• Authors:
    • Shirtliffe, S. J.
    • Johnson, E. N.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Organic farmers in western Canada rely on tillage to control weeds and incorporate crop residues that could plug mechanical weed-control implements. However, tillage significantly increases the risk of soil erosion. For farmers seeking to reduce or eliminate tillage, potential alternatives include mowing or using a roller crimper for terminating green manure crops (cover crops) or using a minimum tillage (min-till) rotary hoe for mechanically controlling weeds. Although many researchers have studied organic crop production in western Canada, few have studied no-till organic production practices. Two studies were recently conducted in Saskatchewan to determine the efficacy of the following alternatives to tillage: mowing and roller crimping for weed control, and min-till rotary hoeing weed control in field pea ( Pisum sativum L.). The first study compared mowing and roller crimping with tillage when terminating faba bean ( Vicia faba L.) and field pea green manure crops. Early termination of annual green manure crops with roller crimping or mowing resulted in less weed regrowth compared with tillage. When compared with faba bean, field pea produced greater crop biomass, suppressed weeds better and had less regrowth. Wheat yields following pea were not affected by the method of termination. Thus, this first study indicated that roller crimping and mowing are viable alternatives to tillage to terminate field pea green manure crops. The second study evaluated the tolerance and efficacy of a min-till rotary harrow in no-till field pea production. The min-till rotary hoe was able to operate in no-till cereal residues and multiple passes did not affect the level of residue cover. Field pea exhibited excellent tolerance to the min-till rotary hoe. Good weed control occurred with multiple rotary hoe passes, and pea seed yield was 87% of the yield obtained in the herbicide-treated check. Therefore, this second study demonstrated that min-till rotary hoeing effectively controls many small seeded annual weeds in the presence of crop residue and thus can reduce the need for tillage in organic-cropping systems.
  • Authors:
    • Desclaux, D.
    • Colomb, B.
    • Duputel, M.
    • Betencourt, E.
    • Hinsinger, P.
  • Source: Soil Biology & Biochemistry
  • Volume: 46
  • Year: 2012
  • Summary: Cereal-legume intercropping can promote plant growth (i.e. facilitation) through an increase in the amount of phosphorus (P) taken up, especially in low P soils. The aim of this study was to test the hypothesis that these positive interactions are supported by rhizosphere processes that increase P availability, such as root-induced pH changes. In neutral and alkaline soils legumes are assumed to increase inorganic P availability by rhizosphere acidification due to N 2 fixation which benefit to the intercropped cereal. Growth, P uptake, changes in inorganic P availability and pH in the rhizosphere of intercropped species were thus investigated in a greenhouse pot experiment with durum wheat and chickpea either grown alone or intercropped. We used a neutral soil from a P fertilizer long-term field trial exhibiting either low (-P) or high (+P) P availability. Phosphorus availability was increased in the rhizosphere of both species, especially when intercropped in -P. Such increase was associated with alkalization. Rhizosphere pH changes could not fully explain the observed changes of P availability though. Low rates of N 2 fixation may explain why no rhizosphere acidification was observed. Increases in P availability did not lead to enhanced P uptake but growth promotion was observed for durum wheat intercropped with chickpea in -P soil. Our hypothesis of an increase in inorganic P availability in intercropping as a consequence of root-induced acidification by the legume was not validated, and we suggested that root-induced alkalization was involved instead, as well as other root-induced processes. Thus, the cereal through rhizosphere alkalization may also enhance P uptake and growth of the intercropped legume. Facilitation can thus occur in both ways.
  • Authors:
    • Chapagain, T.
    • Riseman, A.
