Effect of tillage and residue management on hydrol-thermal regimen, nutrient uptake and yield of wheat in a river deposit

Field experiments were conducted on a river deposit during 1983–1984 and 1984–1985 in order to study the effect of different soil management practices, such as zero tillage with surface-applied crop residue mulch at a rate of 10 t ha⁻¹ (ZT+M), conventional tillage (CT), CT+ surface-applied crop residue mulch at a rate of 10 t ha⁻¹ (CT + M), CT+crop residue incorporation at a rate of 10 t ha⁻¹ (CT + SI), CT + farmyard manure incorporation at a rate of 10 t ha⁻¹ (CT + FYM), on soil hydro-thermal regime root growth, nutrient uptake and dry matter yield of winter wheat (Triticum aestivum L.). The soils of the site are classified as Entisol, Typic Psammaquent with pH 6.0, cation exchange capacity 10 c mol (p⁺) per kg in the surface (0–0.3 m) depth. In the CT + M and CT + FYM treatments, higher water retention was observed compared to CI. The minimum soil temperature was also raised by 3°C under CT + M to CT at 0.1-m depth. CT + M and CT + FYM had significantly higher root mass density compared with other treatments at all stages of crop growth. The nitrogen (N) uptake under these two treatments was also significantly higher compared to CT. Under CT+M, plants did not suffer from N stress compared to other treatments. Phosphorus (P) uptake (except at tillering) and potassium (K) uptake under CT+M and CT + FYM were significantly higher than for all the other treatments. Treatments ZT+M and CT+SI behave simply to CT in terms of hydro-thermal regime, root growth, nutrient uptake and dry matter yield. The grain yield under CT+M and CT+FYM during 1983–1984 and 1984–1985 was significantly higher than that under all the other treatments.     

Moisture conservation for rainfed wheat production with alternative mulches and conservation tillage in the hills of north-west India

In the hills of north–west India, maize (Zea mays L.)-wheat (Triticum aestivum L.) is the dominant cropping system. However, rainfed wheat suffers from lack of optimum moisture at sowing. Field experiments were conducted for 3 years on a silty clay loam (Typic Hapludalf) to evaluate the effectiveness of mulches and conservation tillage for rainfed wheat in mitigating this problem. The treatments were ten factorial combinations of five mulch-tillage practices and two nitrogen levels (N₆₀ and N₁₂₀ kg ha⁻¹). Mulch treatments consisted of application of 10 Mg ha⁻¹ (dry weight basis), to previous standing maize, of either wild sage (Lantana camara L.) or eupatorium (Eupatorium adenophorum Sprengel) in combination with either conventional or conservation (minium) tillage prior to wheat sowing. These alternative practices were compared to the conventional farmer practice of soil tillage after harvest of maize with no mulch. The application of these weed mulches to standing maize maintained friable soil structure owing to a five fold higher mean population of earthworms underneath mulch. Mulches resulted in 0.06–0.10 m³ m⁻³ higher moisture in the seed-zone when wheat was sown compared with the conventional farmer practice of soil tillage after maize harvest. Mulch-conservation tillage treatments favourably moderated the hydro-thermal regime for growing a wheat crop. The mean root mass density under these treatments at wheat flowering was higher by 1.27–1.40 times over the conventional farmer practice during the 3 year study. Conservation tillage holds promise because it does not require elaborate tillage and may ultimately reduce animal draught in the hilly regions. Recycling available organic materials having no fodder value coupled with conservation tillage may help enrich the soil environment in the long-term. The practice also offers gainful use of these obnoxious weeds that cause great menace in grass and forest lands in the region.     

Effect of management of a Himalayan Alfisol on water conservation for rainfed crops

Field experiments were conducted during 1989 and 1990 to study the effect of various soil management practices on water conservation during the two prime planting periods in the lower Himalayan region. Treatments studied were: zero tillage with weed control (ZT+W), zero tillage (ZT), fine tilth (FT), coarse tilth (CT), zero tillage with surface-applied lantana (Lantana camara L.) mulch at 10 t ha⁻¹ (ZT+M), fine tilth with surface-applied lantana mulch at 10 t ha⁻¹ (FT+M), fine tilth with surface-applied farmyard manure mulch at 10 t ha⁻¹ (FT+FYM) and fine tilth with FYM incorporated at 10 t ha⁻¹ (FYM). The soils were Typic Hapludalfs with pH 5.8, organic carbon 6.6 g kg⁻¹ and cation exchange capacity 12 cmol (P⁺) (100 g)⁻¹. The lantana mulch application to fine tilth (FT+M) or zero tillage (ZT+M) maintained higher seed-zone water content and profile water storage as compared with all the other treatments. Highest water depletion was observed under ZT+W treatment. Seed germination is likely to occur only under FT+M and ZT+M during the two prime planting periods, if field capacity water content is considered to be limiting for seed germination. However, for the other treatments rainfall would invariably be required to increase the surface water content, to allow germination and early seedling establishment.     

