Tillage and Lime Rate Effects on Soil Acidity and Grain Yields of a Ten-Year Corn–Soybean Rotation

Reduced tillage and no-tillage systems provide shallow incorporation of surface applied materials at best. Due to concern of over-liming the surface of agricultural soils, producers either reduce lime rates (and apply more often) or perform some sort of soil inversion to mix the lime deeper into the soil profile. The objective of the authors in this field study was to evaluate the effects of tillage, lime rate, and time of limestone application on corn and soybean growth, and assess the changes in soil acidity to an already acidic soil. Treatments consisted of a no lime check, two no-tillage systems with either a 4.5 ton ha^?1 lime application every two years or an annual application of 450 kg pelleted lime ha^?1, a continuous annual chisel tillage system with a 9.0 ton ha^?1 lime application every four years, and two inversion systems utilizing a rotary tiller (Howard Rotovator) where 9.0 ton lime ha^?1 was mixed into the soil followed by either continuous chisel tillage or continuous no-tillage. Inversions occurred in 1999, 2003, and 2007. Soil samples were collected annually in increments of 5 cm to a 30 cm depth for pH determinations. After 10 years, the continuous chisel system increased soil pH in the top 20 cm and had grain yields comparable to the no-tillage system, but not different than the no lime treatment. The no-tillage system increased the pH in the surface 15 cm of soil. The inversion treatments after soybean mixed the lime more thoroughly in the top 15 cm than inversion after corn and also increased the pH to a deeper depth. The pelleted lime had no effect on soil acidity. Soybean yields were affected by lime treatment with the no lime and pelleted lime having the lowest yields. This is most likely due to manganese (Mn) toxicity with these treatments. There was no perceived benefit of inversion of the soil with no-till or chisel systems.     

Effects of no-tillage on chemical gradients and topsoil acidification

No-tillage is an increasing way of management for agricultural soils. The objective of this study was to identify in which extent the chemical properties of a loamy soil could be affected by no-tillage under temperate conditions.Soil chemical properties were investigated on a field subjected to either conventional or no-tillage management of maize (Zea mays L.) and wheat (Triticum aestivum L.) with identical fertilization practices and no lime supply since 1970. On no-tilled soil, maize was cropped exactly on the same line every other year, which enabled soil sampling under the row and under the interrow.Tilled soil had an homogeneous ploughed horizon, whereas soil under no-tillage exhibited strong vertical gradients of pH, exchangeable cations and organic C. No-tilled soil had 11.4% greater organic C than tilled soil, and the difference was concentrated in the upper 5 cm. The proportion of exchangeable cations was highest in the interrow of no-tilled soil and lowest in tilled soil. Tilled soil contained much lower exchangeable K than no-tilled soil, indicating a difference in retention capacity of this cation. The pH of the upper 5 cm of no-tilled soil was low, probably because of surface accumulation of organic residues. Whatever the tillage system, exchangeable Al was significantly related to pH according to the relation: Al_ex = 76441 × 10^−0.99 pH (r² = 0.96; p < 0.001). An expected complexing effect of organic matter on Al was not observed, probably hidden by the influence of pH.Since yields were not negatively affected by long-term no-tillage and organic C content was higher, no-tillage appears to be a cost-saving choice for maize and wheat production under these temperate environmental conditions, as well as a way for C sequestration.     

