Mulch Tillage Research Articles

Soil Conservation Benefits of Large Biomass Soybean (LBS) for Increasing Crop Residue Cover

ABSTRACT Soybeans are planted on approximately eight million hectares (20 M acres) of highly erodible land (HEL) in the United States. Soybean crops have been recognized as deficient in supplying crop residues that reduce soil erosion. A new type of soybean tested at the Beltsville Agricultural Research Center, Maryland, can grow to heights of 1.8-meters (6 ft) or more. The development of the large biomass soybean (LBS) suggested the potential of increased crop residue production to reduce soil loss on erodible soybean lands. An evaluation was conducted of the soil conservation benefits of LBS versus conventional soybean using data from a three-year field experiment. LBS produced more crop residue dry biomass and provided a mean increase of 31 percent more crop residue cover in the spring before mulch tillage and 47 percent more after mulch tillage than conventional cultivars. Soil loss estimates for LBS were much lower than for conventional soybeans as simulated by a revised universal soil loss equation (RUSLE). Breeding for increased residue production in soybeans could produce significant environmental benefits as a soil conservation practice in reducing soil erosion. The conservation benefits of LBS can be realized if enhanced biomass production can be combined with adequate grain production.

Factors affecting runoff and soil loss under simulated rainfall on a sandy Bainsvlei Amalia soil

This study was conducted on a long-term tillage experiment that was designed to evaluate appropriate tillage practices for sustainable dryland crop production. Measurements of runoff and soil loss were conducted on a sandy Bainsvlei Amalia soil (88.0% sand, 3.6% silt, and 8.4% clay) with a rainfall simulator on three tillage practices, namely no-tillage (NT), stubble mulch (ST) and conventional tillage (CT), each combined with four levels of wheat residue cover. The measurements were replicated twice for each of the three tillage practices on 1 m2 area plots. The simulator used for the study produced raindrops at a constant intensity of 60 mm h-1 with a veejet type nozzle, which had kinetic energy comparable to natural rainfall. A sharp decline in runoff and soil loss occurred with an increase in residue ground cover from bare to about 70%, above which the effect was less dramatic. Generally, runoff and soil loss was higher on NT plots compared with ST and CT plots. It is recommended that a crop residue covering at least 70% should be maintained on the soil surface when conservation tillage is practiced to ensure higher infiltration and lower runoff on this type of soil. Tilling the soil to a depth of at least 150 to 250 mm below the mulch gave the lowest runoff and soil loss.

Effect of crop rotation and tillage system on sclerotinia stem rot on soybean

Sclerotinia stem rot (SSR) of soybean is a major disease in the North Central region of the United States. A 3-year study was done to determine if crop rotation and tillage, moldboard plowing then mulch tillage (MP + MT), mulch tillage (MT), and no-till (NT), affected the population density of sclerotia and apothecia, incidence of SSR, and soybean yield. Crop rotation did not significantly affect the number or distribution of sclerotia or SSR incidence, but did affect the number of apothecia and the yield. The highest number of apothecia per square metre was observed in the plots in the continuous soybean rotation. Tillage affected both the number and distribution of sclerotia in the soil profile. Moldboard plowing lowered the number of sclerotia per litre of soil, compared to MT and NT plots, and buried the sclerotia deeper than 10 cm into the soil. Tillage did not affect the total number of apothecia observed, but moldboard plowing did delay emergence of apothecia compared to no-till. The MP + MT plots had the lowest disease incidence and the highest yield, while the NT plots had the highest disease incidence and the lowest yields. One year of moldboard plowing will bury sclerotia at least 10 cm in soil and delay the production of apothecia. How this affects SSR development depends on the other factors involved with disease development.