The impact of tillage and residual nitrogen on wheat

Wheat (Triticum aestivum L.) yield and quality is influenced by management of the previous crop but is highly dependent on current year management. The objective of this study was to evaluate the response of winter wheat seeded in two tillage systems [conventional tillage (CT) and no-till (NT)] to four N rates applied to a previous cotton (Gossypium hirsutum L.) crop (0, 67, 134, and 202 kg ha⁻¹). The experiment with wheat was conducted on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida North Florida Research and Education Center near Quincy, FL from 1995 to 1997. For most plant characteristics, there was a tillage x N x year interaction. Greater plant emergence (79.4 vs. 65.3%) and grain N (23.5 vs. 21.5 g kg⁻¹), and lower grain moisture (139 vs. 142 g kg⁻¹) were obtained under NT than CT, respectively, in one out of two years. Nitrogen applied to a previous cotton crop increased wheat grain yields, plant height and seed number under NT in 1995–1996 and CT in 1996–1997, head density under NT in both years, harvest index under CT in 1996–1997, and grain N concentration in 1995–1996 and 1996–1997 due to residual plant and soil N. With every 1 kg N applied to a previous cotton crop, wheat grain yields increased by 5.38 kg ha⁻¹ under NT, whereas grain yield under CT was not influenced by N application to cotton in 1995–1996. In 1996–1997, grain yields increased by 4.96 and 4.23 kg ha⁻¹ for wheat grown in NT and CT, respectively. Generally, wheat seeded in NT following cotton did not decrease stand or yields compared to CT and wheat grain yields and grain N content increased with N fertilization of the previous crop. However, we would have to apply about 134 kg N ha⁻¹ to a previous cotton crop to maximize wheat production under NT and CT.     

Tillage, nitrogen and crop residue effects on crop yield, nutrient uptake, soil quality, and greenhouse gas emissions

Management practices that simultaneously improve soil properties and yield are crucial to sustain high crop production and minimize detrimental impact on the environment. The objective of this study was to determine the influence of tillage and crop residue management on crop yield, N uptake and C removal in crop, soil organic C and N, inorganic N and aggregation, and nitrous oxide (N₂O) emissions on a Gray Luvisol (Boralf) soil near Star City, Saskatchewan, Canada. The 4-year (1998–2001) field experiment was conducted with two tillage systems: no tillage (NT), and conventional tillage (CT); two levels of straw: straw retained (S), and straw removed (NS); and four rates of fertilizer N: 0, 40, 80, and 120 kg N ha⁻¹, except no N to pea phase of the rotation. The plots were seeded to barley (Hordeum vulgare L.) in 1998, pea (Pisum sativum L.) in 1999, wheat (Triticum aestivum L.) in 2000 and canola (Brassica napus L.) in 2001. Tillage and straw treatments generally had no effect on crop yield during the first three years. But in 2001, NT produced 55, 32, and 20% greater canola seed, straw and chaff than CT, respectively, whereas straw retention increased seed and straw yield by 33 and 19% compared to straw removal. Seed, straw and chaff yield of canola increased with N rate up to 40 kg N ha⁻¹, and root mass (0–15 cm depth) with N rate to 80 kg N ha⁻¹. Amount of N uptake and C removed in wheat and canola generally increased with N rate, but tillage and straw management had no consistent effect. After four crop seasons, total organic C (TOC) and N (TN), light fraction organic matter (LFOM), C (LFC), and N (LFN) were generally greater with S than NS treatments. Tillage did not affect TOC and TN in soil, but LFOM, LFC, and LFN were greater or tended to be greater under NT than CT. There was no effect of tillage, straw and N fertilization on NH₄-N in soil, but CT and S tended to have higher NO₃-N concentration in 0–15 cm soil than NT and NS, respectively. Concentration of NO₃-N increased substantially with N rate ≥80 kg ha⁻¹. The NT + S treatment had the lowest proportion (34%) of wind-erodible (<0.83 mm diameter) aggregates and greatest proportion (37%) of larger (>12.7 mm) dry aggregates, compared to highest (50%) and lowest (18%) proportion of corresponding aggregates in CT + NS, indicating less potential for soil erosion when tillage was omitted and crop residues were retained. Amount of N lost as N₂O was higher from N-fertilized than from zero-N plots, and it was substantially higher from N-applied CT plots than from N-applied NT plots. Retaining crop residues along with no-tillage improved soil properties and may also be better for the environment.     

