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Mixed Vegetable Polyculture Trials - University of Cumbria
- 1. Mixed Vegetable www.permaculture.org.uk Polyculture Trials the results In association with ‘Mixed veg’ can mean so much more than a quick-fix packet from the freezer. For 50 people around the UK last year, it took on a new meaning – a new way of growing vegetables all by Dr Naomi van mixed up together. der Velden Rationale - Learning Photo: C. Atkin from nature? Look around at the natural world to see where plants choose to grow. You will notice that they tend to grow in mixes of different plants rather than large areas of a just one species. Often species grow together in relatively consistent and discernible mixes. For example, we might expect to find bramble and bluebells in lowland oak woodlands. Plants naturally form communities. There is some good scientific evidence that communities of wild plants growing together may be more productive than any one of the component species growing on its own would be 1. Can growing food plants in communities, Figure 1 - A trial layout High-diversity plot is in the foreground, and behind it the low-diversity plot. rather than monocultures, also be more productive (as well as better for the together compared to the same species Studies have found that some species are environment)? grown separately. You might have heard more productive when grown in mixes, People have studied production of crop of the classic “three sisters” of Central but that others are not. However, very plants when several different types America – maize, beans and squash – few studies have looked at mixes of more (usually two or three species) are grown which are said to grow well together. than three crop species, so we thought we’d give it a go. 1 “16-species plots attain 2.7 times greater biomass than monocultures” from: Tilman et al. 2001 Diversity and Productivity in a Long-Term Grassland Experiment. Science 294 (5543) 843-845.
- 2. Mixed vegetable polycultures We conducted our own study to compare low- and high-diversity mixes to find out: Are more diverse (12 species) vegetable mixes more productive than less-diverse (three species) mixes? How easy do gardeners find these systems to use? The vegetables used are as listed below and in Figure 1. We chose common vegetables from a range of plant families and which would complement the spaces available (e.g. some roots, some climbers, some low, some high) above and below ground. How did we investigate this? Fifty sets of seeds were kindly provided by four lovely seed companies and sent to households around the country. Figure 2 - Plant roots and shoots occupy different areas Onion, lettuce, sweet corn, peas, radish, & runner beans. Everyone made two plots – one smaller (Roots drawn after Weaver & Bruner, 1927 “Root development of vegetable crops”) one for three species - Low diversity - and one larger one for the more diverse Some plant ecology: For example, different plants have different rooting zones so could be mix - High diversity (see Figure 1). Plant niches, competition and combined to maximise use of the soil Larger plants (beans, sweet corn, kale) co-operation. area, rather than competing in a single were first grown in pots then planted layer (see above). The growing of plants in mixtures out. Others (onions, peas) were sown in These plants might be described as is effectively a balance between clusters, and the remainder were mixed occupying different niches. competition for resources, and together with some soil and scattered “co-operation” to use all available They can also benefit each other, across the plot. resources as efficiently as possible. for example by fixing nitrogen or Participants were asked to record providing food for pest predators or information about when they visited for pollinators. their plots, how long they spent there, and also to weigh each species each time it was harvested. We measured productivity of the edible plant parts (the bits you’d buy) by What have we found Twenty four participants were able to looking at: out? complete the study and return their data. Weight harvested per area (square-metres) Which plot-type was most productive? Weight harvested per minute of time spent In terms of the total amount produced on the plot per land area, the high diversity plot was What’s in the plots? slightly more productive (see top graph Length of time plots were productive for in Figure 3). (longevity of production) Low diversity: On average, 3.1 kg were produced from Peas, radish and perpetual spinach Participants were also asked to fill in a square metre (m2) in the low diversity (beet). questionnaires before and after so we plot and 3.5 kg in the high diversity could find out what they thought of plot. These slight differences are not growing in this way. significant2 because there is a lot of High diversity: Thirty-one people returned the initial variation in how much was harvested by As above, plus onions, lettuce, questionnaire and twenty-one the final different people (see maps in Figure 4). beetroot, sweet corn, coriander, runner beans, kale, marigolds and questionnaire of whom nineteen had When considered by the amount of time rocket. also returned data. people put into the plots, then the low diversity plot was more productive for the effort (see lower graph in Fig. 3). 2 Wilcoxon signed rank test for 24 samples, z = 1.154, p = 0.130 . The difference between means is considered statistically significant if the value of p is less than 0.05, so in this case, this is not significant. The error bars in the graphs also overlap each other quite a lot which is always a clue that the difference in the average isn’t too important.