Tillage System and Crop Rotation Effects on Dryland Crop Yields and Soil Carbon in the Central Great Plains

Winter wheat (Triticum aestivum L.)–fallow (WF) using conventional stubble mulch tillage (CT) is the predominant production practice in the central Great Plains and has resulted in high erosion potential and decreased soil organic C (SOC) contents. This study, conducted from 1990 through 1994 on a Weld silt loam (Aridic Argiustoll) near Akron, CO, evaluated the effect of WF tillage system with varying degrees of soil disturbance [no‐till (NT), reduced till (RT), CT, and bare fallow (BF)] and crop rotation [WF, NT wheat–corn (Zea mays L.)–fallow (WCF), and NT continuous corn (CC)] on winter wheat and corn yields, aboveground residue additions to the soil at harvest, surface residue amounts at planting, and SOC. Neither tillage nor crop rotation affected winter wheat yields, which averaged 2930 kg ha−1. Corn grain yields for the CC (NT) and WCF (NT) rotations averaged 1980 and 3520 kg ha−1, respectively. The WCF (NT) rotation returned 8870 kg ha−1 residue to the soil in each 3‐yr cycle, which is 2960 kg ha−1 on an annualized basis. Annualized residue return in WF averaged 2520 kg ha−1, which was 15% less than WCF (NT). Annualized corn residue returned to the soil was 3190 kg ha−1 for the CC (NT) rotation. At wheat planting, surface crop residues varied with year, tillage, and rotation, averaging WCF (NT) (5120 kg ha−1) > WF (NT) (3380 kg ha−1) > WF (RT) (2140 kg ha−1) > WF (CT) (1420 kg ha−1) > WF (BF) (50 kg ha−1). Soil erosion potential was lessened with WCF (NT), CC (NT), and WF (NT) systems because of the large amounts of residue cover. Levels of SOC in descending order in 1994 were CC (NT) ≥ WCF (NT) ≥ WF (NT) = WF (RT) = WF (CT) > WF (BF). Although not statistically significant, the CC (NT) treatment appeared to be accumulating more SOC than any of the rotations that included a fallow period, even more rapidly than WCF (NT), which had a similar amount of annualized C addition. Reduced tillage and intensified cropping increased SOC and reduced soil erosion potential.

Corn response to potassium placement in conservation tillage

Improvements in the yield potential of corn ( Zea mays L.) grown using conservation-tillage may depend, in part, on K fertility management. Field research was conducted in 1997 and 1998 on a field which had been in continuous no-tillage (NT) for the previous 12 years near Paris, Ont., Canada to evaluate potassium (KCl) placement effects on corn growth and yields in NT, spring zone-tillage (ZT) and spring mulch-tillage (MT) systems. Soils were classified as moderately well drained and had low soil-test K levels. Potassium was spring-applied (1 day prior to corn planting) at either 0 or 100 kg K ha −1. Potassium was either broadcast applied, deep in-row banded (15 cm deep), or half broadcast applied and half shallow-banded (5 cm beside the row, 5 cm below seeding depth). Early season and mid-season corn ear-leaf K concentrations indicated that spring-applied K fertilizer was available for uptake by corn in conservation-tillage systems. Potassium application sometimes significantly increased corn yields compared to the zero K control in the NT and ZT systems. However, MT corn yields did not show any response to K fertilization in either season despite the low soil-test K levels. There were no significant corn yield increases with deep banding of K fertilizer relative to shallow placement in any tillage system. This study suggests that, for similar low-testing K soils, alternate K placements will have greater impacts on corn plant nutritional status than on final yields. Surface broadcasting of K fertilizer is appropriate for continuous NT corn despite evident K stratification present after long-term NT. MT may improve corn K nutrition after long-term NT.

Evaluation of reduced tillage technologies in corn production based on soil and crop analyses

