Tilled Treatment Research Articles

Mulch and Grass Cover Unevenly Halt Runoff Initiation and Sediment Detachment during the Growing Season of Hazelnut (Corylus avellana L.) in Croatia

Hazelnut orchards are popular for cropping on sloped sites, which are often highly erodible. This study aimed to assess the impact of soil management and season in a hazelnut orchard on soil properties and hydrological response. Three treatments (Tilled, Straw, and Grass) were established in Munije (Croatia) on Stagnosol. In Spring, Summer, and Fall, a rainfall simulation was performed (intensity of 58 mm h−1 for 30 min). Results reveal higher water stable aggregate values were observed for the Straw treatment in all seasons. Higher soil organic matter (SOM) content was noticed for the Grass treatment in all seasons, while lower values were recorded for the Tilled treatment. Sediment loss in Summer was up to 650% and 1300% higher for the Tilled treatment compared with the Straw and Grass treatments. This study strengthens the comprehension of utilizing a permanent ground cover in hazelnut orchards as a sustainable practice, contributing to the mitigation of soil erosion processes and the improvement of soil properties. The Straw treatment is a viable option since it increases soil stability and SOM, consequently preventing high soil erosion.

Straw Mulch Application Enhanced Soil Properties and Reduced Diffuse Pollution at a Steep Vineyard in Istria (Croatia)

Straw mulching is a sustainable practice used to control soil erosion. However, different doses of mulch affect the efficiency of straw conservation. This study presents detailed research on how soil physicochemical properties and the hydrological response react to different types of vineyard soil management (Tilled, Grass, Low Straw, High Straw) and seasons (spring, summer, autumn) under conventional management on Anthrosols in Mediterranean conditions. To assess soil properties, core samples and disturbed samples were taken from the topsoil layer (0–10 cm). To evaluate erosion rates, a rainfall simulation experiment was conducted (58 mm h−1 for 30 min) with 10 replicates per treatment and season (120 in total). The results show higher water-stable aggregates (WSA) and soil organic matter (SOM) and lower bulk density (BD) in the mulch and grass treatment groups compared with the Tilled treatment group. High Straw treatment successfully mitigated runoff, while other treatments had significantly higher runoff that triggered sediment loss (SL) and translocation of P, K, Zn and Ni down the slope. There were 254% and 520% higher K losses with Tilled treatment in autumn compared with Low Straw and Grass treatments, respectively. Statistical analysis showed a strong association between element loss and SL, which indicates an ecological threat in degraded and endangered vineyards. Mulch application and grass cover reduce the vulnerability of vineyards, reduce evaporation, act as insulation against high temperatures, reduce erosion and suppress weed growth. The mulch dosage varies depending on the goals and conditions of the vineyard; thus, lower mulch dosage (2 t/ha) is appropriate when soil conditions are favourable and there is no significant need for moisture retention, while higher mulch dosage is necessary in dry regions to maintain soil moisture during high-temperature periods, as well as in sloped areas subjected to erosion.

Variation in soil organic carbon over time in no-till versus minimum tillage dryland wheat-fallow

Interest in soil organic carbon (SOC) levels is focused on both soil quality and sequestering carbon from the atmosphere. Farmers have developed minimum tillage systems and no-till systems. This study carefully measured SOC at three sites where long-term, randomized, replicated studies compared minimum tillage and no-till rotations in the low-precipitation inland Pacific Northwest, USA. To overcome seasonal, annual, and rotational effects, a soil sample was taken from each plot monthly for three years. The top 250 kg m-2 dry soil mass (representing the 0- to 20-cm depth) from each core was analyzed for SOC. Averages of monthly samples revealed the tilled treatment had 7.21 g kg-1 of SOC compared to 7.04 for the no-till treatment (p < 0.004). Examining variation month-to-month, 93% of sample variation was due to sample date, and 7% due to blocks (replications) within sites. Of 77 individual site-by-date samples, only six produced significant t-tests (p < 0.05) but SOC differences were 46–31 in favor of tillage and those 46 had larger differences. Power calculations estimated 34–100 samples would be required to detect a relative difference of 5% given the data’s standard deviation. Soil water and soil temperature to 30 cm was measured at the time of sampling, and while no-till more often had greater water, temperature differences were inconsistent. We conclude that no-till did not result in more soil carbon in these systems and judicious tillage is an option for sustainable production.

