621. Long-term C-CO 2 emissions and carbon crop residue mineralization in an oxisol under different tillage and crop rotation systems.

• Authors:
  • Fiorin, J.
  • Nicoloso, R.
  • Tornquist, C.
  • Amado, T.
  • Campos, B.
• Source: Revista Brasileira de Ciencia do Solo
• Volume: 35
• Issue: 3
• Year: 2011
• Summary: Soil C-CO 2 emissions are sensitive indicators of management system impacts on soil organic matter (SOM). The main soil C-CO 2 sources at the soil-plant interface are the decomposition of crop residues, SOM turnover, and respiration of roots and soil biota. The objectives of this study were to evaluate the impacts of tillage and cropping systems on long-term soil C-CO 2 emissions and their relationship with carbon (C) mineralization of crop residues. A long-term experiment was conducted in a Red Oxisol in Cruz Alta, RS, Brazil, with subtropical climate Cfa (Koppen classification), mean annual precipitation of 1,774 mm and mean annual temperature of 19.2degreesC. Treatments consisted of two tillage systems: (a) conventional tillage (CT) and (b) no tillage (NT) in combination with three cropping systems: (a) R0 - monoculture system (soybean/wheat), (b) R1 - winter crop rotation (soybean/wheat/soybean/black oat), and (c) R2 - intensive crop rotation (soybean/black oat/soybean/black oat+common vetch/maize/oilseed radish/wheat). The soil C-CO 2 efflux was measured every 14 days for two years (48 measurements), by trapping the CO 2 in an alkaline solution. The soil gravimetric moisture in the 0-0.05 m layer was determined concomitantly with the C-CO 2 efflux measurements. The crop residue C mineralization was evaluated with the mesh-bag method, with sampling 14, 28, 56, 84, 112, and 140 days after the beginning of the evaluation period for C measurements. Four C conservation indexes were used to assess the relation between C-CO 2 efflux and soil C stock and its compartments. The crop residue C mineralization fit an exponential model in time. For black oat, wheat and maize residues, C mineralization was higher in CT than NT, while for soybean it was similar. Soil moisture was higher in NT than CT, mainly in the second year of evaluation. There was no difference in tillage systems for annual average C-CO 2 emissions, but in some individual evaluations, differences between tillage systems were noticed for C-CO 2 evolution. Soil C-CO 2 effluxes followed a bi-modal pattern, with peaks in October/November and February/March. The highest emission was recorded in the summer and the lowest in the winter. The C-CO 2 effluxes were weakly correlated to air temperature and not correlated to soil moisture. Based on the soil C conservation indexes investigated, NT associated to intensive crop rotation was more C conserving than CT with monoculture.

622. Making sense of yield trade-offs in a crop sequence: a New Zealand case study.

• Authors:
  • Zyskowski, R.
  • Ruiter, J.
  • Johnstone, P.
  • Brown, H.
  • Fletcher, A.
• Source: Field Crops Research
• Volume: 124
• Issue: 2
• Year: 2011
• Summary: Crop growth is driven by the capture and utilisation of solar radiation. The most productive crop sequences are those that maximise the interception and use of solar radiation. However, there are yield trade-offs because of the timing of transitions between successive crops. A longer duration of one crop will mean that the following crop is sown later and will therefore produce a lower yield. Maximising the yield of a sequence involves a compromise between the yields of successive crops. We describe a case study of a forage cropping rotation in New Zealand, demonstrating how simulation models can be used to define the best compromise between the yields of successive crops, and thereby maximise the total yield of the full sequence. A case study using a series of long-term simulation experiments for four diverse environments in New Zealand was undertaken in a continuous, summer maize - winter cereal, cropping sequence. Maize sowing dates and hybrid durations, and cereal sowing and harvest times were varied systematically. The actual simulated crop and sequence yields varied from site to site, but there was a consistent trend identifying the most productive combinations of sowing date and hybrid duration. The sequence of comparatively late sowing date of maize (1 December) and a long-season hybrid maximised the total yield of the sequence. The highest sequence yields were achieved by balancing the need to capture a high level of annual solar radiation and the need to have a large proportion of solar radiation captured by maize, which has the greater RUE in summer. This analysis illustrates how crop simulation models can be used to design and understand the processes that give the most productive cropping sequences.

