Subsequent Tillage Research Articles

Adaptation of multipurpose tractors to row spaces of cotton crops

In the Republic of Uzbekistan, cotton cultivation is carried out on row spacings of 60; 76 and 90 cm. The machine-tractor parks of cotton-growing farms are equipped with agricultural machines designed for these inter-row spacings and they are aggregated by tractors with gauges designed for them. Such a variety of tractor gauges creates the problem of mismatch between the gauge and row spacing when moving from one row spacing to another, increases the variety of spare parts and narrows the scope of their use only within one type of row spacing. The discrepancy between the gauge of serial universal row-crop tractors and the cultivated row spacing leads to damage to the plant and compaction of the soil in the area where its root system is located. Overconsolidation of the soil by more than 1.1 g/cm3 leads to a slowdown in plant growth and development, an increase in soil resistivity during subsequent tillage operations and, most importantly, a decrease in crop yield. Studies have established that, despite the variety of designs of known devices used to adjust the track, they change the track stepwise and in an insufficient range, as a result of which the tractor does not fit into the row spacing. To eliminate the shortcomings of the known methods for adjusting the track, a device has been developed for adapting the tractor running system to work on different row spacings. The developed device allows, without the use of attachments or interchangeable axle shafts and their casings, to accurately adapt the tractor’s running system to the aisle of crops cultivated by it, thereby eliminating the existing shortcomings of serial universal row-cultivator tractors. The article provides a description of the proposed technical solution and the method of its application.

Stripping as a snow retention method in the steppe conditions of Western Siberia

The process of snow cover formation on the fields with different surface conditions was studied. The research was conducted in the spring of 2022 in the steppe farming zone of the Omsk region. The effect of high plant stand of cereal crops remaining after harvesting by standing crop stripping on the amount of snow cover and the volume of spring moisture accumulation in the soil as a reserve for increasing the yield in the steppe regions of Western Siberia is considered. The results of determining the height of snow cover on a fallow field (complete fallow), on fields under grain crops harvested by different methods: with a direct harvester followed by flat tillage; with a direct harvester without subsequent tillage; with a combing harvester at the height of the stem during harvesting up to 0.55 m are presented. In the course of the study it was found that during harvesting by the stripping method, the moisture reserves in the snow cover were 2.2 times higher compared to the stubble background, 3.7 times higher compared to the stubble background treated with a flat cutter, and 4.1 times higher compared to the fallow field (control). Based on the data obtained, the conclusion is made about the possibility of using this method to form the conditions for moisture accumulation in the arid steppe zone without additional measures for snow retention, which should have a positive impact not only on the yield of cultivated crops, but also on the agro-economic indicators.

Deforestation effects on soil properties and erosion: a case study in the central Rif, Morocco

In the Central Rif in the north of Morocco, forest ecosystems have suffered a very sharp decline in favor of crops. Deforestation followed by cultivation illustrates the important environmental, economic and social roles of forests. The objective of this work is to assess the impact of deforestation on soil properties and erosion in the southern Central Rif. The loss of fertility of cleared soils was assessed using physico-chemical analyses after 2, 8 and 20 years of cultivation. A manual rainfall simulation was used to assess the impact of cultivation on the hydrodynamic behavior of the soil. The results show that the conversion of forests into agricultural areas has multiple consequences on the natural system. The general trend of soil texture elements after cultivation shows a significant increase in sand content, and a decrease in clay and silt content. Soil erodibility measured by USLE-K factor increased 3.5 times in the cultivated soil for 20 yrs. compared to the forest soil. Subsequent tillage of cultivated land increases bulk density and fragments large aggregates into smaller ones. Cultivation for 8 and 20 yr decreased SOM by 41 and 82% respectively. Total Nitrogen decreased by 45%, acidity increased by 0.8 unit after 20 years of cultivation. Conversion of natural forest to agricultural land significantly increases soil erosion. The erosion rate becomes higher in the cultivated the 8 and 20 yr cultivation, with an average of 219.60 ± 19.3 and 989.17 ± 68.4 g m-2 h-1 respectively. This degradation hinders agricultural productivity, leading farmers to abandon the land and seek new plots at the expense of forests to meet their agricultural land needs.