Wheat yield and weed population as influenced by three tillage systems on a clay soil in temperate continental climate

The potential benefits of conservation tillage practices depend mainly on the soil and climatic conditions of the site. A study was conducted to determine the effects of three tillage systems (conventional, CT; reduced, RT; zero, ZT) on spring wheat (Triticum aestivum L.) and weed growth on a clay soil in temperate continental climate, northern Alberta (55°43′N, 118°41′W), Canada. A medium duty cultivator with 25 cm sweeps spaced 22 cm apart and a working depth of 8–10 cm was used for tillage in the CT (once in fall and twice in spring) and RT (once in spring) plots. The ZT plots received a harrowing to spread straw and a preseeding application of Roundup (glyphosate) to control weeds. Experimental design was a randomized complete block with four replications and the tillage systems were fixed in space for the 1989, 1990 and 1991 seasons. The RT treatment resulted in higher yields than the CT or ZT treatments. However, the differences were not always significant. The ZT treatment produced higher yields than CT in 1989 and 1991, whereas its yields were lower than CT in 1990. The 3 year means of total dry matter (TDM) were 3899 kg ha⁻¹, 3640 kg ha⁻¹ and 3331 kg ha⁻¹ for the RT, ZT and CT treatments, respectively. The corresponding grain yields were 1728 kg ha⁻¹, 1573 kg ha⁻¹ and 1530 kg ha⁻¹. The concentration of total N in plants and grains of wheat, amounts of extractable NO₃-N, NH₄-N and P in soil and soil moisture and bulk density were not significantly affected by tillage. The mean weight diameter of aggregates in surface soil was significantly greater under ZT than under the other systems. Wild buckwheat (Polygonum convolvulus L.) was more abundant under CT, but common groundsel (Senecio vulgaris L.), dandelion (Taraxacum officinale Weber), hemp nettle (Galeopsis tetrahit L.), field horsetail (Equisetum arvense L.) and smartweed (Polygonum scabrum Moench) tended to have higher populations under the ZT system. The populations of foxtail barley (Hordeum jubatum L.) wild rose (Rosa sp.), stinkweed (Thlaspi arvense L.) and wild oats (Avena fatua L.) showed no consistent effect of tillage. Tillage or preseeding application of glyphosate did not provide an effective control of all weed species. The spring tillage of the RT system improved crop yields and weed control relative to ZT, whereas the fall tillage of the CT system (in addition to spring tillage) reduced crop yields and had no significant effect on weed population relative to RT. The overall results showed that tillage intensity could be reduced to the level of RT without any adverse influence on crop yields, soil properties or weed populations. The RT system is also economical and environmentally desirable owing to lower tillage and herbicide requirements.     

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.     

Effects of tillage and seeding methods on soil physical properties and yield of upland rice for an ultisol in southeast Nigeria

The yield of direct-seeded and transplanted upland rice was investigated for seven tillage methods for an ultisol in a high rainfall region of southeastern Nigeria. The tillage methods were: two compaction passes of a 6-t roller with and without residue mulch; six compaction passes with mulch; ploughing with and without mulch and no-till with and without mulch. Soil compaction decreased seedling emergence and shoot and root growth. Residue mulching decreased seedling emergence by 35.6% in direct-seeded rice. There were more leaves, productive tillers and dry matter in the ploughed plots. Root densities at 10–20- and 20–30-cm depths were higher by 157 and 47%, respectively, in ploughed treatments. The highest grain yields of 6.3 and 6.1 Mg ha⁻¹ in ploughed plots for the first and second seasons, respectively, were associated with greater uptake of P, Na, Fe and Zn at flowering and of N, Mg, K, Mn and Cu at both maximum tillering and flowering growth stages. The grain yield in the first season was 2.1 and 2.5 Mg ha⁻¹ for two- and six-compaction pass mulched plots, respectively. In the second season, the yields of no-till and compacted treatments were identical and ranged from 1.5 to 2.4 Mg ha⁻¹. Mulching decreased grain yield by 43, 27 and 12% on compacted, no-till and ploughed plots, respectively, due to transient flooding and mechanical impedance to seedling emergence by the mulch cover. Within the unmulched treatments, ploughing increased rice yield by 71 and 35% over two compaction passes and the no-till treatments, respectively. The least bulk density and penetrometer resistance were also observed in ploughed plots.     