- 3. The results On average, 3.4 kg were harvested from a square-metre of the low diversity plots Yield per square metre The vertical black lines (“error bars”) for every hour of effort put in, and the show standard error and indicate the high diversity plots yielded 2.3 kg. amount of variability in the data. productivity (kg m-2) Although this difference is quite large, Small lines mean that most people it is not quite statistically significant3. It harvested close to the average should be noted that people tended to amount, larger lines mean that some record time to the nearest five minutes, people got lots and some people so the amount of time spent on the low diversity high diversity got a little. low-diversity plot might have been over- estimated. Yield per hour Overall, there’s little difference in productivity (kg per hour) productivity between the two types of plot when we account for area and time. This could be because of the crops chosen or other factors that mean there is a lot of variation in the data. You can see in the maps in Figure 4 that low diversity high diversity some quite high levels of production Figure 3 - Productivity of low and high were reached – up to 10.6 kg of food diversity mixes when considered per area (top graph, kilograms produced from one square metre) and from one square metre of ground! in terms of how much effort was put into growing (lower graph, kilograms produced per hour of effort from one square There are lots of reasons why this might metre of land). One kilogram (kg) is 2.2 lbs. be – better soils, better weather, more time, more experience. Productivity of each plot. The amount of time put into plots was significantly related to the amount of yield people got in the high diversity plot4 and a little so in the low diversity plot 5. People who got a good yield on the high diversity plot also tended to get a good yield on the low diversity plot6, perhaps because their site was better or because they are more experienced gardeners. It is interesting to see from the maps in Figure 4 that areas typically considered more marginal, like Scotland, Wales, and the far north of England, generally had some quite high production. Perhaps success with different types of the crops used might also be important? To give some context, 3.5 kg per metre-square works out at 35 tonnes per hectare! UK wheat yields are about 7-8 tonnes per hectare and that’s Figure 4 - Yellow shows lower production and on the best growing land! red shows higher production in grams, harvested from 0 - 0.75 kg one square-metre, the values are: 0.76 - 1.5 Mind you, it’d take quite a lot 1.6 - 3.0 of time to harvest a hectare 3.1 - 5.0 (that’s an area 100 by 100 5.1 - 10.6 metres) using this method! 3 Wilcoxon Z statistic = 1.680, p = 0.093, 20 people returned data on time spent on the plots. 4 Spearman’s Rank correlation test: Rho = 0.446, p = 0.046 The relationship is considered statistically significant if the value of p is less than 0.05. Rho is a value between +1.000 and -1.000. If it is +1, then there is a perfect straight line fit between increasing time and increasing yield. If it was -1, then increasing time would always lead to a reduced yield. 5 Rho = 0.430, p = 0.052. 6 Rho = 0.845, p < 0.001 (Here you can see Rho is closer to +1.000 meaning that there is a stronger relationship between yield from high diversity plots and low diversity plots, than there is between experience and yield. This is also reflected by the p value being much less than 0.05)
- 4. Mixed vegetable polycultures Which crop types did things that could cope with some shade Longevity of crop (e.g. spinach beet, lettuce, peas, radish, best? plot also tended to get a good yield on the coriander, rocket, beetroot), it their site diversity low diversity plot , perhaps because seems 6 production In the low-diversity plot – Peasgreen fingers. It is that there wasfrom the maps in Figure 4in the was better or because they have and interesting to see a lot of competition that As well as looking at the total amounts spinach were successful for most people High-diversity plot. areas typically considered more marginal, like Scotland, Wales, and the far north of England, produced, it’s also important to look at generally had some quite high production. Perhaps success with different types of the crops used (see left also be side of Figure 5) and gave might hand important? The density of crops is very important when crops are being harvested. high yields (Figure 6). Radish grew for in determining yield – too far apart and In theory, having a greater diversity most people and produced reasonably Which crop types did best? crops are isolated and susceptible to the of different crops might mean more well (given it’s small!) – Peas and spinach were successful for most people (see left hand side of In the low-diversity plot elements. continuous food production, and fewer Figure 5) and gave high yields (Figure 6). Radish grew for most people and produced reasonably In the high-diversity plot - Well, rocket well (given it’s small!) Grow lots of one crop close together and “gluts” where we’re overwhelmed with a grew. Vigorously. This was meant to be the individual plants can’t obtain all the particular crop. a cover crop that