Routine On-farm Soil Tillage Helps Control Asparagus Fly (Plioreocepta Poeciloptera)

Asparagus fly (Plioreocepta poeciloptera (Schrank, 1776)) is a serious pest in German asparagus (Asparagus officinalis L.) production. To evaluate the effects of different routine on-farm soil tillage measures on the number of flies emerging the following spring, asparagus fields in Lower Saxony, Germany, were investigated. Soil samples were taken before and after tillage in autumn 2017 and autumn 2018. Investigations were also conducted in both years on the effect that the soil depth at which asparagus fly pupae were buried had on the emergence of adult flies.This study revealed that the number of emerging flies was not reduced by mulching, but was significantly reduced by subsequent tillage and/or tillage and dam formation. The emergence rate of adult flies was significantly reduced the deeper the pupae had been buried the previous autumn. The effects also depended on the year. The highest mean emergence rate observed was 68% and 45% for pupae buried at a depth of 10 cm and 20 cm, respectively. In conclusion, the key mechanism causing a decrease in asparagus fly population the following spring through routine on-farm tillage could be the burial of pupae when forming dams. Routine on-farm soil tillage can be regarded as a physical measure for controlling asparagus fly and is therefore an essential tool in the integrated pest management of asparagus production.

Совершенствование технологии лесовосстановления на вырубках с применением энергонасыщенных тракторов

Currently applied partial reforestation in cuttings and removal of stumps by uprooting have a number of significant technological, environmental and economic disadvantages. These are removal of the humus layer of soil outside the cleared strips, compaction and reduction of soil porosity; formation of understump holes and their local waterlogging; littering of noncleared belts of trees between strips with felling debris and uprooted stumps; low productivity of uprooting machines and high energy consumption of stump uprooting; termination of agrotechnical tending after 2–3 years after planting and impossibility of cleaning stands due to their obstruction for tractor units; low level of traction force of special forest tractors and their insufficient power for uprooting stumps. Technology, machines and tools for reforestation in cuttings become the subjects of the research. The aim of the research is to provide a comprehensive mechanization of the reforestation process in order to improve work productivity, reduce energy and material consumption of the technology and create conditions for the effective use of machines and tools in combination with energy-efficient tractors of the traction-energy concept, ensuring the elimination of harmful effects on soil and plants ecology. The results of achieving the set aim and objectives are substantiation of forestry and ecological, technical, and economic feasibility of using the technology based on the complete clearing of cuttings from felling residues, dead wood and coppice of shrub vegetation by their crushing using mobile mulchers; removal of stumps in cuttings through crushing them at a depth of 0.15–0.20 m by an upgraded MUP-4A machine with scattering chips over the planting area and subsequent continuous tillage with a disk harrow BDK-2.5. Harmful effects on the ecology of soil and plants are practically eliminated with an increase in productivity, and the grinded woody biomass mixed with the soil turns into an organic fertilizer. The elimination of mechanical obstacles such as felling residues, fallen trees and stumps makes it possible to effectively use energy-efficient tractors by combining technological operations and performing them in one pass of the unit, as well as increasing the working width and operating speeds. Conditions for efficient operation of forestry machines and tools on tractormotor traction to protect the forest from pests, diseases, and fires, and for mechanization of various types of thinning are being created. For citation: Bartenev I.M., Drapalyuk M.V. Improving the Technology of Reforestation in Cuttings with the Use of Energy-Efficient Tractors. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 117–133. DOI: 10.37482/0536-1036-2021-5-117-133

