1. M.Z. Alam1, G. Tremblay2, A. Vanasse3 and D.H. Lynch1
Optimizing green manure and fertility management for organic cereal production
M.Z. Alam1, G. Tremblay2, A. Vanasse3 and D.H. Lynch1
1Department of Plant, Food and Environmental Sciences, Faculty of Agriculture, Dalhousie University, Truro, NS, B2N 5E3, Canada.
2Centre de Recherche sur les Grains (CÉROM), 740, chemin Trudeau, Saint- Mathieu-de-Beloeil, QC, J3G 0E2, Canada.
3Département de Phytologie, Université Laval, 2425 rue de l’Agriculture, QC, G1V 0A6, Canada.
Results
Introduction and Objectives
The demand for organically produced food products is increasing rapidly in North America, driven by widespread perceptions that organic agriculture results in fewer negative environmental impacts, greater human health benefits and a more sustainable alternative than conventional systems (Snyder and Spaner, 2010). Despite the increasing interest in organic grain production, a number of challenges remain to be addressed to ensure its long-term sustainability. Crop yields under organic management, particularly for grain crops such as hard red spring wheat (HRSW), continue to lag conventional production. Well planned crop rotations including legumes to supply the nitrogen (N) needs of crops are critical to success in organic grain production. The relatively high cost of approved soil amendments for organic producers, and the lack of information on the potential for novel green manures (GrM) in Eastern Canada, provide the basis for this integrated project. Here we report on a three-year ( ) project examining organic wheat crop productivity and quality at Nova Scotia and Quebec sites as affected by:
(i) type of GrM pre-crops (oat, hairy vetch, common vetch, red clover and soybean),
(ii) GrM termination timing (fall or spring incorporation) and
(iii) biofertilizer (Actisol, pelletized dehydrated poultry manure, ~5% N) supplementation.
This project is part of a larger multi-regional (Nova Scotia, Quebec, Ontario and Manitoba) research program evaluating the effect of (i) GrM type, timing of GrM tillage and soil fertility and (ii) tillage regime/reduced tillage, on organic grain (wheat, malting barley) productivity and quality, plus soil quality and soil health.
Combined results over two years from each site are presented (2014 & 2016 for Truro site and & 2015 for the CEROM site). At the Truro, NS site, in 2015 excessive early season rain prevented good crop establishment and the 2016 results from the CEROM site are yet not available. The results showed that impacts of GrM and Actisol rates of application were highly significant (P < 0.001) for wheat yield and grain protein content at both sites. An interaction of GrM and Actisol for grain yield was significant only at the NS site.
Truro site:
HVO resulted in the greatest grain yields (4001 kg ha-1). Grain yields for red clover and CVO were at par (~3300 kg ha-1) while a soybean pre-crop resulted in the lowest grain yield (~2962 kg ha-1) (Fig. 1).
Wheat grain yield was 2426 kg ha-1 (average over all GrMs; 3330 kg ha-1 for HVO which was significantly greeter compared to other GrMs) when no Actisol was applied but increased by 30, 55 and 75% in response to 40, 80 and 120 kg N ha-1 as Actisol (Fig. 1).
HRSW protein contents were statistically similar for HVO (15.1%) and CR (14.5%) however, were grater compared to CVO (13.7%) and soybean (13.2%) pre-crops (Fig. 2a).
Grain protein content was 12.5% when no Actisol was applied but significantly (P < 0.001) increased by 11, 17 and 23% in response to 40, 80 and 120 kg (N ha-1) as Actisol (Fig. 2b).
QC site:
HVO also resulted in the greatest grain yields (2656 kg ha-1) followed by RCO (2193 kg ha-1) and oat (1631 kg ha-1) (Fig. 3a).
With no Actisol amendment, grain yield was 1826 kg ha-1. However, this increased by 18, 25 and 31% in response to 40, 80 and 120 kg (N ha-1) Actisol applied, respectively (Fig. 3b).
Grain protein content was the highest with HVO (13.9%) followed by CRO (13.3%) and oat (12.9%) (Fig. 3c). Grain protein content was 13.0% when no Actisol was applied but increased to 13.7% with Actisol at 120 kg N ha-1 Actisol (Fig. 3d).
Other distinguishing results (data not shown):
Around 225, 125 and 100 kg ha-1 total N were accumulated in above ground biomass by HVO, RC, and CVO.
