The consequences of wheel-induced soil compaction and subsoiling for silage maize on a sandy loam soil in Belgium

In Belgium, growing silage maize in a monoculture often results in increased soil compaction. The aim of our research was to quantify the effects of this soil compaction on the dry matter (DM) yields and the nitrogen use of silage maize (Zea mays L.). On a sandy loam soil of the experimental site of Ghent University (Belgium), silage maize was grown on plots with traditional soil tillage (T), on artificially compacted plots (C) and on subsoiled plots (S). The artificial compaction, induced by multiple wheel-to-wheel passages with a tractor, increased the soil penetration resistance up to more than 1.5 MPa in the zone of 0–35 cm of soil depth. Subsoiling broke an existing plough pan (at 35–45 cm of soil depth). During the growing season, the release of soil mineral nitrogen by mineralisation was substantially lower on the C plots than on the T and S plots. Silage maize plants on the compacted soil were smaller and flowering was delayed. The induced soil compaction caused a DM yield loss of 2.37 Mg ha⁻¹ (−13.2%) and decreased N uptake by 46.2 kg ha⁻¹ (−23.2%) compared to the T plots. Maize plants on compacted soil had a lower, suboptimal nitrogen content. Compared with the traditional soil tillage that avoided heavy compaction, subsoiling offered no significant benefits for the silage maize crop. It was concluded that avoiding heavy soil compaction in silage maize is a major strategy for maintaining crop yields and for enhancing N use efficiency.     

Soil and residue management effects on arable cropping conditions and nitrous oxide fluxes under controlled traffic in Scotland 1. Soil and crop responses

Soil compaction can affect crop growth and greenhouse gas emission and information is required of how both these aspects are affected by compaction intensity and weather. In this paper we describe treatments of compaction intensity and their effects on soil physical conditions and crop growth in loam to sandy loam cambisol soils. Soil conditions and crop performance were measured over three seasons in a field experiment on soil compacted by wheels on freshly ploughed seedbeds. Ploughing buried the chopped residues of the previous crop. After ploughing, traffic was controlled such that the experimental plots received wheel traffic only as treatments. The overall objective was to discover how the intensity and distribution of soil compaction just before sowing influenced crop performance, soil conditions and emissions of nitrous oxide. Compaction treatments were zero, light compaction by roller (up to 1 Mg m⁻¹) and heavy compaction by loaded tractor, (up to 4.2 Mg). The experiment was located at Boghall, near Edinburgh (860 mm average annual rainfall) for the first two seasons under spring and winter barley (Hordeum vulgare L.) and in a drier area at North Berwick (610 mm average annual rainfall) for the third season under winter oil-seed rape (Brassica napus L.). Heavy compaction in dry soil conditions had little effect on crop growth. However, in wet conditions heavy compaction reduced air porosity, air permeability and gas diffusivity, increased cone resistance and limited winter barley growth and grain yield. Heavy compaction in wet conditions reduced winter barley yields to 7.1 Mg ha⁻¹, in comparison to 8.8 Mg ha⁻¹ in the zero compaction treatment. The compaction status of the top 15 cm of soil seemed to be particularly important. Loosening of the top 10 cm of soil immediately after heavy compaction restored soil conditions for crop growth. However, zero seed bed compaction gave patchy and uneven crop emergence in dry conditions. Both zero and light compaction to a target depth of 10 cm gave similar crop productivity. Maintenance of a correct compaction level near the soil surface is particularly important for establishment and overwintering of barley and oil seed rape.     

Alternative tillage and crop residue management in wheat after rice in sandy loam soils of Indo-Gangetic plains

A 3-year field study was conducted to evaluate the effect of three tillage practices (conventional, zero and reduced/strip) with two nitrogen levels (120 and 150 kg N ha⁻¹) applied in primary strips and three crop residue management practices (removal, burning and incorporation) in secondary strips in wheat after rice. Reduced tillage resulted in significantly higher overall mean wheat yield (5.10 Mg ha⁻¹) compared to conventional (4.60 Mg ha⁻¹) and zero tillage (4.75 Mg ha⁻¹). Residue incorporation resulted in highest mean yield (5.86 Mg ha⁻¹) during third year. Maximum mean yield (6.1 Mg ha⁻¹) was obtained in reduced tillage followed by conventional tillage (5.8 Mg ha⁻¹) under residue incorporation in third year. The weed dry weight recorded at 30 days after sowing was highest (0.3 Mg ha⁻¹) under zero tillage and lowest under conventional tillage (0.16 Mg ha⁻¹). Among crop residue management practices, the highest dry weight of weeds (0.22 Mg ha⁻¹) was recorded under residue incorporation. The highest infiltration rate (1.50 cm h⁻¹) was recorded in residue incorporation followed by residue burning (1.44 cm h⁻¹) whereas; the lowest (0.75 cm h⁻¹) in zero tillage. Soil bulk density was the highest (1.69 Mg m⁻³) under zero tillage and the lowest in residue incorporation (1.59 Mg m⁻³). There were no changes in soil available P and K after each crop sequence in relation to tillage practices during first 2 years. Higher organic carbon (5.1–5.4 g kg⁻¹) was measured under zero tillage compared to other treatments. Residue incorporation increased soil organic carbon and available P while higher available K was monitored in burning treatment during the third year. These results suggest that reduced tillage and in situ incorporation of crop residues at 5 Mg ha⁻¹ along with 150 kg N ha⁻¹ were optimum to achieve higher yield of wheat after rice in sandy loam soils of Indo-Gangetic plains of India.     

