• Authors:
    • Alonso, J. C.
    • Magana, M.
    • Garcia de Leon, D.
    • Bravo, C.
    • Ponce, C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 141
  • Issue: 1/2
  • Year: 2011
  • Summary: Organic farming is considered an important way to preserve biodiversity in agricultural landscapes. However, more work is still necessary to enable a full appraisal of the potential benefits of this way of farming, since studies differ in the evaluation of its effectiveness. Studies are particularly scarce in the Mediterranean region, where different climatic and ecological conditions prevent simple extrapolations from work carried out at northern latitudes. In the present study, an analysis of weed and arthropod communities was conducted in 28 pairs of organic and conventional fields in a dry cereal farmland in central Spain. Plants were identified to the species level, and arthropods to the family level. Pitfalls and sweep nets were used to sample respectively, ground-dwelling and plant-visiting arthropods. Abundance (total numbers of individuals), richness (total numbers of plant species or arthropod families), diversity (Shannon-Wiener index) and biomass (milligrams per pitfall/sweep-net) were calculated for each field and compared between organic and conventional fields using Generalized Linear Mixed Models (GLMMs). To explore the effect of predictor variables on weed richness and arthropod biomass, GLMMs were used. Organic fields showed higher abundance of weeds and arthropods (3.01 and 1.43 times, respectively), higher weed richness and diversity (2.76 and 2.33 times, respectively), and a 24% reduction in cereal plants. Arthropod diversity was lower in organic fields due to the presence of three dominant groups: Collembola, Chloropidae (Diptera), and Aphididae (Hemiptera). Weed richness increased as cereal cover decreased in organic fields. Total arthropod biomass was slightly higher in organic fields, and was affected by weed abundance and diversity. The differences between organic and conventional fields found in this study were higher than those reported for northern latitudes. This could be explained by the richer weed flora in the Mediterranean region, and a higher weed seed availability favored by the two-year rotation system typical of Iberian dry cereal farmland. We conclude that organic farming may contribute to preserve biodiversity in dryland cereal agroecosystems in the Mediterranean region.
  • Authors:
    • Levy, Y.
    • Raveh, E.
  • Source: Israel Journal of Plant Sciences
  • Volume: 59
  • Issue: 2/4
  • Year: 2011
  • Summary: During the last 50 years world irrigation has doubled while water withdrawal has tripled, leading to a global water crisis. As a result, growers around the world are forced to utilize effluent water for irrigation. In Israel the main source for such water is "SHAFDAN", i.e., tertiary-treated waste water, which is characterized by high chloride content that might increase in the future. These days about 33% of Israeli citrus orchards are irrigated with this water, yet its potential effect on citrus orchards is not clear. Citrus is one of the major fruit crops of the world and is relatively salt-sensitive. Recently it was reported that continuous application of KNO 3 might reduce chloride (Cl) uptake, and thus overcome the toxic effects of salinity. We examined the effect of KNO 3 fertilization and rootstock on grapefruit's response to salinized SHAFDAN reclaimed water over four years. Trees were grafted on five different rootstocks and fertigated with two KNO 3 regimes (118 vs. 148 mg 1 -1 NO 3), and exposed to five levels of salinized reclaimed water (from 221 to 765 mg 1 -1 Cl). During the experiment, soil electrical conductivity (EC) ranged from 2 dS m -1 (above the threshold for yield reduction) to 5 dS m -1. Leaf Cl (with the exception of trees grafted on Troyer) usually kept below toxicity level, i.e., >0.4%. Cumulative yield reduction due to salinity was 37.6, 21.3, 18.2, 17.2, and 12.6 kg per tree per dS m -1 of soil paste extract, for trees grafted on 812, SO, Volk, Gau, and Troy rootstocks, respectively, reflecting their sensitivity to the osmotic component of salt stress. Enhanced application of KNO 3 did not overcome the osmotic effect of salinity. These results indicate that while using reclaimed water, the osmotic component of salinity can be of higher significance than its toxic component, and more attention should be given in the future to the rootstock/scion combination's sensitivity to the osmotic component of salinity.
  • Authors:
    • Stankovic, S.
    • Stojkovic, S.
    • Barac, S.
    • Deletic, N.
    • Jelic, M.
    • Biberdzic, M.
    • Stamenkovic, S.
