• Authors:
    • Pauletti, V.
    • Piva, J.
    • Santos, N.
    • Dieckow, J.
    • Bayer, C.
    • Molin, R.
    • Favaretto, N.
  • Source: Soil & Tillage Research
  • Volume: 111
  • Issue: 2
  • Year: 2011
  • Summary: To improve C sequestration in no-till soils requires further development of crop rotations with high phytomass-C additions. The objectives of this study were (i) to assess long-term (17 years) contributions of cover crop- or forage-based no-till rotations and their related shoot and root additions to the accumulation of C in bulk and in physical fractions of a subtropical Ferralsol (20-cm depth); and (ii) infer if these rotations promote C sequestration and reach an eventual C saturation level in the soil. A wheat ( Triticum aestivum L., winter crop)-soybean ( Glycine max (L.) Merr, summer crop) succession was the baseline system. The soil under alfalfa ( Medicago sativa L., hay forage) intercropped every three years with maize ( Zea mays L., summer crop) had the highest C accumulation (0.44 Mg C ha -1 year -1). The bi-annual rotation of ryegrass ( Lolium multiflorum Lam., hay winter forage)-maize-ryegrass-soybean had a soil C sequestration of 0.32 Mg C ha -1 year -1. Among the two bi-annual cover crop-based rotations, the vetch ( Vicia villosa Roth, winter cover crop)-maize-wheat-soybean rotation added 7.58 Mg C ha -1 year -1 as shoot plus root and sequestered 0.28 Mg C ha -1 year -1. The counterpart grass-based rotation of oat ( Avena strigosa Schreb., winter cover crop)-maize-wheat-soybean sequestered only 0.16 Mg C ha -1 year -1, although adding 13% more C (8.56 Mg ha -1 year -1). The vetch legume-based rotation, with a relative conversion factor (RCF) of 0.147, was more efficient in converting biomass C into sequestered soil C than oat grass-based rotation (RCF=0.057). Soil C stocks showed a close relationship ( R2=0.72-0.98, P<0.10) with root C addition, a poor relationship with total C addition and no relationship with shoot C addition. This suggests a more effective role of root than shoot additions in C accumulation in this no-till soil. Most of the C accumulation took place in the mineral-associated organic matter (71-95%, in the 0-5 cm layer) compared to the particulate organic matter. The asymptotic relationship between root C addition and C stocks in bulk soil and in mineral-associated fraction supports the idea of C saturation. In conclusion, forages or legume cover crops contribute to C sequestration in no-till tropical Ferrasols, and most of this contribution is from roots and stored in the mineral-associated fraction. This combination of soil and rotations can reach an eventual soil C saturation.
  • Authors:
    • Slepetiene, A.
    • Slepetys, J.
  • Source: Grassland farming and land management systems in mountainous regions. Proceedings of the 16th Symposium of the European Grassland Federation
  • Year: 2011
  • Summary: The main objective of the current study was to evaluate the effects of six legume species ( Trifolium pratense, Medicago sativa, Trifolium repens, Galega orientalis, Medicago lupulina, Trifolium resupinatum) ploughed down as green manure, on the seed yield of timothy ( Phleum pratense) and meadow fescue ( Festuca pratensis). Legumes were undersown into barley. In the first year of production legumes were chopped and ploughed down for green manure in June. The sown timothy and meadow fescue were used for organic seed for three years. Although T. resupinatum grew well in the year of sowing it completely disappeared after winter. Based on 3-year mean production data, the highest timothy and meadow fescue seed yield was obtained after ploughing down a mixture of three legumes ( T. pratense+ M. sativa+ T. repens). Seed yield increased by 27.8-33.1%. Ploughed-down pure legumes (except G. orientalis) gave a lower but significant increase in seed yield. Having ploughed down legumes, the positive effect on organic seed was more substantial in the second and third years of production.
  • Authors:
    • Flaten, D. N.
    • Entz, M. H.
    • Vaisman, I.
