• Authors:
    • de Alba, S.
    • Benito, G.
    • Lacasta, C.
    • Alcázar, M.
    • Alba, S. de
  • Source: Advances in Geoecology or Land degradation and rehabilitation: dryland ecosystems. Papers presented at the Fourth International Conference on Land Degradation, Cartagena, Murcia, Spain, 12-17 September 2004.
  • Volume: 40
  • Year: 2009
  • Summary: In Europe, especially in the Mediterranean area, water erosion seriously affects 50% to 70% of agricultural land. However, there is a lack of field-data on water erosion rates for agricultural areas in semiarid Mediterranean climates. This paper describes an experimental field station (La Higueruela Station) for the continuous monitoring of water erosion that was set up in 1992 in central Spain (Toledo, Castilla-La Mancha). In the study area, the annual precipitation is around 450 mm with a very irregular inter-annual and seasonal distribution, which includes a strong drought in summer. The geology is characterized by non-consolidated Miocene materials, mostly arcosics. The area presents a low relief and gentle slopes, generally
  • Authors:
    • Lopez, M. V.
    • Cantero-Martinez, C.
    • Arrue, J. L.
    • Alvaro-Fuentes, J.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 2
  • Year: 2008
  • Summary: Under semiarid conditions, soil quality and productivity can be improved by enhancing soil organic matter content by means of alternative management practices. In this study, we evaluated the feasibility of no-till (NT) and cropping intensification as alternative soil practices to increase soil organic C (SOC). At the same time, we studied the influence of these management practices on two SOC fractions (particulate organic matter C, POM-C, and the mineral-associated C, Min-C), in semiarid agroecosystems of the Ebro River valley. Soil samples were collected from five soil layers (0–5-, 5–10-, 10–20-, 20–30-, 30–40-cm depth) during July 2005 at three long-term tillage experiments located at different sites in the Ebro River valley (northeast Spain). Soil bulk density, SOC concentration and content, SOC stratification ratio, POM-C, and Min-C were measured. Higher soil bulk density was observed under NT than under reduced tillage (RT), subsoil tillage (ST), or conventional tillage (CT). At the soil surface (0–5-cm depth), the highest total SOC concentration, POM-C, and Min-C were measured under NT, followed by RT, ST, and CT, respectively. In the whole soil profile (0–40 cm), similarly, slightly greater SOC content was measured under NT than under CT with the exception of the Selvanera site, where deep subsoil tillage combined with moldboard plowing accumulated more SOC than NT. In semiarid Mediterranean agroecosystems where CT consists in moldboard plowing, NT is a viable management practice to increase SOC.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Year: 2008
  • Authors:
    • Eriksen-Hamel, N. S.
    • Angers, D. A.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 5
  • Year: 2008
  • Summary: While the adoption of no-till (NT) usually leads to the accumulation of soil organic C (SOC) in the surface soil layers, a number of studies have shown that this effect is sometimes partly or completely offset by greater SOC content near the bottom of the plow layer under full-inversion tillage (FIT). Our purpose was to review the literature in which SOC profiles have been measured under paired NT and FIT situations. Only replicated and randomized studies directly comparing NT and FIT for >5 yr were considered. Profiles of SOC had to be measured to at least 30 cm. As expected, in most studies SOC content was significantly greater (P < 0.05) under NT than FIT in the surface soil layers. At the 21- to 25-cm soil depth, however, which corresponds to the mean plowing depth for the data set (23 cm), the average SOC content was significantly greater under FIT than NT. Moreover, under FIT, greater SOC content was observed just below the average depth of plowing (26-35 cm). On average, there was 4.9 Mg ha(-1) more SOC under NT than FIT (P = 0.03). Overall, this difference in favor of NT increased significantly but weakly with the duration of the experiment (R-2 = 0.15, P = 0.05). The relative accumulation of SOC at depth under FIT could not be related to soil or climatic variables. Furthermore, the organic matter accumulating at depth under FIT appeared to be present in relatively stable form, but this hypothesis and the mechanisms involved require further investigation.
  • Authors:
    • Chamorro, L.
    • Romero, A.