Remediation of subsoil compaction and compaction effects on corn N availability by deep tillage and application of poultry manure in a sandy-textured soil

Subsoil compaction may reduce the availability and uptake of water and plant nutrients thereby lowering crop yields. Among the management options for remediating subsoil compaction are deep tillage and the selection of crop rotations with deep-rooted crops, but little is known of the effects of applications of organic amendments on subsoil compaction. The objectives of this study were to determine the effects of subsoil compaction on corn yield and N availability in a sandy-textured soil and to evaluate the use of deep tillage and surface applications of poultry manure to remediate subsoil compaction. A field experiment planted to corn (Zea mays L.) was conducted from 2000 to 2001 on a Reelfoot fine sandy loam (fine-silty, mixed thermic Aquic Argiudolls) formed in silty alluvium located in southeast Missouri near the Mississippi River. Treatments were arranged in a factorial design with three levels of subsoil compaction and subsoiling and four rates (averaging 0, 6, 11 and 18 Mg ha⁻¹) of poultry manure. Subsoil tillage to a depth of 30 cm had multiple effects, including overcoming a natural or tillage-induced dense layer or pan and increasing volumetric soil water content and crop N uptake, especially in the 2001 cropping year with low early season precipitation. N recovery efficiency (NRE) was significantly higher in the subsoil treatment compared to the highest compaction treatment in 2001. No significant interactions between manure rates and compaction and subsoiling treatments were observed for corn grain and silage yields, N uptake and NRE. Average increases in corn grain yields over all manure rates due to subsoil tillage of compacted soil were 2002 kg ha⁻¹ in 2000 and 3504 kg ha⁻¹ in 2001. Application of poultry manure had a consistent positive effect on increasing grain yields and N uptake in 2000 and 2001 but did not significantly alter measured soil physical properties. The results of this study suggest that deep tillage and applications of organic amendments are management tools that may overcome restrictions in both N and soil water availability due to subsoil compaction in sandy-textured soils.     

Subsoil compaction effects on crops in Punjab, Pakistan:II. Root growth and nutrient uptake of wheat and sorghum

Crop yields can be reduced by soil compaction due to increased resistance to root growth, and decrease in water and nutrient use efficiencies. A field experiment was conducted during 1997–1998 and 1998–1999 on a sandy clay loam (fine-loamy, mixed, hyperthermic Typic Haplargids, USDA; Luvic Yermosol, FAO) to study subsoil compaction effects on root growth, nutrient uptake and chemical composition of wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor L. Moench). Soil compaction was artificially created once at the start of the study. The 0.00–0.15 m soil was manually removed with a spade. The exposed layer was compacted with a mechanical compactor from 1.65 Mg m⁻³ (control plot) to a bulk density of 1.93 Mg m⁻³ (compacted plot). The topsoil was then again replaced above the compacted subsoil and levelled. Both compacted and control plots were hoed manually and levelled. Root length density, measured at flowering stage, decreased markedly with compaction during 1997–1998 but there was little effect during 1998–1999. The reduction in nutrient uptake by wheat due to compaction of the subsoil was 12–35% for N, 17–27% for P and up to 24% for K. The reduction in nutrient uptake in sorghum due to subsoil compaction was 23% for N, 16% for P, and 12% for K. Subsoil compaction increased N content in wheat grains in 1997–1998, but there was no effect on P and K contents of grains and N and P content of wheat straw or sorghum stover. During 1997–1998, K content of wheat straw was statistically higher in control treatment compared with compacted treatment. In 1998, P-content of sorghum leaves was higher in compacted treatment than uncompacted control. Root length density of wheat below 0.15 m depth was significantly reduced and was significantly and negatively correlated with soil bulk density. Therefore, appropriate measures such as periodic chiselling, controlled traffic, conservation tillage, and incorporating of crops with deep tap root system in rotation cycle is necessary to minimize the risks of subsoil compaction.     

Land configuration and soil nutrient management options for sustainable crop production on Alfisols and Vertisols of southern peninsular India