    • Gulden, R. H.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 3
  • Year: 2011
  • Summary: The blade roller offers new opportunities to reduce tillage, especially in organic farming. The objective of the study was to reduce tillage in the green manure phase of a green manure-wheat ( Triticum aestivum L.) rotation by substituting tillage with blade rolling. A pea ( Pisum sativum L.) and oat ( Avena sativa L.) green manure was used for two site-years at Carman, MB, while a pea monocrop was used for one site-year at Oxbow, SK. At pea flowering, the green manure was terminated by rolling, tilling, or a combination of the two. Ammonia emissions were greater in the no-till compared with the tilled green manure system, though total ammonia losses were low (<13 kg ha -1). Replacing tillage with rolling reduced soil nitrate N in autumn after green manure by 56 to 88 kg ha -1 in the 0- to 60-cm soil depth. Reduced green manure tillage did not affect wheat establishment but delayed plant development in some instances. Fewer weeds were often observed in wheat in the no-till compared with tilled plots. Total N supply in the green manure-wheat system was reduced in the no-till system compared to the tilled only system at two out of three site-years by an average of 44%. While reduced N supply in the reduced tillage system coincided with reduced wheat yield and protein, it was concluded that factors other than N also were involved. Using the blade roller instead of tillage in the green manure year provides soil conservation benefits and facilitates wheat production the following year.
  • Authors:
    • Wells, M. L.
  • Source: HortScience
  • Volume: 46
  • Issue: 9
  • Year: 2011
  • Summary: Nitrogen (N) fertilizer application to plants at rates not adjusted for the N contribution from soil N availability may result in overapplication of fertilizer. Further understanding of proper timing of N applications based on soil N dynamics and plant demand can be valuable information for the efficient use of fertilizer N. The present study measures soil N dynamics in a pecan orchard under various N fertilizer regimes on a southeastern U.S. Coastal Plain soil. The following treatments were evaluated: 1) crimson clover (Trifolium incarnatum L.); 2) poultry litter; 3) crimson clover + poultry litter; 4) ammonium nitrate (NH(4)NO(3)); and 5) untreated control. Crimson clover provided from 20 to 75 kg.ha(-1) N over the course of the two growing seasons; however, most of the available N from crimson clover became available late in the growing season. As a result, supplemental N may be required in spring where crimson clover is used as an orchard cover crop. Poultry litter, with and without clover, provided available N consistently throughout the growing season with more N becoming available later in the season than earlier. This suggests that poultry litter applications for pecan should be timed before budbreak. Under optimum environmental conditions, N from NH(4)NO(3) is most available within the first 30 days of application. Thus, it appears that synthetic fertilizer applications using NH(4)NO(3) as the N source should be targeted at or 2 to 3 weeks after pecan budbreak.
  • Authors:
    • Li, H.
    • Cheng, J.
    • Zhang, J.
    • Yue, T.
    • Xi, Z.
  • Source: Scientia Agricultura Sinica
  • Volume: 44
  • Issue: 11
  • Year: 2011
  • Summary: Objective: In this paper, the relationship between soil quality and soil biological characteristics such as soil microorganism quantity and soil enzymatic activity was studied in the intercropping system of vineyard, in order to illustrate the function of soil biological characteristics as bio-indicators of soil fertility. Method: Three such cover crops, two perennial legumes (white clover and alfalfa) and a perennial gramineous grass (tall fescue) were sown in vineyard. Soil microorganism quantity, soil enzymatic activities and soil nutrient content were analyzed and compared with that in soil cultivation. [Result] Most detected soil microorganism quantity and soil enzymatic activity, soil organic matter were increased under cover crop treatments, compared to clean tillage, tall fescue treatment decreased urease and sucrase activity. White clover and alfalfa treatments significantly increased the contents of hydrolyzable N, total N and available K, and tall fescue decreased them, while the activated organic P in tall fescue treatment was more effectively than that in white clover and alfalfa treatments. Correlation analysis indicated that soil organic matter, total N, hydrolyzable N, total P, available K showed significant or very significant positive correlation with 10 soil biological characteristic factors such as bacteria, fungi, actinomyces, azotobacter, cellulose-decomposing bacteria, urease, phosphatase, amylase, sucrase, and cellulose. The catalase activity was no significant correlation with all the soil nutrient contents, and the total K content was no significant correlations with all the soil biological characteristic factors. The soil pH in this experiment was negatively correlated with soil biological properties. Conclusion: Cover crops in the inter-rows of vineyard increased soil microorganism quantity, soil enzymatic activity and soil nutrient content, white clover and alfalfa treatments were better than tall fescue. There are significant correlations between soil biological characteristics and nutrients, and soil biological indexes could reflect the changes of soil quality.
  • Authors:
    • Shahid, A.
    • Saghir, A.
    • Jamil, M.
    • Zubair, M.
    • Farooq, M.
    • Awais, R.