Soil organic carbon and nitrogen in a Minnesota soil as related to tillage, residue and nitrogen management

Soil organic carbon (SOC) and nitrogen (N) are directly influenced by tillage, residue return and N fertilization management practices. Soil samples for SOC and N analyses, obtained from a 23-year field experiment, provided an assessment of near-equilibrium SOC and N conditions. Crops included corn (Zea mays L.) and soybean [Glycine max L. (Merrill)]. Treatments of conventional and conservation tillage, residue stover (returned or harvested) and two N fertilization rates were imposed on a Waukegan silt loam (fine-silty over skeletal, mixed, superactive, mesic Typic Hapludoll) at Rosemount, MN. The surface (0–20 cm) soils with no-tillage (NT) had greater than 30% more SOC and N than moldboard plow (MB) and chisel plow (CH) tillage treatments. The trend was reversed at 20–25 cm soil depths, where significantly more SOC and N were found in MB treatments (26 and 1.5 Mg SOC and N ha⁻¹, respectively) than with NT (13 and 1.2 Mg SOC and N ha⁻¹, respectively), possibly due to residues buried by inversion. The summation of soil SOC over depth to 50 cm did not vary among tillage treatments; N by summation was higher in NT than MB treatments. Returned residue plots generally stored more SOC and N than in plots where residue was harvested. Nitrogen fertilization generally did not influence SOC or N at most soil depths. These results have significant implications on how specific management practices maximize SOC storage and minimize potential N losses. Our results further suggest different sampling protocols may lead to different and confusing conclusions regarding the impact of tillage systems on C sequestration.     

Long-Term Cropping System, Tillage, and Poultry Litter Application Affect the Chemical Properties of an Alabama Ultisol

Sustainable agricultural practices have been steadily increasing in the last couple of decades. These management practices frequently involve cover crops, less or no-tillage, and organic fertilization. In this study, we evaluated the effects of cropping systems,tillage and no-tillage, and the application of poultry litter(PL) on selected soil physicochemical properties and soil test nutrients. Soil samples were collected from the topmost surface(0–5 cm) and subsurface(5–10 cm) layers. The general effect trend was PL application no-tillage cover crop cropping type. There were more statistically significant(P ≤ 0.05) correlations between the 18 soil attributes at the topmost surface than at the subsurface. This could be due to the accumulation of external C inputs and nutrients by crop residues and PL application as well as the retaining effects of no-tillage on less mobile nutrient components. Because of their high mobility and volatile nature, total nitrogen(N), ammonia-N(NH_4~+-N), and nitrate-N(NO_3~--N) levels varied greatly(high standard deviations), showing no consistent patterns among the treatments. Compared to the soybean cropping system, corn, especially with the wheat cover crop, contributed more to the total carbon(C) and sulfur(S) in the topmost surface soils(0–5 cm). Poultry litter application greatly increased pH, cation exchange capacity(CEC), base saturation, magnesium(Mg), phosphorus(P), calcium(Ca),sodium(Na), potassium(K), manganese(Mn), copper(Cu), and zinc(Zn) in both soil layers. Contrast comparisons revealed that PL application had more of an effect on these soil chemical properties than no-tillage and cropping systems. These results will shed light on developing better nutrient management practices while reducing their runoff potentials.     

Effect of no‐tillage vs. conventional tillage on soil organic matter and nitrogen contents

Abstract

Four treatments (no‐tillage plus subsoiling, no‐tillage, conventional tillage plus subsoiling, and conventional tillage) were continuously in place for 6 yr and a second set of no‐tillage plus subsoiling and conventional plus subsoiling treatments were continuously in place for 3 yr to study the long‐term effects of conventional and no‐tillage corn on soil organic matter (OM) and N contents. Soil samples were taken at random between the rows and in the rows to a depth of 60 cm, in 5‐cm increments to a depth of 30 cm, and then in 15‐cm increments from the 30 to 60‐cm depth for OM and N determination. No‐tillage resulted in A3 and 20% more Kjeldahl N than conventional tillage in the 0 to 5‐cm soil depth after 6 and 3 yr, respectively. after 6 yr, the 0 to 5‐cm depth had 36% more OM in no‐tillage treatments than in conventional tillage treatments, and soil from no‐tillage treatments averaged 27% more OM than the conventional tillage plus subsoiling treatment at the 0 to 15‐cm soil depth.     