weplot - Well, rocketate Vigorously. This wasneed. to be a cover crop that In the high-diversity pulled up and grew. resources they meant we pulled up and ate early on to give room for other things…but it’s so tempting to just cut a bit off From our data, the High-diversity plot early on toharvesting it. for other things… also harvested well for most people. and keep give room Kale, onions, and beans It is possible that our High-diversity has higher yields earlier in the season but it’s so tempting to just cut a bit off crop mix was too dense to perform at giving a greater spread of when food is and keep harvestingcoriander, and lettuce really didn’t grow for many people (Figure 5) and even Sweet corn, beetroot, it. those who got a harvest didn’t get very much (see the right hand we look at when people were its best. If side of Figure 6). available (see Figure 7). Kale, onions, and beans also harvested harvesting crops, we also see some For the three species grown in both plots, spinach7 and peas8 and radish9 all grew much better in the Looking at individual species, we can well for most people. interesting results that support this. Low-diversity plots than the High-diversity plots (see Figure 6). also see some important differences. Figure 8 shows that peas were harvested for longer from the Low-diversity plot, and spinach was ready much earlier. The radish was generally ready around the same time in both. Spinach, lettuce, and beetroot in the High-diversity plot all started to increase towards the end of our growing season (last harvest on 31st October), suggesting that these all started to do well after some of the other crops (rocket, beans, onion) were harvested (Figure 9). Figure 5 Number of people who harvested each crop (max 24). Organised by most successful Figure 5 - Number of people who harvested each crop (max 24). crops in Low- then High-diversity plots. Organised by most successful crops in Low- then High-diversity plots. Sweet corn, beetroot, coriander, and lettuce really didn’t grow for many people=(Figure<5) and even can see Rho is closer to +1.000 meaning that there is a stronger relationship between 6 Rho 0.845, p 0.001 (Here you those who got athefrom high didn’t get and lowmuch plots, than there is between experience and yield. This is also reflected yield by harvestbeing much less very diversity p value diversity plots than 0.05) (seeSpinach. Difference is highly statistically significant. Wilcoxon signed-rank statistic 3.574, p < 0.0005. So there is a 7 the right hand side of Figure 6). huge difference in the average amount of spinach people are getting from each plot and we can see that much more Forperson’s Low- and High-diversity plot, and so eliminates some of a paired test whichmight occur from people growing in comes three species grown in Wilcoxon signed-rank is the from the Low diversity plot. The both the variations that compares production from each plots, spinach7 ways. peas8 and radish9 all slightly different and 8 grew much better in the statistic 3.782, < 0.0005. Differencethe highly statistically significant. 0.05. 9 Peas. Wilcoxon signed-rank statistic 4.171, p Radish. Wilcoxon signed-rank Low-diversity p < 0.0005. Again, is p-value is much, much less than plots than the High-diversity plots (see Figure 6). Overall, more diverse plots seem to yield a little more for the land area than less diverse plots, although diversity of vegetables harvested might be at the expense of yields of individual species. Figure 66Average productivity of theof the plantstwo the two plots Measured in Figure - Average productivity plants on the on plots Measured in kilograms per metre- squared, organised by most productiveproductive crops Low-Low- then High-diversity plots kilograms per metre-squared, organised by most crops in the in the then High-diversity plots We can see that some crops grew well The vertical black lines show standard error and indicate the amount of variability in the data. Small lines mean but others, like sweetcorn, consistently that most people harvested close to the average amount (e.g. spinach in the High-diversity plot), larger lines The vertical black lines show standard (e.g. spinach in the High-diversity plot), mean that some people got lots and some people got a little (e.g. spinach in the Low-diversity plot). failed to produce. It is interesting to see error and indicate the amount of larger lines mean that some people got that the most productive crop, spinach, variability in the data. seem to yield a little morelotsthe land area than less diverse little (e.g. Overall, more diverse plots for and some people got a plots, did well only on the Low-diversity plot. although diversity of vegetables harvested might be at the expense the Low-diversity plot). spinach in of yields of individual species. Small lines mean that most well but others, like sweetcorn, consistently failed to produce. It is We can see that some crops grew people Most crops need a certain amount of harvested close to the average amount interesting to see that the most productive crop, spinach, did well only on the Low-diversity plot. sunshine, and although we tried to pick Most crops need a certain amount of sunshine, and although we tried to pick things that could cope