81. Soil organic matter content and composition as influenced by soil management in a semi-arid Mediterranean agro-silvo-pastoral system.

• Authors:
  • Agnelli, A.
  • Roggero, P. P.
  • Ledda, L.
  • Porcu, G.
  • Seddaiu, G.
  • Corti, G.
• Source: Agriculture Ecosystems and Environment
• Volume: 167
• Year: 2013
• Summary: The aim of this study was to assess the impact of different long term soil managements on soil organic matter (SOM) quantity and quality in a semi-arid Mediterranean dehesa-like agro-forestry system (North-East of Sardinia, Italy). Seven soil managements were compared: cork oak forest, pasture under oak trees, open pasture, hay crop under oak trees, open hay crop, grass-covered vineyard and tilled vineyard. Analyses include chemical and spectroscopic (FT-IR) characterization of the humic substances (fulvic acids, humic acids and humin) of the A horizons. Lower amounts of total organic C and humic substances were found in the more disturbed soils such as those of the tilled vineyard, while the other soil managements showed a rather similar pattern for many indices of SOM quality (e.g., HA-C/FA-C, fulvic H/C and humic and fulvic C/N ratios) and for spectroscopic characteristics. These results indicated that the impact of soil management on the humic composition was relatively low for these sub-acid (pH ranging from 5.1 to 6.4) sandy soils under Mediterranean type of climate. The relatively small differences between the forest and the grassland land uses also suggested that the periodical light tillage applied to the grassland did not strongly affect SOM accumulation in the topsoil of this land use. In the oak forest soils, a sharp decrease (-77%) of the organic C from the thin A1 to the A2 horizon was observed, which could constrain the resilience of these soils towards disturbance factors, while the grasslands soils, where the organic C sequestration occurred in a thick horizon, may be more resilient. The compared soil managements revealed to be quite conservative, demonstrating that the traditional agro-silvo-pastoral management practices are effective in maintaining relatively good soil quality traits under semi-arid Mediterranean conditions.

82. Root:shoot ratios and belowground biomass distribution for Pacific Northwest dryland crops

• Authors:
  • Albrecht, S. L.
  • Douglas, C. L., Jr.
  • Reardon, C. L.
  • McCool, D. K.
  • Williams, J. D.
  • Rickman, R. W.
• Source: Journal of Soil and Water Conservation
• Volume: 68
• Issue: 5
• Year: 2013
• Summary: Roots, cereal crowns, and stems growing beneath the soil surface provide important resistance to soil erosion. Understanding the amount and distribution of this material in the soil profile could provide insight into resistance to soil erosion by water and improve the performance of soil erosion models, such as the revised universal soil loss equation (RUSLE) and the water erosion prediction project (WEPP). Erosion models use built-in or external crop growth models to populate crop yield and live aboveground and associated belowground biomass databases. We examined two data sets from the dryland small grain production region in the Pacific Northwest of the United States to determine root:shoot ratios, the vertical distribution of root and attached belowground biomass, and incorporated residue from previously grown crops. Data were collected in 1993, 1994, 1995, and 2000 from short-term no-till and conventional tillage experiments conducted near Pendleton, Oregon, and Pullman,Washington, and in 1999 and 2000 from long-term experiments representative of farming practices near Pendleton, Oregon. The crops sampled in the short-term data set included soft white winter and spring wheat (Triticum aestivum L.;WW and SW, respectively), spring peas (Pisum sativum L.; SP), and winter canola (Brassica napus L.;WC). Crops sampled in the long-term study included WW SW, and SP. Data were collected at harvest in both data sets and during three phenologic stages in each of the crops in the short-term data set. Soil samples were collected to a depth of 60 cm (23.6 in) in the short-term and 30 cm (11.9 in) in the long-term experiments. In both sets of measurements, we found greater than 70% of root mass is in the top 10 cm (3.9 in) of the soil profile with the exception of SP, which had 70% of root mass in the top 15 cm (5.9 in) of the soil profile.WC produced significantly more biomass near the soil surface than WW SW, or SP Root-to-shoot biomass ratios, in mature wheat ranged from 0.13 to 0.17 in the top 30 cm (11.9 in) of the soil profile, substantially lower than values suggested for use in WEPP (0.25). In the long-term experiments, soil of the conventionally tilled continuous winter wheat (CWW) plots contained significantly greater biomass than soil of conventionally tilled winter wheat/fallow (CR) and no-till winter wheat/fallow (NT) treatments. There was no significant difference between CWW and conventionally tilled winter wheat/spring pea (WP); however, CWW returned more residue to the soil than WP because SP produced less residue and these residues were incorporated with a field cultivator rather than a moldboard plow. More accurate representation of root development, particularly in winter crops, could improve RUSLE and WEPP performance in the Pacific Northwest where winter conditions have proven difficult to model.