Soil management and seasonality impact on soil properties and soil erosion in steep vineyards of north-western Croatia

Abstract In order to mitigate vineyard degradation, we study different soil management to obtain the most suitable practices. To study the effects of water erosion on vineyards, a rainfall experiment (58 mm h-1 for 30 min) was applied on Anthrosols in humid conditions to assess the impact of treatment (Tilled, Straw and Grass) and season (Spring and Summer). Higher bulk density (BD) and soil water content (SWC) were on the Straw treatment in the Spring period. Also, the Tilled and Grass treatment noticed higher mean weight diameter (MWD) and water-stable aggregates (WSA). In the Summer, BD, SWC and MWD were significantly higher on the Grass treatment. Higher values of time to ponding (TP) and time to runoff (TR) in Spring were recorded on the Grass treatment, Runoff was higher on the Straw treatment. Higher sediment concentration (SC) and soil loss (SL) were noticed during the Tilled treatment. In the Summer period, TP was higher on the Straw treatment, while TR and Runoff were higher on the Straw, SC and SL on the Tilled treatment. This study confirms the positive effects of grass cover and straw mulching as a sustainable agricultural practice in sloped vineyards of north-western Croatia.

Sustainable Intensification of a Rice-Maize System through Conservation Agriculture to Enhance System Productivity in Southern India.

Integrated management of rice–maize systems is an emerging challenge in southern India due to improper rice residues and tillage management in maize crops. Conservation agriculture (CA) practices such as a reduced tillage and maintaining stubble mulch may hold the potential to increase yields, reduce crop establishment costs and increase farm incomes. A five-year trial was performed to study the effect of different CA and establishment methods in rice on system productivity, profitability, and soil carbon status in a rice–maize system. In the rainy season, the trial consisted of two main treatments: (i) normal manual transplanting and (ii) direct-wet seeding, and three sub-main treatments at different sowing dates with fifteen day intervals. In addition, in the winter season, two tillage treatments (conventional and minimum tillage) were imposed over the rainy season treatments. Both rice and maize were grown under irrigated conditions. The results showed that sowing times at 15 day intervals did not impact the yield significantly. Transplanted rice obtained a significantly higher grain yield during the first four years, but in the last year, the yield was similar in both of the establishment methods. In the winter season, conventional tilled maize recorded a higher cob yield than under the minimum tilled treatment, except for the last year, where both the tillage treatment effects were the same. System productivity of CA-based minimum tilled rice–maize was inferior during the first three years but was superior to the conventionally tilled method in the fourth and fifth year. Pooled analysis revealed that the conventionally tilled rice–maize system resulted in a similar system productivity as that of the CA during the study period. The cost–benefit analysis revealed that transplanted rice and conventionally tilled maize fetched higher net returns of INR 111,074 and INR 101,658/ha, respectively, over the direct-wet seeded rice and CA. In addition, the 15 July rice sown followed by the maize system led to an increase in irrigation water productivity by 15.7%, and the total water (irrigation + rainfall) productivity by 27.1% in the maize crop compared with the 30 July sown system. The CA-based rice–maize system resulted in a significantly higher very labile (0.194%) and labile (0.196%) carbon concentration at a 0–5 cm depth of soil compared to those under the conventional system. Thus, CA can be recommended for southern India and similar agro-ecological tropic and sub-tropic conditions. This system can be followed with appropriate location-specific modification in South-Asian countries, where crop yields and soil health are declining as a result of continuous cereal–cereal crop rotation.

