• Authors:
    • Gonzalez, B.
    • Rodriguez, E.
    • Campos, M.
  • Source: Bulletin of Insectology
  • Volume: 65
  • Issue: 1
  • Year: 2012
  • Summary: The use of cover crops is the most effective method to combat soil degradation due to erosion in olive cropping in Spain. Within the framework of Integrated Pest Management (IPM), a compelling question is how cover crops would affect elements of the olive-agroecosystem such as natural enemies. Accordingly, the objective of this study was to examine the effects of cereal cover cropping on natural enemy communities in olive groves. Samples of the anthropod communities were collected in olive groves under tillage and cover cropping systems at five different locations in the same province. Cereal cover crops significantly increased the abundance of parasitoids in the olive canopy, especially Ageniaspis fuscicollis Dalman (Hymenoptera Encyrtidae) a parasitoid of the olive moth Prays oleae Bernard (Lepidoptera Yponomeutidae), the most common insect pest of olive trees. However, parasitoid abundance and structure depended on olive grove location suggesting the importance of crop surroundings in parasitoid community dynamics. Predators numbers were slightly higher in tilled olive groves but no significant differences were found between the two soil management systems.
  • Authors:
    • Marins, A. C. de
    • Souza, S. N. M. de
    • Santos, R. F.
    • Veloso, G.
    • Secco, D.
    • Rosa, H. A.
    • Borsoi, A.
  • Source: Food, Agriculture and Environment (JFAE)
  • Volume: 10
  • Issue: 2 part 3
  • Year: 2012
  • Summary: Certain soil physical characteristics such as resistance to penetration (Rs) and bulk density (Ds) are extremely important, and are also indicators of the soil structural quality. This paper aims at evaluating the use of four cover crop species in the reduction of density and soil resistance to penetration in areas where a no-till farming system is applied. The so-called "regenerator" species, which act in soil structure, were considered treatments, and consisted of four species: showy rattlebox ( Crotalaria spectabilis), moha grass ( Setaria italica), pigeon pea ( Cajanus cajan), sorghum ( Sorghum bicolor), and yet the control (an area without crops). Soil bulk density evaluations were carried out according to the methodology recommended by EMBRAPA, in the following depths: 0.0-0.1, 0.1-0.2 and 0.2-0.3 m. Sampling was carried out with five replications for the crop row and five for the spacing between each crop row, in each experimental unit (5 m * 5 m), up to 0.40 m in depth. An experimental design was 5*4*2 factorial, meaning 5 treatments, 4 depths and 2 sampling conditions. The species studied, especially the pigeon pea and the sorghum, showed a great potential to improve soil structural state, for they showed figures to Ds and Rs that were lower than the ones from the area without crops.
  • Authors:
    • Netland, J.
    • Brandsaeter, L. O.
    • Sjursen, H.
  • Source: Acta Agriculturae Scandinavica, Section B - Soil & Plant Science
  • Volume: 62
  • Issue: 2
  • Year: 2012
  • Summary: Cover crops can be used to reduce leaching and erosion, introduce variability into crop rotation and fix nitrogen (N) for use by the main crops, less is however known about effects on weeds. The effects on weed seed bank, weed growth and grain yield of 4 years of annual undersown clover and ryegrass alone and in combination, and one of the 4 years with clover or clover + grass as green manure, were studied in oat and spring wheat at two experimental sites in south-eastern Norway. These treatments were compared with no undersown crop (control) and with weed harrowing. In contrast to many results in the literature, the undersown clover in this study did not suppress annual weeds, but fertilized the weeds as well as the cereals. Undersown clover resulted in a statistically significant increase of grain yield at the two sites to 116% and 121% of control. During the 4-year period relative seed bank and density of emerged weed (dominated by Spergula arvensis) increased significantly about 4.5 and 10 times respectively in the undersown clover plots at Apelsvoll. At Kise both ryegrass alone and ryegrass mixed with clover significantly suppressed the weed biomass to 70% and 74% of control respectively. It is concluded that fertilization effects of undersown clover may have dominated and overriden the competitive effects. One whole-season clover green manure did not increase the mean yield, but resulted in a significant drop in seed bank size the following year, because of limited weed establishment in an established ley. Only a slight increase in average weed biomass was observed at one of the two experimental sites. The weed seed bank and the weed biomass were essentially kept at steady state during the experimental period in harrowed plots, but harrowing decreased grain yield significantly at both sites.