83. Reduced nitrous oxide emissions and increased yields in California tomato cropping systems under drip irrigation and fertigation

• Authors:
  • Suddick, E. C.
  • Kennedy, T. L.
  • Six, J.
• Source: Agriculture, Ecosystems & Environment
• Volume: 170
• Issue: April
• Year: 2013
• Summary: Understanding the effect of various agricultural management practices on nitrous oxide (N2O) emissions is crucial to advise farmers and formulate policies for future greenhouse gas (GHG) reductions. In order to estimate present N2O emissions, annual N2O budgets must be thoroughly and precisely quantified from current farms under conventional and alternative management, but subject to practical and economic constraints. In this study, field sites were located on two on-farm processing tomato (Lycopersicon esculentum) fields, under contrasting irrigation managements and their associated fertilizer application strategy: (1) furrow irrigation and sidedress fertilizer injection (conventional system) and (2) drip irrigation, reduced tillage, and fertigation (integrated system). Nitrous oxide emissions were monitored for seven to ten days following major events of cultivation, irrigation, fertilization, harvest, and winter precipitations. Total weighted growing season emissions (15 March-1 November 2010) were 2.01 +/- 0.19 kg N2O-N ha(-1) and 0.58 +/- 0.06 kg N2O-N ha(-1) in the conventional and integrated systems, respectively. The highest conventional system N2O emission episodes resulted from fertilization plus irrigation events and the first fall precipitation. In the integrated system, the highest N2O fluxes occurred following harvest and the first fall precipitation. Soil chemical and physical properties of soil moisture, inorganic nitrogen (N), and dissolved organic carbon (DOC) were low and less spatially variable in the integrated system. Used as an index of substrate availability, soil ammonium (NH4+) and nitrate (NO3-) exposures were significantly lower in the integrated system. Of great importance is that the drip irrigation water and fertilizer management of the integrated system also increased crop yield (119 Mg ha(-1) vs. 78 Mg ha(-1)), highlighting the potential for decreasing N2O emissions while simultaneously improving the use of water and fertilizer for plant production. Published by Elsevier B.V.

84. Effects of soil tillage and fertilization on resource efficiency and greenhouse gas emissions in a long-term field experiment in Southern Germany