    • Xavier Sans, F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 124
  • Issue: 1/2
  • Year: 2008
  • Summary: A comparative survey of weed vegetation in organic and conventional dryland winter cereal fields was performed in central Catalonia (NE Spain) in order to assess the effects of agricultural intensification on the diversity, structure and composition of weed communities. A total of 36 cereal fields were surveyed in nine agricultural sites, where a pair of one long-established organic and one conventional farms were selected. Weed surveys were carried out before harvest in 2003 and 2004, taking into account the spatial pattern. Organic practices produced an increase in weed cover, species richness and Hill's first order diversity (but not in equitability), as well as a shift in weed vegetation composition, which favoured potentially rare arable, broad-leaved, insect-pollinated and legume weeds. Weed diversity was concentrated in the crop edges, especially in the weed communities of conventional cereal fields, which were found to be more spatially heterogeneous than the organic ones.
  • Authors:
    • Carbonell, R.
    • Perea, F.
    • González, P.
    • Rodríguez-Lizana, A.
    • Ordóñez-Fernández, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 79
  • Issue: 3
  • Year: 2007
  • Summary: With the aim of assessing the benefits of crop remains left on the soil surface, a study was carried out on the decomposition and characteristics of residue deposited on a clay soil in southern Spain during the agricultural seasons of 2001/02, 2002/03 and 2003/04, in which a legume-cereal-sunflower rotation was followed. Each of the residues studied possessed a characteristic justifying its inclusion in the rotation. The legume residue (Pisum sativum L. cv. Ideal) supplied the highest amount of nitrogen to the soil since, throughout its decomposition cycle, it lost 76.6% of its initial content in nitrogen, compared to the 48 and 56% of N released by wheat residues (Triticum durum L. cv. Amilcar) and sunflower (Helianthus annus L. cv. Sanbro), respectively. At the beginning of its decomposition cycle, the wheat residue had the lowest mass, and gave the most cover, with values of 65%, which was 8.6 and 20.2% more than the cover estimated for the pea and sunflower residues, respectively. The sunflower residue lasted longest, only losing 18% of its initial cover over 109 days of decomposition, compared to 47% for wheat and 53% for pea. The amount of carbon released was similar for the three residues and was around 500 kg ha(-1). The straw decomposition rates under our conditions indicate that the residue of the most common crops in the area under dry farming makes protection possible during the intercrop period.
  • Authors:
    • Sau, F.
    • Pineiro, J.
  • Source: Fourrages
  • Issue: 190
  • Year: 2007
  • Summary: The natural conditions in Galice and northern Spain are favourable for the production of forage, compared to the rest of the country. Agriculture in the country has undergone deep restructurations for the last 50 years, especially on the dairy farms. From 1960s onwards, the acreages of grass-clover leys and of forage maize have been constantly increasing, in parallel with an increasing milk production. The proportion of milk produced from forage crops have remained at 20 to 25%, and a particular effort should be made to reach the goal of 40%. In order to overcome water shortage during summer, the farmers make silage with their spring cuts, use lucerne and purchased feeds, and irrigate at a small scale. The few trials made show that irrigated pastures can increase the average yearly production by 40-45%. Since the water resources are scarce, and must be distributed with other economic activities, there should be no large development of irrigation. To overcome the water shortage during summer, it would seem more realistic to have recourse to more intensive rotations (2 crops per year), in which a crop better adapted to high temperatures and to dry spells would take over the leys. This intensified dry-land system would increase the yearly production by from 50 to 82%.
  • Authors:
    • Herencia, J. F.
    • Ruiz, J. C.
    • Madejón, E.
    • Melero, S.
  • Source: European Journal of Agronomy
  • Volume: 26
  • Issue: 3
  • Year: 2007
  • Summary: Understanding of microbial processes in soil is important for the management of farming systems, particularly those that imply organic inputs of nutrients. In this work the effect of consecutive addition of two mature composts (vegetal and animal compost) at rates of 30 tm ha-1 over a 4-year period under a dryland system on the chemical and biochemical properties of a clay soil (Chromic Haploxeret) was investigated and compared to that of an inorganic fertilization. Soil chemical and biological status was evaluated by measuring the total organic carbon (TOC), humic acids, Kjeldahl-N, bicarbonate-extractable P (Olsen-P), ammonium acetate extractable-K (AAE-K), microbial biomass carbon (Cmic), enzymatic activities (dehydrogenase, protease, glucosidase, alkaline phosphatase) and Cmic/TOC ratio. At the end of the study, soils fertilised with composts showed increases in quantity (TOC) and quality (humic acids) of organic matter compared to inorganically fertilised soil. The nutrient content (Olsen-P and Kjeldahl-N) also showed an increase in the plots fertilised with composts. From the fourth crop cycle the plots fertilised with compost showed more clearly the increase in microbial biomass and enzymatic activities, which can have been related both with leguminous pre-crop and with the organic fertilization. In general, under a dryland system, an improvement of soil fertility was achieved in organically fertilised soils, confirming the positive effect of organic fertilization.