Neoteinic and dwarf weeds: distribution, biology, control

Goal. To determine the features of the distribution, occurrence, biology, harmfulness and methods of control of neoteinic and dwarf weeds in the conditions of the Left Bank Steppе.
 Methods. The studies were carried out during 2017—2020 by route and expeditionary surveys. Weeds were counted 6—12 times.
 Results. Neoteinic forms and dwarf plants were found in agricultural crops throughout the growing season. The number of weeds prone to neotenia made up 43 species. The duration of the period from germination to seed ripening varied in them within 14—34 days. Plant height was 2.8—12.4 cm. Their average seed productivity did not exceed 19—21 pcs. from the plant. The mass of 1000 seeds was 12—19% higher, and the germination rate was 21—34% higher than in conventional forms. At an average density of plants, up to 3.43—3.84 thousand pieces/m2 of seeds entered the soil. Stubble ploughing and subsequent basic tillage provided 100% control of them. Late autumn application of herbicides to control neoteinic and other annual weeds was impractical. Dwarf plant species in agrophytocenoses were represented by 27 species. The number of their seedlings in winter crops ranged from 11—16 to 237—334 pieces/ m2, for spring and row crops — from 37—53 to 365—489 pieces/m2. The height of the plants was 10.8—17.5 cm, and the seed productivity was from 6 to 609 pcs. With the density of these weeds at the level of 145—160 pcs/m2, they were consumed in crops of winter wheat 18.9 kg/hectare of nitrogen, 31.0 kg/hectare of phosphorus and 27.8 kg/hectare of potassium. Average water consumption was 141 m3/hectare. The loss of wheat grain was 0.48 t/h. In the fields for grain, cereals and row spring crops, high efficiency of control in all forms and types of weeds was achieved in a system of combination of soil cultivation, which included harrowing, seed bed preparation of autumn plows, as well as the use of herbicides. In the crops of winter wheat and barley, the maximum destruction of weeds was achieved from the use of leaf herbicides in autumn 10—12 days before the end of the growing season or at the beginning of the spring growing season.
 Conclusions. The main attention in the control system of neotenic and dwarf weeds belongs to the summer-autumn technological method by 1—2-fold stubble plowing. Additionally, in sowing of spring crops, they are destroyed in the system of pre-sowing soil cultivation in combination with herbicides, and in winter crops by the use of leaf herbicides in autumn or early spring.

Effects of farmyard manure application on dust emissions from arable soils

Particulate matter (PM), emitted during agricultural activities, could be a source for the atmospheric dispersal of pathogenic or antibiotic resistant bacteria when agricultural fields are fertilized with contaminated manure. The use of contaminated bedding material from chicken breeding as farmyard manure can initiate a releasing process for resistant bacteria into the environment. In this study, we focus on the physical processes of the release, regarding application and manure mixtures. The addition of several tons per hectare of organic manure to the topsoil has effects on the soil composition and should effect the dust emissions, if the same sorting effects are assumed such as for other organic particles. Based on dust measurements within an agricultural process chain from manure application, soil preparation to maize seeding, dust emissions were measured and PM10 emission factors (PM10 EFs) were derived using a standard dispersion model. The PM10 emissions during manure application ranged between 0.05 and 8.37 kg/ha, depending on the moisture content due to different pretreatments of the manure. In the subsequent tillage operations, a share of 0.39–0.59% of manure in the total PM10 could be determined. Our investigations show that particles in the PM10 fraction of manure origin are released within the entire process chain. These particles are small and light enough to be transported over long distances and be a potential risk for antibiotic resistant bacteria dispersal at remote places as human settlements, when they will deposit there.