Tillage effects on soil aggregation,organic carbon fractions and grain yield in Eum‐Orthic Anthrosol of a winter wheat–maize double‐cropping system,Northwest China

Conservation tillage has been applied in vast semi‐arid regions of the Guanzhong Plain, Northwest China. The tillage effects on soil aggregation, organic carbon (OC) stabilization and grain yield on this plain have not been fully elucidated. A 9‐year field experiment was established from 2002 on a silty clay loam soil (Eum‐Orthic Anthrosol) growing winter wheat–maize in a double‐cropping system. Six conservation tillage treatments were applied by different combinations of rotary tillage (RT), subsoiling (SS) and no‐till (NT), with or without finely chopped straw retention. Conventional tillage (CT) acted as the control. Results showed that in the surface (0–10 cm) soil, the proportion of water‐stable aggregates (WSA) <0.05 mm was 18% less while that for WSA >2 mm was 98% more under NT treatments compared with CT. Additionally, the oxidizable OC content in WSA 0.25–2 mm was 27% greater under NT treatments compared with CT. The OC stocks increased under SS by 17%, RT by 16% and NT by 15% relative to CT. Grain yield (wheat + maize) showed similar increasing trends in all the tillage treatments compared with CT. Both OC stocks and grain yield were larger in treatments with than without straw retentions. These results indicate that NT is beneficial for OC accumulation in WSA but is limited in its ability to improve soil structure in this region. SS plus straw retention (fine‐chopped or as a mulch) is an effective practice to improve soil structural stability, OC accumulation and soil productivity of Eum‐Orthic Anthrosols in Northwest China.     

Long-term effects of tillage and fallow-frequency on soil quality attributes in a clay soil in semiarid southwestern saskatchewan

Reduced tillage management is being adopted at an accelerated rate on the Canadian prairies. This may influence soil quality and productivity. A study conducted on a clay soil (Udic Haplustert) in southwestern Saskatchewan, Canada, to determine the effects of fallow frequency [fallow-wheat (F-W) vs. continuous wheat (Cont W)] and tillage [no-tillage (NT) vs. conventional (CT) or minimum tillage (MT)] on yields of spring wheat (Triticum aestivum L.), was sampled after 3, 7 and 11 years to assess changes in selected soil quality attributes. Tillage had no effect on amount of crop residues returned to the land, but the tilled systems had significantly (P<0.05) lower total organic C and N in the 0–7.5 cm soil depth, though not in the 7.5–15 cm depth. Further, these differences were observed after only 3 years and persisted for the entire 11 years of the study. For example, in the 0–7.5 cm depth, organic C in F-W (MT) after 3 years was 10 480 kg ha⁻¹ and in F-W (NT) 13 380 kg ha⁻¹, while in Cont W (CT) and Cont W (NT) corresponding values were 11 310 and 13 400 kg ha⁻¹, respectively. After 11 years, values for F-W (MT) and F-W (NT) were 11 440 and 14 960 kg ha⁻¹, respectively, and for Cont W (CT) and Cont W (NT), 12 970 and 16 140 kg ha⁻¹, respectively. In contrast to total organic matter, two of the more labile soil quality attributes [i.e., C mineralization (C_min) and N mineralization (N_min)] did not respond to fallow frequency until after 7 years and only in the 0–7.5 cm depth. Microbial biomass (MB) and the ratio of C_min to MB [specific respiratory activity (SRA)], two attributes also regarded as labile, were not influenced by the treatments even after 11 years. After 11 years, only C_min and N_min among the labile soil quality attributes responded to the treatments. Surprisingly, the labile attributes were no more sensitive to the treatments than was total organic C or N. More research is required to determine why responses in this soil differed from those reported elsewhere.     