Despite new cultivation methods, the proportion of conventionally cultivated land is still very high in Hungary.Although these technologies demand more time, labour and fuel, they are still attractive to users because they require less professional skill and simple machinery. In Hungary, conventional tillage methods usually lead to soil deterioration, soil compaction and a decrease in organic content. These side effects have caused gradually strengthening economic and environmental problems.The technologies for those plants which are dominant on Hungarian arable lands use (winter wheat, maize, sunflower and barley) need to be improved both in the interest of environmental protection and the reduction of cultivation costs.The Department of Land Use at Debrecen University is cooperating with KITE Sc. to carry out soil tillage experiments at two pilot locations to prove tillage technologies already used in the USA.The aim of our examination is to adapt new technological developments and machinery, and to improve them on Hungarian soil for local environmental conditions. With these improved machines, the field growing of plants could be executed by less manipulation and better suited to economic and environmental needs. The most significant task is to investigate and improve the conventional cultivation replacing, new soil-protecting tillage technologies, and to apply no-till and mulch tillage systems.On the basis of the experiments’ survey data, we established that the looseness and moisture content of the soil using reduced tillage is more favourable than after using conventional technologies. The results of no-till and shallow spring tillage are behind those of winter plough or disk ripper cultivation in corn yield and production elements.To preserve moisture content in the soil, the ground clearing and sowing while simultaneously performing no-till method presents the most favourable results. The surplus moisture gained using no-till technology is equal to 40 mm precipitation.Regarding the yield of winter wheat we established that the tillage methods do not affect plant yield. Both disk ripper and conventional disc cultivation showed nearly the same harvest results (5.55 or 5.5 t/ha), where the difference is statistically hardly verifiable from the no-till method. From the individual production of corn and the number of plants planted in unit area, calculated results prove that no significant difference can be detected between the production of winter plough and disk ripper technology. Although the yield achieved with the no-till method is less than with the previously mentioned technologies, the difference is only 9-10%. We received the lowest production at shallow spring tillage.Evaluations have shown a 1.1 t/ha (13%) difference in the yield of maize, between winter tillage and the disk ripper method, in this case the traditional method resulted in higher yield. In winter tillage, the yield of maize was 1.9-2.1 t/ha (23-25%) higher than in the case of direct sowing and cultivator treatments. No significant difference could be noted between the yields of direct sowing and cultivator treatments.Our research so far has proved the industrial application of reduced tillage methods in crop cultivation technologies.

Residual effect of poultry litter applied to cotton in conservation tillage systems on succeeding rye and corn

The burgeoning poultry industry in the southeastern US is presenting a major environmental problem of safe disposal of poultry litter (PL). In a comprehensive study, we explored ways of PL use in conservation tillage-based cotton ( Gossypium hirsutum L.) production systems on a Decatur silt loam soil in north Alabama, from 1996 to 1999. The study reported here-in presents the residual effects of PL applied to cotton in mulch-till (MT) and no-till (NT) conservation tillage systems in 1997 and 1998 cropping seasons on N uptake, growth, and yield of rye ( Secale cereale, L.) cover crop and rotational corn ( Zea mays L.) in 1999. Rye was grown without additional N, whereas corn was grown at three inorganic N levels (0, 100, and 200 kg N ha −1). Poultry litter was applied to cotton in 1997 and 1998 at 0, 100, and 200 kg N ha −1. Residual N from PL applied to cotton in 1997 and 1998 produced up to 2.0 and 17.3 Mg ha −1, respectively, of rye cover crop and corn biomass (includes 7.1 Mg ha −1 of corn grain yield) without additional fertilizer. Therefore, in addition to supplying crop residues which reduce soil erosion, increase soil organic matter, and conserve soil moisture, the rye cover crop was able to scavenge residual N left by the cotton crop, which would otherwise, be at risk of being leached and pollute groundwater resources. Poultry litter applied to cotton also increased corn grain quality as shown by up to 100% increase in grain N content compared to the 0N treatment. Using PL with a slower rate of N release compared to inorganic fertilizer to meet some of the N requirements of corn, will not only reduce N fertilizer costs for corn, but will also reduce the risk of nitrate N leaching into groundwater. The maximum amount of crop residues added to the cotton based cropping system by residual N from PL and inorganic N was 21.3 Mg ha −1. This will lead to an increase in soil organic carbon and soil structure in the long term and a reduction in soil erosion, thereby further improving soil productivity, while at the same time, protecting the environment from nitrate pollution and soil degradation. Our study demonstrates that cotton under conservation tillage system in combination with rye cover crop and rotational corn cropping could use large quantities of PL thereby avoiding serious potential environmental hazards.