Weed seedbank dynamics: Estimation and management in groundnut

Effective weed management necessitates sound knowledge of weed seedbank dynamics. The experiment was laid out in split plot design with three replications. The main plots have three residue management treatments and sub-plots comprised seven weed management treatments. Results revealed that highest pod yield (1.47 t/ha) was recorded under wheat residue incorporation fb soil solarization. Among weed management, the highest pod yield (1.68 t/ha) and haulm yield (3.35 t/ha) was recorded with weed free and unweeded check registered lowest pod yield (722 kg/ha). The lowest dry weight of weeds was obtained under wheat residue incorporation fb soil solarization and weed free. Wheat residue incorporation fb soil solarization depleted correspondingly 54 (25.32%), 10 (5.29%) and 32 (16.16%) seeds per core from the initial weed seedbank in 2014, 2015 and pooled results, respectively. The highest seedbank depletion was observed with weed free by depletion of 147 (68.37%), 123 (68.20%) and 135 (68.29%) weed seeds per core. Pendimethalin 900 g/ha as preemergence fb IC and HW at 45 DAS depleted 129 (59.84%), 103 (57.09%) and 116 (58.59%) weed seeds per core. Pendimethalin 900 g/ha as pre-emergence fb premix imazethapyr + imazamox 70 g/ha as post-emergence at 25 DAS depleted 126 (58.40%), 101 (55.86%) and 113 (57.24%) weed seeds per core and suicidal germination fb killing the weed flush by subsequent tillage fb IC and HW at 45 DAS depleted 116 (53.85%), 86 (47.64%) and 101 (51.01%) weed seeds per core in 2014, 2015 and pooled results, respectively as compared to the initial weed seedbank. While, unweeded check resulted in to addition of 609 (283.31%), 695 (384.16%) and 652 (329.41%) weed seeds per core sample (15 cm depth and 4 cm diameter) in the soil weed seedbank in comparison to initial weed seedbank.

Compaction and sowing date change soil physical properties and crop yield in a loamy temperate soil

Timing of tillage operations is of utmost importance in arable farming because tillage performed under inappropriate soil water conditions results in soil structural damage and creation of undesirable seedbeds for crop establishment and growth. In a field experiment on a loamy soil in Ås, Norway, we investigated the effect of compaction and sowing dates on (i) seedbed physical properties, (ii) crop yield, and (iii) the range of water contents for tillage. The experiment was established in 2014 and the same experimental treatments were repeated in 2015, 2016 and 2017. The sowing dates included early (A1), normal/timely (A2) and late (A3) sowing dates. The compaction treatments applied each year were done wheel-by-wheel by a MF 4225 tractor weighing 4.5 Mg with a single pass (B1) and compared with a control treatment (B0). This study reported soil physical properties for only 2016 and small grain cereal yield for the four years. The soil pore characteristics determined were soil bulk density (ρb), volumetric water content (θ), air-filled porosity (εa), air permeability (ka) and pore organization indices (PO1= ka/εa and PO2= ka/εa2); strength properties measured were tensile strength (Y), soil penetration resistance (PR), degree of soil fragmentation by drop-shatter test, and water contents for tillage by calculating the range of water content for tillage (ΔθRANGE). The interaction of compaction with sowing date, generally affected soil pore characteristics, particularly at 1–5 cm depth. The A1 treatment significantly affected the strength characteristics of seedbed by decreasing soil friability and increasing Y at 1–10 cm depth, and PR down to 27 cm depth. The A3 treatment decreased yield of spring-sown small grain cereal crops, but this may be ascribed to a shorter growing season rather than an influence of soil physical properties. The A1 and A3 decreased the range of water contents for tillage compared to the A2, although the difference was not significant at any of the depths studied. Findings of the study have practical implications for cropping regimes in colder climates where farmers can be faced with a short growing period by showing that cultivation in wet soil conditions such as early spring can adversely affect seedbed physical properties and soil workability for subsequent tillage operations.

ASSESSMENT OF SOIL PROPERTIES CHANGE UNDER EFFECT OF SOIL CULTIVATING AGRICULTURAL MACHINES

High-quality and timely soil cultivation allows forming the basis of the future crop and reducing costs of subsequent tillage operations. The structure of soil determines the energy intensity and quality of its mechanical treatment. The quality of soil treatment is determined by crumbling, mixing, leveling and compacting of the surface layer. To determine these parameters, different mathematical dependencies are used, allowing for calculation of varied accuracy degree. The article dwells on analysis of the existing and development of new dependencies, allowing to determine qualitative indicators of soil condition before and after the effect of operating units of agricultural machines. The article presents analysis of the existing dependencies, allowing to determine the effect degree of agricultural machines’ rollers on the soil. As a result of the studies, the possibility of using the Rozin-Rammler formula for determining the degree of soil crumbling is substantiated and dependency between stress and porosity coefficient was determined to substantiate the optimum pressure during soil cultivation rollers impact. The obtained results supplement the theory of impact of soil cultivation rollers on soil when designing combined soil cultivation agricultural machines.