Influence of long-term tillage, straw and N fertilizer on barley yield, plant-N uptake and soil-N balance

Long-term influence of N fertilizer, tillage and straw on crop production and soil properties are not well known in central Alberta. Field experiments were established in autumn 1979, on a Black Chernozemic soil and on a Gray Luvisolic soil in north-central Alberta to determine the long-term effect of tillage, straw and N fertilizer on yield and N uptake of barley (Hordeum vulgare L.). Fertilizer N was applied annually at 56 kg ha⁻¹. The 11 year averages of barley yields and N uptake under zero tillage were lower than under conventional tillage. Retention rather than removal of straw tended to reduce barley yield for the initial 6 years and 2 year at Site 1 and Site 2, respectively. A simple mathematical model of average annual plant N uptake and grain yield could account for most of the variation in the data observed at both sites (R² = 0.907; P < 0.01). Final values of soil N, calculated using a mass balance approach, agree closely with values measured at the end of the eleventh year. Conventional tillage and zero tillage, with addition of fertilizer N and retention of straw, were the only treatments with apparent but small net addition of N to soil at Site 1 (40 kg ha⁻¹ and 117 kg ha⁻¹, respectively). At Site 2, only the zero tillage treatment with addition of fertilizer and retention of straw gained soil N (29 kg ha⁻¹). In conclusion, soil ecosystems functioning in subhumid environments with slight to moderate heat limitations such as those in central Alberta can adapt, within a few years, to zero tillage practices with full retention of straw.     

Tillage, mulch and irrigation effects on corn (Zea mays L.) in relation to evaporative demand

The effects of deep tillage, straw mulching, and irrigation on corn (Zea mays L.) yield on a loamy sand (mixed, hyperthermic, Typic Ustipsamment) were studied for early (high evaporativity) and normally sown (relatively low evaporativity) crop for 3 years in a semi-arid sub-tropical monsoon region at Punjab Agricultural University, Ludhiana, India. Treatments included all combinations of two tillage systems (conventional tillage — harrowing the soil to a 10-cm depth; deep tillage — chiselling 40 cm deep, 35–40 cm apart), two irrigation regimes (75 mm irrigation when net open pan evaporation accumulated to 75 mm or 50 mm), and two straw mulch rates (0 and 6 Mg ha⁻¹).

Deep tillage significantly reduced soil strength (cone index) and caused deeper and denser rooting than conventional tillage, more so in the dry season and with the infrequent irrigation regime than in the wet season and frequent irrigation regime. Mulch also improved rooting by influencing the hydrothermal regime of the soil. Better rooting with deep tillage and/or mulch helped the crop to extract stored soil water more efficiently, which was reflected in a favourable plant water status (indicated by canopy temperature). Averaged across years, irrigation, and mulch, deep tillage increased grain yield by 1.6 Mg ha⁻¹ for the early season and 0.5 Mg ha⁻¹ for the normal season crop over the yield of 2.0 Mg ha⁻¹ achieved with conventional tillage regardless of season. Yield increase with mulching was also greater for the early season crop. Crop response to deep tillage and mulching was generally linked to the interplay between water supply (rain + irrigation) and demand (seasonal evaporativity) during the growing season. Increasing irrigation frequency increased crop yield when evaporativity exceeded rainfall early in the growing season. The results show that higher corn yields on coarse-textured soils in these regions may be achieved by advancing the seeding time and by using a proper combination of deep tillage, mulch, and irrigation.     

Effects of tillage methods on physical and hydrological properties of a tropical Alfisol

The results of a long term study of the effects of no-tillage and conventional plowing with or without crop residue mulch on soil physical and hydrological properties and on yield of maize are reported for an Alfisol in southwest Nigeria. After 10 years, total porosity of the 0 to 10 cm depth were 48, 50, 39 and 39 percent for no-tillage without mulch (NT-M), no-tillage with mulch (NT+M), conventional tillage without mulch (CT-M) and conventional tillage with mulch (CT+M) respectively. Saturated hydraulic conductivity for the same depth were 753, 750, 183 and 908 cm/day for NT-M, NT+M, CT-M and CT+M respectively. Laboratory measured moisture retention at 50 cm suction for the same depth was 30, 29, 19 and 28 percent. The maximum available water storage capacity for the surface 40 cm layer was 59 and 41 mm for no-tillage compared with 44 and 33 mm for the conventional tillage treatments with and without mulch, respectively. Grain yield increased at the rate of 0.17 t/ha for 1 mm increase in the available water capacity between the range of 33 and 59 mm.     

