1161. Soil organic carbon accumulation and carbon costs related to tillage, cropping systems and nitrogen fertilization in a subtropical Acrisol

• Authors:
  • Mielniczuk, J.
  • Vieira, F. C. B.
  • Dieckow, J.
  • Bayer, C.
  • Zanatta, J. A.
• Source: Soil & Tillage Research
• Volume: 94
• Issue: 2
• Year: 2007
• Summary: Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha-1 year-1 (0 N) and 180 kg N ha-1 year-1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0-5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0-20 cm layer varied from 0.09 to 0.34 Mg ha-1 year-1 in CT and from 0.19 to 0.65 Mg ha-1 year-1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.

1162. Soil carbon and nitrogen stores and storage potential as affected by land-use in an agro-pastoral ecotone of northern China

• Authors:
  • Han, X.
  • Liu, P.
  • Li, L.
  • Huang, J.
  • Sun, O.
  • Zhou, Z.
• Source: Biogeochemistry
• Volume: 82
• Issue: 2
• Year: 2007
• Summary: Equilibrium carbon stock is the result of a balance between inputs and outflows to the pool. Changes in land-use are likely to alter such balance, resulting in different carbon stores under different land-use types in addition to the impacts of global climate change. In an agro-pastoral ecotone of Inner Mongolia, northern China, we investigated productivity and belowground carbon and nitrogen stores under six different types of land-uses, namely free grazing (FG), grazing exclusion (GE), mowing (MW), corn plantation (CP), fallow (FL), and alfalfa pasture (AP), and their impacts on litter and fine roots in semiarid grassland ecosystems. We found that there were great variations in aboveground net primary production (ANPP) across the six land-use types, with CP having markedly high ANPP; the FG had significantly reduced soil organic carbon (SOC) and nitrogen stores (SON) to 100 cm depth compared with all other types of land uses, while very little litter accumulation was found on sites of the FG and CP. The top 20 cm of soils accounted for about 80% of the root carbon and nitrogen, with very little roots being found below 50 cm. About 60% of SOC and SON were stored in the top 30 cm layer. Land-use change altered the inputs of organic matters, thus affecting SOC and SON stores accordingly; the MW and GE sites had 59 and 56% more SOC and 61% more SON than the FG. Our estimation suggested that restoring severely degraded and overgrazed grasslands could potentially increase SOC and SON stores by more than 55%; conversion from the native grasses to alfalfa could potentially double the aboveground biomass production, and further increase SOC and SON stores by more than 20%. Our study demonstrated significant carbon and nitrogen storage potential of the agro-pastoral ecotone of northern China through land-use changes and improved management in the context of mitigating global climate change.

1163. Spatial and temporal variability of grain yield under no-tillage cropping system.; Variabilidade espacial e temporal da produtividade de culturas sob sistema plantio direto.

• Authors:
  • Amado, T. J. C.
  • Pontelli, C. B.
  • Santi, A. L.
  • Viana, J. H. M.
  • Sulzbach, L. A. de S.
• Source: Brazilian Journal of Agricultural Research (PAB)
• Volume: 42
• Issue: 8
• Year: 2007
• Summary: The objective of this work was to analyze the spatial and temporal yield variability of soybean, corn and wheat in a 57 ha cropland, without irrigation, under no-till for more than ten years in a Typic Hapludox, located in Palmeira das Missões, RS. Yield data of crops from 2000 to 2005 were collected using a combine equipped with yield monitor. Statistical and geostatistical analysis were performed to monitor the range of the spatial variability and its spatial dependence, as well as its behavior over the years. Soybean, corn and wheat yield present spatial variability, which is maintained over time. In dry years, yield variance coefficient increases compared to wet years. Corn was more efficient than soybean to identify spatial yield variability in the cropland.

1164. High yielding, drought resistant maize hybrids with good quality traits.; Hibrizi de porumb productivi, rezistenti la seceta si cu insusiri calitative superioare.