Long-term N fertilization and conservation tillage practices conserve surface but not profile SOC stocks under semi-arid irrigated corn

No tillage (NT) and N fertilization can increase surface soil organic C (SOC) stocks, but these gains are frequently not observed through the soil profile and could be subject to loss through subsequent tillage events. We evaluated a long-term irrigated continuous corn no-tillage (NT) and N rate study near Fort Collins, CO that was split into continuous NT or strip till (ST) treatments after five years. We measured grain and residue yields yearly, and SOC and particulate organic matter C (POM-C) at baseline, 5 yrs and 11yrs later. Continuous NT depressed grain yields (10%) but not stover yields compared to ST. Continuous NT and increasing N fertilization rate increased surface (0–7.5cm) SOC stocks 10 and 13%, respectively, compared to baseline. Seven years of ST completely negated initial surface (0–7.5cm) SOC gain under NT and was only partially explained by POM-C loss (8–25%). All treatments lost between 14 and 19MgCha−1 in the soil profile (0–120cm) compared to baseline with no N or tillage effects. Soil C cycling appears to be rapid in this irrigated system, requiring greater C inputs to maintain SOC stocks. Effective conservation practices will need to balance crop yield, surface erosion protection, and profile-wide SOC stock losses.

Effect of wheel traffic on the physical properties of a Luvisol

The effects of machine traffic were assessed on a Luvisol in a temperate climate area in Belgium. Soil samples were taken from topsoil (0.07–0.25m) and subsoil (0.35–0.50m), on plots under long-term reduced tillage (RT) and conventional tillage (CT). Cone index (CI), bulk density (BD) and precompression stress (Pc) were chosen as indicators of mechanical strength. Mercury intrusion porosimetry was used to characterise the soil microporosity structure. It was presented in two forms: (i) cumulative pore volume vs. equivalent pore radius r, from which four classes of porosity were defined: r<0.2μm, 0.2≤r<9μm, 9≤r<73μm and r≥73μm and (ii) pore-size distribution (PSD). In the reference situation where there had been no recent passage of machines, the voids with 0.2≤r<9μm were the most important class in RT topsoil. The voids with r≥73μm represented the main porosity class in the topsoil of CT. In the subsoil, for both tillage systems, the porosity was almost equally distributed between voids with 0.2≤r<9μm and voids with r greater than 9μm.Machine traffic was carried out when the soil water content was close to the optimum Proctor. Although unfavourable, these wet conditions often occur during the beet harvesting period in Belgium. The highest modifications in soil structure (increase in BD and Pc, reduction of macroporosity r≥73μm) were observed in the topsoil of CT. More limited modifications were noticed in the soil structure of RT topsoil and subsoil layers but these latter are problematic in that the soil would no longer be loosened by subsequent tillage. These modifications could lead to soil consolidation as a result of wheel traffic year after year.

Effects of Soil Quality Arising from the Conversion of Intrazonal Grassland in an Agro-Pasturage Ecotone of China

Understanding the effects of land-use changes on soil property is crucial for the sustainable development in an agro-pastoral ecotone of China. Although grassland conversion is an important land-use change in northern China, most studies have focused on zonal grassland areas and the intrazonal grassland areas have been ignored, which is not climatic climax of natural grassland, because it is constrained by terrain, surface water, components of the earth surface and other ecological factors. The present study aims to determine the effects of the conversion of intrazonal grassland into cropland on soil properties in the Bashang area where a typical agro-pastoral ecotone of northern China is found. The results showed that intrazonal grassland conversion and subsequent tillage practices increased soil bulk density and decreased soil porosity, capillary moisture capacity, and soil nutrients content. Available soil zinc content in the study area was at extremely low level, which could not meet the need of crop growing based on the soil trace elements appraisal criteria of China. On the average, the conversion of intrazonal grassland into cropland led soil organic carbon density (SOCD) decreased from 22.49 kg m-2 to 13.24 kg m-2, and soil total nitrogen density (STND) from 2.23 kg m-2 to 1.27 kg m-2; that is, the meadow conversion resulted in a 41-43% reduction of SOCD and STND in 0–60 cm soil depth over about 20 years. To conserve the present status, the further conversion of grassland into cropland should be stopped, and encourage the restoration of cropped area into grassland to combat the soil desertification and degradation in the agro-pasturage ecotone of Northern China.