Land configuration in combination with nutrient management has the potential to improve the productivity of Alfisols and Vertisols in the semi-arid tropics. A four year (1989–1990 and 1992–1993) field experiment was conducted at Coimbatore, India on Alfisols (Chromic Cambisol) to compare the effect of land configuration and nutrient management practices on yield of rainfed sorghum (Sorghum bicolor (L.) Moench). The land configuration treatments were flat bed (FB, the traditional practice), open ridging (OR, ridges, 45 cm apart and 30 cm high) and tied ridging (TR, same as OR plus ridges were tied randomly). The manure and fertilisers were farm yard manure (FYM, livestock excreta plus litter at 5 Mg ha⁻¹) and coir dust (CD, by-product after the extraction of coir from the coconut (Cocos nucifera L.) husk at 12.5 Mg ha⁻¹) in combination with nitrogen (N) and phosphorus (P) fertiliser levels. Tied ridges stored 14% more soil water and produced 14% and 11% more grain and straw yields of sorghum, respectively, than did flat bed. However, crop yield in TR was comparable with OR. Application of CD at 12.5 Mg ha⁻¹ combined with 40 kg N ha⁻¹ and 9 kg P ha⁻¹ was beneficial for more soil water storage and increased yield of sorghum by 7% over FYM at 5 Mg ha⁻¹ + 40 kg N ha⁻¹ and 9 kg P ha⁻¹. In Vertisols (Vertic Cambisols), experiments were conducted for two years (1991–1992 and 1992–1993) to evaluate land configuration practices. The treatments were broad bed furrow (BBF, 120 cm wide bed with 30 cm wide and 15 cm deep furrows on both sides), compartmental bunding (CB, bunds of 15 cm height formed in all the four sides to form a check basin of 6 m × 5 m size), ridging (RD, ridges were formed for each and every row of the crop manually at four weeks after sowing) and FB under sorghum + pigeonpea (Cajanus cajan (L.) Millsp) and pearl millet (Pennisetum glacum (L.) Stuntz) + cowpea (Vigna unguiculata (L.) Walp) intercropping separately. Compartmental bunding stored 22% more soil moisture and increased the yield of sorghum + pigeonpea intercropping than did FB in a low rainfall year. In a high rainfall year, BBF produced 34% and 33% more grain yield of sorghum and pearl millet base crops, respectively, over FB. However, BBF and CB were comparable. Pigeonpea intercrop under sorghum followed the same trend as its base crop, whereas, yield of cowpea differed compared to the pearl millet base crop. Tied ridging and application of manures (CD or FYM) in combination with inorganic N and P fertiliser can increase the soil water storage and yield of crops compared to traditional flat bed cultivation in rainfed Alfisol and related soils of semi-arid tropics. Similarly BBF and CB land configuration practices could be adopted on Vertisols for better water conservation to increase the soil fertility and productivity of intercropping systems.     

The effect of urban refuse compost and different tractors tyres on soil physical properties, soil erosion and maize yield

Application of urban refuse compost to agricultural soil could help to solve municipalities' problems related to the increasing production of waste only if soil property improvement and environmental conservation can be demonstrated. The use of low-pressure tractor tyres is another proposal in modern agriculture for reducing soil compaction. This study thus aimed to detect the effects of both compost and low-pressure tractor tyres on soil loss, runoff, aggregate stability, bulk density, penetrometer resistance and maize (Zea mays L.) yield. A 3-year field experiment was carried out on a hilly (15% slope) clay loam soil in central Italy. Twelve plots (200 m² each) were monitored with tipping-pot devices for runoff and soil erosion measurement. Treatments were: compost addition (64 Mg ha⁻¹), mineral fertilisation, use of low-pressure tyres, use of traditional tyres, with three replicates, in a fully randomised block design. Compost was applied once at the beginning of the experiment. Runoff reduction due to compost ranged between 7 and 399 m³ ha⁻¹ during seasons, while soil erosion was reduced between 0.2 and 2.4 Mg ha⁻¹. Mean weight diameter (MWD) of stable aggregates, measured on wheel tracks, increased by 2.19 mm, then progressively decreased. Compost significantly increased bulk density by 0.08 Mg m⁻³ due to its inert fraction content. This effect was less evident in the second and third year, probably due to harrowing. Maize yields were slightly, but significantly, reduced in composted plots by 1.72 Mg ha⁻¹ in the third year. Low-pressure tyres significantly reduced soil loss in the third year by 1 Mg ha⁻¹. Furthermore, they did not significantly influence runoff volumes and soil structural stability. Low-pressure tyres or compost addition were singly able to prevent an increase in penetrometer resistance due to agricultural machinery traffic. Low-pressure tyres increased the maize yield during the 3 years and the difference (0.4 Mg ha⁻¹) became significant in the third year. In conclusion, results show the positive lasting effect of compost in ameliorating soil physical properties and reducing runoff and soil erosion. Low-pressure tyres appear justifiable both for the observed increase of grain production and reduction of soil compaction. This latter effect is, nevertheless, masked by compost addition which is also able to reduce penetrometer resistance. Further research is required to explain the causes of the slight inhibition of grain yield observed when compost was compared with mineral fertilisation.     

Do effects of soil compaction persist after ploughing? Results from 21 long-term field experiments in Sweden

The extent and persistence of the effect of soil compaction in a system with annual ploughing were investigated in 21 long-term field experiments in Sweden with a total of 259 location-years. Crop yield, soil physical properties and plant establishment were determined. All experiments had two common treatments: control (no extra traffic) and compacted (350 Mg km ha⁻¹ of experimental traffic in the autumn prior to ploughing), using a tractor and trailer with traditional wheel equipment and an axle load restricted to 4 Mg. During the rest of the year, both treatments were conventionally and equally tilled. The compaction was repeated each autumn for at least 7 years, and the yield was determined each year until 5 years after the termination of the compaction treatment.

Compaction decreased the porosity and the proportion of large pores and increased the tensile strength of dry aggregates. On clay and loam soils, it decreased the proportion of fine aggregates in the seedbed and the gravimetric soil water content in the seedbed.