  • Source: American Journal of Plant Sciences
  • Volume: 3
  • Issue: 5
  • Year: 2012
  • Summary: A cultivar trial, including commercial and heirloom cultivars of major cereals and grain legumes was conducted in Vancouver, BC, under low input organic conditions. We assessed 19 wheat (6 commercial and 13 heirloom), 17 barley (8 commercial and 9 heirloom), 5 pea, 5 favabean, 5 kidneybean, 2 lentil, and 2 soyabean cultivars for plant performance metrics, and their potential in a small grain:legume intercropping system. Heirloom wheat cultivars showed notable response in a number of parameters including late maturity, taller plants, greatest number of spikes per m 2, longest spike, highest number of seed per spike, greater seed weight to volume ratio, and resistance to stripe rust compared with commercial cultivars. For the heirloom-type, 6 of 14 wheat cultivars, ( i.e., "Reward", "Glenn", "Cerebs", "Red Bobs", "Sounders" and "Black Bearded") produced yields comparable to the commercial cultivars ( i.e., nearly 5 t/h or higher). Also, heirloom cultivars typically contained higher protein levels most suitable for baking and blending purposes with "Einkorn" displaying the highest level (16.2%). Heirloom and commercial barley cultivars did not differ significantly with respect to plant height, spike length, and seed weight to volume ratio. However, a number of heirloom cultivars (e.g., "Jet", "Dolma", "Andie" and "Himalayan") displayed greater responses on earliness, number of spikes per m 2, grain yield, protein content and seed weight to volume ratio. Pea and lentil yielded lower than the national average under trial conditions. However, heirloom peas "Corgi", "De Grace", "Snowbird", and "Golden" were earlier compared to the commercial cultivar "Reward". All kidney bean cultivars yielded ~3 t/h with the highest yield from "Red Kidney" (3.8 t/h). Fava and soyabean appeared as promising crops as the cultivars produced good growth and yields. Neither lentil ("Crimson" and "Essex") produced satisfactory responses though they had excellent vegetative growth and flowered. Therefore, significant variation was observed including several heirloom cultivars displayed great potential in terms of yield, protein content, and disease resistance and that specific cultivars were better suited for an intercropping system.
  • Authors:
    • Handoo, Z. A.
    • Cram, M. M.
    • Fraedrich, S. W.
    • Zarnoch, S. J.
  • Source: Nematology
  • Volume: 14
  • Issue: 4
  • Year: 2012
  • Summary: Tylenchorhynchus ewingi, a stunt nematode, causes severe injury to slash pine seedlings and has been recently associated with stunting and chlorosis of loblolly pine seedlings at some forest tree nurseries in southern USA. Experiments confirmed that loblolly pine is a host for T. ewingi, and that the nematode is capable of causing severe damage to root systems. Initial population densities as low as 60 nematodes (100 cm 3 soil) -1 were sufficient to damage the root systems of loblolly pine seedlings. Populations of T. ewingi increased on pine from two- to 16-fold, depending on the initial population density. Evaluations of various cover crops used in southern forest tree nurseries indicated that legumes, rye and several varieties of sorghum were excellent hosts for T. ewingi. Other small grains such as ryegrass, oats and wheat were poorer hosts. A cultivar of pearl millet was a non-host for T. ewingi, and a cultivar of brown top millet appeared to be either a very poor host or a non-host. Nurseries that have seedling production losses caused by T. ewingi should consider rotating with non-host cover crops such as pearl millet or leaving fields fallow as part of their pest management programme.
  • Authors:
    • Pannacci, E.
    • Onofri, A.
    • Graziani, F.
    • Tei, F.
    • Guiducci, M.
  • Source: European Journal of Agronomy
  • Volume: 39
  • Year: 2012
  • Summary: Long-term effects of organic (ORG) and conventional low-input (CONV) farming systems on size and composition of weed seedbank were assessed in 2007 in central Italy, in an on-farm experiment set up in 1996. In this experiment, six rotations (R1-R6) were considered, basically consisting on the same crop sequence with different starting points, i.e. (1) legume crop (soybean/field bean/common pea), (2) vegetable crop (pepper/melon), (3) winter cereal (soft/durum wheat), (4) summer cereal (maize) (5) industrial vegetable (processing tomato), (6) winter cereal (soft/durum wheat). All rotations were established both in ORG and in CONV, in strict adherence to EU regulations (ORG: EU reg. 2092/91; CONV: EU reg. 2078/92). Intercrops with green manuring purposes were included in ORG, while weed control was performed mechanically in ORG and chemically/mechanically in CONV. Weed seedbank was determined on 10 soil samples (0-0.30 m depth) in each plot and seeds were directly extracted, identified and counted. In all rotations, the adoption of ORG resulted in a significant increase in weed seedbank density, particularly in the case of summer weed species ( Portulaca oleracea L., Amaranthus retroflexus L. and Chenopodium album L.), which are more competitive and difficult to control in summer crops under organic farming systems in the Mediterranean climates. Small differences between ORG and CONV were found in terms of number of weed species (23 in ORG and 20 in CONV, on average), but the index of diversity in CONV was on average higher than in ORG. Furthermore, the most dominant weeds in CONV represented a lower percentage of total seedbank (40%, 23% and 5%, respectively, for P. oleracea, A. retroflexus and C. album in CONV and 56%, 32% and 4% for the same three weeds in ORG). These results confirm that the wider availability of effective weed control methods in integrated low-input farming systems (CONV) is helpful to maintain a low seedbank size, with a lower dominance structure. However, the adoption of ORG systems based on long rotation cycles, very competitive crops and accurate weed control, especially at the beginning of the ORG management, may be sustainable in the long run, in terms of potential weed infestation levels.