Tillage and traffic effects on runoff

Traffic and tillage effects on runoff and crop performance on a heavy clay soil were investigated over a period of 4 years. Tillage treatments and the cropping program were representative of broadacre grain production practice in northern Australia, and a split-plot design used to isolate traffic effects. Treatments subject to zero, minimum, and stubble mulch tillage each comprised pairs of 90-m 2 plots, from which runoff was recorded. A 3-m-wide controlled traffic system allowed one of each pair to be maintained as a non-wheeled plot, while the total surface area of the other received a single annual wheeling treatment from a working 100-kW tractor. Rainfall/runoff hydrographs demonstrate that wheeling produced a large and consistent increase in runoff, whereas tillage produced a smaller increase. Treatment effects were greater on dry soil, but were still maintained in large and intense rainfall events on wet soil. Mean annual runoff from wheeled plots was 63 mm (44%) greater than that from controlled traffic plots, whereas runoff from stubble mulch tillage plots was 38 mm (24%) greater than that from zero tillage plots. Traffic and tillage effects appeared to be cumulative, so the mean annual runoff from wheeled stubble mulch tilled plots, representing conventional cropping practice, was more than 100 mm greater than that from controlled traffic zero tilled plots, representing best practice. This increased infiltration was reflected in an increased yield of 16% compared with wheeled stubble mulch. Minimum tilled plots demonstrated a characteristic midway between that of zero and stubble mulch tillage. The results confirm that unnecessary energy dissipation in the soil during the traction process that normally accompanies tillage has a major negative effect on infiltration and crop productivity. Controlled traffic farming systems appear to be the only practicable solution to this problem.

Nitrates in soil after long‐term management for dryland grain sorghum and winter wheat

Long‐term cropping with clean and stubble mulch tillage (SMT) resulted in soil organic carbon and total nitrogen (N) decreases at numerous Great Plains locations. Crops at some locations now respond to applied ? fertilizers. Objective of this study was to compare soil nitrate‐N (NO3‐N) contents after a 12‐year field study for which different management practices [cropping systems (rotations or continual cropping), tillage methods (SMT or no‐tillage), land leveling (level or nonlevel), and ? fertilizer (applied or not applied)] were used for dryland grain sorghum [Sorghum bicolor (L.) Moench] and winter wheat (Triticum aestivum L.) production. Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) was sampled by increments to a 20‐cm depth. Relatively few differences in NO3‐N contents due cropping system, land leveling, or tillage treatments were significant for individual depths or means across all depths. Cropping systems had no effect, but contents were greater in wheat than in sorghum or fallow plots. Land leveling and tillage methods resulted in no consistent differences, but contents usually were greater with than without applied fertilizer. Although ? fertilizer treatments were imposed early in the field study because plant ? deficiencies symptoms were noted, crops did not respond to applied fertilizer. This suggests the NO3‐N content differences found will have little effect on dryland crop yields under present management conditions.

Tillage, Cover Cropping, and Poultry Litter Effects on Cotton: II. Growth and Yield Parameters

The development of conservation tillage systems for cotton (Gossypium hirsutum L.), capable of reducing soil erosion and improving soil quality while increasing yields and profits, remains a challenge in the southeastern USA. Poor emergence and growth, delayed maturity, and reduced yield are some of the problems that have been encountered in the use of conservation tillage on cotton. The objectives of this study was to evaluate the effects of tillage (no‐till, mulch‐till, conventional till), cropping system [cotton–winter fallow, cotton–winter rye (Secale cereale L.) cover crop] and N source (poultry litter, ammonium nitrate) on growth and yield of cotton from 1996 to 1998 in northern Alabama. In 1997, cotton lint yield under no‐till (NT) was 24 and 18% greater than that under conventional till (CT) and mulch‐till (MT) systems, respectively. In 1998, cotton lint yield under the NT system was 7% greater than that under CT. Poultry litter (PL) at 100 kg N ha−1 gave similar lint yield to ammonium nitrate (AN), whereas at 200 kg N ha−1, lint yields were significantly greater. No‐till, cotton–winter rye cropping, and surface application of 200 kg N ha−1 in form of PL conserved soil moisture in the top 7 cm of the soil. This resulted in early seedling emergence, high seedling vigor, good plant growth, and high lint yield of cotton. These treatments would be appropriate for use in the southeastern USA where soil erosion is a problem and plenty of PL is available each year from the poultry industry.