The yield in the compacted treatment declined compared with the control during the first 4 years, after which it reached steady state. During this steady state, the compaction treatment caused a yield loss of 11.4%, averaged over 107 location-years. Within 4–5 years after the termination of the compaction treatment, the yield returned to the control level. The average yield loss at individual sites increased with increasing clay content.

Results from additional treatments indicated that yield loss was linearly correlated with the amount of traffic up to 300–400 Mg km ha⁻¹. With greater ground contact pressure or a greater soil water content at time of traffic, there was a greater yield loss.

Soil compaction effects on yield were similar for all spring-sown crops, and the percentage yield loss seemed to be independent of the yield. In a few location-years with winter wheat there was on average no yield decrease.

There were 5.1% less plants in the compacted treatment than in the control. The yield decrease was significantly correlated with the number of plants.

Between years results were highly variable, and no consistent correlations between yield loss and soil water content at the time of traffic or the weather conditions during the growing period were found. Soil compaction affected yield during years with good as well as poor conditions for crop growth.     

Physical characterization of a soil amended with organic residues in a rice–wheat cropping system using a single value soil physical index

The effect of soil incorporations of lantana (Lantana spp.) biomass, an obnoxious weed, on physical environment of a silty clay loam soil (Typic Hapludalf) under rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping was studied in a long-term field experiment conducted in a wet temperate region of north India. Fresh lantana biomass was incorporated into the plough layer at 10, 20 and 30 Mg ha⁻¹ annually, 7–10 days before puddling. Plant-available water capacity (PAWC), non-limiting water range (NLWR) and NLWR:PAWC ratio were determined to characterize soil physical environment during wheat crop in the tenth cropping cycle.

Ten annual applications of lantana at 10, 20 and 30 Mg ha⁻¹, increased organic carbon (OC) content over control by 12.6, 17.6 and 27.9% in 0–15 cm soil layer, and 17.1, 26.3 and 39.5% in 15–30 cm soil layer, respectively. The OC content in 0–15 and 15–30 cm soil layer of control plots was 11.1 and 7.6 g kg⁻¹ soil. Bulk density decreased by 3–14% in 7.5–10.5 cm layer and 1–6% in 15–18 cm layer. Volumetric moisture contents at 10% air-filled porosity were 38.4, 40.0, 54.5 and 55.7% at 7.5–10.5 cm depth, and 31.4, 32.2, 33.9 and 34.6% at 15–18 cm depth corresponding to 0, 10, 20 and 30 Mg ha⁻¹ lantana treatment, respectively. At 15–18 cm soil depth, volumetric moisture contents at 2 MPa soil penetration resistance were 26.9, 24.8, 23.0 and 19.6% in zero, 10, 20 and 30 Mg ha⁻¹ lantana-treated plots, respectively. Lower soil water contents associated with 10% air-filled porosity and greater soil water contents associated with a limiting penetration resistance of 2 MPa resulted in a lower NLWR (4.3%) for control as compared to lantana-treated soil (7.4–15.1%). The PAWC showed slight increase from 12.9 to 13.4–14.9% due to lantana additions. The NLWR:PAWC ratio was also lower in control (0.33) as compared to lantana-treated soil (0.55–1.01). The NLWR was significantly and positively correlated with wheat grain yield (r=0.858^**).     

Long-term effects of tillage systems and rotations on soil structural stability and organic carbon stratification in semiarid central Spain

Under semiarid Mediterranean climatic conditions, soils typically have low organic matter content and weak structure resulting in low infiltration rates. Aggregate stability is a quality indicator directly related to soil organic matter, which can be redistributed within soil by tillage. Long-term effects (1983–1996) of tillage systems on water stability of pre-wetted and air dried aggregates, soil organic carbon (SOC) stratification and crop production were studied in a Vertic Luvisol with a loam texture. Tillage treatments included conventional tillage (CT), minimum tillage (MT) and zero tillage (ZT) under winter wheat (Triticum aestivum L.) and vetch (Vicia sativa L.) rotation (W–V), and under continuous monoculture of winter wheat or winter barley (Hordeum vulgare L.) (CM). Aggregate stability of soil at a depth of 0–5 cm was much greater when 1–2 mm aggregates were vacuum wetted prior to sieving (83%) than when slaked (6%). However, slaking resulted in tillage effects that were consistent with changes in SOC. Aggregate stability of slaked aggregates was greater under ZT than under CT or MT in both crop rotations (i.e., 11% vs. 3%, respectively).

SOC under ZT tended to accumulate in the surface soil layer (0–5 and 5–10 cm) at the expense of deeper ones. At depths of 10–20 and 20–30 cm no differences in SOC were encountered among tillage systems, but CT exhibited the highest concentration at 30–40 cm depth. Nevertheless, when comparisons were made on mass basis (Mg ha⁻¹), significant differences in stocked SOC were observed at depths of 0–10 and 0–20 cm, where ZT had the highest SOC content in both rotations. The stock of SOC to a depth of 40 cm, averaged across crop rotations, was greater under ZT (43 Mg ha⁻¹) than under CT (41 Mg ha⁻¹) and MT (40 Mg ha⁻¹) although these figures were not significantly different. Likewise, no significant differences were encountered in the stock of SOC to a depth of 40 cm among crop rotations (i.e., 42 Mg ha⁻¹ for W–V vs. 40 Mg ha⁻¹ for CM).