  • Source: Pakistan Sugar Journal
  • Volume: 26
  • Issue: 2
  • Year: 2011
  • Summary: Sugarcane is a long duration crop and is suitable for intercropping with other short duration crops to maximize the farmer income from the unit area. Thus, this study was designed to find out the possibility of wheat, lentil and gram intercropping with autumn planted sugarcane crop. The study was carried out at National Agricultural Research Centre, Islamabad during 2004-05 cropping season. Sugarcane variety RB-72-454 was used as test crop and planted at 1.2 meter row distance in the first week of September, 2004. Two rows of each wheat, lentil and gram crop were seeded in the month of November in between cane rows. Sugarcane crop was harvested in the month of December, 2005. Lentil and gram were harvested in the month of April while, wheat in May. The results of the study indicted that sugarcane planted alone produced highest cane yield of 130.5 t ha -1, while sugarcane intercropped with wheat produced lowest cane yield of 105.5 t ha -1. The yields of wheat, lentil and gram were 1.18, 0.57 and 0.43 t ha -1, respectively. However, it was observed that intercropping of wheat, lentil and gram with sugarcane decreased cane yield by 19.2, 18.6 and 14.3%, respectively. The maximum economic return of Rs. 156641 ha -1 was noticed when sugarcane was planted without intercropping, whereas, intercropping of sugarcane with wheat resulted in minimum return of Rs. 138889 ha -1. Findings of the study revealed that autumn planting of sugarcane without any intercropping is more profitable than intercropping with cereal and leguminous crops.
  • Authors:
    • Escobar-Gutierrez, A.
    • Louarn, G.
    • Barillot, R.
    • Huynh, P.
    • Combes, D.
  • Source: Annals of Botany
  • Volume: 108
  • Issue: 6
  • Year: 2011
  • Summary: Background and Aims: Most studies dealing with light partitioning in intercropping systems have used statistical models based on the turbid medium approach, thus assuming homogeneous canopies. However, these models could not be directly validated although spatial heterogeneities could arise in such canopies. The aim of the present study was to assess the ability of the turbid medium approach to accurately estimate light partitioning within grass-legume mixed canopies. Methods: Three contrasted mixtures of wheat-pea, tall fescue-alfalfa and tall fescue-clover were sown according to various patterns and densities. Three-dimensional plant mock-ups were derived from magnetic digitizations carried out at different stages of development. The benchmarks for light interception efficiency (LIE) estimates were provided by the combination of a light projective model and plant mock-ups, which also provided the inputs of a turbid medium model (SIRASCA), i.e. leaf area index and inclination. SIRASCA was set to gradually account for vertical heterogeneity of the foliage, i.e. the canopy was described as one, two or ten horizontal layers of leaves. Key Results: Mixtures exhibited various and heterogeneous profiles of foliar distribution, leaf inclination and component species height. Nevertheless, most of the LIE was satisfactorily predicted by SIRASCA. Biased estimations were, however, observed for (1) grass species and (2) tall fescue-alfalfa mixtures grown at high density. Most of the discrepancies were due to vertical heterogeneities and were corrected by increasing the vertical description of canopies although, in practice, this would require time-consuming measurements. Conclusions: The turbid medium analogy could be successfully used in a wide range of canopies. However, a more detailed description of the canopy is required for mixtures exhibiting vertical stratifications and inter-/intra-species foliage overlapping. Architectural models remain a relevant tool for studying light partitioning in intercropping systems that exhibit strong vertical heterogeneities. Moreover, these models offer the possibility to integrate the effects of microclimate variations on plant growth.
  • Authors:
    • Gibson, L. R.
    • Singer, J. W.
    • Blaser, B. C.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 4
  • Year: 2011
  • Summary: Interseeding red clover ( Trifolium pratense L.) or alfalfa ( Medicago sativa L.) into winter cereals in the North Central United States can provide forage and a green manure crop. We hypothesized that winter cereal canopy traits such as leaf area index (LAI) and whole plant dry matter (DM) would influence interseeded legume establishment and productivity, yet the effect of canopy traits on resource competition in intercropping systems is not well understood. This study was conducted from 2005 to 2007 to evaluate the impact of diverse cereal canopy traits on the establishment of frost-seeded legume intercrops. In March, red clover and alfalfa were frost-seeded into three winter wheat ( Triticum aestivum L.) and three triticale (X Triticosecale Wittmack) varieties selected for differences in maximum LAI, plant height, and DM. Across three growing seasons, the cereals produced a range of LAI from 2.1 to 6.2 and whole plant harvest DM of 817 to 2029 g m -2. In the 2 yr with legume data, densities were influenced by cereal 1 yr and DM was affected by cereal both years. Alfalfa and red clover densities were similar, yet DM production was 42% higher in red clover 40 d after grain harvest. The presence of a legume intercrop did not affect grain yield, but reduced weed densities and weed DM 40 d after harvest. Producers implementing this intercrop may select cereal varieties based on grain yield, but must be cautious of varieties known to produce above normal LAI values because of the potential to reduce legume productivity.