Tillage and cropping effects on selected properties of an Argiudoll in Argentina

Abstract

Soils of the Argentine humid pampa region are usually weakly structured due to its high silt content. Selecting crop sequence or tillage systems are an alternative in small farms for the protection of the soil against physical degradation and erosion given that conservation practices, grass meadows, and fertilizers are expensive and therefore rarely used. Evaluation of selected soil properties was conducted on soil sampled from a long‐term tillage experiment with continuous soybean established in 1975 on a Typic Argiudoll silty loam soil in Argentina. Tillage treatments included conventional tillage with moldboard plow (CT), chisel plow (CP), and no till (NT). A comparison with continuous corn under NT was also carried out. Sampling was performed after the emergence of both crops in 1990. Tillage and cropping treatments affected properties related to soil slacking and dispersion to a greater extent than they did on aggregate size distribution. According to the De Leenheer and De Boodt index, aggregate stability within soybean soil classified as bad for CT, unsatisfactory for CP, and very good for NT, whereas the soil with corn under NT classified as excellent. The no tillage treatment within soybean had significantly more organic carbon in the 0–5 cm depth than CP or CT. Soil respiration was significantly higher in NT than in CT in the surface layer, while CT showed higher values in the 10–15 cm depth. Tillage treatments did not significantly affect microbial biomass under soybean cropping. The effect of monoculture corn versus monoculture soybean under NT on soil respiration, biomass and organic carbon was not significant. Soil pH in the 0–5 cm depth under soybean was in the order NT > CP > CT, whereas the soil with corn under NT was more acid than the soybean soil (P=0.05). Cation exchange capacity and exchangeable bases followed a similar trend. Organic carbon (0–5 cm depth) and aggregate stability were significantly correlated when samples from all treatments were considered.     

INFLUENCE OF TWENTY-THREE ANNUAL APPLICATIONS OF NITROGEN AND SULFUR FERTILIZERS,AND ONE-TIME LIMING ON DRY MATTER YIELD OF GRASS AND SOME SOIL PROPERTIES ON A DARK GRAY CHERNOZEM SOIL

Most soils in the Prairie Provinces of Canada are deficient in plant-available nitrogen (N), and many soils in the Parkland region also contain insufficient amounts of plant-available sulfur (S) for high crop production. A field experiment with perennial grass stand was conducted to determine the effects of long-term annual N (112 kg N ha^?1), S (11 kg S ha^?1) and potassium (K) (40 kg K ha^?1) fertilization, and one-time lime application on forage dry matter yield (DMY) and soil properties [pH, total organic carbon (TOC) and N (TON), and light fraction organic C (LFOC) and N (LFON)] on a Dark Gray Chernozem (Boralfic Boroll) loam at Canwood in north-central Saskatchewan, Canada. The experiment had surface-broadcast annual treatments of no fertilizer (Nil), N, S, NS, and NSK fertilizers from 1980 to 2002, and one-time lime application in 1992 to bring soil pH to about 7. Application of N or S alone had only a little effect on DMY compared to unfertilized Nil treatment, while application of both NS together substantially increased DMY, and forage yield was further increased when K was also applied (NSK). The DMY following one-time liming was greater in limed plots than in unlimed plots for at least 10 years. Decline of soil pH by fertilization mainly happened in the 0–10 cm depth with N only, and in the 0–5 cm layer with NS treatment, whereas these treatments tended to increase soil pH in layers below 10 cm. One-time surface application of granular lime increased soil pH, mainly in the 0–5 cm layer, and the effect was maintained for at least 9 years. Mass of TOC, TON, LFOC, and LFON in different soil layers increased with combined applications of N and S fertilizers (NS), but the effect was much more pronounced in the 0–7.5 cm soil layer, and also varied with organic fraction. Light organic fractions were more responsive to applied NS than total organic fractions. The findings suggest that application of N and S together was effective in sustaining high forage yield and increasing C and N sequestration in a soil deficient in both N and S.     