Soil organic carbon accumulation and carbon costs related to tillage, cropping systems and nitrogen fertilization in a subtropical Acrisol

Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha⁻¹ year⁻¹ (0 N) and 180 kg N ha⁻¹ year⁻¹ (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0–5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0–20 cm layer varied from 0.09 to 0.34 Mg ha⁻¹ year⁻¹ in CT and from 0.19 to 0.65 Mg ha⁻¹ year⁻¹ in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.     

No-till effects on organic matter, pH, cation exchange capacity and nutrient distribution in a Luvisol in the semi-arid subtropics

No-till (NT) system for grain cropping is increasingly being practised in Australia. While benefits of NT, accompanied by stubble retention, are almost universal for soil erosion control, effects on soil organic matter and other soil properties are inconsistent, especially in a semi-arid, subtropical environment. We examined the effects of tillage, stubble and fertilizer management on the distribution of organic matter and nutrients in the topsoil (0–30 cm) of a Luvisol in a semi-arid, subtropical environment in southern Queensland, Australia. Measurements were made at the end of 9 years of NT, reduced till (RT) and conventional till (CT) practices, in combination with stubble retention and fertilizer N (as urea) application strategies for wheat (Triticum aestivum L.) cropping.

In the top 30 cm depth, the mean amount of organic C increased slightly after 9 years, although it was similar under all tillage practices, while the amount of total N declined under CT and RT practices, but not under NT. In the 0–10 cm depth, the amounts of organic C and total N were significantly greater under NT than under RT or CT. No-till had 1.94 Mg ha⁻¹ (18%) more organic C and 0.20 Mg ha⁻¹ (21%) more total N than CT. In the 0–30 cm depth, soil under NT practice had 290 kg N ha⁻¹ more than that under the CT practice, most of it in the top 10 cm depth. Microbial biomass N was similar for all treatments. Under NT, there was a concentration gradient in organic C, total N and microbial biomass N, with concentrations decreasing from 0–2.5 to 5–10 cm depths.

Soil pH was not affected by tillage or stubble treatments in the 0–10 cm depth, but decreased significantly from 7.5 to 7.2 with N fertilizer application. Exchangeable Mg and Na concentration, cation exchange capacity and exchangeable Na percentage in the 0–10 cm depth were greater under CT than under RT and NT, while exchangeable K and bicarbonate-extractable P concentrations were greater under NT than under CT.

Therefore, NT and RT practices resulted in significant changes in soil organic C and N and exchangeable cations in the topsoil of a Luvisol, when compared with CT. The greater organic matter accumulation close to the soil surface and solute movement in these soils under NT practice would be beneficial to soil chemical and physical status and crop production in the long-term, whereas the concentration of nutrients such as P and K in surface layers may reduce their availability to crops.     

Soil organic carbon changes after 12 years of no-tillage and tillage of Grantsburg soils in southern Illinois

Many factors including management history, soil type, climate, and soil landscape processes affect the dynamics of soil organic carbon (SOC). The primary objective of this research was to determine the effects of no-tillage and tillage systems on the SOC content after 12 years of controlled treatments. A tillage experiment with three treatments (no-till (NT), chisel plow (CP) and moldboard plow (MP)) was initiated in the spring of 1989 in southern Illinois. The plot area was previously in a tall fescue hayland for 15 years and had a 6% slope. Maize (Zea mays L.) and soybean (Glycine max L. Merr.) were grown in the plot area on a yearly rotation system starting with maize. Periodically, the SOC content of various soil layers, to a depth of either 30 or 75 cm, was measured and expressed on both a gravimetric and volumetric basis. After 12 years, the 0–15 cm surface soil layer of MP was significantly lower in SOC than the NT and CP plots. For all but 2 values, the significance of findings did not change with the form of expression (gravimetric versus volumetric). The surface layer (0–15 cm), subsoil (15–75 cm), and rooting zone (0–75 cm) of all treatments had reduction in SOC on a volumetric basis when compared to the pre-treatment values for sod. At the end of the 12-year study, the MP system had significantly less SOC in the surface layer, subsurface layer and rooting zone than the NT system at comparable depths. After 12 years of tillage under a maize–soybean rotation, the NT treatment sequestered or maintained more SOC stock (47.0 Mt ha⁻¹) than the CP (43.7 Mt ha⁻¹) and MP (37.7 Mt ha⁻¹) treatments. The annual rate of SOC stock build up in the root zone (0–75 cm), above the MP system base, was 0.71 Mt ha⁻¹ year⁻¹ for the NT system and 0.46 Mt ha⁻¹ year⁻¹ for the CP system. For land coming out of the Conservation Reserve Program and returning to row crop production, NT and CP systems would maintain more SOC stock than MP system and reduce CO₂ emissions to the atmosphere.     