Spring-planted cover crops for weed control in soybean

AbstractReplacing tillage with cover crops (CC) for weed management in corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] systems with mechanical weed control has many soil health benefits but in the western Corn Belt, CC establishment after harvest is hampered by cold temperatures, limited labor and few compatible CC species. Spring-planted CC may be an alternative, but information is lacking on suitable CC species. Our objective was to evaluate four spring-planted CC with respect to biomass production and weed suppression, concurrent with CC growth and post-termination. Cover crop species tested were oat (Avena sativa L.), barley (Hordeum vulgare L.), brown mustard [Brassica juncea (L.) Czern.] and yellow mustard (Brassica hirta Moench). They were compared to no-CC treatments that were either tilled pre- and post-planting of soybean (no-CC tilled) or not tilled at all (no-CC weedy). CC were planted in late March to early April, terminated 52–59 days later using an undercutter, and soybean was planted within a week. The experiment had a randomized complete block design with four replications and was repeated for 3 years. Mustards and small grains produced similar amounts of biomass (1.54 Mg ha−1) but mustard biomass production was more consistent (0.85–2.72 Mg ha−1) than that of the small grains (0.35–3.81 Mg ha−1). Relative to the no-CC weedy treatment, mustards suppressed concurrent weed biomass in two out of 3 years, by 31–97%, and small grains suppressed concurrent weed biomass in only 1 year, by 98%.Six weeks after soybean planting, small grains suppressed weed biomass in one out of 3 years, by 79% relative to the no-CC weedy treatment, but mustards did not provide significant weed suppression. The no-CC tilled treatment suppressed weeds each year relative to the no-CC weedy treatment, on average 87%. The ineffective weed control by CC reduced soybean biomass by about 50% six weeks after planting. While spring-planted CC have the potential for pre-plant weed control, they do not provide adequate early season weed suppression for soybean.

Effect of vegetal ground cover crops on wine anthocyanin content

Wine colour is a quality index that can provide information about conservation state, age or the presence of defects. Anthocyanin compounds are colour-related molecules and their concentration is affected by several factors such as grape variety, berry maturity degree or cultural practices. The aim of this work was to determine the anthocyanin composition of Mencía wines and how this is affected by the establishment of different cover crops (native vegetation, ryegrass and subterranean clover) respect to soil tillage treatment. This study was carried out during two consecutive seasons in the same vineyard. The use of cover crops significantly affected wine anthocyanin content; even though, their basic attributes were not altered by the treatments. In 2013, the wines from the ryegrass treatment had a significantly greater total anthocyanins concentration and, in 2014, the wines under the native cover had the highest concentration of these compounds. In both years, wines coming from the treatment under subterranean clover had a lower concentration of total anthocyanins when compared with those from the rest of the treatments. Cover crops increased wine anthocyanin concentrations when compared to the tilled treatment. However, the type of cover crop causing the highest increases differed from year to year.

Weed Community Dynamics and Suppression in Tilled and No-Tillage Transitional Organic Winter Rye–Soybean Systems

Grower adoption of no-tillage (NT) approaches to organic soybean production has been limited, in part because of the perceived risks of ineffective cover crop management and lack of season-long weed suppression. We conducted research in 2008 and 2009 to assess those risks by quantifying the effects of winter rye cover-crop management (tilling, crimping, or mowing), soybean planting date (mid May or early June), and row width (19 or 76 cm) on weed recruitment, emergence patterns, season-long suppression, and late-season weed community composition in transitional organic production systems. The weed plant community consisted largely of summer annual species in each year, with velvetleaf or common lambsquarters as the most abundant species. Seedling recruitment from the soil seedbank varied between years, but velvetleaf recruitment was consistently greater in the tilled rye than in the NT rye treatments. Weed emergence tended to peak early in the season in the tilled rye treatment, but in the NT rye treatments, the peak occurred in mid or late season. More-diverse summer annual and perennial species were associated with the NT rye treatments. Even so, weed suppression (as measured by late-season weed shoot mass) was much greater in crimped or mowed rye NT treatments than it was in the tilled treatment. Weed suppression among NT rye treatments was greater in 19- than in 76-row spacing treatments in each year and was greater for mid May than it was for early June planted soybean in 2009. The NT planting of soybean into standing rye before termination (crimping or mowing) facilitated timely planting of soybean, as well as effective, season-long weed suppression, suggesting that those approaches to rye and weed management are of less risk than those typically perceived by growers. Our results suggest that NT systems in winter rye provide effective weed-management alternatives to the typical tillage-intensive approach for organic soybean production.

Araneae communities associated with the canopies of chestnut trees in the northeastern part of Portugal: The influence of soil management practices