with some shade (e.g. spinach beet, lettuce, peas, radish, coriander, rocket, beetroot), it seems that 7 Spinach. Difference is highly statistically significant. Wilcoxon signed-rank statistic lot ofp < 0.0005. So there is a huge difference in the average amount of spinach people are getting from each there was a 3.574, competition in the High-diversity plot. plot and we can see that much more comes from the Low diversity plot. The Wilcoxon signed-rank is a paired test which compares production from each person’s Low- and High-diversity plot, and so eliminates some of the variations that might occur from peopleThe density of crops is very important in determining statistic 4.171, far 0.0005.and crops is highly statistically growing in slightly different ways. 8 Peas. Wilcoxon signed-rank yield – too p < apart Difference are isolated and significant. 9 Radish. Wilcoxon signed-rank statistic 3.782, p < 0.0005. susceptible to themuch, much less thanlots of one crop close together and the individual plants can’t Again, the p-value is elements. Grow 0.05. obtain all the resources they need. It is possible that our High-diversity crop mix was too dense to perform at its best. If we look at when people were harvesting crops, we also see some interesting
- 5. in amount of sunshine, and although we tried to pick things that could cope pinach beet, lettuce, peas, radish, coriander, rocket, beetroot), it seems that Looking at individual at individual species,also see some important differences. Figure 8 shows that peas Looking species, we can we can also see some important differences. Figure 8 shows that peas The results etition in the High-diversity plot. were harvested for longer from the Low-diversity plot, and spinach was ready much earlier. The were harvestedradish was generally readyLow-diversitytime in and spinach lettuce, and beetroot in the High-The for longer from the around the same plot, both. Spinach, was ready much earlier. radish was generally ready aroundto increase towards the both. our growing lettuce, and beetrootst in the High- very important in determining yield – too far apart and crops are isolated and diversity plot all started the same time in end of Spinach, season (last harvest on 31 ents. Grow lots of one crop close together and the individual plants can’t diversity plot all started to increasethese all started to do well after some of the other crops (rocket, beans, 31st they need. It is possible that our High-diversity crop mix was too dense to October), suggesting that towards the end of our growing season (last harvest on October), suggestingwere harvested (Figure 9). to do well after some of the other crops (rocket, beans, we look at when people were harvesting crops, we also see some interesting onion) that these all started onion) were harvested (Figure 9). duction e total also en crops theory, ty of ean gluts” med with h- r yields ing a Figure 7 Continuity of production. Amount harvested each month. Figure 7 - Continuity of production Solid line shows High-diversity plot, dashed line the Low-diversity. Amount harvested each month. Solid line shows High-diversity plot, dashed line the Low-diversity. What about the quality of the food produced? Overall, the High-diversity plot had a What about the quality of the food produced? Most of what was harvested was of high quality for more sustained availability of crops, Most of what was harvested was of highwith relatively little damage. Peas did garden produce quality for Figure 8 Timing of harvests for crops in both plots. Solid with different crops peaking at different garden producethe cropswell, spinachdamage. Peas did and radish fared rather Figure 8 - Timing of harvests for Low- line shows High-diversity plot, dashed line with relatively little reasonably well, times. well, spinach reasonably well, and radish fared rather in both plots Solid line shows High-diversity one diversity. Amount harvested each month in grams from less well. (Figure 10). The low-diversity plot tended to square-metre. line the Low-diversity. (Figure 10). The low-diversity plot tended to plot, dashed less well. have slightly better quality food, but the overall It’s also likely that several crops only Amount harvested each month in grams from one quality food, but the overall have slightly better differences between the plots are not significant10. square-metre. really started to grow after other crops differences a more sustainedplots are not significant10. Overall, the High-diversity plot hadbetween theIdeally, we would like to compare these results to those availability of crops, with different would likeat compare these results to those Ideally, we crops peaking to (like rocket) were removed. from own-grown crops under “normal” growing different times. It’s also likely that several crops only Figure 8 Timing of really startedforgrow after own-grown crops methods. harvests to crops in both plots. rocket) were “normal” growing from other crops (like Solid under It is important to understand howshows High-diversity plot,important to understand how these line these removed. It is dashed line the Low- methods. systems can work to provide adiversity. Amount harvested eachto providein sustainedfromof food. sustained systems can work month a grams