• Authors:
  • Antohe, I.
  • Cosmin, O.
  • Sarca, T.
  • Dicu, G.
  • Naidin, C.
  • Naescu, V.
• Source: Analele Institutului National de Cercetare-Dezvoltare Agricola Fundulea
• Volume: 74
• Year: 2007

1165. A comparison of greenhouse gas emissions from inputs into farm enterprises in Southeast Queensland, Australia

• Authors:
  • Apan, A.
  • Maraseni, T. N.
  • Cockfield, G.
• Source: Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering
• Volume: 42
• Issue: 1
• Year: 2007

1166. Trends in grain yields and soil organic carbon in a long-term fertilization experiment in the China Loess Plateau.

• Authors:
  • Fan, T.
  • Xu, M.
  • Zhou, G.
  • Ding, L.
• Source: American-Eurasian Journal of Agricultural and Environmental Science
• Volume: 2
• Issue: 5
• Year: 2007
• Summary: Grain yield trends and changes in Soil Organic Carbon (SOC) from a 26-yr rainfed fertilization trial in Pingliang, Gansu, China, were recorded. Mean wheat ( Triticum aestivum L.) yields for the 18-yr ranged from 1.72 t ha -1 for the unfertilized plots (CK) to 4.65 t ha -1 for the plots that received Manure (M) annually with inorganic Nitrogen (N) and Phosphorus (P) fertilizers (MNP). Corn ( Zea mays L.) yields for the 6-yr averaged 2.43 and 5.35 t ha -1 in the same treatments. Yields declined with year except the CK for wheat. Wheat yields for the N only declined 117.8 kg ha -1 yr -1 that was the highest among all treatments and that for the NP declined 84.7 kg ha -1 yr -1, similar to that of 77.4 kg ha -1 yr -1 for the treatment receiving straw and N annually and P every second year (SNP). Likewise, the corn yields declined highly for all treatments and the declined amounts ranged from 108 to 258 kg ha -1 yr -1 that was much higher than in wheat. SOC gradually increased with time except the CK and N treatments, in which SOC remained almost stable. The SOC increases of 190.1, 166.8 and 164.5 mg C kg -1 yr -1 occurred in MNP and SNP and M treated soils, respectively. About 24% of the total C-input from manure and root residue and about 14% of the total C-input from straw and root residue remained in the soil as organic matter. Losses of 1 t SOM ha -1 were associated with a decrease in wheat yield of approximately 80 kg ha -1, showing the importance of using management practices that minimize losses of SOC in the China Loess Plateau. Grain yield declines were likely related to gradual dry weather and soil available N decline. It is concluded that C sequestration can be enhanced by increasing manure and straw additions in these dryland soils.

1167. Legume effect for enhancing productivity and nutrient use-efficiency in major cropping systems - an Indian perspective: a review.