  • Authors:
    • Vencill, W.
    • Schomberg, H. H.
    • Phatak, S. C.
    • Díaz-Pérez, J. C.
    • Skinner, E. M.
  • Source: HortScience
  • Volume: 47
  • Issue: 1
  • Year: 2012
  • Summary: Sunnhemp (Crotalaria juncea L.) is a tropical legume that could be an important summer cover crop in the southeastern United States, but it has the potential for suppressing both crops and weeds. Allelopathic effects of sunnhemp on weeds, vegetable crops, and cover crops were evaluated in greenhouse and growth chamber experiments. In the greenhouse, ground dried sunnhemp residues (applied mixed with the soil at 1.6% w/w) reduced percent germination of lettuce (Lactuca sativa L.) and smooth pigweed (Amaranthus hybridus L.) to a similar degree as that caused by cereal rye (Secale cereale L. subsp. cereale) residues (applied at 1.5% w/w). The allelopathic activity of sunnhemp was greater in the leaves than in the roots or stems. In growth chamber studies, the mean reduction in germination (relative to the control) caused by sunnhemp leaf aqueous extracts was: bell pepper (100%), tomato (100%), onion (95%), turnip (69%), okra (49%), cowpea (39%), collard (34%), cereal rye (22%), sweet corn (14%), Austrian winter pea (10%), crimson clover (8%), cucumber (2%), and winter wheat (2%). In lettuce, carrot, smooth pigweed, and annual ryegrass, sunnhemp aqueous leaf extract reduced seedling length to a degree similar as that produced by rye aqueous leaf extract. Sicklepod [Senna obtusifolia (L.) H.S. Irwin & Barneby CA] germination was not inhibited by any of the sunnhemp or rye aqueous extracts. In conclusion, sunnhemp reduced the germination percentage and seedling growth of various crop species. The allelochemical activity in sunnhemp was primarily in the leaves and remained active at least 16 d after harvest under dry conditions. Sunnhemp's allelochemical effect may be a useful attribute for weed management in sustainable production systems. However, plant growth in the field in crops such as bell pepper, tomato, onion, and turnip may be impacted as a result of allelopathic activity of sunnhemp residues. Thus, weed management may be more effective when sunnhemp is grown in rotation with crops that tolerate the allelochemicals from sunnhemp, resulting in optimization of the rotation effects.
  • Authors:
    • Pereira Nóbrega, L. H.
    • dos Santos, D.
    • Gonçalves Junior, A. C.
    • de Souza, E. G.
    • Tavares-Silva, C. A.
  • Source: Food, Agriculture and Environment (JFAE)
  • Volume: 10
  • Issue: 1
  • Year: 2012
  • Summary: No-tillage system is an alternative agricultural management to protect soil; however, the cover crops association is required in crop rotation or succession, allowing an amount of nutrients supply and organic matter to soil through mineralization of plant residues. Thus, this trial aimed at evaluating the effects of crops succession on soybean yield and on chemical properties of soil: calcium, magnesium and aluminium saturation (m%). The trial was carried out in Cafelandia (PR) city, in a typical eutrophic red latosol, from June 2008 to March 2010. The experimental design was completely randomized with five treatments: black oat; consortium 1 (turnip and black oat); consortium 2 (turnip, black oat and common vetch), wheat and fallow, with six replications in a 2 ha area, in four periods during two agricultural harvests, in order to record chemical analyses of soil in a depth from 0 to 0.2 m. The cover crops management was with roll-knife, while wheat was harvested with an automotive combine. Soybean was sown in summer and its yield was determined for each treatment. Winter cover crops influenced on Mg concentration in soil when evaluated after soybean harvest in 2010, so that, black oat and the second consortium were the main responsible for such increase, although, the treatments showed no effect on soybean yield during the 2009/2010 harvest.
  • Authors:
    • Dresboll, D. B.
    • Thorup-Kristensen, K.
    • Kristensen, H. L.