Crop production with wheat–vetch and continuous cereal showed no differences among tillage systems. Yields were strongly limited by the environmental conditions, particularly the amount of rainfall received in the crop growth season and its distribution. Similar yield and improved soil properties under ZT suggests that it is a more sustainable system for the semiarid Mediterranean region of Spain.     

Amelioration of soil compaction can take 5 years on a Vertisol under no till in the semi-arid subtropics

Heavy wheel traffic causes soil compaction, which adversely affects crop production and may persist for several years. We applied known compaction forces to entire plots annually for 5 years, and then determined the duration of the adverse effects on the properties of a Vertisol and the performance of crops under no-till dryland cropping with residue retention. For up to 5 years after a final treatment with a 10 Mg axle load on wet soil, soil shear strength at 70–100 mm and cone index at 180–360 mm were significantly (P < 0.05) higher than in a control treatment, and soil water storage and grain yield were lower. We conclude that compaction effects persisted because (1) there were insufficient wet–dry cycles to swell and shrink the entire compacted layer, (2) soil loosening by tillage was absent and (3) there were fewer earthworms in the compacted soil. Compaction of dry soil with 6 Mg had little effect at any time, indicating that by using wheel traffic only when the soil is dry, problems can be avoided. Unfortunately such a restriction is not always possible because sowing, tillage and harvest operations often need to be done when the soil is wet. A more generally applicable solution, which also ensures timely operations, is the permanent separation of wheel zones and crop zones in the field—the practice known as controlled traffic farming. Where a compacted layer already exists, even on a clay soil, management options to hasten repair should be considered, e.g. tillage, deep ripping, sowing a ley pasture or sowing crop species more effective at repairing compacted soil.     

Effect of cropland management and slope position on soil organic carbon pool at the North Appalachian Experimental Watersheds

Soil organic matter is strongly related to soil type, landscape morphology, and soil and crop management practices. Therefore, long-term (15–36-years) effects of six cropland management systems on soil organic carbon (SOC) pool in 0–30 cm depth were studied for the period of 1939–1999 at the North Appalachian Experimental Watersheds (<3 ha, Dystric Cambisol, Haplic Luvisol, and Haplic Alisol) near Coshocton, OH, USA. Six management treatments were: (1) no tillage continuous corn with NPK (NC); (2) no tillage continuous corn with NPK and manure (NTC-M); (3) no tillage corn–soybean rotation (NTR); (4) chisel tillage corn–soybean rotation (CTR); (5) moldboard tillage with corn–wheat–meadow–meadow rotation with improved practices (MTR-I); (6) moldboard tillage with corn–wheat–meadow–meadow rotation with prevalent practices (MTR-P). The SOC pool ranged from 24.5 Mg ha⁻¹ in the 32-years moldboard tillage corn (Zea mays L.)–wheat (Triticum aestivum L.)–meadow–meadow rotation with straight row farming and annual application of fertilizer (N:P:K=5:9:17) of 56–112 kg ha⁻¹ and cattle (Bos taurus) manure of 9 Mg ha⁻¹ as the prevalent system (MTR-P) to 65.5 Mg ha⁻¹ in the 36-years no tillage continuous corn with contour row farming and annual application of 170–225 kg N ha⁻¹ and appropriate amounts of P and K, and 6–11 Mg ha⁻¹ of cattle manure as the improved system (NTC-M). The difference in SOC pool among management systems ranged from 2.4 to 41 Mg ha⁻¹ and was greater than 25 Mg ha⁻¹ between NTC-M and the other five management systems. The difference in the SOC pool of NTC-M and that of no tillage continuous corn (NTC) were 16–21 Mg ha⁻¹ higher at the lower slope position than at the middle and upper slope positions. The effect of slope positions on SOC pools of the other management systems was significantly less (<5 Mg ha⁻¹). The effects of manure application, tillage, crop rotation, fertilizer rate, and soil and water conservation farming on SOC pool were accumulative. The NTC-M treatment with application of NPK fertilizer, lime, and cattle manure is an effective cropland management system for SOC sequestration.     

Tillage effects and energy efficiencies of subsoiling and direct seeding in light soil on yield of second crop corn for silage in Western Turkey

The objective of this study was to examine tillage effects and energy efficiencies of subsoiling and direct seeding on yield of second crop corn (Zea mays L.) for silage in light soil of Odemis located in the western part of Turkey. In this research, tillage and direct seeding were applied in dry and wet soil conditions after winter wheat (Triticum aestivum L.) harvesting in the years 2002 and 2003. The effects of conventional tillage method, reduced tillage methods that include one and cross pass subsoiling, and direct seeding applications on corn yield were examined. In the experiment, a regular four-row corn planter was used. Tillage speed, slip, fuel consumptions, seedling emergence, plant height, and yield were measured. From the data, total energy requirement and effectiveness of each method were calculated.