Effects of Conventional and Mulch Tillage on Dicamba Transport1

Abstract: Leaching and runoff losses of the postemergence-applied herbicide dicamba were evaluated over a 3-yr period (1989 to 1991). Dicamba was applied at the recommended rate (0.56 kg ai/ha) to conventional and mulch tillage planted corn fields on Hagerstown silty clay loam (fine, mixed, mesic Typic Hapludalf). Mulch tillage followed several years of no-tillage corn. Root zone leachates were collected utilizing pan lysimeters placed 1.2 m below the soil surface. Surface runoff was monitored and collected with an HS-flume and automated sampling equipment. Leaching was greatest during 1989, and runoff events were recorded only during this season. Leachate samples containing measurable levels of dicamba were obtained within 21 d of herbicide application or within slightly more than one soil half-life of this chemical. More dicamba leached under mulch tillage than conventional tillage management. Tillage rotation (no tillage to mulch tillage) did not alter the leaching loss potential of dicamba beneath the...

Reduced Tillage Increases Population Density of Soil Macrofauna in a Semiarid Environment in Central Queensland

The effects of modified tillage practices on population densities of beneficial and harmful soil macrofauna were investigated. Soil-inhabiting macrofauna were sampled during 5 yr in a field experiment on a black Dermasol and Vertisol in semiarid central Queensland. The experimental treatments were 4 tillage practices applied during the fallow periods between grain crops. Reduced frequency and intensity of tillage increased the level of crop residues providing surface cover. Zero tillage had the highest population of macrofauna (74/m2), followed by reduced tillage (50/m2), stubble mulch tillage (44/m2), and traditional tillage (31/m2). Detritivore populations also were highest in zero tillage (44/m2) followed by reduced tillage (29/m2), stubble mulch tillage (26/m2), and traditional tillage (15/m2). Earthworm populations were highest in zero tillage (17/m2) and lowest in traditional tillage (5/m2). The incidence of termite colonies was higher in zero tillage (7.0/m2) than in reduced tillage (0.9/m2), stubble mulch tillage (0.3/m2), or traditional tillage (0.2/m2). Zero tillage usually had the greatest diversity of macrofauna species. Population density of herbivores, which are generally agricultural pests, was similar in all tillage treatments. These results indicate that long-term reduced or zero tillage will not lead to increased problems with soil insect pests.

Aggregation of Soil Cropped to Dryland Wheat and Grain Sorghum

AbstractSuccessful and sustainable semiarid dryland cropping depends on effective soil water storage and erosion control, which are influenced by surface soil aggregate size and stability. We hypothesized long‐term tillage and cropping system treatments affect water‐stable aggregate size distribution, aggregate water stability, and dry soil aggregation. A study on a Torrertic Paleustoll from 1982 to 1994 at Bushland, TX, involved tillage methods (no‐tillage, NT; stubble mulch tillage, SMT) and cropping systems for dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] production. In 1994, mean percentages of >4‐mm water‐stable aggregates at 0 to 2 cm were 3.5 with NT and 1.0 with SMT in wheat, sorghum, fallow, rotation phase, or crop comparison plots. Mean percentages of <0.25‐mm aggregates were 49.0 with NT and 37.8 with SMT. More small aggregates with NT help explain why infiltration was 90% greater with SMT than with NT during fallow after sorghum and 26% greater with SMT during fallow after wheat in a similar study on the same soil when surface coverage by residues was limited (25% with SMT, 57% with NT for sorghum; 73% with SMT, 86% with NT for wheat). Aggregate sizes differed due to cropping system, rotation phase, and crop, but aggregate water stability and dry aggregation differences generally were nonsignificant. Both NT and SMT are deemed suitable for dryland crops under conditions as in this study because neither resulted in unfavorable soil conditions or major yield differences.

Long-term tillage and cropping systems affect bulk density and penetration resistance of soil cropped to dryland wheat and grain sorghum