623. Reduction of farmland runoff contamination with maize and vegetables intercropping system.

• Authors:
  • Li, Y.
  • Zu, Y.
  • Wu, B.
  • An, T.
  • Zhan, F.
  • Yang, J.
  • Fu, Z.
• Source: Research of Environmental Sciences
• Volume: 24
• Issue: 11
• Year: 2011
• Summary: In order to explore the effects of different planting patterns for the effective control of farmland runoff contamination, loss of TN, TP, COD Cr and SS under different planting patterns were analyzed with field plot experiments. The results showed that the surface runoff, loss of TN, TP, COD Cr and SS under a mono-cropping system were higher than under a maize and vegetables intercropping system. The surface runoff, loss of TN, TP, COD Cr and SS could be reduced using a maize and vegetables intercropping system. The maize || cauliflower/potato intercropping pattern was the most effective. Comparing with cauliflower/potato mono-cropping system, its reduction percentages of surface runoff, TN, TP, COD Cr and SS were 79.59%, 86.87%, 84.23%, 91.41% and 82.46%, respectively.

624. T-2 toxin occurrence in cereals and cereal-based foods.

• Authors:
  • Damiescu, L.
  • Trif, A.
  • Galbenu-Morvay, P.
  • Simion, G.
• Source: Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture
• Volume: 68
• Issue: 2
• Year: 2011
• Summary: T-2 toxin is a secondary metabolite mainly produced by fungi belonging to the genus Fusarium, principally by F. sporotrichioides, F. poae, F. equiseti and F. acuminatum which are common contaminants in staple foods of cereal origin such as oats, barley, rice, maize, wheat etc., and different by-products. T-2 toxin belongs to the closely related sesquiterpenoid family of thrichotecenes and is a potent inhibitor of protein synthesis. Its main effects are usually observed in the immune system which has strong impact on the health of both humans and animals. Although is one of the most toxic type A trichothecene, T-2 toxin occurrence data is scarce and European Commission (EC) legal limits are not yet available. The objective of the present study was to monitor the occurrence of T-2 toxin in cereals and cereal-based foods marketed in an area of western Romania (Timis and Arad counties), using enzyme-linked immunosorbent assay (ELISA) kits. T-2 toxin was present in all analyzed samples (maize, wheat, corn flakes, breakfast cereals, biscuits), with values ranging between 0.8 g/kg and 23.4 g/kg and median value of 4.9. This study points out also the necessity of a continuous survey of cereals and cereal-based products for T-2 toxin presence and levels, and stresses the need for establishing legislative maximum admitted levels in foods.

625. Promoting smallholder seed enterprises: quality seed production of rice, maize, sorghum and millet in northern Cameroon.

• Authors:
  • Silue, D.
  • Barra, A.
  • Guei, R.
• Source: International Journal of Agricultural Sustainability
• Volume: 9
• Issue: 1
• Year: 2011
• Summary: Food and Agriculture Organization of the United Nations (FAO) conducted two projects in Cameroon on strengthening rice, and sorghum, maize and millet seed production by smallholder seed enterprises (SSEs). Farmer groups (respectively, 25 SSEs and 114 SSEs) were formed or strengthened and trained. Sixty-six selected lead farmers were trained on the administering and managing of revolving funds. The groups were then linked to the Extension Service (for continuous technical advice), Agriculture Research for Development Institution (continuous supply of needed seed), National Seed Service (seed certification) and to financial institutions (financial support). The results obtained showed that 60 and 59.6 per cent, respectively, of the groups sustained their activities two to three years after the projects ended. Total certified rice seed produced increased to 800 tonnes (t) against 267t at the beginning. For the other cereal project, the total certified seed produced was 719.2t against 497t at its beginning. The use of quality seed rice together with good agronomic practices increased yields (up to 8.0t/ha against a scant 2t/ha before). All interviewed farmers stressed that the seed business was profitable and helped achieve higher living standards and diversify their activities. Seasonal incomes were more than US$1,783.31. Finally, both FAO projects helped generate farmers' income to about US$2,114.871, produced 447,954t of cereal grain and thus improved food security and alleviated poverty. The Cameroonian success could be repeated elsewhere.