• Authors:
  • Huelsbergen, K.-J.
  • Munch, J. C.
  • Kuestermann, B.
• Source: European Journal of Agronomy
• Volume: 49
• Issue: August
• Year: 2013
• Summary: Two factorial long-term field experiments were carried out at the experimental site of Scheyern, located in southern Germany, 40 km north of Munich (48 degrees 30'0' N, 11 degrees 26'60' E). Here three soil tillage systems were investigated: CT (conventional tillage with moldboard plough, 25 cm plowing depth), RT1 (reduced tillage with chisel plow, 18 cm working depth), and RT2 (reduced tillage with chisel plow, 8 cm working depth). At the same time, three fertilization systems were analyzed (high (N3), medium (N2) and low (N1) mineral N input) with a crop rotation of winter wheat (Triticum aestivum L) - potatoes (Solanum tuberosum L.) - winter wheat-corn (Zea mays L). The long-term effects of tillage and fertilization on yields, soil properties, nitrogen and energy efficiency, as well as greenhouse gas emissions (GGE) were investigated for the period of 1994-2005. On average conventional tillage (CT) produced yields of 8.03 (N1), 8.82 (N2) and 8.88 (N3) GE (grain equivalents) ha(-1) yr(-1); reduced tillage (RT1) yields of 7.82 (N1), 8.54 (N2) and 9.10 (N3) GE ha(-1) yr(-1) and RT2 yields of 6.9 (Ni), 7.82 (N2) and 8.6 (N3) GE ha(-1) yr(-1). The benefit of reduced soil tillage over CT. is a lower consumption of diesel fuel (reduced by 35%) and fossil energy (by 10%), C sequestration and N accumulation in soil. We recorded the highest soil organic carbon (SOC) in the RT2 treatments with the lowest tillage intensity (52.5 Mg ha(-1)) and the lowest SOC reserves in the CT plowed treatments (41.1 Mg ha(-1)). During the reported period, SOC reserves in the plowed treatments decreased by about 300 kg C ha-1 yr-1, whereas they increased by 150-500 kg C ha(-1) yr(-1) in the chiseled treatments. Similar results were achieved with the soil organic nitrogen (SON) reserves based on the type of tillage. This amounted to around 4000 kg ha-1 (CT), 4500 kg ha (RT1) and more than 5000 kg N ha-1 (RT2). The RT1 treatments were marked by high nutrient and energy efficiency. The disadvantage of reduced tillage lies in higher pesticide consumption and stronger soil compaction. The influence of reduced tillage was more pronounced in RT2 than in RT1 (higher SOC and SON content, higher soil dry bulk density, lower consumption of diesel fuel, higher pesticide input). The significant decreases in yield in the RT2 treatments reduced the nitrogen and energy efficiency and raised yield-related greenhouse gas emissions (GGE) in comparison to the RT1 treatments. In the case of reduced tillage combined with high N doses (RT1/N3, RT2/N2, RT2/N3), high N2O emissions of 10 to 12 kg ha(-1) yr(-1) were measured using closed chambers. It was found that as input of mineral N increased, GGE for tillage treatments, both area and yield related also increased. In RT1/N1, negative net GGE were recorded due to high C sequestration combined with moderate N2O and CO2 emissions (-220 kg CO2 (eq) ha(-1) yr(-1), -28 kg CO2 eq GE-(1)), whereas CT/N3 produced the highest net GGE (3587 kg CO2 (eq) ha(-1) yr(-1), 404 kg CO2 eq GE(-1)). (C) 2013 Elsevier B.V. All rights reserved.

85. Chemical and biological properties as affected by no-tillage and conventional tillage systems in an irrigated Haploxeroll of Central Chile

• Authors:
  • Silva, P.
  • Pino, V.
  • Fuentes, J.-P.
  • Martinez, E.
  • Acevedo, E.
• Source: Soil and Tillage Research
• Volume: 126
• Year: 2013
• Summary: Soil management practices may change the soil properties. The magnitude of the change varies according to the soil property, the climate, and the type and time of implementation of a particular management system. The aim of this study was to evaluate the effects of no-tillage (NT) on the chemical and biological properties of an Entic Haploxeroll in Central Chile. Soil organic carbon (SOC), microbial biomass and associated indicators q(CO2), q(Mic), q(Min), available N, P and K, pH, electrical conductivity (EC), and crop yield were determined in a field experiment having a wheat (Triticum turgidum L)-maize (Zea mays L.) crop rotation. The change in soil chemical properties was further evaluated using a greenhouse bioassay in which ryegrass (Lolium perenne L) was grown in soil samples extracted at 0-2,2-5, and 5-15 cm depth. After nine years SOC in the NT treatment was 29.7 Mg ha(-1) compared to 24.8 Mg ha(-1) of CT, resulting in 4.98 Mg ha(-1) C gain. The NT therefore resulted in an average annual sequestration of 0.55 Mg C ha(-1) yr(-1) in the upper 15 cm soil. The soil organic C stored under NT was mainly accumulated in the top 2-cm of soil. The biological indicators showed a greater biological soil quality under NT than under CT. Soil organic C was positively associated with available N, P. and K, but negatively with soil pH. The iyegrass bioassay yielded higher biomass in NT than CT. An improvement in the soil chemical quality of the NT soil was considered to be the main reason for this result. The maize yield under NT had the tendency to improve in time as compared to CT. Wheat, however, had lower yield under NT. It was concluded that NT increased C sequestration and SOC improving the chemical and biological properties of this soil. (C) 2012 Elsevier B.V. All rights reserved.