The highest fuel consumption was measured in conventional method (PLG) whereas the lowest value was found in direct seeding method (DIR) as 60.5 l ha⁻¹ and 7.5 l ha⁻¹ in 2002, respectively. The conventional method required seven times more fuel than the direct seeding method. For field efficiencies, as parallel to the finding in fuel consumption, the highest value was 1.34 ha h⁻¹ in DIR and 0.40 ha h⁻¹ in one pass subsoiling method (SUB I). DIR method had nine times more field efficiencies as compared to the conventional method. The highest yield was found in cross pass subsoiling method (SUB II) as 72.6 Mg ha⁻¹ and 61.6 Mg ha⁻¹ in the first and second year, respectively. Although DIR has minimum fuel consumption and maximum field efficiency, this method gave the lowest yield as 64.7 Mg ha⁻¹ in the first year and 37.2 Mg ha⁻¹ in the second year.     

Response of conservation tillage sorghum to growing season precipitation

In earlier crop rotation studies in which grain sorghum (Sorghum bicolor (L.) Moench) followed winter wheat (Triticum aestivum L.) after a 10- to 11-month fallow period during which the wheat residues were managed by different tillage methods, sorghum yields increased in response to increases in soil water content at sorghum planting time. Similar results were obtained when residues were placed on the surface at the start of the fallow period. The soil water contents at planting time were positively correlated with amounts of wheat residue maintained on the soil surface during fallow.

The studies also suggested that sorghum responded positively to growing season precipitation when increasing of residue remained on the soil during the growing season. The objective of this study was to evaluate this response to growing season precipitation through statistical analyses of data from five earlier tillage and residue placement studies. Regression analyses of data from the studies showed that sorghum grain yields increased with increasing amounts of surface residues at planting time. Differences in response of grain yield to precipitation were greatest in the vegetative period. For the period, grain yields increased 0.014 Mg ha⁻¹ per mm of precipitation when residue amounts ranged from 0 to 0.4 Mg ha⁻¹ per mm of precipitation when residue amounts ranged from 0 to 0.4 Mg ha⁻¹, and 0.027 Mg ha⁻¹ per mm of precipitation when residue amounts were 3.2 Mg ha⁻¹.

Differences in response to rainfall in the heading and grain filling period were lower or negligible. High responses for the vegetative period were attributed to the residues which increased infiltration and reduced evaporation before canopy development. Lower responses during heading and lack of responses during grain filling were attributed to: (1) canopy development, which minimized the effect of residues on imfiltration and evaporation; (2) soil cracking, which resulted in similar infiltration with all treatments; and (3) residue decomposition, which minimized differences among residue amounts on the soil with different treatments.     

Surface-soil responses to paraplowing of long-term no-tillage cropland in the Southern Piedmont USA

The type of conservation-tillage management employed could impact surface-soil properties, which could subsequently affect relationships between soil and water quality, as well as with soil C sequestration and greenhouse gas emissions. We determined soil bulk density, organic C and N fractions, plant-available N, and extractable P on Typic Kanhapludults throughout a 7-year period, in which four long-term (>10 years), no-tillage (NT) water catchments (1.3–2.7 ha each) were divided into two treatments: (1) continuation of NT and (2) paraplowing (PP) in autumn (a form of non-inversion deep ripping) with NT planting. Both summer [cotton (Gossypium hirsutum L.), maize (Zea mays L.), sorghum (Sorghum bicolor L. Moench), soybean (Glycine max L. Merr.)] and winter [wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.)] crops were NT planted throughout the study under each management system. Soil bulk density was reduced with PP compared with NT by as much as 0.15 Mg m⁻³, but the extent of reduction was inversely related to the time lag between PP operation and sampling event. Soil organic C became significantly enriched with time during this study under NT (0.49 Mg C ha⁻¹ year⁻¹), but not under PP, in which poultry litter was applied equivalent to 5.7 Mg ha⁻¹ year⁻¹ to all water catchments. Soil maintained a highly stratified depth distribution of organic C and N fractions and extractable P under both NT and PP. Inability to perform the PP operation in the last year of this study resulted in rapid convergence of soil bulk density between tillage systems, suggesting that PP had <1-year effectiveness on soil loosening. The high energy cost of PP (ca. 30 kW shank⁻¹) and the lack of sustained improvement in surface-soil properties put into question the value of PP for improving upon long-term NT management in sandy loam and sandy clay loam Ultisols of the Southern Piedmont USA, unless large effects on crop yield, water quality, or other ecosystem processes warrant its use.     

Puddling, irrigation, and transplanting-time effects on productivity of rice–wheat system on a sandy loam soil of Punjab, India

Rice–wheat productivity in irrigated tract of the Indo-Gangetic plains is constrained by water and energy limitations. In order to minimize unproductive soil water evaporation and percolation loss at a field scale, management practices include soil puddling, water-economizing irrigation schedule, and matching growth cycle with periods of low evaporative demand. This 3-year field study examines combined effects of these options on rice–wheat productivity and water-use efficiency (WUE) and energy-use efficiency (EUE) on a sandy loam soil in an irrigated semi-arid sub-tropical environment. Treatments included combinations of three puddling intensities, viz., one (P₁), two (P₂), and four (P₄) runs of a tine cultivator in ponded water after a common pre-puddling tillage; with two irrigation regimes, viz., continuous submergence (I₁) throughout the growing season, and intermittent submergence (I₂) with continuous submergence for 2 weeks after transplanting followed by 2-day interval between successive irrigations, and two transplanting dates, viz., first fortnight of June (D₁) and end June (D₂) to impose variation in seasonal evaporative demand. Residual effect of puddling in rice on succeeding wheat was also evaluated during the 3 years.