Chestnut (Castanea sativa Mill.) is one of the economically more important trees in the north of Portugal. Spiders, as generalist predators, are potential controlling agents of pests, yet the composition of the community of spiders associated with this crop is only poorly known. The objective of this study was to determine the spider communities in the canopies of chestnut trees subject to three different soil management practices in northeastern Portugal. Three chestnut groves each subject to a different agricultural practice (grazed, tilled or untilled) were studied in 2008 and 2009. The Araneae communities were sampled by beating the branches and the individuals collected were identified to family and species when possible. To investigate the structure of the spider community in each grove the abundance and family richness of spiders were calculated and compared between managements. In total, 4172 spiders were collected and, in both years, the three most abundant families were Araneidae, Philodromidae and Linyphiidae. In 2008, there was a greater abundance of spiders in the grazed, followed by the tilled and untilled groves, but no significant differences among groves. However, in 2009 there was a greater abundance of spiders in the tilled grove, followed by grazed and untilled groves and the differences between the untilled and the other two groves were significant. Araniella, Oxyopes and Anyphaena were the most abundant genera in the three groves. This study showed that soil management may influence the diversity of spiders, but the effects were weak and not consistent between years. The reduction or absence of a suitable habitat for spiders under the trees in the tilled treatment might have resulted in the spiders migrating up into the canopy. However, based on the weak effects on spider abundance recorded and its potentially adverse effects on soils, tillage is not recommended for managing the incidence of pests in chestnut groves.

Soil microbial diversity and C turnover modified by tillage and cropping in Laos tropical grassland

Agricultural practices should modify the diversity of soil microbes. However, the precise relationships between soil properties and microbial diversity are poorly known. Here, we study the effect of agricultural management on soil microbial diversity and C turnover in tropical grassland of north-eastern Laos. Three years after native grassland conversion into agricultural land, we compared soils from five land use management systems: one till versus two no-till rotational cropping systems, one no-till improved pasture and the natural grassland. Soils were incubated in microcosms during 64 days at optimum temperature and humidity. Bacterial and fungal diversity were evaluated by metagenomic 454-pyrosequencing of 16S and 18SrRNA genes, respectively. Changes in soil respiration patterns were evaluated by monitoring 12C- and 13C-CO2 release after soil amendment with 13C-labelled wheat residues. Results show that residue mineralization increased with bacterial richness and diversity in the tilled treatment 7 days after soil amendment. Native soil organic C mineralization and priming effect increased with fungal richness and diversity in improved pasture and natural grassland. No-till cropping systems represented intermediate situations between tillage and pasture systems. Our findings evidence the potential of controlling soil microbial diversity by agricultural practices to improve soil biological properties. We suggest the promotion of no-till systems as a fair compromise between the need for agriculture intensification and soil ecological processes preservation.

Clay soil moisture in spring cereal cultivation as related to tillage management

Conservation tillage with crop covered soil surface has been found to reduce the risk of erosion and nutrient leaching. The reduction of tillage intensity changes topsoil structure affecting soil physical conditions relevant to crop growth. In this study, the effects of autumn tillage management on soil moisture during the growing season of spring barley (Hordeum vulgare) was examined on two fi eld experiments on clay soils (Vertic Cambisol, Eutric Cambisol) in southwestern Finland in 2004–11. The objective of the study was to investigate the effects of reduced tillage intensity on soil moisture conditions of two different clay soils in different weather conditions. Autumn mouldboard ploughing (to 20–25 cm depth, P) was compared to stubble cultivation (10–15 cm, S) and zero tillage (N). During the growing season, soil moisture was determined once a week at the depth of 0−30 cm with a TRASE system I (Time Domain Refl ectometry (TDR)). Daily weather conditions (precipitation, air temperature) were also determined. Zero tilled soil stayed moister than the soil in other tillage treatments. When the beginning of the growing season was dry, higher soil moisture content in zero tilled soil improved the growth conditions of barley. In an unexceptional rainy beginning of growing season, the wetness of clay soils in zero tilled treatment hampered the crop growth and yield production clearly.

Clay soil moisture in spring cereal cultivation as related to tillage management

Conservation tillage with crop covered soil surface has been found to reduce the risk of erosion and nutrient leaching. The reduction of tillage intensity changes topsoil structure affecting soil physical conditions relevant to crop growth. In this study, the effects of autumn tillage management on soil moisture during the growing season of spring barley ( Hordeum vulgare ) was examined on two fi eld experiments on clay soils (Vertic Cambisol, Eutric Cambisol) in southwestern Finland in 2004–11. The objective of the study was to investigate the effects of reduced tillage intensity on soil moisture conditions of two different clay soils in different weather conditions. Autumn mouldboard ploughing (to 20–25 cm depth, P) was compared to stubble cultivation (10–15 cm, S) and zero tillage (N). During the growing season, soil moisture was determined once a week at the depth of 0−30 cm with a TRASE system I (Time Domain Refl ectometry (TDR)). Daily weather conditions (precipitation, air temperature) were also determined. Zero tilled soil stayed moister than the soil in other tillage treatments. When the beginning of the growing season was dry, higher soil moisture content in zero tilled soil improved the growth conditions of barley. In an unexceptional rainy beginning of growing season, the wetness of clay soils in zero tilled treatment hampered the crop growth and yield production clearly.

