that the mulch materials were unlikely to contain phytotoxic substances. Provided the practical diff iculties of laying paper film can be overcome and the high cost of biodegra dable polymer is reduced these materials appear to be the best of the biode gradable alternatives tested to polyethylene film.