Organic vegetable cropping systems: Results from compost trials

Transcription

1 Organic vegetable cropping systems: Results from compost trials Josée Owen, M.Sc. and Serge LeBlanc, B.Sc. Fredericton Research and Development Centre

2 The context of our project Large vegetable farm, 75 acre beans La Ferme Michaud in New Brunswick Organic market opportunities Farm stand Supermarkets Worried about how well he could produce beans Can it really be done? What will replace fertiliser? Worried about how to control weeds Won t tillage burn up my soil organic matter?

3 Compost: advantages Reduces the amount of material to spread Puts waste products to good use Using compost increases organic matter in soil Releases nutrients over time for plant growth Increases soil ph (less acid) Improves soil water holding capacity Reduces soil compaction and density Is compatible with organic production

4 Compost: disadvantages Difficult to know how the nutrients in compost will become available over time Difficult to judge how much to put May be expensive to buy and spread

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6 Established in 2002 to look at snap bean production systems organic vs conventional practices Research farm site -small plots Beatrice Site -commercial farm land -large plots -commercial scale machinery

7 Long term experiment Two sites, replication at sites Rotations: Continuous Beans (BBB) Beans/Winter Rye/Beans (BRB) Winter Rye/Beans/Winter Rye (RBR) Fertility treatments: Fertilizer (SF) Low rate of compost (LRC) High rate of compost (HRC) Weeding treatments Herbicide Mechanical weeding

8 Experimental Farm Map

9 Compost rates We were fertilizing beans with 50 kg N per ha Compost analysis, varied by year C:N = 16 to 20 Total N = 0.5 to 0.85 % We decided that our low rate compost would apply the tons required to deliver 50 kg N per ha Ex: if compost N was 0.85%, the 50/0.85 = 58 t per ha Our high rate was 3x higher Common to calculate compost by P content instead, if worried about high P in soil, but we are studying N

10 Treatment summary Tab. 1: Summary of treatments applied in the first rotation cycle ( ) Treatment Source of nutrients Yearly N-P-K on Beans (kg/ha) Yearly N-P-K on Rye (kg/ha) Weeding method F1x -M Fertiliser Mechanical F1x-H Fertiliser Herbicide C1x-M Compost Mechanical C1x-H Compost Herbicide C3x-M Compost Mechanical C3x-H Compost Herbicide Note: P and K rates are averages for the three years. For fertiliser, rates varied according to soil test. For compost, rates varied according to compost composition.

11 Photo of incorporation of compost

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17 Data collection Yields Nitrogen use by the crop Soil bulk density (how compact the soil is) Wet aggregate stability (if aggregates are stable in water, they erode less, therefore they measure soil health)

18 Data collection continued Soil organic matter Total organic carbon Light fraction soil organic matter (is the medium-resistant o.m. that is sensitive to changes due to cropping practice) Amount of N and C, as well as C:N ratio Nutrient availabilities Over the course of the season In the 24 hours after mechanical weeding (soil disturbance)

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23 Bean yields Both green and yellow beans were sown at the Beatrice site, but only yellow were used at the Experimental Farm Green bean yields were 25-30% higher than yellow beans

24 Mean yellow bean yield from in plots treated with combinations of synthetic fertiliser (SF), Low Rate Compost (LRC), High Rate Compost (HRC) and mechanical weeding (M) or herbicide (H) 10 8 Yield (t/ha) SF-M SF-H LRC-M LRC-H HRC-M HRC-H Treatment

25 Mean yellow bean yield in synthetic fertilizer and low rate compost plots in 2003, 2004, 2005 and across years Yield (t/ha) Synthetic Fertilizer Low Rate Compost Fertility treatment

26 Cumulative season-long nutrient supplies ( ) Measured using 2 week long burials, one after the other, of ion exchange membrane probes Membranes capture soil nutrients just as plant roots would Relative measures between different treatments

27 Cumulative season-long nutrient supplies ( ) Ion capture (mg ion*cm -2 *2 weeks) NO 3 - -N P K Ca Mg Ion capture (mg ion*cm -2 *2 weeks) NO 3 - -N P K Ca Mg June 15 July 1 July 15 August 1 August 15 Sept 1 June 15 July 1 July 15 August 1 August 15 Sept 1 Date Date Synthetic Fertiliser High Rate Compost

28 Nutrients released from compost due to soil disturbance Lots of research showing that soil disturbance (tillage) causes loss of organic matter Does this happen in organic production when mechanical weeding disturbs soil? If it does, it should cause a flush of nutrient availability in the soil Measured using short (24 hour) burials of ion exchange membranes following weeding events

29 Nitrogen released from compost due to soil disturbance Nitrate-N captured on ion exchange membranes hours following weeding NO 3 -N (mg N 10cm hours) SEM= FH FM 1xH 1xM 3xH 3xM Treatment

30 Next phase Beginning 2006 Fertility treatments maintained in some plots In other plots, no further fertilisation To see compost s residual contribution of nutrients Rotation changed Brocoli +/or potato/barley underseeded/red clover