• Authors:
  • Bandyopadhyay, K. K.
  • Wanjari, R. H.
  • Manna, M. C.
  • Misra, A. K.
  • Mohanty, M.
  • Rao, A. S.
  • Ghosh, P. K.
• Source: Journal of Sustainable Agriculture
• Volume: 30
• Issue: 1
• Year: 2007
• Summary: This article deals with the beneficial effect of important legumes on increasing productivity and nutrient use efficiency in various systems. Sorghum, pearl millet, maize, and castor are mainstay in dry lands and marginal and sub-marginal lands. Sorghum yield increased when sown after cowpea, green gram, and groundnut. Grain legumes like groundnut or cowpea provide an equivalent to 60 kg N ha on the subsequent crop of pearl millet. Various studies have shown that among legume/cereal intercropping system, the combination of maize/pigeon pea is considered to be highly suitable with a minimum competition for nutrients, while legume/legume intercropping system, pigeon pea/groundnut system is the most efficient one in terms of resource use-efficiency. In alley cropping system, Leucaena leucocephala (Subabul) prunings provide N to the extent of 75 kg, which benefits the intercrop castor and sorghum. Nitrogen economy through intercropped legume is still a researchable issue because the key point for leguminous crop grown in intercropping system is the problem of nodulation. Incorporation of whole plant of summer green gram/black gram into soil (after picking pods) before transplanting rice resulted in the economizing (40-60 kg N ha -1, 30 kg P 2O 5, and 15 kg K 2O per ha) of rice in rice-wheat system. Similarly, 6-8 weeks old green manure crop of sunhemp or dhaincha accumulates approximately 3-4 t ha -1 dry matter and 100-120 kg N ha -1 which, when incorporated in situ, supplements up to 50% of the total N requirement of rice. Legumes with indeterminate growth are more efficient in N 2 fixation than determinate types. Fodder legumes in general are more potent in increasing the productivity of succeeding cereals. The carryover of N for succeeding crops may be 60-120 kg in berseem, 75 kg in Indian clover, 75 kg in cluster bean, 35-60 kg in fodder cowpea, 68 kg in chickpea, 55 kg in black gram, 54-58 kg in groundnut, 50-51 kg in soyabean, 50 kg in Lathyrus, and 36-42 kg per ha in pigeon pea. Direct and residual effect of partially acidulated material and mixture of rock phosphate + single superphosphate were observed to be better when these were applied to green gram in winter season than to rice in rainy season simply because of legume effect.

1168. Net biome productivity of irrigated and rainfed maize-soybean rotations: modeling vs. Measurements.

• Authors:
  • Arkebauer, T. J.
  • Grant, R. F.
  • Dobermann, A.
  • Hubbard, K. G.
  • Schimelfenig, T. T.
  • Verma, S. B.
  • Suyker, A. E.
  • Walters, D. T.
• Source: Agronomy Journal
• Volume: 99
• Issue: 6
• Year: 2007
• Summary: Estimates of agricultural C sequestration require an understanding of how net ecosystem productivity (NEP) and net biome productivity (NBP) are affected by land use. Such estimates will most likely be made using mathematical models that have undergone well-constrained tests against field measurements of CO 2 exchange as affected by management. We tested a hydraulically driven soil-plant-atmosphere C and water transfer scheme in ecosys against CO 2 and energy exchange measured by eddy covariance (EC) over irrigated and rainfed no-till maize-soybean rotations at Mead, NE. Correlations between modeled and measured fluxes ( R2>0.8) indicated that <20% of variation in EC fluxes could not be explained by the model. Annual aggregations of modeled fluxes indicated that NEP of irrigated and rainfed soybean in 2002 was -30 and -9 g C m -2 yr -1 (net C source) while NEP of irrigated and rainfed maize in 2003 was 615 and 397 g C m -2 yr -1 (net C sink). These NEPs were within the range of uncertainty in annual NEP estimated from gap-filled EC fluxes. When grain harvests were subtracted from NEP to calculate NBP, both the modeled and measured maize-soybean rotations became net C sources of 40 to 80 g C m -2 yr -1 during 2002 and 2003. Long-term model runs (100 yr) under repeated 2001-2004 weather sequences indicated that a rainfed no-till maize-soybean rotation at Mead would lose about 30 g C m -2 yr -1. Irrigating this rotation would raise SOC by an average of 6 g C m -2 yr -1 over rainfed values. Modeled and measured results indicated only limited opportunity for long-term soil C storage in irrigated or rainfed maize-soybean rotations under the soil, climate, and management typical of intensive crop production in the U.S. Midwest.