Organically Managed No‐Tillage Rye–Soybean Systems: Agronomic, Economic, and Environmental Assessment

A major challenge that organic grain crop growers face is weed management. The use of a rye (Secale cereale L.) cover crop to facilitate no‐tillage (NT) organic soybean [Glycine max (L.) Merr.] production may improve weed suppression and increase profitability. We conducted research in 2008 and 2009 to determine the effect of rye management (tilling, crimping, and mowing), soybean planting date (mid‐May or early June), and soybean row width (76 or 19 cm), on soybean establishment, soil moisture, weed suppression, soybean yield, and profitability. Soybean establishment did not differ between tilled and NT treatments; and soil moisture measurements showed minimal risk of a drier soil profile in NT rye treatments. Rye mulch treatments effectively suppressed weeds, with 75% less weed biomass than in the tilled treatment by mid‐July. However, by this time, NT soybean competed with rye regrowth, were deficient in Cu, and accumulated 22% as much dry matter (DM) and 28% as much N compared to the tilled treatment. Soybean row width and planting date within NT treatments impacted soybean productivity but not profitability, with few differences between mowed and crimped rye. Soybean yield was 24% less in the NT treatments than the tilled treatment, and profitability per hectare was 27% less. However, with fewer labor inputs, profitability per hour in NT rye treatments was 25% greater than in tilled soybean; in addition, predicted soil erosion was nearly 90% less. Although soybean yields were less in NT rye mulch systems, they represent economically viable alternatives for organic producers in the Upper Midwest.

Vineyard weed management practices influence nitrate leaching and nitrous oxide emissions

Successive years of multiple tillage passes have been linked to reductions in soil carbon (C) and shifts in soil physical properties, which are often linked to changes in soil nitrogen (N) retention. ‘Under the vine’ cultivation is becoming a more common practice in vineyards as growers seek alternative means of weed control. Therefore, we (1) investigated the effects of cultivation or herbicide on soil N leaching during a 1 year cycle of vineyard management and (2) determined differences in short-term nitrous oxide (N 2O) emissions and N transformations between ‘under the vine’ treatments during summer fertigation, a period in which we hypothesized that high N 2O emission rates would occur under warm, moist soil conditions. Few differences were found in the chemical and physical characteristics of soil profiles in cultivated and herbicide treatments. In the surface depths, total C and microbial biomass (i.e., total phospholipid fatty acids) were greater in the tilled than herbicide soils. This contrasts with other findings, but suggests that the greater weed biomass in the tilled treatment contributed labile C to soil C pools. Greater soil nitrate was found at depth (1.2 m) in the herbicide than cultivated treatment. Also, the cultivated soil had nearly 50% less nitrous oxide emissions during fertigation than the herbicide soil. We suggest that greater weed presence, soil C and microbial biomass in the tilled treatment contributed to the greater N retention.

Soilborne Pathogens of Cereals in an Irrigated Cropping System: Effects of Tillage, Residue Management, and Crop Rotation.

An irrigated cropping systems experiment was conducted for 6 years in east-central Washington State to examine agronomic and economic alternatives to continuous annual winter wheat (Triticum aestivum) with burning and plowing, and to determine how root diseases of cereals are influenced by management practices. The continuous winter wheat treatment with burning and plowing was compared with a 3-year no-till rotation of winter wheat-spring barley (Hordeum vulgare)-winter canola (Brassica napus) and three straw management treatments: burning, straw removal, and leaving the straw stubble standing after harvest. Take-all disease and inoculum increased from years 1 to 4 in the continuous winter wheat treatment with burning and plowing, reducing plant growth compared to the no-till treatments with crop rotations. Inoculum of Rhizoctonia solani AG-8 was significantly lower in the tilled treatment compared to the no-till treatments. Inoculum concentration of Fusarium pseudograminearum was higher than that of F. culmorum, and in one of three years, the former was higher in treatments with standing stubble and mechanical straw removal compared to burned treatments. Residue management method had no effect on Rhizoctonia inoculum, but spring barley had more crown roots and tillers and greater height with stubble burning. This 6-year study showed that irrigated winter wheat can be produced in a no-till rotation without major disease losses and demonstrated how cropping practices influence the dynamics of soilborne cereal diseases and inoculum over time.