  • Authors:
    • Ercoli, L.
    • Masoni, A.
    • Mariotti, M.
    • Arduini, I.
  • Source: Grass and Forage Science
  • Volume: 67
  • Issue: 2
  • Year: 2012
  • Summary: Intercropping (IC) cereals and legumes could be an option for obtaining forage suitable for ensiling and enabling reduced N fertilization. Two experiments were performed in central Italy with durum wheat ( Triticum durum Desf.) and field bean ( Vicia faba L. var. minor) grown for forage production in IC and as sole crops (SC) with different N rates (20 and 50 kg ha -1) and row ratios (1:1 and 2:1 cereal/legume). The aims were to assess (i) whether IC is a feasible option to reduce N fertilization; (ii) the best combination of practices to obtain forage suitable for ensiling; and (iii) competition/facilitation effects exerted by field bean on durum wheat. Results showed IC allowed fertilizer-N reduction and led to improved forage yield with better quality, compared with SC. Land equivalent ratio indicated a high efficiency of the IC, by up to 26% with respect to SC. Field bean was the dominant species of IC, but N fertilization reduced its competitive ability and enhanced that of wheat. In the intercrop fertilized with 50 kg N ha -1, the proportion of the wheat in the herbage (0.34-0.41 of the total dry matter) was sufficient for ensiling of the forage mass. Field bean exerted both competition and facilitation effects on the cereal. N uptake of durum wheat was greater under IC with beans than as wheat SC.
  • Authors:
    • Gaillard, B.
    • Foissy, D.
    • Dorvillez, D.
    • Carrouee, B.
    • Boucheny, P.
    • Biarnes, V.
    • Bedoussac, L.
    • Baranger, E.
    • Al-Rifai, M.
    • Naudin, C.
    • Corre-Hellou, G.
    • Makowski, D.
    • Bazot, M.
    • Pelzer, E.
    • Guichard, L.
    • Mansard, M.
    • Omon, B.
    • Prieur, L.
    • Yvergniaux, M.
    • Justes, E.
    • Jeuffroy, M.
  • Source: European Journal of Agronomy
  • Volume: 40
  • Year: 2012
  • Summary: Intensive agriculture ensures high yields but can cause serious environmental damages. The optimal use of soil and atmospheric sources of nitrogen in cereal-legume mixtures may allow farmers to maintain high production levels and good quality with low external N inputs, and could potentially decrease environmental impacts, particularly through a more efficient energy use. These potential advantages are presented in an overall assessment of cereal-legume systems, accounting for the agronomic, environmental, energetic, and economic performances. Based on a low-input experimental field network including 16 site-years, we found that yields of pea-wheat intercrops (about 4.5 Mg ha -1 whatever the amount of applied fertiliser) were higher than sole pea and close to conventionally managed wheat yields (5.4 Mg ha -1 on average), the intercrop requiring less than half of the nitrogen fertiliser per ton of grain compared to the sole wheat. The land equivalent ratio and a statistical analysis based on the Price's equation showed that the crop mixture was more efficient than sole crops particularly under unfertilised situations. The estimated amount of energy consumed per ton of harvested grains was two to three times higher with conventionally managed wheat than with pea-wheat mixtures (fertilised or not). The intercrops allowed (i) maintaining wheat grain protein concentration and gross margin compared to wheat sole crop and (ii) increased the contribution of N 2 fixation to total N accumulation of pea crop in the mixture compared to pea sole crop. They also led to a reduction of (i) pesticide use compared to sole crops and (ii) soil mineral nitrogen after harvest compared to pea sole crop. Our results demonstrate that pea-wheat intercropping is a promising way to produce cereal grains in an efficient, economically sustainable and environmentally friendly way.
  • Authors:
    • Xu, Z.
    • Wu, H.
    • Chen, C.
    • Zhou, X.