Tillage,lime, and poultry litter effects on soil zinc,manganese, and copper

Abstract

Long‐term no‐tillage has profound effects on soil properties which can affect the availability of plant nutrient elements. The objectives were to study the effects of tillage and lime treatments on soil pH and extractable soil micronutrients where poultry litter was used as a nitrogen (N) source. Surface soil samples were taken in the spring and fall for two years from a long‐term tillage experiment that had been in place for nine years. There were two tillage treatments [conventional (CT) and no‐tillage (NT)] and six lime/ gypsum treatments (control, 8,960 kg gypsum ha^‐1 every fourth year, 4,480 kg lime ha^‐1 every fourth year, and three treatments of 8,960 kg lime ha^‐1 in a four‐year period divided by application times into 1, 2, and 4 treatments per year). Poultry litter was applied each year of the two‐year experiment at a rate of 8.96 Mg ha^‐1 on a dry weight basis. The crop was corn (Zea maize L.). Soil samples were analyzed for pH and Mehlich‐1 zinc (Zn), manganese (Mn), and copper (Cu). Soil pH was higher for NT than CT and was higher in the spring than in the fall. Lime rates resulted in soil pH increases, but showed less difference for CT than NT. The three 8,960 kg ha^‐1 per four yr treatments caused an interaction in that for CT the pH increased more for 2,240 kg ha^‐1each year than for 8,960 kg ha^‐1 every fourth year and the opposite was true for NT. Extractable Zn, Mn, and Cu all responded to this interaction being lower for the higher pH plots. Extractable Zn was higher for NT possibly due to high Zn from the poultry litter and non‐incorporation for NT. Extractable Cu was lower for NT as expected from the soil pH, whereas extractable Mn was not affected by tillage. Extractable Zn and Cu both increased over time due to inputs from the poultry litter. Neither extractable Zn nor Mn responded to increasing lime rates, however Cu decreased with increasing lime rate. Extractable Cu was influenced mainly by soil pH differences due to tillage and lime. Extractable Zn was influenced much more by tillage and from inputs by the poultry litter and not as much by pH differences. Extractable Mn was the least responsive to tillage and lime treatments of the three micronutrients studied.     

免耕与常规耕作潮棕壤交换性阳离子的剖面分布特征

通过田间定位试验.研究了不同耕作方式对潮棕壤0-100 cm深度6个土层土壤交换性阳离子的影响.结果表明,与常规耕作相比,免耕使土壤表层pH显著增,.而电导率下降;同时,免耕增加了表层土壤可交换性K~+含量,降低了可交换性Na~+含量,但对可交换性Ca~(2+),Mg~(2+)和阳离子交换量没有产生显著影响.相关分析结果表明,可交换性K~+与土壤养分含量没有显著相关性,而可交换性Na~+,Ca~(2+),Mg~(2+)和阳离子交换量与有机质和全氮含量均呈负相关关系.     

华北潮土区不同耕作方式下土壤动物丰富度与多样性

在黄淮海平原小麦-玉米一年两熟地区,试验设置了5个处理,分别为玉米小麦每年均翻耕(CTWT)、玉米免耕+小麦每年翻耕(CNTWT)、玉米免耕+小麦每2年翻耕(CNTW2T)、玉米免耕+小麦每4年翻耕(CNTW4T)、玉米小麦每年均免耕(CNTWNT),所有处理的农作物地上秸秆全部移出。调查结果显示,中小型土壤动物在数量上占总数的比例为83%～91%,土壤动物主要分布在表层,占有其总量的71.9%～73.2%。土壤动物存在显著的季节性动态,其丰富度在玉米季高于小麦季。土壤动物Shannon多样性指数在整体上表现为翻耕高于免耕处理,玉米季翻耕处理下有更高的均匀度指数,但小麦季均匀度指数差异不显著。多元典范冗余分析表明,耕作方式主要是对土壤动物的时间动态和垂直分布产生影响,从而间接地影响了土壤动物的数量和组成。     