  • Source: Research Journal of Agricultural Science
  • Volume: 43
  • Issue: 1
  • Year: 2011
  • Summary: This paper deals with the effect of fertilization systems on weed infestation degree and grain yield of some small grains on the vertisol soil type. The trial was set in random complete block design with three replications. The trial included control variant and three variants fertilized by mineral fertilizers, lime and manure (1. NP 1K, 2. NP 2K, and 3. NP 1K+CaCO 3+manure). Small grain crops involved in the trial were wheat, barley, triticale and rye. Results of the study showed significant effect of fertilization on decreasing weed infestation degree of the all investigated small grain crops. The highest degree of infestation by weeds (average 2.2) was observed at the variant without fertilization, while the lowest one (1.2) was found at the variant fertilized by the combination of mineral fertilizers, lime and manure. The highest degree of infestation by weeds was observed in wheat, and the lowest one in rye. Grain yield at fertilized variants was significantly higher comparing with the control variant. The highest average grain yield of the all small grains (3961 kg ha -1) was reached at the variant with combined application of mineral fertilizers, lime and manure, while the lowest one was observed at the unfertilized variant (1378 kg ha -1). Combined application of mineral fertilizers, lime and manure gave high-significantly greater grain yield in regard to mineral fertilizers alone with lower phosphorus dose. The difference between the variant with combined NPK, lime and manure and the variant NP 2K was not statistically significant. The highest average grain yield in the all variants of 3884 kg ha -1 was given by wheat, and it was high-significantly greater than in the other crops, while the lowest one (2290 kg ha -1) was observed in rye. The difference between grain yields of barley and triticale was not significant. The highest grain yield of 4770 kg ha -1 was given by wheat at the variant with combination of NPK, lime and manure. The lowest grain yield was observed in rye and it was significantly lower than in other crops at every variant, which was expected. Triticale had greater grain yield than barley at the all variants, but the difference at the variant with combination of NPK, lime and manure was not significant.
  • Authors:
    • Brennan, E.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 3
  • Year: 2011
  • Summary: Cone planters (CP) uniformly distribute seed over research plots; however, preparing seed for CP by weighing is time-consuming. This study evaluated (i) the effect of seed preparation method (scooping with a calibrated cup vs. weighing) on population density of monoculture cover crops planted with a CP, (ii) time required for scooping vs. weighing, and (iii) the effect of scooping on segregation of pre-made cover crop mixtures. Monocultures included mustard [ Brassica juncea (L.) Czern.], rye ( Secale cereale L.), common vetch ( Vicia sativa L.), and faba bean ( Vicia faba L.) planted at 1*, 2*, and 4* seeding rates; 1* rates in pure live seed m -2 were 24 (faba bean), 43 (common vetch), 291 (rye), and 310 (mustard). Mixtures contained rye, oat ( Avena sativa L.), barley ( Hordeum vulgare L.), faba bean, common vetch, or pea ( Pisum sativum L.), and by weight included: Mix 1 (10% rye, 90% faba bean), Mix 2 (10% oat, 90% faba bean), Mix 3 (10% barley, 90% faba bean), Mix 4 (10% common vetch, 90% rye), and Mix 5 (10% rye, 25% pea, 30% common vetch, 35% faba bean). Seed preparation method did not affect the population densities of the monocultures. Preparing seed packets was at least two times more time-consuming with the weighing than scooping method. Calibrating cups to scoop within 1% of the desired seed packet weight was not difficult. However, segregation occurred while scooping some mixtures from a bucket whereby smaller-seeded components increased with scooping depth. Simple methods to detect seed segregation in mixtures are discussed.
  • Authors:
    • Mueller-Warrant, G.
    • Dick, R.
    • Banowetz, G.
    • Griffith, S.
    • Whittaker, G.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 4
  • Year: 2011
  • Summary: Understanding the impact of crop rotation and residue management in grass seed production systems on soil quality and, in particular soil C dynamics, is critical in making long-term soil management decisions supporting farm sustainability. The effects of a 6-yr rotation and residue management (high vs. low residue) on soil quality were investigated at three locations in Oregon, each contrasting in soil drainage classification. The crop rotations were continuous perennial grass seed production, grass/legume seed production, and grass/legume/cereal seed production. The grass species grown at each location were different and represented those most commonly produced in each environment; perennial ryegrass ( Lolium perenne L.), tall fescue [ Schedonorus phoenix (Scop.) Holub], and creeping red fescue ( Festuca rubra L.). All three grass seed crop rotations and residue methods maintained high soil quality in conventional or direct seeded soils, but under some situations, soil quality was higher with continuous grass rotation and high residue. Data suggest that straw removal for value-added use, like bioenergy production, can be accomplished in the Pacific Northwest Marine climate without appreciably affecting soil quality. Furthermore, grass seed cropping systems play an important role in soil C storage and enhancement, a valuable ecosystem service in this region where grass seed is produced on land that is not suitable for production of conventional crops that require better-drained soil. We conclude that by nature perennial grass seed crops promote high soil fertility and enriched soil C pools and consequently contribute to the tolerance of these systems to the use of less conservation-oriented crop management methods at times when crop loss could be potentially high. This attribute provides producers greater latitude in selecting soil and crop management options to address issues of soil fertility, pest, weed, or seed certification to minimize economic crop yield losses.