Reducing the germinable weed seedbank with soil disturbance and cover crops

Mirsky SB, Gallandt ER, Mortensen DA, Curran WS &amp; Shumway DL (2010). Reducing the germinable weed seedbank with soil disturbance and cover crops. Weed Research50, 341–352.SummaryEcologically based weed management relies heavily on a greater integration of cultural and mechanical control tactics than conventional weed management. As such, management outcomes are more dependent on biotic interactions among the crop, weed and methods of management. In this study, we assessed the influence of soil disturbance and cover cropping on the germinable seedbank of Chenopodium album, Abutilon theophrasti and Setaria spp. across a range of initial weed seedbank densities. Cover crop system treatments ranged from greater reliance on tillage at one extreme, to a greater reliance on cover cropping to accomplish weed suppression at the other. In general, seedbank losses to germination were highest when soil disturbance was associated with cover cropping. Of the five cover crop systems (1 year duration), the summer fallow and the yellow mustard/buckwheat/winter rape mixture consistently decreased the weed seedbank. The magnitude of decline in these high disturbance systems reached complete depletion of the Setaria spp. germinable seedbank and an 85% and 80% reduction for C. album and A. theophrasti respectively. Both systems included tilling the soil three to four times throughout the growing season. In contrast, treatments which involved less soil disturbance had weed escapes that set seed in one or more site years. Cover crop systems that stimulated weed seed germination and where weeds were either suppressed by the cover crop or where subsequent tillage provided control, resulted in the greatest weed seedbank declines.

Peanut Yield and Grade Responses to Timing of Bahiagrass Termination and Tillage in a Sod-based Crop Rotation

Abstract Rotation of row crops with perennial grasses has been shown to improve soil quality characteristics, decrease pest incidence, and increase crop yield. Experiments were conducted in Florida during 2006 and 2007 at Marianna and Quincy to determine effects of termination date and subsequent tillage of established bahiagrass (Paspalum notatum L.) on peanut (Arachis hypogea L.) yield and market grade characteristics when rotating from bahiagrass to a row crop. Treatments included two bahiagrass termination dates (fall vs. spring) and six tillage methods [strip-till (in-row subsoiling), disk plus moldboard plow, disk plus chisel, disk plus paratill plus strip-till, disk, and strip-till with 45 kg N/ha]. Bahiagrass termination timing did not affect soil mechanical resistance, peanut yield or market grade characteristics, including percentages of sound mature kernels, split kernels, other kernels, and hulls. Although significant differences in soil mechanical resistance were detected among tillage treatments, peanut yield did not differ among the tillage methods except for the disk alone in 2007 at Quincy. Strip-till peanut yield did not respond to N application. When pooled over termination timing, peanut yields in strip-till, disk plus moldboard plow, disk plus chisel, disk plus paratill plus strip-till, disk, and strip-till plus 45 N were 4830, 5000, 4810, 4810, 4770, and 4620 kg/ha, respectively. These results indicate that when using perennial grasses in sod-based rotations, farmers have a wide window from fall to spring to terminate bahiagrass for optimum peanut production regardless of tillage system.