Intensive puddling and water-economizing schedule caused a significant reduction in seasonal percolation loss primarily due to puddling-induced changes in soil bulk density and hydraulic behavior. Increasing puddling intensity from P₁ to P₂ enhanced mean rice yield by 0.2–0.3 Mg ha⁻¹, but additional puddling did not improve yield significantly. Mean grain yield increase with I₁ over I₂ ranged between 0.3 and 0.6 Mg ha⁻¹. Interaction effect between puddling and irrigation indicate that yield benefit with I₁ over I₂ was greatest in P₁ regime (0.6 Mg ha⁻¹), and the effect decreased with increase in puddling intensity. Delayed transplanting caused a decline of 0.3–0.5 Mg ha⁻¹ in rice yield. Although maximum yield was realized with combination of P₂ or P₄ regime with I₁ regime, but water-use efficiency was greater with I₂ compared to I₁ regime by 1.1 kg ha⁻¹ mm⁻¹ in 2000 and by 0.3 kg ha⁻¹ mm⁻¹ in 2001. It indicates that yield gain with additional irrigation were not commensurate with additional water input. Energy analysis also showed that energy-use efficiency was 6.8, 7.2, and 6.6 kg kWh⁻¹ for P₁, P₂, and P₄ regimes suggesting that yield gain with P₄ did not match energy input for additional puddling. Further, there was a greater risk of yield reduction of succeeding wheat with P₄ (by 0.2–0.3 Mg ha⁻¹) compared to P₁ or P₂ regime.     

Effects of subsoil compaction on yield and yield attributes of wheat in the sub-humid region of Pakistan

The prolonged use of vehicular traffic for farming creates subsoil compaction, which reduces crop yield and deteriorates the physical conditions of the soil. Field experiments were conducted during 2002–2003 and 2003–2004 in Pakistan to study subsoil compaction effects on soil bulk density, total porosity, yield and yield components of wheat. Soil compaction was artificially created at the start of the experiment using 7.0 t roller having length of 1.5 m and diameter of 1.22 m. Treatments consisted of T₁ = control (no compaction), T₂ = two passes of roller, T₃ = four passes of roller, T₄ = six passes of roller. The experiments were arranged in randomised complete block with four replications. Results indicated that subsoil compaction adversely affected the bulk density, total porosity of soil and root length during both the years. Soil compaction increased the bulk density (BD) from 1.37 for T₁ to 1.57, 1.61 and 1.72 Mg m⁻³ whereas decreased the total porosity from 47.3% for T₁ to 40.0, 37.4 and 34.5% for T₂, T₃ and T_4, respectively. Similarly grain yield decreased from 4141.7 for T₁ to 3912.8, 3364.5 and 3010.3 kg ha⁻¹ for T₂, T₃ and T_4, respectively. The deteriorating effect of compaction depended upon the degree of compaction. Subsoil compaction adversely affected the yield and yield attributes of wheat during both years of experiments. The subsoil compaction adversely affected soil physical conditions, which substantially decreased the yield of wheat. Therefore, appropriate measures of periodic chiselling, controlled traffic, conservation tillage, and incorporating of crops with deep tap root system in rotation cycle is necessary to minimize the risks of subsoil compaction.     

Soil compaction and poultry litter effects on factors affecting nitrogen availability in a claypan soil

Soil compaction may affect N mineralization and the subsequent fate of N in agroecosystems. Laboratory incubation and field experiments were conducted to determine the effects of surface soil compaction on soil N mineralization in a claypan soil amended with poultry litter (i.e., Turkey excrement mixed with pine shavings as bedding). In a laboratory study, soil from the surface horizon of a Mexico silt loam soil was compacted to four bulk density levels (1.2, 1.4, 1.6 and 1.8 Mg m⁻³) with and without poultry litter and incubated at 25 °C for 42 days. A field trial planted to corn (Zea mays L.) was also conducted in 2002 on a Mexico silt loam claypan soil in North Central Missouri. Soil was amended with litter (0 and 19 Mg ha⁻¹) and left uncompacted or uniformly compacted. Soil compaction decreased soil inorganic N by a maximum of 1.8 times in the laboratory study; this effect was also observed at all depths of the field trial. Compacted soil with a litter amendment accumulated NH₄⁺-N up to 7.2 times higher than the noncompacted, litter-amended soil until Day 28 of the laboratory incubation and in the beginning of the growing season of the field study. Ammonium accumulation may have been due to decreased soil aeration under compacted conditions. Application of litter increased soil N mineralization throughout the growing season. In the laboratory study, soil inorganic N in unamended soil was negatively correlated with soil bulk density and the proportion of soil micropores, but was positively related with soil total porosity and the proportion of soil macropores. These results indicate that soil compaction, litter application and climate are interrelated in their influences on soil N mineralization in agroecosystems.     

