151. Influence of ley duration on the yield and quality of the subsequent cereal crop (spring oats) in an organically managed long-term crop rotation experiment.

• Authors:
  • Topp, C.
  • Walker, R.
  • Rees, R.
  • Edwards, A.
  • Baddeley, J.
  • Watson, C.
• Source: Organic Agriculture
• Volume: 1
• Issue: 3
• Year: 2011
• Summary: The ability to maintain crop yield and quality in systems based on nitrogen (N) fixed by legumes rather than from synthetic N fertilisers is fundamental to the long-term viability of organic farming. This paper reports crop yield and nitrogen uptake parameters for the first spring oat crop after grass/clover ley in organically managed ley/arable rotations to indicate the amount of fertility built-up during the ley period. The trial site, at Tulloch in North East Scotland, underwent two complete cycles of 6-year ley/arable rotations with different lengths of grazed ley (3 or 4 years). Trials were sufficiently replicated so that each course of the rotation was present in every year. The rotation containing 3 years of ley was also compared with a similar rotation at a nearby site (Woodside) with lower rainfall and soil fertility over one and a half rotational cycles. Grain yields were consistently higher at Tulloch (5.1 tha -1 compared with 4.5 tha -1 at Woodside) and were unaffected by the length of ley. However, grain N percentage was higher following the 4-year ley (1.38% compared with 1.30% following the 3-year ley). While yields were maintained between the first and second cycles of all the rotations, grain N percentage declined. Annual grain yields of the organically grown oats at Tulloch were not significantly different from National List/Recommended List yields in NE Scotland for oats receiving 100 kg N ha -1. Results suggest that these particular rotation designs were suitable for maintaining acceptable grain yields under organic management conditions.

152. Carbon and nitrogen dynamics in an Oxisol as affected by liming and crop residues under no-till.

• Authors:
  • Alleoni, L. R. F.
  • Murphy, D. V.
  • Caires, E. F.
  • Garbuio, F. J.
  • Jones, D. L.
• Source: Soil Science Society of America Journal
• Volume: 75
• Issue: 5
• Year: 2011
• Summary: The short-term effects of surface lime application and black oat ( Avena strigosa Schreb.) residues, with or without N fertilization, were evaluated in a long-term no-till (NT) system on a sandy clay loam, a kaolinitic, thermic Typic Hapludox from the state of Parana, Brazil. The main plot treatments were: control and dolomitic lime applied on soil surface at 8 Mg ha -1. Three treatments with crop residues were evaluated on the subplots: (i) fallow, (ii) black oat residues, and (iii) black oat residues after N fertilization at 180 kg ha -1. Black oat dry biomass was not affected by the treatments during 3 yr. Surface liming increased soil pH, microbial biomass, microbial activity, and bacterial/fungal ratio at the soil surface (0-5 cm), resulting in increased amino acid turnover, water-soluble humic substances formation, and N mineralization and nitrification. While the application of black oat did increase the soil pH, overall it had much less effect on soil biological processes and C and N pools than did lime. We concluded that black oat cannot replace the need for lime to optimize crop production in these tropical NT systems. In the long term, however, black oat should aid in the amelioration of acidity and replenishment of soil organic C pools and should help reduce erosion. Overall, this study suggests that overapplication of inorganic fertilizer N may occur in some tropical NT systems. Further experiments are required in NT systems to investigate the use of slow-release N fertilizers in combination with lime and black oat as a mechanism to reduce acidification and promote sustainability.

153. Microbial Biomass and Soil Fauna during the Decomposition of Cover Crops in No-Tillage System

• Authors:
  • Gatiboni, L. C.
  • Meirelles Coimbra, J. L.
  • Nicoloso Denardin, R. B.
  • Wildner, L. do P.
• Source: Revista Brasileira de Ciência do Solo
• Volume: 35
• Issue: 4
• Year: 2011
• Summary: The decomposition of plant residues is a biological process mediated by soil fauna, but few studies have been done evaluating its dynamics in time during the process of disappearance of straw. This study was carried out in Chapeco, in southern Brazil, with the objective of monitoring modifications in soil fauna populations and the C content in the soil microbial biomass (C-SMB) during the decomposition of winter cover crop residues in a no-till system. The following treatments were tested: 1) Black oat straw (Avena strigosa Schreb.); 2) Rye straw (Secale cereale L.); 3) Common vetch straw (Vicia sativa L.). The cover crops were grown until full flowering and then cut mechanically with a rolling stalk chopper. The soil fauna and C content in soil microbial biomass (C-SMB) were assessed during the period of straw decomposition, from October 2006 to February 2007. To evaluate CsmB by the irradiation-extraction method, soil samples from the 0-10 cm layer were used, collected on eight dates, from before until 100 days after residue chopping. The soil fauna was collected with pitfall traps on seven dates up to 85 days after residue chopping. The phytomass decomposition of common vetch was faster than of black oat and rye residues. The C-SMB decreased during the process of straw decomposition, fastest in the treatment with common vetch. In the common vetch treatment, the diversity of the soil fauna was reduced at the end of the decomposition process.