中国黄土高原区轮耕对土壤团聚体、有机碳氮含量的影响

In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage (no-tillage and subsoiling) could decrease soil bulk density, and increase soil aggregates and organic carbon in the 0-40 cm soil layer. A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon (SOC), total nitrogen (TN), water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia. Three tillage treatments were tested: no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 (NT-ST-NT); subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 (ST-NT-ST); and conventional tillage over years 1-3 (CT). Mean values of soil bulk density in 0-40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%, respectively, compared with CT, while soil total porosity was greatly improved. Rotational tillage increased SOC, TN, and water-stable aggregates in the 0-40 cm soil, with the greatest effect under ST-NT-ST. In 0-20 and 20-40 cm soils, the tillage effect was confined to the 2-0.25 mm size fraction of soil aggregates, and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage. No significant differences were detected in SOC and TN contents in the >2 mm and <0.25 mm aggregates among all treatments. In conclusion, rotational tillage practices could significantly increase SOC and TN levels, due to a fundamental change in soil structure, and maintain agroecosystem sustainability in the Loess Plateau area of China.     

耕作方式对土壤水分入渗、有机碳含量及土壤结构的影响

为探明不同耕作方式对土壤剖面结构、水分入渗过程等的作用机理,采集田间长期定位耕作措施(常规耕作、免耕、深松)试验中的原状土柱(0~100 cm)及0~10 cm、10~20 cm、…、90~100 cm环刀样、原状土及混合土样,通过室内模拟试验进行了0~100 cm土层土壤入渗过程和饱和导水率的测定,分析了不同土层的土壤有机碳含量、土壤结构特征及相互关系。结果表明:从土柱顶部开始供水(恒定水头)到水分全部入渗到土柱底部的时间为:常规耕作免耕深松;土柱土壤入渗速率和累积入渗量为:深松免耕常规耕作;土柱累积蒸发量为:常规耕作免耕深松。土壤的饱和导水率表现为:0~10 cm和50~60 cm土层,免耕深松常规耕作;20~50 cm和60~100 cm土层,深松免耕常规耕作。随土层的加深,0.25 mm水稳性团聚体含量和土壤有机碳含量均表现为先增加(10~20 cm)再降低的趋势。在0~40 cm土层和80~100 cm土层,均以深松处理0.25 mm水稳性团聚体含量最高。在60 cm以上土层,土壤有机碳含量表现为:免耕深松常规耕作,而60 cm土层以下土壤有机碳显著降低,均低于4 g·kg?1,且在70 cm以下土层,常规耕作免耕深松。综上,耕作措施能够改变土壤有机碳含量,改善土壤结构,促进土壤蓄水保墒;深松更利于水分就地入渗,而免耕则更利于有机碳的提升和水分的储存,其作用深度在0~60 cm土层。     

麦稻轮作下耕作模式对土壤理化性质和作物产量的影响

为了探明不同耕作模式对土壤理化性质和作物产量的影响,采用田间定位试验方法,于2007-2010连续4a在麦稻轮作制下开展了本试验研究。结果表明,免耕提高了耕层土壤体积质量,降低了土壤含水率。但是免耕土壤表层(0～10cm)的体积质量仍在作物适宜生长的范围内,并未对作物的生长产生不利影响。免耕促进了土壤有机质和全氮在表层土壤的富集。0～10cm土层有机质和全氮含量比翻耕处理显著增加,而>10～20cm土层上述养分含量明显低于翻耕处理。小麦季免耕土壤的碱解氮、速效磷和速效钾含量的变化趋势与有机质和全氮含量相似,而水稻季免耕处理整个耕层土壤碱解氮、速效磷和速效钾含量均低于翻耕处理。免耕显著的提高了小麦产量,但降低了水稻产量,起主要作用的产量构成因素是小麦和水稻的有效穗数。整个轮作周期的作物产量以小麦免耕水稻翻耕模式的产量较高,比小麦翻耕水稻免耕模式产量增加了5.70%。     