yield one Looking at damage to the crops shown in Figure 11, Perhaps this is a good way of getting lots of food but yield of food. square-metre. avoiding gluts. However if youat damage to the crops shown the Low diversity plot suffered less Looking really want lots of people felt that in Figure 11, spinach, then giving plenty felt that the Low diversity plot suffered less people food to grow will be What about the qualityitof theof space produced? Perhaps this is a good way of getting important. damage than the High-diversity plot and the usual way Most of what was harvested was of high High-diversity plot9and thefood. The High-diversity plot damage than the quality for Figure Timing ofusual way other crops in which they grew harvests for lots of food but avoiding gluts. However the High-diversity relatively more angrew food. Thein the High-diversityplot Amount harvested Overall, garden produce with plot had a little damage.for perhaps suffered a little more pest and disease damage. It should also be noted whichgave sustained Peas didHigh-diversity plot. in that we they end date our if you really want lots of spinach, then well, spinach reasonably well, andpeakingfared rather pestmonth diseasefrom one square-metre. availability of crops, with different crops harvest everything perhaps suffered a at more each and in grams damage. experiment and asked everyone to radish little giving it plenty of space to grow will be times.that was remainingThe low-diversitySome crops different It’s also likely thatend of October. only at the several less well. would have10). growing for longer.crops plot tended to (Figure kept really started to grow after other crops (like rocket) were important. have slightly better quality food, but the overall removed. It is important to understand how these differences between the plots are not significant10. It should also be noted that we gave an can work to provide a sustained yield of food. systems Perhaps this is a good like to compare of food but to those Ideally, we would end date for our experiment and askedfrom own-grownway of getting“normal” growing lots these results crops under avoiding gluts. However if you really want lots of everyone to harvest everything that was then giving it plenty of space to grow will be methods. spinach, remaining at the end of October. important. Looking at damage to the crops shown in Figure 11, Figure 9 Timing of harvests for other crops Figure 9 - Timing of harvests for other Some crops would have kept growing for It should also be that the Low diversity plot suffered less in crops in the High-diversity plot harvested people felt noted that we gave an end date for our the High-diversity plot. Amount longer. Amount harvested each month in grams from one damage than the High-diversity plot and the usual way month in grams from one square-metre. experiment and asked everyone to harvest everything each square-metre. that was remaining at the end of October. Some cropsplot in which they grew food. The High-diversity would have kept growing for longer. pest and disease damage. perhaps suffered a little more What about the quality of the food produced? Most of what was harvested was of high quality for garden produce with Figure 10 Quality of c relatively little damage. Amount of damage in a, none – will eat all; b Looking at damage to the crops shown c, moderate – will eat h in Figure 10, people felt that the Low eat little; e, devastated diversity plot suffered less damage than the High-diversity plot and the usual way in which they grew food. The High-diversity plot perhaps suffered Figure 11 Perceived damage on Low-diversity, Figure 11 Perceived damage on Low-diversity, Figure 10 - Perceived damage on Low-diversity, High-diversity and growing methods. High-diversity and “Normal” a little more pest and disease damage. “Normal” growing methods Note that Normal methodsgrowing methods. High-diversity and “Normal” are the usual growing methods of participants and differed between people. Answers based on questionnaire responses for pests – 24 usual growing Note that Normal methods are theNormal methods are the Note that usual growing The low-diversity plot tended to have responses, for disease - 15 responses. methods of participantsQuality of crops harvested. Figure 10 and differed between people. methods of participants and differed between people. slightly better quality food, but the Answers based on questionnaire responsesquestionnaire responses for pests – Answers based on forof damage in categories: Amount pests – overall differences between the plots are 24 responses, for disease - eat responses. – will eat most; a, none – will 15 all; b, mild 24 responses, for disease - 15 responses. not significant10. c, moderate – will eat half; d, severe – will 10 10 Chi-squared tests little; e, devastated – will eat none. 4.60 p>0 2 eat for; Peas Χ2 = 3.89 p>0.05; Spinach2 Χ2 = 2 Chi-squared tests for; Peas Χ = 3.89 p>0.05; Spinach Χ = 4.60 p>0.05; Radish Χ = 3.09 p>0.05 10 Chi-squared tests for; Peas Χ2 = 3.89 p>0.05; Spinach Χ2 = 4.60 p>0.05; Radish Χ2 = 3.09 p>0.05. No significant differences between Low- between Low- and High-diversity plots. differences and High-diversity plots. differences between Low- and High-diversity plots.