  • Authors:
    • Dobermann, A.
    • Walters, D. T.
    • Binder, D. L.
    • Haddix, M. L.
    • Adviento-Borbe, M. A. A.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 9
  • Year: 2007
  • Summary: Crop intensification is often thought to increase greenhouse gas (GHG) emissions, but studies in which crop management is optimized to exploit crop yield potential are rare. We conducted a field study in eastern Nebraska, USA to quantify GHG emissions, changes in soil organic carbon (SOC) and the net global warming potential (GWP) in four irrigated systems: continuous maize with recommended best management practices (CC-rec) or intensive management (CC-int) and maize-soybean rotation with recommended (CS-rec) or intensive management (CS-int). Grain yields of maize and soybean were generally within 80-100% of the estimated site yield potential. Large soil surface carbon dioxide (CO2) fluxes were mostly associated with rapid crop growth, high temperature and high soil water content. Within each crop rotation, soil CO2 efflux under intensive management was not consistently higher than with recommended management. Owing to differences in residue inputs, SOC increased in the two continuous maize systems, but decreased in CS-rec or remained unchanged in CS-int. N2O emission peaks were mainly associated with high temperature and high soil water content resulting from rainfall or irrigation events, but less clearly related to soil NO3-N levels. N2O fluxes in intensively managed systems were only occasionally greater than those measured in the CC-rec and CS-rec systems. Fertilizer-induced N2O emissions ranged from 1.9% to 3.5% in 2003, from 0.8% to 1.5% in 2004 and from 0.4% to 0.5% in 2005, with no consistent differences among the four systems. All four cropping systems where net sources of GHG. However, due to increased soil C sequestration continuous maize systems had lower GWP than maize-soybean systems and intensive management did not cause a significant increase in GWP. Converting maize grain to ethanol in the two continuous maize systems resulted in a net reduction in life cycle GHG emissions of maize ethanol relative to petrol-based gasoline by 33-38%. Our study provided evidence that net GHG emissions from agricultural systems can be kept low when management is optimized toward better exploitation of the yield potential. Major components for this included (i) choosing the right combination of adopted varieties, planting date and plant population to maximize crop biomass productivity, (ii) tactical water and nitrogen (N) management decisions that contributed to high N use efficiency and avoided extreme N2O emissions, and (iii) a deep tillage and residue management approach that favored the build-up of soil organic matter from large amounts of crop residues returned.
  • Authors:
    • Gracia, R.
    • Lopez, M.
    • Arrue, J.
    • Moret, D.
  • Source: European Journal of Agronomy
  • Volume: 26
  • Issue: 1
  • Year: 2007
  • Summary: Winter barley is the major crop on semiarid drylands in central Aragon (NE Spain). In this study we compared, under both continuous cropping (BC) (5-6-month fallow) and a crop-fallow rotation (BF) (16-18-month fallow), the effects of three fallow management treatments (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) on the growth, yield and water use efficiency (WUE) of winter barley during three consecutive growing seasons in the 1999-2002 period. Daily precipitation measurements and monthly measurements of soil water storage to a depth of 0.7 m were used to calculate crop water use (ET) and its components. The average growing season precipitation was 195 mm. Above-ground dry matter (DM) and corresponding WUE were high in years with high effective rainfalls (>10 mm day -1) either in autumn or spring. However, the highest values of WUE for grain yield were mainly produced by effective rainfalls during the time from stem elongation to harvest. Despite the similarity in ET for the three tillage treatments, NT provided the lowest DM production, corresponding to a higher soil water loss by evaporation and lower crop transpiration ( T), indicated by the lowest T/ET ratio values found under this treatment. No clear differences in crop yield were observed among the tillage treatments in the study period. On average, and regardless of the type of tillage, BF provided the highest values of DM and WUE and yielded 49% more grain than BC. These differences between cropping systems increased when water-limiting conditions occurred in the early stages of crop growth, probably due to the additional soil water storage under BF at sowing. Although no significant differences in precipitation use efficiency (PUE) were observed between BC and BF, PUE was higher under the BC system, which yielded 34% more grain than the BF rotation when yields were adjusted to an annual basis including the length of the fallow. The crop yield under BF was not dependent on the increase in soil water storage at the end of the long fallow. In conclusion, this study has shown that, although conventional tillage can be substituted by reduced or no-tillage systems for fallow management in semiarid dryland cereal production areas in central Aragon, the practice of long-fallowing to increase the cereal crop yields is not longer sustainable.