Response of organic matter to reduced tillage and animal manure in a temperate loamy soil

The impacts of tillage and organic fertilization on soil organic matter (SOM) are highly variable and still unpredictable, and their interactions need to be investigated under various soil, climate and cropping system conditions. Our work examined the effect of reduced tillage and animal manure on SOM stocks and quality in the 0–40 cm layer of a loamy soil under mixed cropping system and humid temperate climate. The soil organic carbon (SOC) and N stocks, particulate organic matter (POM), and C and N mineralization potential (301 days at 15 °C) were measured in a 8‐yr‐old split‐plot field trial, including three tillage treatments [mouldboard ploughing (MP), shallow tillage (ST), no tillage (NT)] and two fertilization treatments [mineral (M), poultry manure 2.2 t/ha/yr C (O)]. No statistically significant interactive effects of tillage and fertilization were measured except on C mineralization. NT and ST showed greater SOC stocks (41.2 and 39.7 t/ha C) than MP (37.1 t/ha C) in the 0–15 cm increment, while no statistical differences were observed at a greater depth. N stocks exhibited similar distribution patterns with regard to tillage effect. Animal manure, applied at a rate representative of typical field application rates, had a smaller impact on SOC and N stocks than tillage. The mean SOC and N stocks were higher under O than M, but the differences were statistically significant only in the 0–5 cm increment. MP showed lower C‐POM stocks than NT and ST in the 0–5 cm increment, whereas greater C‐POM stocks were measured under MP than under NT or under ST in the 20–25 cm increment. Organic fertilization had no impact on C‐POM or N‐POM stocks. In the 0–25 cm increment, NT showed a lower C and N mineralization potential than MP. Our work shows that the sensitivity of SOM to reduced tillage for the whole soil profile can be relatively small in a loamy soil, under humid‐temperate climate. However, POM was particularly sensitive to the differential effects of tillage practices with depth, and indicative of differentiation in total SOM distribution in the soil profile.     

Changes in soil chemical properties following a 12-year fallow: A 2-year comparison of conventional tillage and no-tillage agroecosystems

Soil chemical parameters including total N, exchangeable ammonium, soluble nitrate, and extractable phosphate, potassium, calcium and magnesium, were compared between conventional and no-tillage treatments on land which had been left fallow in old-field vegetation for 12 years. Tillage treatments were also compared to an adjacent old-field which was not cropped. The study was carried out on the Georgia Piedmont for 2 years following the fallow period. Soil nutrient availability was related to chemical concentrations in the soil solution, plant nutrient uptake and litter decomposition. During 1978–1979, soil nitrate concentrations were highest in plowed systems and lowest in the old field. Extractable cation concentrations were generally higher in conventional tillage than in no-tillage soil during the 1st year after fallow (1978). However, during the 2nd year, higher cation concentrations in no-tillage soil prevailed. Nitrate concentrations in the soil solution at 60 cm depth were generally highest in conventional tillage, followed by no-tillage and lowest in old-field systems. During 1978–1979, total nutrient uptake by crops (grain sorghum and rye) and weeds was higher in conventional than in no-tillage systems. From 1978–1979 to 1979–1980, uptake decreased in both cropping systems, but proportionately more in conventional tillage systems so that uptake in 1979–1980 was similar in the two cropping treatments. Higher nitrate concentrations in leachate of conventional than in no-tillage and old-field systems suggested that plowing stimulated nitrification processes.     