Stubble mulch tillage (SMT) and no-tillage (NT) are well adapted for dryland crops in the US Great Plains. Long-term use of NT, however, may impair soil physical conditions and crop yields, and, by inference, soil quality and production sustainability. We determined effects of using SMT and NT in several cropping systems for dryland winter wheat ( Triticum aestivum L.) and grain sorghum ( Sorghum bicolor (L.) Moench) production on soil bulk density (BD), penetration resistance (PR), and water content (WC). We determined these in 1994 in plots of a tillage method and cropping system study started in 1982 on Pullman (Torrertic Paleustoll) clay loam at Bushland, TX, USA. Due to the nature of the study, a common statistical analysis of the data was not appropriate, but eight separate analyses were possible. Besides tillage method and cropping system, these allowed comparisons due to rotation phase, land condition (level or non-level), and crop grown. Soil BD and PR always increased with depth and WC often increased. The tillage×depth interaction effect also was significant. Soil BD and PR were lower in the tillage layer (0–10 cm depth) in SMT than in NT plots, but no definite trends for BD were evident below 10 cm. Based on regression analyses, PR with SMT was related to BD and WC of the entire profile and most depth increments. With NT, PR was related to profile BD and WC, but only to WC for individual depths. These results indicate some strength factor largely independent of BD and affected by WC strongly influences PR of NT soil. Because NT does not disturb the soil, we concluded that stable biopores created by soil organisms and root channels reduced the effects of BD differences among NT plots and that NT soils developed a rigid structure independent of BD. Reports of improved trafficability on NT soils support this conclusion. Results of this study and previously reported crop yields suggest long-term use of NT will not impair the quality and production sustainability of this and similar soils under dryland cropping conditions.

The environmental consequences of the conservation tillage adoption decision in agriculture in the united states

The environmental consequences of conservation tillage practices are an important issue concerning the impact of agricultural production on the environment. While it is generally recognized that water runoff and soil erosion will decline as no tillage and mulch tillage systems are used more extensively on cropland, what will happen to pesticide and fertilizer use remains uncertain. To gain some insight into this, the conservation tillage adoption decision is modelled. Starting with the assumption that this dicision is a two step procedure – the first is the decision whether or not adopt a conservation tillage production system and the second is the decision on the extent to which conservation tillage should be used – appropriate models of the Cragg and Heckman (dominance) type are estimated. Based on farm-level data on corn production in the United States for 1987, the profile of a farm on which conservation tillage was adopted is that cropland had above average slope and experienced above average rainfall, the farm was a cash grain enterprise, and it had an above average expenditure on pesticides and a below average expenditure on fuel and a below average expenditure on custom pesticide applications. Additionally, for a farm adopting a no tillage production practice, an above average expenditure was made on fertilizer.

Link between conservation tillage and factor inputs

One important issue concerning the impact of agricultural production on the environment involves the environmental consequences of conservation tillage practices. While it is generally recognized that water runoff and soil erosion will decline as no tillage and mulch tillage systems are used more extensively on cropland, what will happen to pesticide and fertilizer use remains uncertain. To gain some insight into this, the conservation tillage adoption decision is modelled. Starting with the assumption that this decision is a two step procedure‐the first is the decision whether or not to adopt a conservation tillage production system and the second is the decision on the extent to which conservation tillage should be used‐appropriate models of the Cragg and Heck‐man (dominance) type are estimated. Based on farm‐level data on corn production in the United States for 1987, the profile of a farm on which conservation tillage was adopted is that the cropland had above average slope and experienced above average rainfall, the farm was a cash grain enterprise, and it had an above average expenditure on pesticides and a below average expenditure on fuel and a below average expenditure on custom pesticide applications. Additionally, for a farm adopting a no tillage production practice, an above average expenditure was made on fertilizer.

Management-induced aggregation and organic carbon concentrations in the surface layer of a Torrertic Paleustoll

Soil organic carbon concentrations (OCCs) decline when semiarid grasslands are brought under cultivation. As a result, soil aggregate size and stability may decline, which, with the decreases in OCC, may degrade soil quality and reduce crop yields. Effects of cropping systems, crop or field conditions, and tillage methods on dry and water-stable aggregation and OCCs in the surface layer of a Torrertic Paleustoll (Pullman clay loam) were determined. Samples were obtained from the 0–3-cm depth in plots of four dryland studies and three non-replicated field areas. Areas sampled ranged from those cropped to winter wheat ( Triticum aestivum L.) and grain sorghum ( Sorghum bicolor (L.) Moench) for over 20 years to grasslands converted to cropland in 1994. In general, soil aggregates were smaller and OCCs were greater with no-tillage (NT) than with stubble mulch tillage (SMT) on areas cropped for over 20 years. On areas recently converted to cropland, aggregates were larger and OCCs were greater with NT than with other tillage methods. The 0.42–0.84- and 0.84–2.0-mm dry aggregates were among those most stable when sieved in water. The results indicate practices that maintain soil OCCs at the higher levels and promote development of dry aggregates in the 0.42–2.0-mm size range are important for production sustainability of Torrertic Paleustolls such as Pullman clay loam and similar soils.