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34 Fertility treatments as of 2006 Treatment Abbr. Treatment goal Synthetic fertiliser (135 N -125 P -160 K) SF+ Annual application, standard commercial recommendations Synthetic fertiliser not applied SF- Annual application suspended in 2006 Low rate compost LRC+ Annual application of organic compost, applied to deliver same N as SF treatment Low rate compost not applied LRC- Annual application suspended in 2006 High rate compost HRC+ Annual application of organic compost applied at 3x the LRC rate High rate compost not applied HRC- Annual application suspended in 2006

35 Measurements Yield and grading (marketable, unmarketable) Soil organic matter Soil bulk density Tissue N on aerial plant parts Ion capture on ion exchange membranes

36 Marketable (solid) and unmarketable (hatched) broccoli yields 5000 Yield (kg ha -1 ) Mktb Unmktb SF+ SF- LRC + LRC- HRC+ HRC- 2xSEM 1 (n=12) Fertility treatment

37 Nitrogen (%) in dry matter of broccoli heads (solid), stems and leaves (hatched) and roots (cross-hatched) 5 Nitrogen (% dry matter basis) Heads Leaves & stems Roots 0 SF+ SF- LRC + LRC- HRC+ HRC- 2xSEM 1 Fertility treatment (n=18)

38 Source of variation: organoleptic qualities of organic produce Animal damage Coincidence or not? Approximately 75% more damaged broccoli in high rate compost plots.

39 Challenges: deficiencies Nutrient imbalance Some of the compost plots showed symptoms of nutrient deficiency. Phosphorus deficiency? HRC plots attained a ph of Synthetic fertiliser plots have a ph of Above a ph of 6.2, phophorus, boron and manganese are less available.

40 Cummulative seasonal capture of NH 4 + -N by ion exchange membranes in fertility treatments from 2006 to Cummulative NH 4 + -N, ug/cm 2 /2wk SF+ SF- LRC+ LRC- HRC + HRC - 2 x SEM, Mean, n=9 2 x SEM Line, n=9 2 x SEM Season, n=9 0 Jun 17 Jul 2 Jul 16 Jul 30 Aug 13 Mean Date Synthetic Fertiliser vs Compost, Mean; p = Fertilisation +/-, Mean; p = Synthetic Fertiliser vs Compost, Quadratic Line; p = Fertilisation +/-, Season; p = 0.038

41 1000 Cummulative seasonal capture of NO 3 - -N by ion exchange membranes in fertility treatments from 2006 to 2010 Cummulative NO 3 - -N, ug/cm 2 /2wk SF+ SF- LRC+ LRC- HRC+ HRC- 2 x SEM Mean, n=9 2 x SEM Line, n=9 2 x SEM Season, n=9 0 Jun 17 Jul 2 Jul 16 Jul 30 Aug 13 Mean Date (Synthetic Fertiliser vs Compost) x Fertilisation +/-, Mean; p < (Synthetic Fertiliser vs Compost) x Fertilisation +/-, Linear Line; p < (Synthetic Fertiliser vs Compost) x Fertilisation +/-, Season; p < 0.001

42 Conclusions Compost affected soil bulk density and ph considerably Not shown in this presentation High Rate Compost gave no consistent yield advantage over Low Rate Compost Low Rate Compost yields were equivalent to fertiliser treatment yields in beans, but in broccoli, yields were lower with compost Our High Rate Composted plots were far more attractive to grazing wildlife Organic really does taste better?

43 Conclusions, continued Tissue N was greatest with ongoing synthetic fertilisation, and in composted plots, was slightly higher once application ceased High Rate Compost did not increase plant N uptake compared with Low Rate Compost Mechanical weeding reduced the availability of soil N in all plots over 3 years, most likely by reducing soil moisture and reducing organic matter mineralisation The effect of year in season-long nutrient availabilities was pronounced, and was not related to the length of time plots had been treated, so the effect was related to temperature and moisture Not shown in this presentation

44 Questions When I fertilize with 1x compost, do I get the same yields as with synthetic fertilizer? Bean, yes. Very consistent. Broccoli, no. Slightly lower yields with compost. Consistent. With potato, compost sometimes gave much higher yields than fertiliser, but not consistent. Is 3x more compost giving me 3x more benefit? No. But 3x compost did reduce bulk density and increase ph, so if those effects are desirable, it may have a place

45 More questions How often do I need to apply compost? It s interesting that the effect of ceasing compost application resulted in greater concentrations of some nutrients. No answer for now, but an interesting question. Can I combine compost and synthetic fertilizer? Yes! (But in organic production you d need to use organic fertilisers rather than synthetic ones.) We did this in sweet corn and squash to great effect.

46 Working toward answers Our results show clear benefits to soil health using compost, without sacrificing yield But also increased GHG emissions 3x compost gives clear reduction in soil bulk density and increase in ph, but agronomically was not advantageous We added very high rates in order to study the effects on soil health in a shorter time More work is needed to know how little compost could be used to maximize the benefits and be affordable

47 Complex compost requires collaborative efforts! Thanks to our collaborators! Ferme Michaud Beatrice Allain Western Ag Innovations Cardwell Farms Compost Products (supplier of all compost applied in these experiments) Derek Lynch and Dave Burton (NSAC/OACC)

48 Thank you