有机肥施用量和耕作方式对旱地土壤水分利用效率及作物生产力的影响

为了探索旱地农业连作春玉米田不同保护性耕作措施下土壤蓄水保墒效果与不同施肥处理组合下春玉米的增产增收效应,在2014—2016年通过大田试验,研究了旱地农田冬闲期免耕、深松和翻耕3种耕作方式对玉米田冬闲期蓄水保墒效果及玉米生育期3种耕作处理与高、中、低有机肥3种施肥处理组合对春玉米生育期土壤水分动态、产量和经济效益的影响。结果表明,免耕和深松与翻耕相比,蓄水效果较好;2个试验年度冬闲期,免耕和深松较翻耕分别高1.3,0.9个百分点。免耕、深松较翻耕处理0—200 cm土层2年土壤平均贮水量分别增加20.8,22.1 mm;玉米生长生育期在高有机肥条件下,免耕、深松较翻耕处理0—200 cm土层土壤平均贮水量分别高44.2,34.6 mm;以高有机肥深松处理产量、WUE和纯收益最高。2年平均产量、WUE和纯收益分别为9 332.40 kg/hm^2,22.01 kg/(hm^2·mm)和5 104.1元/hm^2,高有机肥免耕处理次之,较高有机肥免耕处理增产和增收分别为7.4%和3.9%。综合考虑各处理土壤蓄水保墒效果和玉米增产增收效应,高有机肥深松是旱区连作玉米田最优的耕作和施肥处理组合。     

Tillage and N application effects on crop yield,N uptake and soil properties in a corn-based rotation

The objective of this study was to determine the influence of tillage methods (conventional tillage (CT) and minimum tillage (MT)) and N rates (0, 50, 150, 250 kg N ha^?1) on crop yield, N uptake and soil organic carbon (SOC), bulk density (BD), total N (TN), electrical conductivity (EC), pH and soil nutrient contents on a clay-loam near Hashtgerd, Iran. A successive corn-based rotation (2012–2014) was conducted as a split-plot in a randomized complete block design in which tillage methods were considered as main plots, and N rates as subplots. Tillage had no significant effect on corn 2012 and canola 2012–2013 grain yields. CT and MT systems showed different critical N rates to reach their maximum grain yield in corn (2013) and wheat (2013–2014). MT system required more N application to reach its maximum grain yield. Tillage × N rate effect on none of the soil properties was significant. Tillage had no significant (P ≤ 0.05) effect on soil pH, BD, TN and SOC. However, soil EC of 0–5 cm depth in MT system was higher than CT system by 64%. MT system under higher N application could increase corn grain yield, but on the other hand probably adversely changes soil chemical properties.     

Tillage,lime, and poultry litter effects on plant concentrations of zinc,manganese, and copper

Minimum tillage cropping systems and the use of animal manures on cropland are becoming more prevalent. An experiment was initiated to determine the effects of tillage and lime/gypsum variables on uptake of zinc (Zn), manganese (Mn), and copper (Cu) by corn (Zea mays L.) and to show correlations between plant uptake of these metals and soil pH and Mehlich 1‐extractable soil metals where poultry litter was used as a nitrogen (N) source. Surface soil samples were taken in the spring and fall for two years from a long‐term tillage experiment that had been in place for nine years. There were two tillage treatments [conventional (CT) and no‐tillage (NT)] and six lime/gypsum treatments (control, 8,960 kg gypsum ha^‐1 every fourth year, 4,480 kg lime ha^‐1 every fourth year, and three treatments of 8,960 kg lime ha^‐1 in a four‐year period divided by application times into 1, 2, and 4 treatments). Poultry litter was applied each year of the two‐year experiment at a rate of 8.96 Mg ha^‐1 on a dry weight basis. Soil samples were analyzed for pH and Mehlich 1‐extractable Zn, Mn, and Cu, and plant tissue (small plant, ear leaf, stalk, and grain) was analyzed for Zn, Mn, and Cu concentrations. Lime treatments resulted in lower Zn in the small plant and ear leaf for CT, but not for NT. Plant Mn was decreased by lime and gypsum rates for small plant, ear leaf, stalk and grain for both years for CT and NT. Correlations for plant Zn versus soil pH were generally non‐significant, except for one year for ear leaf Zn (R=‐0.413**). Correlations for soil pH and plant tissue Cu were all nonsignificant. Correlations for plant Mn and soil pH were strong with R values over 0.80. Plant Mn response to treatments was found at a pH range of 4.2 to 5.8 for ear leaf and pH 5.2 to 6.2 for stalks. Plant Mn and Zn versus Mehlich 1‐extractable soil Mn and Zn, respectively, were negative. This response was possibly due to oxidation‐reduction and non‐incorporation of the lime for Mn and non‐incorporation of the lime for Zn. Also, the poultry litter was high in Zn (447 mg kg^‐1), which could have masked pH effects. It was concluded that soil sampling for plant micronutrients for NT, especially where a waste material high in micronutrients is applied, can give erratic and even erroneous results. However, lime and tillage treatments had a predictable effect on micronutrient uptake as related to soil pH.     