Habitat manipulation in potato affects Colorado potato beetle dispersal

AbstractIncreased habitat complexity in agricultural fields can alter the movement of pests into or within a field. Using a mark–release–recapture method with Colorado potato beetle [Leptinotarsa decemlineata (Say)], we compared the tenure time and dispersal of marked insects released within experimental potato fields to those released at the field borders in three trials in summer 2006. Plots within fields had rye, vetch or no plant residues. Movement of marked Colorado potato beetles into the tilled plots was significantly higher than into vetch or rye cover treatments. The abundance of naturally occurring beetles in the three cover treatments followed the general patterns of the number of marked immigrants over all releases. Marked beetles released inside the potato field tended to move along the release row rather than across rows; this pattern was stronger for the tilled treatment than for the two mulch cover treatments. Marked beetles disappeared from within the potato fields differently, depending on the cover crop treatment, but the patterns were not consistent over the season. Incorporation of dispersal patterns into pest management strategies should improve methods of pest population regulation, especially for the initial colonization of fields.

Surface versus incorporated residue effects on water-stable aggregates

Reduced tillage methods for field crop production result in less disruption of soil structure and often increased amounts of crop residue maintained on the soil surface. The combination of these two factors produces increased surface soil aggregation. This study was conducted in the field and within pots to determine whether surface residue by itself improves soil aggregation within a short period of time. The soil was a silt loam loess deposit in the Pacific Northwest, USA, where summers are hot and dry, and most precipitation (420 mm) is received during the mild winters. Two pot studies were conducted over winter, one under a shelter with controlled irrigations (183 mm), and the other outdoors receiving natural precipitation (77 mm). In both pot studies 640 g m −2 wheat ( Triticum aestivum L.) residue was either placed on the surface of the soil or thoroughly mixed into the soil. The field study was conducted on plots where, for the past 7 years, wheat crop residues were either incorporated through chisel/disk tillage or removed before tillage and replaced on the surface after tillage. The field study included plots where wheat was grown with no tillage. In the pots, there was no significant effect due to residue treatment on aggregate mean weight diameter, measured monthly for 4 winter months. This was true despite dissolved organic carbon being leached from the surface residue. In the 7-year-old field plots, replacing residues on the surface resulted in slightly greater mean weight diameter of aggregates at 5–10 cm depth compared to the mixed residue treatment. The no-till plots had significantly greater mean weight diameter at 0–5 cm depth than either tilled treatment. Our conclusion is that surface residue by itself failed to increase aggregation of tilled surface soil within the first rainy season after tillage.

Effects of Soil Management Practices and Tillage Systems on Soil Moisture Conservation and Maize Yield on a Sandy Loam in Semiarid Kenya

ABSTRACT Maize is an important crop in the high and medium rainfall areas of Kenya and thus, there is a need for additional information on the effect of tillage and soil management practices on water conservation and yield of maize. The objective of this study was to determine the effects of seven soil management practices: bare with conventional tillage (BC), bare with minimum tillage (BM), incorporated mulch with conventional tillage (IMuC), manure with conventional tillage (MaC), manure with minimum tillage (MaM), surface mulch with conventional tillage (SMuC), and surface mulch with minimum tillage (SMuM) on water conservation and yield of maize. Soil water content was greater in minimum tilled plots than in the conventionally tilled (hand hoeing) plots during the study period. This was demonstrated by the manure with minimum tilled treatment, which had the highest soil moisture (7.6% and 8.3%) both at 0-7 cm and 7-23 cm depth. However, when organic matter additions were analyzed separately, it was observed that manure irrespective of tillage had the highest soil moisture in both depths (7.6% and 8.1%). The differences within the treatments occurred when soil water contents were highest shortly after the rains. When the amount of soil water for each management practice was averaged for all the seasons, a significant difference was found at P = 0.0001. Manure (Ma) and surface mulched (Smu) treatments had significantly higher soil moisture content than the other treatments. The higher moisture content found under these treatments was attributed to higher infiltration rates, better cover that reduced the rainfall kinetic energy, and to better structural stability contributed to by higher organic carbon. Compared with the traditional form of hand hoeing, minimum tillage increased available soil water content drastically and crop performance was improved. Grain yields were greatest in manure and lowest in bare treatments. There were significant differences in grain yield in all treatments.