  • Authors:
    • Brennan, E. B.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 5
  • Year: 2011
  • Summary: Winter cover crops can add soil organic matter, improve nutrient cycling, and suppress weeds in organic vegetable systems. A 2-yr study was conducted on organic farms in Salinas and Hollister, CA, to evaluate the effect of seeding rate (SR) and planting arrangement on cover crop density, ground cover, and cover crop and weed dry matter (DM) with a mixed cover crop. The mix contained legumes (35% Vicia faba L., bell bean; 15% Vicia dasycarpa Ten., woolypod vetch; 15% Vicia benghalensis L., purple vetch; and 25% Pisum sativum L., pea) and 10% oat (Avena sativa L.) by seed weight. Three SRs (112, 224, and 336 kg ha(-1)) and two planting arrangements (one-way versus grid pattern) were evaluated. Planting arrangement had no effect on the variables measured. When weeds were abundant, weed DM declined linearly with increasing SR from approximately 300 kg ha(-1) at the low SR to <100 kg ha(-1) at the high SR. Increasing SR increased oat and legume DM early in the season, but did not affect final cover crop DM that ranged from 7 to 12 Mg ha(-1). Year affected final cover crop DM production at both sites. The legume DM portion of the total cover crop declined through the season but varied between sites and year, probably due to soil and climatic differences. Higher SRs may be cost effective because weed control is expensive and cover crop seed is a relatively small component of cover cropping costs in this region.
  • Authors:
    • Radicetti, E.
    • Mancinelli, R.
    • Campiglia, E.
    • Marinari, S.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 89
  • Issue: 3
  • Year: 2011
  • Summary: There is not sufficient knowledge concerning the risks involved in NO 3-N leaching in relation to the use of cover crops and mulches. A 2 year field experiment was carried out in a pepper ( Capsicum annuum L.) crop transplanted into different soil management treatments which involved the addition of mulch of three different types of winter cover crops (CC) [hairy vetch ( Vicia villosa Roth.), subclover ( Trifolium subterraneum L.), and a mixture of hairy vetch/oat ( Avena sativa L.)], and an un-mulched plot. At the time of CC conversion into mulch, the hairy vetch/oat mixture accumulated the highest aboveground biomass (5.30 t ha -1 of DM), while hairy vetch in pure stand accumulated the highest quantity of N (177 kg ha -1) and showed the lowest C/N ratio (12). The marketable pepper yield was higher in mulched than in conventional (on average 33.5, 28.9, 27.7 and 22.2 t ha -1 of FM for hairy vetch, subclover, hairy vetch/oat mixture, and conventional, respectively). Generally, the NO 3-N content of the soil was minimum at CC sowing, slightly higher at pepper transplanting and maximum at pepper harvesting (on average 15.2, 16.8, and 23.3 mg NO 3-N kg -1 of dry soil, respectively). The cumulative leachate was higher during the CC period (from October to April) than the pepper crop period (from April to September), on average 102.1 vs 66.1 mm over the years, respectively. The cumulative NO 3-N leached greatly depended on the type of mulch and it was 102.3, 95.3, 94.7, and 48.2 kg ha -1 in hairy vetch, subclover, hairy vetch/oat mixture, and conventional, respectively. A positive linear correlation was found between the N accumulated in the CC aboveground biomass and the NO 3-N leached during pepper cultivation ( R2=0.87). This research shows that winter legume cover crops, especially hairy vetch in pure stand, converted into dead mulch in spring could be used successfully for adding N to the soil and increasing the yield of the following pepper crop although the risks of N losses via leaching could be increased compared to an un-mulched soil. Therefore when leguminous mulches are used in the cultivation of a summer crop, appropriate management practices of the system, such as a better control of the amount of irrigation water and the cultivation of a graminaceous or a cruciferous catch crop after the harvesting of the summer crop, should be adopted in order to avoid an increase in NO 3-N leaching.