1169. Irrigated, no-till corn and barley response to nitrogen in northern Colorado

• Authors:
  • Reule, C. A.
  • Halvorson, A. D.
• Source: Agronomy Journal
• Volume: 99
• Issue: 6
• Year: 2007
• Summary: Converting irrigated, conventional-till (CT) systems to no-till (NT) production systems can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions. Nitrogen fertilization effects on irrigated corn (Zea mays L.) and malting barley (Hordeum distichon L.) yields in a corn-barley rotation were evaluated for 6 yr on a clay loam soil to determine the viability of using a NT system and N needs for optimum crop yield. Six N treatments were established with N rates varying from 0 to 224 kg N ha(-1) for corn and 0 to 1.12 kg N ha(-1) for barley. Corn and barley grain yields were significantly increased by N fertilization each of 3 yr in the rotation. Three year average corn grain yields were near maximum with an available N (AN) (soil + fertilizer + irrigation water N) level of 274 kg N ha(-1). Barley yields increased linearly with increasing N rate with grain protein content near 130 kg protein Mg-1 grain at the highest N rate. Nitrogen use efficiency (NUE) by corn and barley, based on grain N removal, decreased with increasing AN level and ranged from 204 to 39 and 68 to 31 kg grain kg(-1) AN for the low and high N treatments for corn and barley, respectively. Total plant N uptake required to produce one Mg grain at near maximum yield in this study averaged 21 kg N for corn and 27 kg N for barley. Corn and barley residue production increased with increasing N rate. Irrigated, NT corn yields obtained in this corn-barley rotation were acceptable (>10 Mg ha(-1)) for northern Colorado; however, barley yields did not meet our expected yield goal of 5.4 Mg ha(-1) with the N rates used in this study, but grain protein was near maximum for malting barley. An irrigated, NT corn-barley production system appears to be feasible in northern Colorado.

1170. The adoption of annual subsoiling as conservation tillage in dryland maize and wheat cultivation in northern China.

• Authors:
  • Jin, H.
  • Hongwen, L.
  • Xiaoyan, W.
  • McHugh, A. D.
  • Wenying, L.
  • Huanwen, G.
  • Kuhn, N. J.
• Source: Soil & Tillage Research
• Volume: 94
• Issue: 2
• Year: 2007
• Summary: Soil compaction caused by random traffic or repetitive tillage has been shown to reduce water use efficiency, and thus crop yield due to reduced porosity, decreased water infiltration and availability of nutrients. Conservation tillage coupled with subsoiling in northern China is widely believed to reduce soil compaction, which was created after many years of no-till. However, limited research has been conducted on the most effective time interval for subsoiling, under conservation tillage. Data from conservation tillage demonstration sites operating for 10 years in northern China were used to conduct a comparative study of subsoiling interval under conservation tillage. Three modes of traditional tillage, subsoiling with soil cover and no-till with soil cover were compared using 10 years of soil bulk density, water content, yield and water use efficiency data. Cost benefit analysis was conducted on subsoiling time interval under conservation tillage. Yield and power consumption were assessed by based on the use of a single pass combine subsoiler and planter. Annual subsoiling was effective in reducing bulk density by only 4.9% compared with no-till treatments on the silty loam soils of the Loess plateau, but provided no extra benefit in terms of soil water loss, yield increase or water utilization. With the exception of bulk density, no-till and subsoiling with cover were vastly superior in increasing water use (+10.5%) efficiency and yield (+12.9%) compared to traditional tillage methods. Four years of no-till followed by one subsoiling reduced mechanical inputs by 62%, providing an economic benefit of 49% for maize and 209% for wheat production compared to traditional tillage. Annual subsoiling reduced inputs by 25% with an increased economic benefit of 23% for maize and 135% for wheat production. Yield and power consumption was improved by 5% and 20%, respectively, by combining subsoiling with the planting operation in one pass compared with multipass operations of subsoiling and planting. A key conclusion from this is that annual subsoiling in dryland areas of northern China is uneconomical and unwarranted. Four years of no-till operations followed by 1 year subsoiling provided some relief from accumulated soil compaction. However, minimum soil disturbance and maximum soil cover are key elements of no-till for saving water and improving yields. Improved yields and reduced farm power consumption could provide a significant base on which to promote combined planter and subsoiling operations throughout northern China. Further research is required to develop a better understanding of the linkages between conservation tillage, soil quality and yield, aimed at designing most appropriate conservation tillage schemes.