Changes in total, mineralizable and light fraction soil organic matter with cropping and tillage intensities in semiarid southern Alberta, Canada

There has been a trend toward increased cropping intensity and decreased tillage intensity in the semiarid region of the Canadian prairies. The impact of these changes on sequestration of atmospheric CO₂ in soil organic carbon (C) is uncertain. Our objective was to quantify the changes in total, mineralizable and light fraction organic C and nitrogen (N) due to the adoption of continuous cropping and conservation tillage practices. We sampled three individual long-term experiments at Lethbridge, Alberta, in September 1992: a spring wheat (Triticum aestivum L.)-fallow tillage study, a continuous spring wheat tillage study and a winter wheat rotation-tillage study. Treatments had been in place for 3–16 years. In the spring wheat-fallow study, different intensities (one-way disc > heavy-duty cultivator > blade cultivator) of conventional tillage (CT) were compared with minimum tillage (MT) and zero tillage (ZT). After 16 years, total organic C was 2.2 Mg ha⁻¹ lower in more intensively worked CT treatments (one-way disc, heavy-duty cultivator) than in the least-intensive CT treatment (blade cultivator). The CT with the blade cultivator and ZT treatments had similar levels of organic C. The CT treatments with the one-way disc and heavy-duty cultivator had light fraction C and N and mineralizable N amounts that were about 13–18% lower than the CT with the blade cultivator, MT or ZT treatments. In the continuous spring wheat study, 8 years of ZT increased total organic C by 2 Mg ha⁻¹, and increased mineralizable and light fraction C and N by 15–27%, compared with CT with a heavy-duty cultivator prior to planting. In the winter wheat rotation-tillage study, total organic C was 2 Mg ha⁻¹ higher in a continuous winter wheat (WW) rotation compared with that in a winter wheat-fallow rotation. The lack of an organic C response to ZT on the WW rotation may have been due to moldboard plowing of the ZT treatment in 1989 (6 years after establishment and 3 years before soil sampling), in an effort to control a severe infestation of downy brome (Bromus tectorum L.). Our results suggest that although relative increases in soil organic matter were small, increases due to adoption of ZT were greater and occurred much faster in continuously cropped than in fallow-based rotations. Hence intensification of cropping practices, by elimination of fallow and moving toward continuous cropping, is the first step toward increased C sequestration. Reducing tillage intensity, by the adoption of ZT, enhances the cropping intensity effect.     

Deep tillage management for high strength southeastern USA Coastal Plain soils

Southeastern USA production is limited in Acrisols (Paleudults and Kandiudults) because they have high strengths and low water holding capacities. Production systems with crop rotations or deep tillage before planting were compared with less intensive management. Production systems included double-crop wheat (Triticum aestivum L.) and soybean (Glycine max L. Merr.) that were drilled in 0.19 m-row widths and grown in 15 m wide, 150 m long plots with soils of varying hardpan depths. Treatments included surface tillage (disked or none), deep tillage (paratilled or none), deep tillage with winter fallow and maize (Zea mays L.) in rotation, and disked/deep tillage with an in-row subsoiler where soybean was planted in conventional 0.76 m-wide rows. Cone indices were measured near the ends of each plot (120 m apart) to assess soil strength differences among soil types and among treatments. Cone indices were 1.50 MPa higher for non-deep tilled treatments than for deep tilled treatments and 0.44 MPa higher in wheel-track mid rows than in non-wheel-track mid rows. Cone indices were also 0.28 MPa higher for soils with shallower Bt horizons. Cone indices were not significantly different for subsoiled treatments and paratilled treatments. Rainfall was erratic throughout the 5-year experiment with dry periods lasting more than 2 weeks at a time and with annual totals ranging from 520 to 1110 mm. Wheat yields were 0.67 Mg ha⁻¹ greater for deep-tilled soils (subsoiled and paratilled) than for non-deep-tilled soils. Soybean yields were 0.36 Mg ha⁻¹ greater for paratilled than for subsoiled or non-deep-tilled treatments partly as a result of the more complete disruption of the paratill and partly because paratilled treatments were managed with narrow rows. Yields did not vary significantly among the soil types despite the fact that they had different cone indices. Tillage was a more dominant factor than soil type. For wheat, lower cone indices from tillage led to higher yields. For soybean, management of uniform loosening from deep tillage and narrow rows led to higher yields.     