Effects of age of cattle, turning technology and compost environment on disappearance of bone from mortality compost

As residual bones in mortality compost negatively impact subsequent tillage, two studies were performed. For the first study, windrows of mature cattle or calves were placed on a base of barley straw and covered with beef manure. Windrows were divided into two sections and turned at 3-month intervals. Approximately 5000 kg of finished compost per windrow was passed through a 6 mm trommel screen, with bones collected and weighed. Bone weight was 0.66% of mature cattle compost and 0.38% of calf compost on a dry matter basis, but did not differ after adjustment for weights of compost ingredients. In a subsequent study, four windrows were constructed containing mortalities, straw and beef manure (STATC) or straw, manure and slaughter waste (STATW). Also, straw, beef manure and slaughter waste was added to an 850 L rolling drum composter (DRUMW). Fresh bovine long-bones from calves were collected, weighed and embedded in the compost. Bones were retrieved and weighed when windrows were turned, or with DRUMW, after 8 weeks. Temperatures achieved followed the order STATW > STATC > DRUMW ( p < 0.05). Rate of bone disappearance followed a pattern identical to temperature, with the weight of bones in STATW declining by 53.7% during 7 weeks of composting. For STATC, temperatures were uniform over three composting periods, but bone disappearance was improved ( p < 0.05) when compost dry matter was lower (46%), as compared to 58%. Using a ratio of five parts manure to one part mortalities, results of this study demonstrated that residual bone was <1% of cured cattle compost and may be reduced by maintaining a high compost temperature and moisture content.

Pharmaceutical and personal care products in tile drainage following surface spreading and injection of dewatered municipal biosolids to an agricultural field

Land application of municipal biosolids can be a source of environmental contamination by pharmaceutical and personal care products (PPCPs). This study examined PPCP concentrations/temporally discrete mass loads in agricultural tile drainage systems where two applications of biosolids had previously taken place. The field plots received liquid municipal biosolids (LMB) in the fall of 2005 at an application rate of ∼ 93,500 L ha − 1 , and a second land application was conducted using dewatered municipal biosolids (DMB) applied at a rate of ∼ 8 Mt dw ha − 1 in the summer of 2006. The DMB land application treatments consisted of direct injection (DI) of the DMB beneath the soil surface at a nominal depth of ∼ 0.11 m, and surface spreading (SS) plus subsequent tillage incorporation of DMB in the topsoil (∼ 0.10 m depth). The PPCPs examined included eight pharmaceuticals (acetaminophen, fluoxetine, ibuprofen, gemfibrozil, naproxen, carbamazepine, atenolol, sulfamethoxazole), the nicotine metabolite cotinine, and two antibacterial personal care products triclosan and triclocarban. Residues of naproxen, cotinine, atenolol and triclosan originating from the fall 2005 LMB application were detected in tile water nearly nine months after application (triclocarban was not measured in 2005). There were no significant differences ( p > 0.05) in PPCP mass loads among the two DMB land application treatments (i.e., SS vs. DI); although, average PPCP mass loads late in the study season (> 100 days after application) were consistently higher for the DI treatment relative to the SS treatment. While the concentration of triclosan (∼ 14,000 ng g − 1 dw) in DMB was about twice that of triclocarban (∼ 8000 ng g − 1 dw), the average tile water concentrations for triclosan were much higher (43 ± 5 ng L − 1 ) than they were for triclocarban (0.73 ± 0.14 ng L − 1 ). Triclosan concentrations (maximum observed in 2006 ∼ 235 ng L − 1 ) in tile water resulting from land applications may warrant attention from a toxicological perspective.

Persistência de palhada e liberação de nutrientes do nabo forrageiro no plantio direto

A palhada das plantas de cobertura, mantida sobre o solo no plantio direto, representa uma reserva de nutrientes para cultivos subseqüentes. O objetivo deste trabalho foi avaliar a decomposição e a liberação de macronutrientes de resíduos de nabo forrageiro. O experimento foi realizado no campo, durante o ano de 1998, no Município de Marechal Cândido Rondon, PR. O nabo forrageiro foi dessecado e manejado com rolo-faca 30 dias após a emergência. Avaliaram-se a persistência de palhada e a liberação de nutrientes dos resíduos aos 0, 13, 35 e 53 dias após o manejo. O delineamento experimental foi de blocos casualizados, com quatro repetições. O nabo forrageiro produziu, até o estádio de pré-florescimento, elevada quantidade de massa seca da parte aérea em cultivo de inverno (2.938 kg ha-1), acumulando 57,2, 15,3, 85,7, 37,4, 12,5 e 14,0 kg ha-1, respectivamente, de N, P, K, Ca, Mg e S. O manejo do nabo forrageiro no estádio de pré-florescimento apresenta rápida degradação da palhada, acarretando liberação de quantidades significativas de macronutrientes. Os nutrientes disponibilizados em maior quantidade e velocidade para a cultura subseqüente, são o K e o N. A maior velocidade de liberação de macronutrientes pelo nabo forrageiro ocorre no período compreendido entre 10 e 20 dias após o manejo da fitomassa.