154. Predicting Agricultural Management Influence on Long-Term Soil Organic Carbon Dynamics: Implications for Biofuel Production

• Authors:
  • Rickman, R. W.
  • Liang, Y.
  • Albrecht, S. L.
  • Machado, S.
  • Kang, S.
  • Gollany, H. T.
• Source: Agronomy Journal
• Volume: 103
• Issue: 1
• Year: 2011
• Summary: Long-term field experiments (LTE) are ideal for predicting the influence of agricultural management on soil organic carbon (SOC) dynamics and examining biofuel crop residue removal policy questions. Our objectives were (i) to simulate SOC dynamics in LTE soils under various climates, crop rotations, fertilizer or organic amendments, and crop residue managements using the CQESTR model and (ii) to predict the potential of no-tillage (NT) management to maintain SOC stocks while removing crop residue. Classical LTEs at Champaign, IL (1876), Columbia, MO (1888), Lethbridge, AB (1911), Breton, AB (1930), and Pendleton, OR (1931) were selected for their documented history of management practice and periodic soil organic matter (SOM) measurements. Management practices ranged from monoculture to 2- or 3-yr crop rotations, manure, no fertilizer or fertilizer additions, and crop residue returned, burned, or harvested. Measured and CQESTR predicted SOC stocks under diverse agronomic practices, mean annual temperature (2.1-19 degrees C), precipitation (402-973 mm), and SOC (5.89-33.58 g SOC kg(-1)) at the LTE sites were significantly related (r(2) = 0.94, n = 186, P < 0.0001) with a slope not significantly different than 1. The simulation results indicated that the quantities of crop residue that can be sustainably harvested without jeopardizing SOC stocks were influenced by initial SOC stocks, crop rotation intensity, tillage practices, crop yield, and climate. Manure or a cover crop/intensified crop rotation under NT are options to mitigate loss of crop residue C, as using fertilizer alone is insufficient to overcome residue removal impact on SOC stocks.

155. On the way towards conservation tillage-soil moisture and mineral nitrogen in a long-term field experiment in Germany

• Authors:
  • Gruber, S.
  • Möhring, J.
  • Claupein, W.
• Source: Soil & Tillage Research
• Volume: 115
• Year: 2011
• Summary: Ten years of a long-term field experiment using different strategies of conventional and conservation tillage in SW Germany were evaluated for soil mineral nitrogen (SMN) and soil moisture content. Treatments analysed were combinations of stubble tillage (S) or no stubble tillage with primary tillage P: mouldboard plough, CP: chisel plough, RTT: rototiller, NT: no-till, and VAR: alternating SIP or S/CP. Best management practices were used for crop rotation, fertilisation and plant protection. CP, VAR and NT resulted in 18.7-19.0% gravimetric water content in spring. Partially significantly lower water content was observed in spring under S/P and CP with 18.2%; P and S/RTT resulted in 18.5%. Autumn soil moisture ranged from 15.3 to 15.8% and did not significantly differ between the treatments. Interactions between treatment and depth were not significant. There was no clear trend for spring soil moisture. No treatment showed a particular response to dry or wet season. Total SMN ranged between 8 and 49 kg ha(-1) in spring and 5-26 kg ha(-1) in autumn; significant effects of the treatments or interactions of treatment x depth did not occur. The effect of the season was most relevant for the amount of SMN, probably as a result of different conditions for mineralisation. Downward movement of nitrogen in spring was low in all treatments if catch crops were grown in the previous autumn. Overall, different soil tillage methods had little effect on soil moisture and soil SMN under temperate conditions. Seriously adverse effects of any tillage treatment in terms of nitrate leaching or reduced mineralisation seem unlikely. Similarly, the tillage systems did not exhibit obvious advantages or disadvantages in terms of soil water content. An exception may have been the higher water content in autumn in 0-30 cm under high soil disturbance which provided more suitable conditions for germination of the following crop. The decision of whether or not to adopt conservation tillage in temperate climates seems not to be primarily dependent on soil moisture and nitrogen mineralisation or on nitrogen leaching.

156. Cover crops and disturbance influence activity-density of weed seed predators Amara aenea and Harpalus pensylvanicus (Coleoptera: Carabidae).

• Authors:
  • Barbercheck, M. E.
  • Curran, W. S.
  • Ryan, M. R.
  • Ward, M. J.
  • Mortensen, D. A.
• Source: Weed Science
• Volume: 59
• Issue: 1
• Year: 2011
• Summary: The activity-density of Amara aenea (DeGeer) and Harpalus pensylvanicus (DeGeer) (Coleoptera: Carabidae) was monitored in an experiment that compared five management treatments representing a range of disturbance frequencies, crops, and aboveground biomass production. In 2004 and 2005, three treatments comprised of multiple summer cover crops were compared to bare fallow and soybean, the latter of which used mechanical cultivation to manage weeds. In 2005 weed seed predation was assessed from June to September in two of the treatments (bare fallow and oat-pea/rye-hairy vetch). Beetle activity-density varied with treatment, time of sampling, and year. In 2004 peak activity-density of A. aenea was highest in the mustard/buckwheat/canola, but there was no difference in H. pensylvanicus activity-density. In 2005 activity-density of H. pensylvanicus was higher in oat-pea/rye-hairy vetch than in soybean treatment. Seed predation rates were relatively consistent across treatments, averaging between 38 and 63%. In fallow and oat-pea/rye-hairy vetch, H. pensylvanicus activity-density accounted for 29 and 33% of the variation in seed predation, respectively. Our findings suggest cover crops have a positive effect on the activity-density of A. aenea and H. pensylvanicus and that disturbance negatively influences their activity-density in the absence of cover crops.

157. Modification of the existing MRL for epoxiconazole in various cereals.