  • Authors:
    • Hontoria, C.
    • Lammerding, D.
    • Tenorio, J.
    • Walter, I.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 2
  • Year: 2011
  • Summary: It is widely accepted that conservation tillage management affords benefits to soil properties and reduces production costs; therefore these practices could be attractive to farmers from semiarid regions. The objective of this study was to assess the long-term effects of different tillage practices under semiarid conditions on macroaggregate stability (water stable aggregates, WSA), soil organic carbon (SOC), and particulate organic carbon (C-POM) content of an Alfisol from Spain. The experimental design involved a split plot and four randomized blocks in which tillage was the main factor and crop rotation (fallow-wheat-pea-barley) the secondary factor. Three tillage systems were compared: no tillage (NT), minimum tillage (MT), and conventional tillage (CT). Soil samples were collected on November 2006 and October 2007. In November 2006 no significant differences in WSA were found among the tillage treatments. In October 2007, however, the mean WSA in the upper soil layer for the NT was significantly higher, 24%, that in the CT. No significant differences were seen for the subsurface layer. Under NT, the SOC and C-POM values for the surface soil layer were significantly higher than those for the other treatments on both sampling dates. At the subsurface depth, no significant differences were seen in either of these variables. The SOC and C-POM values were more homogeneous throughout the soil profile in the plowed soil than in the NT for which the corresponding values were more stratified. The results show that NT will help improve soil structure and soil fertility, which is particularly relevant to semiarid conditions like the area studied.
  • Authors:
    • Cabrera, D.
    • Liso, A.
    • Coelho, J.
    • Lopez-Pineiro, A.
    • Nunes, J.
    • Pena, D.
  • Source: Spanish Journal of Rural Development (SJRD)
  • Volume: 2
  • Issue: 1
  • Year: 2011
  • Summary: In order to determine the effect of different irrigated crop rotation (1. corn, 2. intensive olive grove (300-400 trees/ha), 3. Corn - barley/oat/wheat (1 or 2 years) sugar beet and 4. Tomato - barley/oat/wheat (1 or 2 years) - Beet) on the organic matter content, pH, electrical conductivity and soil sodicity, we collect and georeferenced 6280 samples from the surface layer of soils (0-20 cm) in the Caia Irrigation Perimeter (located in Elvas and Campo Maior Counties, Portalegre District, Portugal) occupied with those rotations. These samples were mixed in groups of 10, resulting 1 sample, corresponding to an area of 11.1 ha, the one was sent to the laboratory where we proceeded to examine the above parameters. With the use of appropriate software (Geographic Information Systems - GIS), it was possible to correlate these individual soil samples with crop rotations and with the group of soil present (Fluvisols, Luvisols and Calcisols). We found that the use of the abovementioned crop rotations, over about two decades, led to significant differences in soil characteristics, although not always significant from a statistical point of view. The crop rotations using larger water and fertilizers amounts in irrigated crop systems are the ones causing a more evident decrease in soil organic matter and pH and, at the same time, leading to an increase in soil electrical conductivity and exchangeable sodium content.
  • Authors:
    • Diekmann, J.
    • Singh, M.
    • Masri, S.
    • Ryan, J.
    • Sommer, R.