Effects of tillage and nitrogen management on soil chemical and physical properties after 23 years of continuous sorghum

Long-term tillage and nitrogen (N) management practices can have a profound impact on soil properties and nutrient availability. A great deal of research evaluating tillage and N applications on soil chemical properties has been conducted with continuous corn (Zea Mays L.) throughout the Midwest, but not on continuous grain sorghum (Sorghum bicolor (L.) Moench). The objective of this experiment was to examine the long-term effects of tillage and nitrogen applications on soil physical and chemical properties at different depths after 23 years of continuous sorghum under no-till (NT) and conventional till (CT) (fall chisel-field cultivation prior to planting) systems. Ammonium nitrate (AN), urea, and a slow release form of urea were surface broadcast at rates of 34, 67, and 135 kg N ha⁻¹. Soil samples were taken to a depth of 15 cm and separated into 2.5 cm increments. As a result of lime applied to the soil surface, soil pH in the NT and CT plots decreased with depth, ranging from 6.9 to 5.7 in the NT plots and from 6.5 to 5.9 in the CT plots. Bray-1 extractable P and NH₄OAc extractable K was 20 and 49 mg kg⁻¹ higher, respectively, in the surface 2.5 cm of NT compared to CT. Extractable Ca was not greatly influenced by tillage but extractable Mg was higher for CT compared to NT below 2.5 cm. Organic carbon (OC) under NT was significantly higher in the surface 7.5 cm of soil compared to CT. Averaged across N rates, NT had 2.7 Mg ha⁻¹ more C than CT in the surface 7.5 cm of soil. Bulk density (Δ_b) of the CT was lower at 1.07 g cm⁻³ while Δ_b of NT plots was 1.13 g cm⁻³. This study demonstrated the effect tillage has on the distribution and concentration of certain chemical soil properties.     

Nutrient availability and cocoyam yield under different tillage practices

Research information on the effect of tillage systems on cocoyam (Xanthosoma sagittifolium (L.) Schott) growth, nutrient status and yield is lacking in Africa. The effects of zero tillage with mulch, zero tillage without mulch, manual mounding, manual ridging and conventional tillage on cocoyam yield, growth and nutrient availability were compared during 2 years on an Alfisol (Oxic Tropuldaf) at Owo in the rainforest zone of Nigeria. The surface soil (0–20 cm) was chemically analyzed before and after crop harvest and selected soil physical properties were determined. Concentration of soil organic C, N, P, K and Mg and the leaf N, P and K were significantly influenced (p = 0.05) by tillage, with zero tillage with mulch being the most effective treatment in conserving the fertility of the surface soil (0–20 cm). Soil fertility, as indicated by organic C, N, P, K, Ca and Mg, declined significantly (p = 0.05) over time in all tillage systems, but this decline was more pronounced in the conventional tillage. Zero tillage with mulch, zero tillage without mulch, manual mounding, manual ridging and conventional tillage reduced the soil organic C concentration by 20, 23, 23, 24 and 33%, respectively over the 2-year period. The decreases in soil N concentration were 25, 31, 31, 38 and 56%, soil P concentration were 13, 15, 17, 16 and 26%, and soil K concentration were 16, 26, 31, 37 and 53%, respectively. Tillage did not affect corm and cormel yields in the first year. In the second year, due to the elimination of ploughing, significant differences were obtained in the cormel yield but not of corm yield. In 2005, zero tillage with mulch produced the highest cormel yield (13.5 mg ha⁻¹) of cocoyam followed by zero tillage without mulch (13.2 mg ha⁻¹), manual mounding (12.7 mg ha⁻¹) and manual ridging (12.5 mg ha⁻¹). The lowest cormel yield (9.5 mg ha⁻¹) of cocoyam was produced by conventional tillage. Soil water contents in zero tillage with mulch and zero tillage without mulch were significantly higher (p = 0.05) than in the other tillage systems. Soil bulk density ranging from 1.21 to 1.40 mg m⁻³ correlated positively with leaf nutrient concentration and yield. Cocoyam can be grown successfully on zero tillage, with mulch and without mulch or minimum tillage systems on an Alfisol of the humid tropics.