86. Application of nonparametric method to improve energy productivity and CO 2 emission for barley production in Iran.

• Authors:
  • Shahamat, E. Z.
  • Salehi, M.
  • Taki, M.
  • Mobtaker, H. G.
• Source: AGRICULTURAL ENGINEERING INTERNATIONAL CIGR JOURNAL
• Volume: 15
• Issue: 4
• Year: 2013
• Summary: The nonparametric method of data envelopment analysis (DEA) was used to investigate the energy efficiency and CO 2 emission of barley farm in Hamedan province of Iran. The method was used based on eight energy inputs including human labor, machinery, diesel fuel, fertilizers, farmyard manure, biocide, electricity and seed energy and single output of barley yield and technical, pure technical, scale and cross efficiencies were calculated using CCR and BCC models. The results showed that the average values of technical, pure technical and scale efficiency scores of farmers were 0.788, 0.941 and 0.833, respectively. Also, energy saving target ratio for barley production was calculated as 11.45%, indicating that by following the recommendations of this study, about 2,865 MJ ha -1 of total input energy could be saved with the same constant level of barley yield. Moreover the contribution of chemical fertilizer input from total saving energy was 34.88% which was the highest share followed by diesel fuel (25.88%) and electricity (20.89%) energy inputs. On one hand, optimization of energy use improved the energy use efficiency, energy productivity and net energy by 12.94%, 15.55% and 6.16%, respectively. On the other hand, total greenhouse gases (GHG) emission was 885.56 kg CO 2eq ha -1, which indicated that, the total CO 2 emissions can be reduced by 11.06%.

87. Modeling for relationships between soil properties and yield components of wheat using multiple linear regression and structural equation modeling.

• Authors:
  • Nazmi, L.
• Source: Advances in Environmental Biology
• Volume: 7
• Issue: 2
• Year: 2013
• Summary: Since soil properties influence the behavior of soils, the knowledge related to these properties is important in using them for different agricultural purposes. This study aimed to develop a structural equation model of yield components of wheat (YCW) in northwest of Iran using soil physical and chemical properties. Soil samples were collected from Mollaahmad watershed of Ardabil province in northwest of Iran for the greenhouse experiment. The primary purpose of this research was to develop a conceptual model in order to determine the sources of variations within the dataset and to explore equations for the sampled soils. The findings revealed that two soil properties components (chemical and physical properties) were significant in explaining YCW. The accepted model in the multiple linear regression (MLR) analysis demonstrated that the soil's chemical and physical properties measures are statistically significant in estimating YCW. Following this, and according to R square statistic, 87% of the variance in YCW was explained by the soil chemical properties and 83% was accounted for by soil physical properties. Considering the relative importance of the estimation of YCW variable and from the perspective of regression equations, the organic carbon and saturated point moisture made the largest contribution through the two proposed models for the soil productivity. According to the structural equation modeling (SEM) results, the final model has proved that YCW was controlled by soil chemical properties more than physical properties. The obtained general model can be useful for wheat and also an analytical pattern for Gramineae family. The improved estimation of production might be valuable in practice because crop productions are widely applied, for instance, to assess agroenvironmental policy measures to compare cropping systems or the need of a better soil quality managing.