  • Source: Journal of Soils and Sediments
  • Volume: 12
  • Issue: 6
  • Year: 2012
  • Summary: Purpose: Cover crop residue is generally applied to improve soil quality and crop productivity. Improved understanding of dynamics of soil extractable organic carbon (EOC) and nitrogen (EON) under cover crops is useful for developing effective agronomic management and nitrogen (N) fertilization strategies. Materials and methods: Dynamics of soil extractable inorganic and organic carbon (C) and N pools were investigated under six cover crop treatments, which included two legume crops (capello woolly pod vetch and field pea), three non-legume crops (wheat, Saia oat and Indian mustard), and a nil-crop control (CK) in southeastern Australia. Cover crops at anthesis were crimp-rolled onto the soil surface in October 2009. Soil and crop residue samples were taken over the periods October-December (2009) and March-May (2010), respectively, to examine remaining crop residue biomass, soil NH 4++N and NO 3--N as well as EOC and EON concentrations using extraction methods of 2 M KCl and hot water. Additionally, soil net N mineralization rates were measured for soil samples collected in May 2010. Results and discussion The CK treatment had the highest soil inorganic N (NH 4+-N+NO 3--N) at the sampling time in December 2009 but decreased greatly with sampling time. The cover crop treatments had greater soil EOC and EON concentrations than the CK treatment. However, no significant differences in soil NH 4+-N, NO 3--N, EOC, EON, and ratios of EOC to EON were found between the legume and non-legume cover crop treatments across the sampling times, which were supported by the similar results of soil net N mineralization rates among the treatments. Stepwise multiple regression analyses indicated that soil EOC in the hot water extracts was mainly affected by soil total C ( R2=0.654, P
  • Authors:
    • Chen, C.
    • Xu, Z.
    • Koetz, E.
    • Wu, H.
    • Zhou, X.
  • Source: Applied Soil Ecology
  • Volume: 53
  • Year: 2012
  • Summary: The conservation farming systems coupled with stubble retention are now widely adopted in southern Australia to improve soil fertility. However, little information is available about the effects of winter crops on soil labile organic carbon (C) and nitrogen (N) pools, especially in an arid agricultural ecosystem. In this study, eight winter cover crop treatments were used to investigate their effects on soil labile organic C and N pools and microbial metabolic profiles and diversity in temperate Australia. These treatments included two legume crops (capello woolly pod vetch and field pea), four non-legume crops (rye, wheat, Saia oat and Indian mustard), and a mixture of rye and capello woolly pod vetch as well as a nil-crop control. At the crop flowering stage, soil and crop samples were collected from the field and we examined aboveground crop biomass, soil NH 4+-N, NO 3--N, extractable organic C (EOC) and N (EON) concentrations using methods of 2 M KCl and hot water, microbial biomass, biologically active organic C (C Bio), and substrate-induced respiration (SIR) using the MicroResp method. Results showed that the crop treatments had lower soil moisture content, NO 3--N and the ratios of EOC to EON, but higher pH, NH 4+-N, EOC, EON, C Bio, microbial metabolic diversity index ( H) and evenness index compared with the control. There were no significant differences in microbial biomass C and N among the treatments. Although no pronounced differences in EOC and EON concentrations were found between the legumes and non-legumes, the legume treatments had lower SIR and higher H than the non-legume treatments. Principal component analysis showed that soil microbial metabolic profiles under the crops were different from those of the control, and the crop treatments had a clear separation along principal component 2. In addition, redundancy analysis showed that soil pH and moisture content were the most important influencing factors, along with EON and crop biomass, determining the patterns of microbial metabolic profiles under the crops.
  • Authors:
    • Calderón, F. J.
    • Vigil, M. F.
    • Nielsen, D. C.
    • Benjamin, J. G.
    • Poss, D. J.
  • Source: Field Crops Research
  • Volume: 125
  • Year: 2012
  • Summary: Grasspea (GP) (Lathyrus sativus) is a drought-tolerant legume that can be grown for forage and grain. It has potential value to be used as a nitrogen-fixing crop in dryland rotations with non-legume grain crops. However, the agronomy of GP for the Central Great Plains region have not been investigated. The objective of this research was to compare the grain and biomass yield, as well as N accumulation of GP relative to field pea (FP) in two planting configurations. We carried out a 3-year field experiment to compare dryland GP with Admiral yellow field pea (Pisum sativum) in two configurations: (1) a wide row spacing with lower population (WL) with 76-cm rows with 75 kg seeds planted per ha, and (2) a narrower row spacing with a higher population (NH) with 19-cm rows with 136 kg seeds planted per ha. We measured the biomass, grain yield. N content, and soil water use. Our results show that the NH treatment out-yielded the WL treatment in both pea species. The GP had higher yield then FP on the lowest yielding year, while FP yielded better when overall yields were higher. Biomass production was also higher for the NH configuration, and GP was a higher biomass producer than FP over the 3-year study. The GP had higher N concentration in shoots and seed compared to FP, indicating higher N-fixing capacity. The FP matured faster than GP, and had marginally higher grain water use efficiency than GP. Our results show that GP is a viable alternative legume for the Central Great Plains, with comparable yields in low precipitation years. However, the longer growing season required by GP to mature has water use implications in years with reduced water availability in mid to late summer.