  • Source: European Journal of Agronomy
  • Volume: 37
  • Issue: 1
  • Year: 2012
  • Summary: One of the core ideas behind organic production is that cropping systems should be less dependent on import of resources, and minimize negative effects on the surrounding environment compared to conventional production. However, even when clearly complying with regulations for organic production, it is not always obvious that these goals are reached. As an example, strong dependence on import of manure is often seen in current organic production, especially in systems producing high value crops such as vegetable crops. The aim of the present study was to test novel approaches to organic rotations, designed to reduce the reliance on import of external resources significantly. We compared a conventional system (C) and an organic system relying on manure import for soil fertility (O1) to two novel systems (O2 and O3) all based on the same crop rotation. The O2 and O3 systems represented new versions of the organic rotation, both relying on green manures and catch crops grown during the autumn after the main crop as their main source of soil fertility, and the O3 system further leaving rows of the green manures to grow as intercrops between vegetable rows to improve the conditions for biodiversity and natural pest regulation in the crops. Reliance on resource import to the systems differed, with average annual import of nitrogen fertilizers of 149, 85, 25 and 25 kg N ha(-1) in the C, O1, O2 and O3 systems, respectively. As expected, the crop yields were lower in the organic system. It differed strongly among crop species, but on average the organic crops yielded c. 82% of conventional yields in all three organic systems, when calculated based on the area actually grown with the main crops. In the O3 system some of the area of the vegetable fields was allocated to intercrops, so vegetable yields calculated based on total land area was only 63% of conventional yields. Differences in quality parameters of the harvested crops, i.e. nutrient content, dry matter content or damages by pests or diseases were few and not systematic, whereas clear effects on nutrient balances and nitrogen leaching indicators were found. Root growth of all crops was studied in the C and O2 system, but only few effects of cropping system on root growth was observed. However, the addition of green manures to the systems almost doubled the average soil exploration by active root systems during the rotation from only 21% in C to 38% in O2 when measured to 2.4m depth. This relates well to the observed differences in subsoil inorganic N content (N-inorg. 1-2 m depth) across the whole rotation (74 and 61 kg N ha(-1) in C and O1 vs. only 22 and 21 kg N ha(-1) in O2 and O3), indicating a strongly reduced N leaching loss in the two systems based on fertility building crops (green manures and catch crops). In short, the main distinctions were not observed between organic and conventional systems (i.e. C vs. O1, O2 and O3). but between systems based mainly on nutrient import vs. systems based mainly on fertility building crops (C and O1 vs. O2 and O3). (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Satkus, A.
    • Velykis, A.
  • Source: Žemdirbystė (Agriculture)
  • Volume: 99
  • Issue: 1
  • Year: 2012
  • Summary: Research was done at the Joniskelis Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry on a clay loam Endocalcari-Endohypogleyic Cambisol (CMg-n-w-can). The objective of this study was to determine the effects of reduced (shallow ploughing and ploughless tillage) tillage as well as its combinations with supplementary agronomic practices, improving soil conditions - incorporation of lime sludge, cover crop (mixture of white mustard and oilseed radish) for green manure and mulch on the emergence, growth and development of field pea (Pisum sativum L.) crop. Data revealed that shallow ploughing caused the worst field pea emergence in 2008. Ploughless tillage in combination with lime sludge incorporation resulted in a significantly higher soil water content in seedbed layer (0-5 cm) directly after field pea sowing in 2009, better field pea germination within the prolonged droughty post-sowing periods (18 and 20 days respectively in 2008 and 2009) and higher grain yield in 2008 as compared to deep ploughing. Due to the ploughless tillage together with incorporation of the cover crop biomass for the green manure late in autumn, significantly higher soil water content was registered in the seedbed directly after sowing in 2010 and at 5-15 cm depth according to the average data of 2008-2010; however the emergence and growth of field pea under droughty conditions were worse, and yield decreased in 2009 and 2010. Application of ploughless tillage with no supplementary practices resulted in significantly higher soil water content in seedbed directly after field pea sowing in 2010; however, in field pea yield decreased in 2009. Cover crop winter mulch without tillage in autumn led to a significantly higher soil water content in the seedbed directly after sowing in 2010, while the soil water content after field pea emergence at 5-15 cm depth in 2008 and at 15-25 cm depth according to the average data of 2008-2010 was lower, seedbed structure was mostly worse, field pea growth and development were poor and crop yield was lower in all years of study as compared to deep ploughing. Rapid capillary water movement, characteristic of clay loam with predominant silty fractions, could lead to a higher drying of soil layers unloosened in the autumn. Field pea yield was influenced by the amount of rainfall during one month after sowing in a droughty year 2008 and by the soil structure in a seedbed in 2009.