88. Plant inter-species effects on rhizosphere priming of soil organic matter decomposition

• Authors:
  • Kuzyakov, Y.
  • Zhu, B.
  • Pausch, J.
  • Cheng, W.
• Source: Soil Biology & Biochemistry
• Volume: 57
• Year: 2013
• Summary: Living roots and their hizodeposits can stimulate microbial activity and soil organic matter (SOM) decomposition up to several folds. This so-called rhizosphere priming effect (RPE) varies widely among plant species possibly due to species-specific differences in the quality and quantity of rhizodeposits and other root functions. However, whether the RPE is influenced by plant inter-species interactions remains largely unexplored, even though these interactions can fundamentally shape plant functions such as carbon allocation and nutrient uptake. In a 60-day greenhouse experiment, we continuously labeled monocultures and mixtures of sunflower, soybean and wheat with C-13-depleted CO2 and partitioned total CO2 efflux released from soil at two stages of plant development for SOM- and root-derived CO2. The RPE was calculated as the difference in SOM-derived CO2 between the planted and the unplanted soil, and was compared among the monocultures and mixtures. We found that the RPE was positive under all plants, ranging from 43% to 136% increase above the unplanted control. There were no significant differences in RPE at the vegetative stage. At the flowering stage however, the RPE in the soybean-wheat mixture was significantly higher than those in the sunflower monoculture, the sunflower-wheat mixture, and the sunflower-soybean mixture. These results indicated that the influence of plant inter-specific interactions on the RPE is case-specific and phenology-dependent. To evaluate the intensity of inter-specific effects on priming, we calculated an expected RPE for the mixtures based on the RPE of the monocultures weighted by their root biomass and compared it to the measured RPE under mixtures. At flowering, the measured RPE was significantly lower for the sunflower wheat mixture than what can be expected from their monocultures, suggesting that RPE was significantly reduced by the inter-species effects of sunflower and wheat. In summary, our results clearly demonstrated that inter-species interactions can significantly modify rhizosphere priming on SOM decomposition. (C) 2012 Elsevier Ltd. All rights reserved.

89. Environmental analysis of the logistics of agricultural products from roof top greenhouses in Mediterranean urban areas

• Authors:
  • Rieradevall, J.
  • Ignacio Montero, J.
  • Oliver-Sola, J.
  • Ceron-Palma, I.
  • Sanye-Mengual, E.
• Source: Journal of the science of food and agriculture
• Volume: 93
• Issue: 1
• Year: 2013
• Summary: BACKGROUND: As urban populations increase so does the amount of food transported to cities worldwide, and innovative agro-urban systems are being developed to integrate agricultural production into buildings; for example, by using roof top greenhouses (RTGs). This paper aims to quantify and compare, through a life cycle assessment, the environmental impact of the current linear supply system with a RTG system by using a case study for the production of tomatoes. RESULTS: The main results indicate that a change from the current linear system to the RTG system could result in a reduction, per kilogram of tomatoes (the functional unit), in the range of 44.4-75.5% for the different impact categories analysed, and savings of up to 73.5% in energy requirements. These savings are associated with re-utilisation of packaging systems (55.4-85.2%), minimisation of transport requirements (7.6-15.6%) and reduction of the loss of product during transportation and retail stages (7.3-37%). CONCLUSIONS: The RTG may become a strategic factor in the design of low-carbon cities in Mediterranean areas. Short-term implementation in the city of Barcelona could result in savings of 66.1 tonnes of CO2 eq. ha(-1) when considering the global warming potential, and of 71.03 t ha(-1) when considering that the transformation from woodland to agricultural land is avoided. (C) 2012 Society of Chemical Industry

90. N2O emissions due to nitrogen fertilizer applications in two regions of sugarcane cultivation in Brazil

• Authors:
  • Conant, R.
  • Cerri, C.
  • Signor, D.
• Source: Environmental Research Letters
• Volume: 8
• Issue: 1
• Year: 2013
• Summary: Among the main greenhouse gases (CO2, CH4 and N2O), N2O has the highest global warming potential. N2O emission is mainly connected to agricultural activities, increasing as nitrogen concentrations increase in the soil with nitrogen fertilizer application. We evaluated N2O emissions due to application of increasing doses of ammonium nitrate and urea in two sugarcane fields in the mid-southern region of Brazil: Piracicaba (Sao Paulo state) and Goianesia (Goias state). In Piracicaba, N2O emissions exponentially increased with increasing N doses and were similar for urea and ammonium nitrate up to a dose of 107.9 kg ha(-1) of N. From there on, emissions exponentially increased for ammonium nitrate, whereas for urea they stabilized. In Goianesia, N2O emissions were lower, although the behavior was similar to that at the Piracicaba site. Ammonium nitrate emissions increased linearly with N dose and urea emissions were adjusted to a quadratic equation with a maximum amount of 113.9 kg N ha(-1). This first effort to measure fertilizer induced emissions in Brazilian sugarcane production not only helps to elucidate the behavior of N2O emissions promoted by different N sources frequently used in Brazilian sugarcane fields but also can be useful for future Brazilian ethanol carbon footprint studies.