  • Source: Soil & Tillage Research
  • Volume: 115/116
  • Year: 2011
  • Summary: Sustainability of dryland cropping is a major issue in the typical Mediterranean climatic environment of West Asia and North Africa. Management of crop residues and soil organic matter (SOM) and its interrelationship with tillage and crop rotation is of central importance for maintaining soil quality and sustaining crop yields. We examined the medium-term influence of conventional moldboard plowing compared with shallow tillage, under barley-vetch and barley-vetch-wheat-vetch rotation, with different levels of straw management (burned, removed, or incorporated) and compost addition (10 Mg ha -1 every 2 or 4 years) on the distribution with soil depth (0-30 cm) of SOM, total organic nitrogen (N tot), and labile as well as microbial carbon (C) and nitrogen (N). Shallow tillage increased SOM in 0-20 cm across all residue management treatments by on average 2.7 g kg -1. Compost addition every 2 years instead of burning or removing residues significantly increased N tot in 0-20 cm by 0.22 g kg -1, doubled labile N and C in 0-5 cm depth, and increased the ratio of labile N to N tot in 0-20 cm by 4%. Consequently, SOM accumulated in the labile pool, which reacts readily to changes in soil management practice, but which may also be depleted as quickly. Thus, shallow tillage in combination with compost addition can help build-up of SOM, and therefore soil quality. Under conditions of intensive cultivation, where crop residues are not in demand for livestock fodder, the system assessed constitutes a new agronomic direction under dryland agriculture in the Mediterranean region.
  • Authors:
    • Sarauskis, E.
    • Karayel, D.
  • Source: Žemės Ūkio Inžinerija, Mokslo Darbai
  • Volume: 43
  • Issue: 3
  • Year: 2011
  • Summary: Seed placement uniformity and failure to establish a uniform plant stand are critical problems associated with no-tillage production of maize ( Zea mays L.) following wheat ( Triticum aestivum). The objective of this research was to evaluate the effect of different downforces (680, 880, 1150 and 1400 N) on performance of disc furrow openers and determine the optimum downforce for modified precision seeder equipped with single or double disc-type openers. The study was conducted in two different field conditions (field I and field II). The soil of field I and II were clay-loam and loamy, respectively. Seed spacing uniformity, sowing depth uniformity, mean emergence time and percentage of emergence were determined. Sowing depth and seed spacing uniformity, mean emergence time and percentage of emergence of both furrow openers were increased as a result of increasing downforce for both fields. The downforce of modified conventional precision seeder should be greater than 880 N for more precise no-till sowing using with single and double disc furrow openers for clay-loam and loamy soils.
  • Authors:
    • Fahed, S.
    • Rana, G.
    • Katerji, N.
  • Source: Hydrological Processes
  • Volume: 25
  • Issue: 1
  • Year: 2011
  • Summary: In this paper two models are presented for calculating the hourly evapotranspiration lambda E (W m -2) using the Penman-Monteith equation. These models were tested on four irrigated crops (grass, soya bean, sweet sorghum and vineyard), with heights between 0.1 and 2.2 m at the adult growth stage. In the first model (Katerji N, Perrier A. 1983. Modelisation de l'evapotranspiration reelle ETR d'une parcelle de luzerne: role d'un coefficient cultural. Agronomie 3(6): 513-521, KP model), the canopy resistance rc is parameterized by a semi-empirical approach. In the second model (Todorovic M. 1999. Single-layer evapotranspiration model with variable canopy resistance. Journal of Irrigation and Drainage Engineering-ASCE 125: 235-245, TD model), the resistance rc is parameterized by a mechanistic model. These two approaches are critically analysed with respect to the underlying hypotheses and the limitations of their practical application. In the case of the KP model, the mean slope between measured and calculated values of lambda E was 1.010.6 and the relative correlation coefficients r2 ranged between 0.8 and 0.93. The observed differences in slopes, between 0.96 and 1.07, were not associated with the crop height. This model seemed to be applicable to all the crops examined. In the case of the TD model, the observed slope between measured and calculated values of lambda E for the grass canopy was 0.79. For the other crops, it varied between 1.24 and 1.34. In all the situations examined, the values of r2 ranged between 0.73 and 0.92. The TD model underestimated lambda E in the case of grass and overestimated it in the cases of the other three crops. The under- or overestimation of lambda E in the TD model were due: (i) to some inaccuracies in the theory of this model, (ii) to not taking into account the effect of aerodynamic resistance ra in the canopy resistance modelling. Therefore, the values of rc were under- or overestimated in consequence of mismatching the crop height. The high value of air vapour pressure deficit also contributed to the overestimation of lambda E, mainly for the tallest crop. The results clarify aspects of the scientific controversy in the literature about the mechanistic and semi-empirical approaches for estimating lambda E. From the practical point of view the results also present ways for identifying the most appropriate approach for the experimental situations encountered.