  • Authors:
    • Weirich Neto, P. H.
    • Lopes, A. R. C.
  • Source: Engenharia Agrícola
  • Volume: 32
  • Issue: 2
  • Year: 2012
  • Summary: The seeding process was the operation that suffered the most changes in no-tillage system due the cover crop soil and new particle soil arrangement. The objective of this study was to verify the effects of loads applied to the wheels and adjustments of sowing depth on seedling emergence of corn in no-tillage system. The experimental design was completely randomized with a factorial arrangement 5*4, with five loads applied to the wheels and four theoretical sowing depth adjustments. The real sowing depth increased in the lower theoretical depth and decreased in the higher theoretical depth, due to the compaction loads. Regarding the time of emergence, loads applied had not influence at the greater depths. Emergence time decreased with the load increase in the lower depths. Thus, the adjustment of the compactor wheels can influence in the corn seeding process.
  • Authors:
    • Munoz-Carpena, R.
    • Gabriel, J. L.
    • Quemada, M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 155
  • Year: 2012
  • Summary: Using cover crops (CC) in semiarid irrigated areas is often limited by low nutrient and water-use efficiency. This work was conducted over 3.5 years to determine the effect on NO 3- leaching, water balance and soil mineral N accumulation of replacing fallow with CC in irrigated systems. Treatments studied during the maize ( Zea mays L.) intercrop period were: barley ( Hordeum vulgare L.), vetch ( Vicia villosa L.) and fallow. Soil water content was monitored daily to a depth of 1.3 m and used with the numerical model WAVE to describe the water balance. Determination of crop canopy parameters was based on digital image analysis, and root depth in capacitance sensor readings. Nitrate leaching was calculated multiplying drainage by the soil solution nitrate concentration. Soil mineral N was determined before sowing CC and maize. Over the study, cumulative nitrate leaching in the fallow, vetch, and barley was 346, 245, and 129 kg N-NO 3- ha -1, respectively; occurring more than 77% during the intercrop period. In dry winters, NO 3- accumulated in the topsoil, and CC controlled the NO 3- leaching during the initial maize growth stages. Vetch was less efficient than barley at controlling leaching, but enhanced soil N retention. The CC controlled NO 3- leaching and recycled N inside the cropping system.
  • Authors:
    • Lucas, S. T.
    • Weil, R. R.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 4
  • Year: 2012
  • Summary: Permanganate (KMnO 4) oxidizable C (POXC), an estimate of labile soil C, was evaluated for use as a soil test to identify soils that may respond positively to soil organic matter (SOM) management. We hypothesized that soils lower in POXC would be more likely than soils higher in POXC to show increased crop productivity in response to practices that increase SOM. At four sites, paired fields of the same soil but contrasting management history (cropping vs. sod) were studied. Fields with sod history tested higher in total organic C (TOC) and POXC than fields with cropped history. Permanganate-oxidizable C was strongly related to TOC ( r=0.94). We examined crop stover, grain, and biomass responses to two cover crop treatments within each field: winter rye ( Secale cereale L.) or no rye. After at least 1 yr of treatment, there was a significant negative correlation between relative stover response to rye and POXC ( r=-0.60) at sites with finer textured soils. After at least 2 yr of treatment, crop responses to rye showed a significant negative correlation with POXC and TOC. The strongest relationships to POXC occurred in the stover response at two sites with finer textured soils (Keedysville: r=-0.74; Holtwood: r=-0.84). Permanganate-oxidizable C was comparable to TOC at predicting crop responses to rye. These results suggest that POXC may be a useful test for identifying soils where improved SOM management is likely to improve productivity. The rapid, simple POXC methodology enables on-site or laboratory soil testing.