626. Diversity and dominance of crop plantations in the agroecosystems of the Kujawy and Pomorze region in Poland.

• Authors:
  • Jaskulska, I.
  • Jaskulski, D.
• Source: Acta Agriculturae Scandinavica Section B-Soil and Plant Science
• Volume: 61
• Issue: 7
• Year: 2011
• Summary: The Kujawy and Pomorze Province with 127 rural and municipal-and-rural communes in 19 districts is a typical agricultural region, with the highest plant farming intensity in Poland. The diversity and dominance of crop plantations in the agroecosystems in communes were calculated based on percentage share of 21 kinds of crops in the cropland structure. The algorithms applied in ecological research of biodiversity were used: the Shannon-Weaver diversity index (H') and Simpson's dominance index (lambda). The diversity (H′) of crops in arable land in the Kujawy and Pomorze Province ranges from 1.68 to 2.54. The diversity of crop plantations in the region was bigger in the communes in which there are: better soil, a higher share of arable land in the agricultural acreage and cropland in the arable land as well as with a higher share of barley, corn for grain and sugar beet in the cropland structure. The highest dominance index (lambda) for crops in the whole province is 0.291. The index of dominance of agricultural crops in this region increases with an increase in the share of: woodland in the total area, meadows and pasture in the agricultural acreage and rye in the cropland structure.

627. Low temperature and oxidative stress in cereals.

• Authors:
  • Kovacs, V.
  • Boldizsar, A.
  • Szalai, G.
  • Soltesz, A.
  • Pal, M.
  • Kocsy, G.
  • Janda, T.
• Source: Acta Agronomica Hungarica
• Volume: 59
• Issue: 2
• Year: 2011
• Summary: Low temperature stress results in significant yield losses in cereals. Cereals of subtropical origin like maize and rice are severely damaged at temperatures below 10°C and are killed at subzero temperatures. This stress effect is called chilling. In contrast, cereals originating from the temperate zone (wheat, barley, rye and oat) may survive short periods even between -10 and -20°C, depending on the species and varieties, so they are freezing-tolerant to various extents. For the winter type of these cereals a gradual decrease in temperature up to -4°C results in cold acclimation, which increases their freezing tolerance. In addition, it fulfils their vernalization requirement, which is necessary for the correct timing of the vegetative to generative transition. During both chilling and freezing, oxidative stress is induced. Although the accumulation of high concentrations of reactive oxygen species may be lethal, a moderate increase in their level may activate various defence mechanisms. In this review the role of reactive oxygen species, antioxidants, carbohydrates, free amino acids, polyamines and hormones in the response to low temperature stress in cereals will be described. The effect of light and the use of the model plant Brachypodium distachyon L. to reveal the biochemical and molecular biological background of this response will also be discussed.

628. Horizontal and vertical seed distribution under different field crops.

• Authors:
  • Korac, M.
  • Meseldzija, M.
  • Konstantinovic, B.
  • Mandic, N.
• Source: Herbologia
• Volume: 12
• Issue: 1
• Year: 2011
• Summary: Soil surface contains huge amount of seed of different weed species. By examination of weed seed distribution in the soil, it can be predicted which weeds will occur under different crops and to what extent. Detailed data analysis enables determination of timely soil tillage, as well as herbicide use. In the period 2008-2010, the weed seed bank was studied in different localities on the territory of Vojvodina (Krivaja, Ratkovo, Zmajevo, Bac, and Despotovo). Soil samples were collected from fields under different crops (soybean, sugar beet, maize, clover and sunflower). The sampling was performed diagonally in four replications from several arable depth layers of 0-10, 10-20 and 20-30 cm. Each sample was sieved through the system of cooper sieves of different diameter, according to the method of Conn (1987). After extraction from the samples, weed seeds were determined (Skender et. al., 1998; Kronaveter and Boar, 1994) and abundance of weed seed per m 2 was established for all three studied soil layers. The most abundant weed species in the weed seed bank under all studied crops were: Amaranthus retroflexus, Chenopodium album, Datura stramonium, Polygonum lapathifolium and Solanum nigrum, while less abundant were seeds of: Echinochloa cruss-galli, Euphorbia helioscopia, Sinapis arvensis, Sorghum halepense and Stachys annua. The highest abundance of weed seed was found at locality Zmajevo under sunflower crop in the soil layer of 0-10 cm, in the amount of 8.487 seeds per m 2. At locality Krivaja, under soybean crop, the highest number of seeds was recorded in layers of 10-20 and 20-30, in the amount of 9.252 and 10.609 seeds per m 2, respectively. The results were statistically processed and it was calculated that the highest coefficient of variance, i.e. the maximum deviation between number of seeds of weed species per soil layers was 40.53% at locality Despotovo.

629. Soil organic carbon and crop yield under different soil amendments and cropping systems in the semi-deciduous forest zone of Ghana.