深耕及培肥对砂姜黑土理化性质和小麦产量的影响

  目的  比较不同耕作培肥方式对土壤理化性质和小麦产量的影响,以解决砂姜黑土耕层浅薄、养分容量低的问题,实现小麦优质高产。  方法  田间试验（2018 ~ 2020年）采用裂区实验设计,旋耕和深耕为主区;5种培肥方式为副区,包括:单施化肥（CK）,增施有机肥15 t hm?2（15M）、有机肥22.5 t hm?2（22.5M）、生物炭15 t hm?2（15B）和生物炭22.5 t hm?2（22.5B）,分土层研究土壤理化指标和小麦产量的变化。  结果  深耕、施用生物炭和有机肥均显著提高0 ~ 10 cm 土壤pH值,深耕显著提高10 ~ 30 cm土壤含水率,降低10 ~ 30 cm土壤容重和紧实度,生物炭对土壤容重和紧实度的改善优于有机肥。深耕配合生物炭或有机肥显著提高10 ~ 30 cm土层有机质和全氮含量;高量有机肥对速效养分的提升效果最佳。旋耕增施有机肥显著增加小麦赤霉病病穗率;深耕显著降低赤霉病病情指数,深耕22.5M处理比旋耕22.5M处理降低52.6%。连续2年的产量表明,深耕显著提高小麦产量,深耕配合高量生物炭和有机肥处理分别比深耕CK处理显著增产18.3%和9.0%。结构方程模型分析表明,深耕和生物炭主要通过影响土壤物理性质促进小麦增产,有机肥显著改善土壤化学性质,但高量有机肥能促进赤霉病的发生。  结论  深耕配合高量生物炭或适量有机肥有效改良砂姜黑土障碍因素并增加小麦产量。     

免耕和稻草还田对稻田土壤氮素转化强度的影响

为了明确土壤氮素转化对免耕和稻草还田的响应,研究了不同耕作对土壤(0～5 cm、5～12 cm和12～20 cm土层)氮素转化强度和铵态氮含量的影响。结果表明,免耕显著提高0～5 cm土层土壤氨化强度和铵态氮含量,但对于5～12 cm和12～20 cm土层趋势则相反;各土层土壤硝化势、反硝化强度免耕明显低于常耕,表明免耕促进0～5 cm土层有机氮的氨化作用和降低5～20 cm土层有机氮的氨化及0～20 cm土层土壤硝化-反硝化损失。稻草还田对土壤氮素转化强度的影响因耕作而异,免耕下,稻草还田促进5～20 cm土层土壤氨化强度及各土层反硝化强度和铵态氮含量,对0～5 cm土层土壤氨化强度和各土层土壤硝化势影响不大;常耕下,稻草还田降低5～20 cm土层铵态氮含量和硝化势,提高各土层氨化强度和反硝化强度。因而,免耕结合稻草还田更有利于土壤氮素的释放、供应,但需注意防止反硝化损失。