The relative effect of three mulches on rainbow silver beet chard yields Jakub Gawronski Abstract Mulches are a sustainable alternative to herbicides This study looked at the relative effect of newspaper mulch subterranean clover mulch coffee residue mulch and bare ground control on rainbow silver beet chard yields with the mulches and control having been left unweeded for three months prior to planting Newspaper mulch and coffee mulch were expected to harbor the highest chard yields while the control was expected to harbor the lowest yields The field is located in Albany CA There were four replicates per mulch type and control Each replicate measured 3 5 by 2 5m The mulches were laid down and left unweeded After three months weed cover was visually estimated per plot and rainbow silver beet chard crops were transplanted into the mulches Eight chard crops per plot were harvested one month after transplanting The chard crops were weighed together per plot One way ANOVA was used on the crop weights and weed cover The ANOVA test came out with a P value of 0 0318 for the chard weights and a P value of 0 0001 for weed cover The only significant difference between chard weights was between the newspaper mulch and the clover mulch Newspaper mulch had higher chard weights than clover mulch Percent weed control was significantly different between all combinations of mulch treatments and control The control plots had the highest weed cover followed by clover mulch then coffee mulch and newspaper mulch had the lowest weed cover The results show that newspaper mulch supports higher yields than subterranean clover mulch if chard crops are planted three months after laying down the mulch and leaving it unweeded The chard crops were probably in the ground too short to see significant differences in yields Also a eucalyptus tree probably released allelopathic chemicals in two plots which probably confounded the results This study implies that newspaper mulch should be used rather than subterranean clover mulch if chard is planted into mulch that has been left unweeded for 3 months prior to planting Introduction Herbicides have a negative effect on the life of birds and beneficial insects Freemark and Boutin 1995 They leach into groundwater and drift off to kill plants in the neighboring ecosystem Radosevich 1997 Thus in order to avoid the harm that herbicides do to the environment alternatives have been sought that sustain human and environmental health A mulch is a material or legume that covers the ground in between crop rows that is used as a form of weed control to maintain soil moisture to maintain a steady temperature within the soil and to keep fruits from spoiling if they touch the ground Pierce 1998 Mulches can be inorganic organic or living The inorganic form usually consists of clear or black plastic sheets tucked into the ground This form Organic forms include straw leaves compost newspaper used coffee grounds sawdust tree bark and various others Living mulches are usually patches of various species of clover or vetch and all tend to be nitrogen fixing Mulches can affect crop yields by influencing weed cover soil moisture nutrients and pH Gliessman 1998 By reducing weed cover mulches can have a positive impact on crop yields Organic mulches can conserve soil moisture which allows crops to withstand longer drought periods Organic mulches can add nutrients to the soil and living mulches can remove nutrients from the soil Some organic mulches such as coffee residues can affect the acidity of the soil which may affect crop yields positively or negatively depending on specific crop pH tolerance ranges Nogueira and Flores 1987 In this study I am going to evaluate the relative effect of newspaper mulch coffee residues as mulch and subterranean clover Trifolium subterraneum L mulch left unweeded on the yields of Silver Beet Chard Some farmers do not have labor or capital inputs to keep their land weed free This study takes these farmers into account by examining how the three mulches will affect chard yields if they are to be left unweeded for a period of time We have chosen newspaper and used coffee grounds as organic mulch material because they are a cheap easily available material that would otherwise be on its way to the landfill Thus using these mulch materials is a way of reuse and a benefit for the environment Previous studies have looked at the effects of various organic and living mulches on crop yields most showing that mulches have a positive effect on crop yields Kamara Akobundu Sanginga and Jutzi 2000 Carter et al 1992 Brandsaeter et al 1998 and others Three studies examined the effects of newspaper and subterranean clover on crop yields but without comparing the two mulches Monks et al 1997 stated that chopped newspaper and shredded newspaper provided yields in tomato similar to the area treated by two herbicides A study done on subterranean clover as a living mulch indicated that subterranean clover is great in reducing weed biomass but has no effect on crop yield on corn sweet corn cabbage snap peas and tomato Ilnicki and Enache 1992 Another study on subterranean clover found that grape yields were higher in synthetically fertilized plots than ones with the clover Favretto et al 1992 However no study compared the effects of subterranean clover newspaper and coffee residue mulches on crop yields Without such a study a farmer does not know which mulch has the best impact on crop yields Newspaper mulch decomposes slowly and provides a physical barrier for weed growth thus providing great weed control Kamara Akobundu Chikoye and Jutzi 2000 Vasilikiotis 2000 pers comm This would result in minimal competition from weeds on crops Coffee residues were reported to increase sweet potato yields and act as a great fertilizer D Souza and Bourke 1986 Organic mulches retain soil moisture allowing crops to have good yields during drought periods Gliessman 1998 Subterranean clover competes with crops for water and nutrients but not as intensely as most weeds since clover fixes nitrogen and thus competes less for that nutrient Brandsaeter et al 1998 Vasilikiotis 2000 pers comm Unmulched ground allows plenty of weeds to grow and compete with crops resulting in low yields Vasilikiotis 2000 pers comm Thus my hypothesis is that Silver Beet Chards planted in newspaper mulch and coffee mulch result in the highest yields while those planted in unmulched control result in the lowest yields
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