Effect of red clover ( Trifolium pratense L.) kill with glyphosate on tillage implement draft

Forages are often used in crop rotations in eastern Canada to both improve soil structure, add soil organic matter, and provide livestock feed. After the last cut of forage has been harvested in the forage year, the forage regrowth is usually killed with the non-selective herbicide glyphosate prior to fall tillage. Producers have noticed lower tractor power requirements for primary tillage for areas treated with glyphosate compared to non-treated areas. Field experiments were conducted over 2 years on a fine sandy loam soil near Charlottetown, PEI, Canada to measure the effect of red clover ( Trifolium pratense L.) kill by glyphosate on implement draft requirements in a subsequent tillage operation. Plots were established in a field of red clover, with three glyphosate treatments, early, late, and control (none). The glyphosate was applied with a field sprayer at the recommended rate of 0.9 kg a.i. ha −1. Draft measurements for a chisel plow at three nominal depths, 70, 140 and 210 mm, and for a moldboard plow at nominal 170 mm depth were made using an instrumented research tractor. In 2000, results showed a reduction in draft of 20, 25 and 18% for a chisel plow operating at 70, 140 and 210 mm nominal depths, respectively, and a 12% reduction in draft for a moldboard plow following the glyphosate treatment. In 1999, the treatment effect was not significant ( P>0.05) for the moldboard plow, and all but one chisel plow depth. However, there was a trend towards lower draft for both plows accompanying the glyphosate treatment. It is suggested that the reduction in tillage implement draft was due to breakdown of tissue structure and loss of mechanical strength of the plant roots accompanying translocation of glyhposate into the plant roots.

Population dynamics of volunteer oilseed rape ( Brassica napus L.) affected by tillage

Volunteer plants of oilseed rape ( Brassica napus L.) from persistent seeds in soil can affect subsequent crops. Apart from the agricultural disadvantages, the environment and the marketing of the seeds may also be affected, particularly if plants with special ingredients or genetically modified (gm) plants are grown. In order to investigate the influence of soil cultivation and genotype on seed persistence and gene flow via volunteers, a field experiment was set up testing four tillage treatments and two cultivars in a split-plot design. The cultivars tested were near-isogenic to two gm cultivars. To simulate harvesting losses, 10 000 seeds m −2 were broadcast on a soil in July. The subsequent tillage treatments were combinations of immediate or delayed stubble tillage by a rotary tiller, primary tillage with plough or cultivator, or zero tillage. Over the following year, the fate of the seeds was determined. Immediate stubble tillage with following cultivator or plough resulted in 586 resp. 246 seeds m −2 in the soil seed bank. After delayed stubble tillage with following plough, 76 seeds m −2 were found, and no soil seed bank was built up in the zero tillage treatment. Nevertheless, in the zero tillage treatment, several robust volunteer plants survived the herbicide application before the direct drilling in autumn until following spring. In the zero tillage treatment and in the cultivator treatment, 0.19 volunteers m −2 resp. 0.06 volunteers m −2 flowered simultaneously to ordinarily sown oilseed rape in the following crop of winter wheat and produced 73 resp. 18 seeds m −2. Delayed stubble tillage reduced the risk of gene escape via the soil seed bank, while zero tillage resulted in the highest risk of gene escape by pollen and by production of a new generation of seeds. In terms of a labelling threshold for gm food this number of seeds would be below the threshold of 0.9% of transgenic parts in conventially bred food or feed.