Tillage Mulch Depth Effects during Fallow on Wheat Production and Wind Erosion Control Factors

AbstractBlowing dust from summer fallow is a major soil loss and air quality concern in winter wheat (Triticum aestivum L.) production areas of the inland Pacific Northwest (PNW). The objective of our 3‐yr on‐farm study in a 286‐mm precipitation zone in eastern Washington was to determine the effects of tillage mulch depth during fallow on surface soil roughness, residue retention, seed‐zone water storage, wheat establishment, and grain yield. Soil is a Ritzville silt loam (coarse‐silty, mixed, mesic Calcidic Haploxeroll). Mulch depth combinations were created by primary spring tillage with noninversion implements at 100‐ or 160‐mm depths, and with subsequent rodweedings at 50‐ or 100‐mm depths. Tillage mulch depth during fallow did not affect seedling emergence after two wet fallow cycles, but wheat spike density was consistently greatest in deep‐tilled plots. In a dry fallow cycle, when dry soil extended beneath the rodweeder or secondary tillage layer, deep tillage increased stand establishment from 30 to 62 seedlings m‐2, grain yield from 4.4 to 5.3 Mg ha‐1, and residue production from 5.7 to 8.4 Mg ha‐1 compared with shallow tillage. Surface soil clods >50‐mm diameter, desirable for wind erosion control, increased with tillage mulch depth from 14 to 21 Mg ha‐1 in 1994, and from 22 to 37 Mg ha‐1 in 1995. A drawback to deep tillage mulches was the need to reduce tractor speed during planting. Surface residue retention was not affected by tillage mulch depth. Results show that surface clod structure and roughness during fallow can be maintained to protect the soil from erosion, mostly benefiting wheat production potential.

Survival of downy brome (Bromus tectorum) seed in four environments

Downy brome is one of the most troublesome winter annual weeds in winter wheat-fallow rotations in the central Great Plains. A 3-yr seed burial study was initiated to determine how long downy brome seed remained germinable when placed on the soil surface or 2.5 cm deep at four different times in four environments. Only 1 to 7% of the downy brome seed survived after 1 yr on the soil surface in chemical fallow and stubble mulch when deposited in August, but survival varied in September, October, and November. In 1970, a year with low fall and winter precipitation, 36 to 46% of the seed placed on the soil surface of chemical fallow in September, October, and November survived, compared with 1 to 8% for stubble mulch tillage. Early spring tillage covered more seed with soil, and downy brome seed survival decreased. When fall and winter precipitation was normal, stubble mulch and chemical fallow had 1 to 20% germinable seed remaining. Induced dormancy existed in some years. More downy brome seed survived when placed on the soil surface of crested wheatgrass sod (14 to 50%) than on smooth brome sod (0 to 36%). No differences existed among environments when downy brome seed was buried 2.5 cm deep. Only 0.4% of downy brome seed buried 2.5 cm survived after 1 yr when averaged across all environments.

Conservation tillage and input use

There continues to be a question as to the overall effectiveness of conservation tillage practices in reducing the impact of agricultural production on the environment. While it is generally recognized that water runoff and soil erosion will decline further, as tillage and mulch tillage systems are not used more extensively on cropland, what will happen to pesticide and fertilizer use remains uncertain. To gain some insight into this, the conservation tillage adoption decision is modelled. On the assumption that the decision to adopt conservation tillage is a two-step procedure, the first decision is whether or not to adopt a conservation tillage production system and the second concerns the extent to which conservation tillage should be used – appropriate models of the Cragg and Heckman (dominance) type are estimated. Based on farm-level data on corn production in the United States for 1987, the profile of a farm on which conservation tillage was adopted is that the cropland had above-average slope and experienced above-average rainfall, the farm was a cash grain enterprise, and it had an above-average expenditure on pesticides and a below-average expenditure on fuel and custom pesticide applications. Additionally, for a farm adopting a no-tillage production practice, an above-average expenditure was made on fertilizer.