• Authors:
  • Ewusi-Mensah, N.
  • Logah, V.
  • Tetteh, F.
• Source: Journal of Plant Sciences
• Volume: 6
• Issue: 4
• Year: 2011
• Summary: A field experiment to evaluate Soil Organic Carbon (SOC) and maize grain yield under different soil amendments and cropping systems was conducted in 2006 and 2007 at the Soil Research Institute, Kwadaso, Kumasi. The experiment was a split plot with three replications. The main plot factor (cropping systems) consisted of continuous maize, maize/soybean intercropping and maize cowpea rotation systems, the sub-plot (amendments) comprised of Poultry Manure (PM) at 4 t ha -1, poultry manure+chemical fertilizer (PM+CF) at 2 t ha -1 (PM)+45-30-30 kg ha -1 (NPK 15-15-15), Chemical Fertilizer (CF) at 90-60-60 kg ha -1 NPK 15-15-15 and a control (no amendment). Soil samples were taken at 21 and 84 days after amendment (DAA). Generally, PM+CF produced the highest range of SOC (1.14-1.37%). The least (0.98-1.28%) was recorded on the control plots. Plots amended with chemical fertilizer alone or in combination with poultry manure out-yielded the control in maize grain yield. Positive correlations between SOC at 84 DAA and maize grain yield were recorded in the major (r=0.70*) and minor (r=0.89**) rainy seasons of 2006 which established crop yield a function of SOC at harvest. Land equivalent ratios of sole maize (maize grown under continuous maize system) and maize intercropped with soybean were

630. Long-term experiments for sustainable nutrient management in China. A review.

• Authors:
  • Zhang, F.
  • Stewart, B.
  • Miao, Y.
• Source: Agronomy for Sustainable Development
• Volume: 31
• Issue: 2
• Year: 2011
• Summary: China is facing one of the largest challenges of this century to continue to increase annual cereal production to about 600 Mt by 2030 to ensure food security with shrinking cropland and limited resources, while maintaining or improving soil fertility, and protecting the environment. Rich experiences in integrated and efficient utilization of different strategies of crop rotation, intercropping, and all possible nutrient resources accumulated by Chinese farmers in traditional farming systems have been gradually abandoned and nutrient management shifted to over-reliance on synthetic fertilizers. China is now the world's largest producer, consumer and importer of chemical fertilizers. Over application of nitrogen (N) is common in intensive agricultural regions, and current N-uptake efficiency was reported to be only 28.3, 28.2 and 26.1% for rice, wheat and maize, respectively, and less than 20% in intensive agricultural regions and for fruit trees or vegetable crops. In addition to surface and groundwater pollution and greenhouse gas emissions, over-application of N fertilizers has caused significant soil acidification in major Chinese croplands, decreasing soil pH by 0.13 to 2.20. High yield as a top priority, small-scale farming, lack of temporal synchronization of nutrient supply and crop demand, lack of effective extension systems, and hand application of fertilizers by farmers are possible reasons leading to the over-application problems. There is little doubt that current nutrient management practices are not sustainable and more efficient management systems need to be developed. A review of long-term experiments conducted around the world indicated that chemical fertilizer alone is not enough to improve or maintain soil fertility at high levels and the soil acidification problem caused by overapplication of synthetic N fertilizers can be reduced if more fertilizer N is applied as NO 3- relative to ammonium- or urea-based N fertilizers. Organic fertilizers can improve soil fertility and quality, but long-term application at high rates can also lead to more nitrate leaching, and accumulation of P, if not managed well. Well-managed combination of chemical and organic fertilizers can overcome the disadvantages of applying single source of fertilizers and sustainably achieve higher crop yields, improve soil fertility, alleviate soil acidification problems, and increase nutrient-use efficiency compared with only using chemical fertilizers. Crop yield can be increased through temporal diversity using crop rotation strategies compared with continuous cropping and legume-based cropping systems can reduce carbon and nitrogen losses. Crop yield responses to N fertilization can vary significantly from year to year due to variation in weather conditions and indigenous N supply, thus the commonly adopted prescriptive approach to N management needs to be replaced by a responsive in-season management approach based on diagnosis of crop growth, N status and demand. A crop sensor-based in-season site-specific N management strategy was able to increase Nuptake efficiency by 368% over farmers' practices in the North China Plain. Combination of these well-tested nutrient management principles and practices with modern crop management technologies is needed to develop sustainable nutrient management systems in China that can precisely match field-to-field and year-to-year variability in nutrient supply and crop demand for both single crops and crop rotations to not only improve nutrient-use efficiency but also increase crop yield and protect the environment. In addition, innovative and effective extension and service-providing systems to assist farmers in adopting and applying new management systems and technologies are also crucially important for China to meet the grand challenge of food security, nutrient-use efficiency and sustainable development.