- 6. ed in and completed the initial survey did have some experience of growing inner out of 31people), so we don’t really know what it would be like for Mixed vegetable polycultures It did seem that people with more experience of vegetable growing got a little gh diversity plot, but it didn’t make a difference for the low diversity one11, but istically significant, so if you grow veg you could give this method a go and Peas did well, spinach reasonably well, and radish fared rather less well (see How easy was it to How much effort is it? figure 11). grow? Was the yield worth the effort? t? Ideally, we would like to compare these Most people who joined in and Overwhelmingly, people thought it was he effort? completed the initial survey did have worth having a go, especially with the results to those from own-grown crops ple thought it“normal” growing methods. under was some experience of growing veg before smaller Low-diversity plot (see pie charts pecially with the (just one beginner out of 31 people), so in Figure 12). y plot (see pie charts we don’t really know what it would be Overall, people enjoyed trying out this like for complete beginners. method of growing and were keen to It did seem that people with more give it a go (Figure 13). yed trying out this experience of vegetable growing got a But – be careful! nd were keen to little bit more out of the high diversity 3). plot, but it didn’t make a difference for Although the results look good, they are the low diversity one11, but neither of by no means the final answer. There are Figure 12 Was yield worth the effort? these is statistically significant, so if you some important things to consider: Reponses from finalgrow veg you could give this method a questionnaire (21 responses) We’re really happy that 24 people ook good, they are go and get good results! completed the trial. However, it’s still answer. There are some important only a relatively small number of plots. appy that 24 people completed the Any one grower can have a large influence on the overall results. r, it’s still only a relatively small ts. Any one grower can have a large We’d like to repeat it again with he overall results. We’d like to hundreds of people joining in to get a real feel for what is happening! with hundreds of people joining in el for what is happening! It was a strange year for weather and asy wasweather grow? people e year for it to and many many people agreed it was a difficult growing season. a difficult growing season. Perhaps ople who joined in and completed the initial survey did have some experience of growing yield r would yield different results Perhaps a different year would ore (just 1 beginner vegetable binations and types of out of 31people), so we don’t really know what itdifferent resultslike for would be e beginners. It did seem that people with more experience of vegetable growing got aand types give very different results – there’s Different combinations little hout of the high diversity plot, but it didn’t make a difference for the low diversity one11give very isn’t known about polycultures! of vegetable species might , but Figure 12 - Would you plant a mixed different results – there’s still a lot which 13 grow you of these is statistically significant, FigureyouWould again?you could give isn’t known abouta go and so if vegetable bed veg plant a mixed this method polycultures! d results! vegetable bed again? ctive method of growing; on average 3.5 kg of food were produced from one me people achieved over 10kg. Gardens and allotments have the potential to uch effort is it? tyield worth a small amount of space. They also generally avoid many of the of food from the effort? wildlife and the environment that might be associated with other methods of elmingly, people thought it was wever, this is a much more labour-intensive method of production which people aving growing as much aswith the product, tasty though that may be! ent in a go, especially for the final Low-diversity plot (see pie charts e 12). Figure 10 Quality of crops harvested. ation on experience11 - Quality of crops harvested Figure and production per metre-square: High diversity plot Rho is 0.420, p = Amount of damage in categories: , people a:enjoyed all; b, will eatoutwill eat most; would be +1.000 if all the data a, increasing – willeat trying most; this and -1.000 if increasing experience but 05); Low diversityofplot Rho is 0.311, p = 0.159 . Rho Amount damage in categories: ine of none – will eat all; b: mild – mild – yield, none experience and increasing means experience and were bit, d, severe – will experience can still get high yields. of c, moderate counts