Nitrogen dynamics during till and no-till pasture restoration sequences in Rondônia, Brazil

The clearing of tropical rain forest in the Amazon basin has created large areas of cattle pasture that are now declining in productivity. Practices adopted by ranchers to restore productivity to degraded pastures have the potential to alter soil N availability and gaseous N losses from soils. We examined how soil inorganic N pools, net N mineralization and net nitrification rates, nitrification potential and NO and N2O emissions from soils of a degraded pasture responded to the following restoration treatments: (1) soil tillage followed by replanting of grass and fertilization, (2) no-till application of non-selective herbicide, planting of rice, harvest followed by no-till replanting of grass and fertilization, and (3) the same no-till sequence with soybeans instead of rice. Tillage increased soil NH4+ and NO3? pools but NH4+ and NO3? pools remained relatively constant in the control and no-till treatments. Cumulative rates of net N mineralization and net nitrification during the first 6 months after treatment varied widely but were hightest in the tilled treatment. Emissions of NO and N2O fluxes increased with tillage and with N fertilization. There were no clear relationships among rates of N fertilizer application, net N mineralization, net nitrification, NO, N2O and total N oxide emissions. Our results indicate that pasture restoration sequences involving tilling and fertilizing will increase emissions of N oxides, but the magnitude of the increase is likely to differ based on timing of fertilizer application relative to the presence of plants and the magnitude of plant N demand. Emissions of N oxides appear to be decreased by the use of restoration sequences that minimize reductions in pasture grass cover.

Small-Grain Cover Crop Interaction with Glyphosate-Resistant Corn (Zea mays)1

A 2-yr field study was conducted in Blackville, SC, to assess the potential for using small- grain cover crops and glyphosate as a means of reducing or eliminating the need for atrazine in irrigated Southeastern corn production. Oats, rye, and wheat were no-till, drill seeded each fall and subsequently desiccated in early spring before corn planting. A bareground conventional tilled treatment also was included. Within each cover crop system, the herbicides evaluated included (1) no herbicide; (2) 1.68 kg ai/ha atrazine plus 1.08 kg ai/ha S-metolachlor at corn planting followed by 0.84 kg ae/ha glyphosate; or (3) two applications of 0.84 kg/ha glyphosate alone, applied sequentially. All systems were compared with conventional tillage without a cover crop with 1.68 kg/ha atrazine plus 1.08 kg/ha S-metolachlor at planting followed by 1.12 kg/ha atrazine. Biomass of rye, oats, and wheat at dessication was 497, 369, and 340 g/m2, respectively. All cover crops delayed early-season corn growth. Detrimental effects on early-season corn growth from the oats cover crop were still apparent 7 wk after emergence (WAE), with corn height and biomass reduced 8 and 19%, respectively. Weed biomass in nontreated plots was reduced 84, 68, and 21% by oats, rye, and wheat, respectively, 3 WAE. Oats were more inhibitory of corn and weed growth than rye, although rye produced greater surface residue, indicating possible allelopathy affects. In the presence and absence of each cover crop, atrazine plus S-metolachlor followed by glyphosate or sequential glyphosate applications alone were effective in providing season-long control of pitted morningglory, entireleaf morningglory, Palmer amaranth, Florida pusley, large crabgrass, and common bermudagrass. Corn yields and gross profit margins in sequential glyphosate–treated plots were equivalent or superior to the standard atrazine-based program, which indicates that effective and economical alternatives to atrazine are available.Nomenclature: Atrazine; glyphosate; S-metolachlor; common bermudagrass, Cynodon dactylon (L.) Pers. #3 CYNDA; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray # IPOHG; Florida pusley, Richardia scabra L. # RCHSC; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; corn, Zea mays L. ‘DK662 RR’; oats, Avena sativa L. ‘Coker 820’; rye, Secale cereale L. ‘Wrenz’; wheat, Triticum aestivum L. ‘Pioneer 2684’.Additional index words: Allelopathy, conservation tillage, integrated weed management, strip tillage, transgenic corn.Abbreviations: POST, postemergence; WAE, weeks after emergence.