Tillage, crop residue and N fertilizer effects on crop yield, nutrient uptake, soil quality and nitrous oxide gas emissions in a second 4-yr rotation cycle

An 8-yr (1998–2005) field experiment was conducted on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada, to determine the effects of tillage (no-tillage – NT and conventional tillage – CT), straw management (straw retained – R and straw not retained – NR) and N fertilizer (0, 40, 80 and 120 kg N ha⁻¹, except no N to pea (Pisum sativum L.) phase of the rotation) on seed and straw yield, mass of N and C in crop, organic C and N, inorganic N and aggregation in soil, and nitrous oxide (N₂O) emissions for a second 4-yr rotation cycle (2002–2005). The plots were seeded to barley (Hordeum vulgare L.) in 2002, pea in 2003, wheat (Triticum aestivum L.) in 2004 and canola (Brassica napus L.) in 2005. Seed, straw and chaff yield, root mass, and mass of N and C in crop increased with increasing N rate for barley in 2002, wheat in 2004 and canola in 2005. No-till produced greater seed (by 51%), straw (23%) and chaff (13%) yield of barley than CT in 2002, but seed yield for wheat in 2004, and seed and straw yield for canola in 2005 were greater under CT than NT. Straw retention increased seed (by 62%), straw (by 43%) and chaff (by 12%) yield, and root mass (by 11%) compared to straw removal for barley in 2002, wheat in 2004, and seed and straw yield for pea in 2003. No-till resulted in greater mass of N in seed, and mass of C in seed, straw, chaff and root than CT for barley in 2002, but mass of N and C were greater under CT than NT for wheat in 2004 and for canola in 2005 in many cases. Straw retention had greater mass of N and C in seed, straw, chaff and root in most cases compared to straw removal for barley in 2002, pea in 2003 and wheat in 2004. Soil moisture content in spring was higher under NT than CT and with R than NR in the 0–15 cm depth, with the highest moisture content in the NT + R treatment in many cases. After eight crop seasons, tillage and straw management had no effect on total organic C (TOC) and N (TON) in the 0–15 cm soil, but light fraction organic C (LFOC) and N (LFON), respectively, were greater by 1.275 Mg C ha⁻¹ and 0.031 Mg N ha⁻¹ with R than NR, and also greater by 0.563 Mg C ha⁻¹ and 0.044 Mg N ha⁻¹ under NT than CT. There was no effect of tillage, straw and N fertilization on the NH₄-N in soil in most cases, but R treatment had higher NO₃-N concentration in the 0–15 cm soil than NR. The NO₃-N concentration in the 0–15, 15–30 and 30–60 cm soil layers increased (though small) with increasing N rate. The R treatment had 6.7% lower proportion of fine (<0.83 mm diameter) and 8.6% greater proportion of large (>38.0 mm) dry aggregates, and 4.5 mm larger mean weight diameter (MWD) compared to NR treatment. This suggests a lower potential for soil erosion when crop residues are retained. There was no beneficial effect of elimination of tillage on soil aggregation. The amount of N lost as N₂O was higher from N-fertilized (580 g N ha⁻¹) than from zero-N (155 g N ha⁻¹) plots, and also higher in CT (398 g N ha⁻¹) than NT (340 g N ha⁻¹) in some cases. In conclusion, retaining crop residues along with no-tillage improved some soil properties and may also be better for the environment and the sustainability of high crop production. Nitrogen fertilization improved crop production and some soil quality attributes, but also increased the potential for NO₃-N leaching and N₂O-N emissions, especially when applied in excess of crop requirements.     

Interaction of soil compaction, phosphorus and zinc on clover growth and accumulation of phosphorus

Soil compaction generally reduces crop performance because of degraded soil physical and biological properties, and possibly inappropriate soil nutritional status. The effects of varying compaction, and phosphorus (P) and zinc (Zn) supplies on the growth of Berseem or Egyptian clover (Trifolium alexandrimum), and accumulation of P and Zn in shoots and roots were investigated in a pot experiment using a surface layer of a Typic Torrifluvent (USDA), Calcaric Fluvisols (FAO) soil. Plants were treated with three soil compaction levels, three rates of P and three rates of Zn in a factorial combination. Phosphorus accumulation in shoots did not change up to bulk densities of 1.65 Mg m⁻³ and declined at bulk density of 1.80 Mg m⁻³. Increasing the levels of Zn and P resulted in a significant increase in shoot dry mass (from 0.3 to 0.8 g pot⁻¹), and root length (from 11.4 to 32.5 m pot⁻¹). Shoot and root growth were reduced by soil compaction particularly at low P and Zn application rates. Shoot dry mass was reduced from 0.8 to 0.3 g pot⁻¹, and root length from 43 to 5 m pot⁻¹ at bulk densities of 1.4 and 1.8 Mg m⁻³, respectively. However, the accumulation of P (from 0.06 to 0.15 g kg⁻¹) and Zn per unit length of roots (from 0.8 to 1.8 μg pot⁻¹) increased as soil compaction increased. As the Zn supply increased, Zn accumulation per unit length of roots, and total Zn accumulation increased. Severe compaction reduced P and Zn accumulation in shoots and also decreased shoot dry mass, and root length compared to lower soil compaction levels. The present study suggests that Zn and P supply can moderate the adverse effect of soil compaction on clover performance.