eathalf; d: severe –but eatto with less growing – –will aeat half; will people e: devastated – will little keen c: moderate will eat little; none goeat little; e,13). (Figure devastated – will eat none. Figure- 12 yield worth the effort? the effort? Figure 13 Was Was yield worth e careful! Reponses from final questionnaire (21 responses) Reponses from final questionnaire (21 responses) h the results look good, they are eans the final answer. There are some important o consider: We’re really happy that 24 people completed the plot Rho is 0.420, p = 0.051 (almost less than 0.05); Low diversity plot Rho is 0.311, p = 0.159 . Rho 11 Spearman’s rank correlation on experience and production per metre-square: High diversity rial. However,if all the data formedonlystill get high yields. smalland increasing yield, and -1.000 if increasing experience but decreasing yield. So this means experience counts would be +1.000 it’s still a perfect straight line of increasing experience a little bit, but people with less experience can a relatively number of plots. Any one grower can have a large nfluence on the overall results. We’d like to
- 7. The results In summary, This is a highly productive method of growing. On average 3.5 kg of food were produced from one square-metre and some people achieved over 10kg. Gardens and allotments have the potential to give us a large amount of food from a small amount of space. They also generally avoid many of the negative impacts on wildlife and the environment that might be associated with other methods of food production. However, this is a much more labour- intensive method of production which people tend to do for enjoyment in growing as much as for the final product, High-diversity plot in June tasty though that may be! Comparing the plots, the High-diversity from competition for space and nutrients Some of the seed onions have also crop was slightly more productive, and and less able to cope with additional started to grow well this year. gave a longer period for harvesting food; pressures. Perhaps we need to consider these however, the crops grown in the Low- Getting a balance between different food systems in terms of year-long diversity plot were individually more plants can be important for many production, or continuous production? productive, perhaps because they had reasons. Maddy Harland’s article on the less competition with other species. People enjoyed having a go at this, and Permaculture Magazine website There is a balance between growing a most were inspired to do it again. (22nd May 2012), talks about choosing variety of different food and growing a perennial varieties or annuals which Generally, they found the Low-diversity large amount of any one crop. self-seed, to create a naturalistic self- plot easier to manage, perhaps because It is also likely that the more time you put sustaining polyculture. it was smaller, perhaps because the mix into your garden the more it will reward of species was less confusing, or perhaps There are many ideas here which you you with food. because it wasn’t overwhelmed with might like to explore further. This Having a mix of some species may also rocket early on! summer, several of us are working on reduce damage from pests and diseases, different species mixes so that we are It’s June now, and I am still harvesting but it is not clear how much diversity is prepared for our future trials. spinach from both plots, even though I needed. cut them right back in October. If you have suggestions of crop mixes Our results suggest that the High- that have worked for you, we would love I’m sure the kale would have kept going diversity plot suffered most damage. It to hear from you! through the winter too but I honestly may be that plants were more stressed couldn’t face any more so pulled it up! The polyculture research team Acknowledgements Dr Naomi van der Velden - Plant ecologist at the Massive thanks to Celia Ashman for all her help in co- University of Cumbria ordinating the trials and all the data collection, and Edgars Andy Goldring, Tomas Remiarz, Roz Brown, Dr Ian Fitzpatrick - our Latvian hard-working student placement. - the Permaculture Association mixed veg team Big shout out to Garden Organic, Edwin Tucker & Son Ltd., Please note that we have a research co-ordinator in place - Beans and Herbs, and Chase Organics for supplying the Chris Warburton-Brown. seeds for this trial. Send any enquiries to [email protected] Thanks to Chris Evans for advice on appropriate plant mixes. To everyone who participated, and especially those who completed the trials, many, many thanks – we couldn’t have done it without you!