Thirty-day total soil mineral nitrogen (SMN; NO3-N + NH4-N) levels measured under HRSW ranged between 19 to 35 kg N ha-1 among crop rotations, being the highest with HVO.
Among Actisol treatments, 30d total SMN ranged between 18 to 48 kg N ha-1being the highest with 120 kg Actisol N ha-1.
Time of GrM incorporation largely had no impact on these parameters measured
Figure 1. Impacts of green manure and Actisol on grain yield of wheat at Nova Scotia site (average of 2014 and 2016). Data are presented as mean (± SE, n = 48) over replicates, year, GrM termination and/or crop rotations/Actisol rates. RC = red clover; HVO = hairy vetch/oat mix; CVO = common vetch/oat mix; and Soy = soybean. Means with different lower case letters within a group are significantly different at p < Boxed values on the bars indicate average over all green manure types.
Materials and Methods
The trial at Nova Scotia site (Dalhousie University Faculty of Agriculture, Truro, NS) was a factorial split-split-plot design with three replications on a Pugwash sandy loam soil (Orthic Humo-Ferric Podzol). Rotation sequences of three 3-year rotations, and one 2-year wheat-soybean rotation lacking a GrM, plus one continuous brown fallow treatment were established as the main plots (n=36, plot size 14 m × 10 m). The four rotations were:
Spring planted red clover monocrop (RC) – hard red spring wheat (HRSW) – soybean (Sb)
Spring planted common vetch/oats (CVO) – HRSW – Sb
Spring planted hairy vetch/oats (HVO) – HRSW – Sb
HRSW – Sb
Each phase of each rotation was present every year. Green manure termination timing (fall vs. spring), implemented on GrM planted in 2013, 2014, 2015 comprised the sub-plots (n=72, subplot size 5 m × 14 m).
At CEROM (Saint-Mathieu-de-Beloeil), Quebec site the trial was established on a Saint-Urbain clay loam (Dark-Grey Gleysol) in a factorial split-split-plot design with four replicates with termination timing (fall and spring) as the main plots, and GrM type [HVO, red clover/oat (RCO) and oats] as the subplots (n=24, subplot size 6 m×12 m).
Actisol applied at both sites at rates of 0, 40, 80 and 120 kg N/ha prior to seeding of wheat only comprised the sub-sub-plots (5 × 3.5 m2 (Nova Scotia); 6 × 3 m2 (Quebec) each year .
Figure 2. Impacts of green manure (a) and Actisol rate (b) on protein content of wheat at Nova Scotia site (average of 2014 and 2016). Data are presented as mean (± SE, n = 48) over replicates, year, GrM termination and/or crop rotations/Actisol rates. RC = red clover; HVO = hairy vetch/oat mix; CVO = common vetch/oat mix; and Soy = soybean. Means with different lower case letters are significantly different at p < 0.05.
Discussion and conclusion
Wheat yield improved following all GrM, with a pattern of greater response following HVO, and also in response to increasing Actisol rates at both locations and in all years. These were reflected in soil mineral N availability, wheat biomass yield, tissue N content, total plant N uptake, grain yield and grain protein content. Benefits of Actisol amendments were most apparent where no GrM preceded wheat, and following CVO and RC. These findings suggest that hairy vetch can be an effective substitute for red clover resulting in satisfactory yields for organic wheat without any N fertilization in the Eastern Canada region. With no or CVO/RC green manures, Actisol amendment at a rate between kg N ha-1 may be appropriate for sustainable and economically viable organic wheat production.
Ref:
Snyder C. and D. Spaner (2010). The sustainability of organic grain production on the Canadian prairies - a review. Sustainability 2: ; doi: /su
Figure 3. Impacts of green manure and Actisol rate on grain yields (a and b) and protein content (c and d) of wheat at Quebec site (average of 2014 and 2015). Data are presented as mean (± SE, n = 48) over replicates, year, GrM termination and/or crop rotations/Actisol rates. RCO = red clover/oat mix; HVO = hairy vetch/oat mix. Means with different lower case letters are significantly different at p < 0.05.
Acknowledgement: Agriculture and Agri-Food Canada; Actisol Inc. QC; and Natural Sciences, Engineering Research Council of Canada (NSERC) and Canada Research Chair program for providing funds for this research.
Nova Scotia trial with visible impacts of Acrtisol on wheat growth apparent.