不同耕作措施下旱作农田土壤团聚体中有机碳和全氮分布特征

以连续进行12年的保护性耕作长期定位试验为研究对象,探索了传统耕作(T)、传统耕作+秸秆还田(TS)、免耕不覆盖(NT)、免耕+秸秆覆盖(NTS)4种耕作措施对陇中黄土高原旱作农田豌豆-小麦双序列轮作系统的土壤团聚体中有机碳和全氮分布特征的影响。结果表明:各处理均以≥0.25 mm团聚体为优势团聚体,且≥0.25 mm团聚体含量随土层深度增加而增加,而其他粒径团聚体含量随土层深度的变化并无明显规律。较之T处理,TS、NT、NTS处理均可提升≥0.25 mm团聚体含量和平均重量直径,NTS处理提升效果最明显。TS、NT、NTS处理土壤有机碳和全氮含量均高于T处理,其中TS、NTS处理显著高于T处理,NTS处理高于TS处理;各处理土壤有机碳和全氮含量均随土层增加而减小。较之T处理,NT、TS、NTS处理可不同程度提高各粒径团聚体中有机碳和全氮含量,NTS处理的含量最高;各粒径团聚体中有机碳和全氮含量均随土层深度增加而减小;同时,团聚体中有机碳和全氮含量随粒径减小而增加。2~5 mm和0.25~2 mm和≥5 mm团聚体含量与相应粒径团聚体有机碳含量呈极显著正相关、极显著正相关和极显著负相关;0.25~2 mm和≥5 mm团聚体含量与相应级别团聚体全氮含量分别呈极显著正相关和显著负相关。T处理不同粒径团聚体有机碳和全氮贡献率按其大小排序均为(0.25 mm)(≥5 mm)(0.25~2 mm)(2~5 mm),其他3种耕作措施各粒径团聚体有机碳和全氮贡献率在各土层中的排序各有不同,并无明显规律。     

The effects of long-term conservation tillage, crop residues and P fertilizer on soil conditions and responses of summer and winter crops on an Andosol in Japan

A field experiment was conducted from 1983 to 1992 in Tsukuba, Japan to investigate the effects of tillage on soil conditions and crop growth in a light-colored Andosol. Three tillage methods (NT: no-tillage, RT: no-tillage for summer cropping and moldboard plowing for winter cropping, and CT: conventional rotary tillage to a depth of 15 cm) were employed in combination with crop residue application (+R, −R) and fused magnesium phosphate (FMP) fertilization (+P, −P). Under the combination of NT and +R, diurnal variation of soil temperature at a depth of 5 cm was smaller during the summer cropping season and soil temperature in the daytime was lower during the winter cropping season than under CT. Soil inorganic N concentration at a depth of 0–30 cm was +R > −R and NT > RT > CT. The early growth of summer crops was accelerated under NT in comparison with CT, and yields were higher under NT and RT in comparison with CT. On the other hand, winter crop yields were significantly reduced under NT, while they were still higher under RT in comparison with CT. Yields were higher with +R and +P application, respectively, and these effects were more pronounced in winter cropping. The positive effect of FMP fertilization was greater in combination with NT, and that of residue treatment was greater in combination with RT and NT than with CT. In conclusion, the best tillage practice for Andosols on the Kanto Plain is RT, i.e. a combination of NT for summer cropping and CT for winter cropping. The application of NT for winter cropping is not recommended, although the application of phosphate and crop residues could reduce the risk of yield reduction, because of improved soil nutrient status and moderation of diurnal soil temperature.     

黄土丘陵沟壑区水土保持综合治理关键措施及其组合的研究

 通过对黄土丘陵沟壑区几条典型小流域和现有治理模式的分析评价,初步确定了该区不同侵蚀类型区水上保持综合治理的关键措施及其组合方案。各区的组合比例如下。第1副区和第2副区:水平梯田18％～25％,人工造林45％～55％,人工种草20％～25％,坝地5.5％～7.5％,水地0.5％～2.7％;第3副区:水平梯田42％～48％,人工造林32％～38％,人工种草18％～22％;第4副区和第5副区:水平梯田28％～35％,人工造林40％～46％,人工种草13％～17％,坝地小于5％,水地小于6％。     

Hayland conversion to wheat production in semiarid eastern Montana: tillage, yield and hay production comparisons

When converting grass- and haylands to cultivated crop production, care must be taken to conserve and maintain soil resources while considering economic issues. Methods of breaking sod can have a bearing on erosivity, physical and chemical properties of soils, and cost of production. Our objective was to compare three methods of converting crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.] hayland to wheat (Triticum aestivum L.) production vs. leaving the land for hay production. We initiated a study in 1990 on Dooley sandy loam (fine-loamy, mixed Typic Argiboroll) near Froid in semiarid eastern Montana, USA. Plots, replicated three times, were 12- by 30-m oriented east to west on a north-facing slope. We converted sod to cultivated crop production by: (1) moldboard plow, (2) toolbar with sweeps, (3) herbicides (no-till). Plots were fallowed until spring 1991 and then seeded to spring wheat each of the next four years. All wheat plots were fertilized with 224 kg ha⁻¹ of 18-46-0 in 1991 and 1992, and 34 kg ha⁻¹ nitrogen as 34-0-0 in 1993 and 1994. Grass was either fertilized same as wheat or not fertilized. Wheat yields averaged 2540 kg ha⁻¹ on tilled treatments and 2674 kg ha⁻¹ on no-till. Fertilized grass consistently out-yielded unfertilized, and averaged 3.2 Mg ha⁻¹ vs. 1.8 Mg ha⁻¹. Toolbar with sweeps had highest economic return of US$169.48 ha⁻¹ to pay for land, labor, and management. Moldboard plow had US$162.05 ha⁻¹. Because of herbicide costs, no-till only returned US$148.64 ha⁻¹. Unfertilized grass hay returned US$67.68 ha⁻¹ and fertilized grass hay, US$97.95 ha⁻¹. Results may be tempered because our wheat yields were high: a 2016 kg ha⁻¹ wheat yield would have returned the same as fertilized grass. Before converting grass- and hay-lands to small grains production, consideration must be given to such variables as sod conversion methods, management practices, labor requirements, market conditions, total precipitation and its temporal distribution, soil conditions, growth environment, soil conservation, and economics.     

Soil translocation resulting from multiple passes of tillage under normal field operating conditions

Until now, most tillage erosion experiments were conducted under controlled soil and operating conditions. However, soil condition, tillage depth, speed and direction generally show substantial within-field variation. In this study, a series of tillage experiments were set up to investigate the erosivity of tillage under normal operating conditions. The effect of a typical tillage sequence, including multiple mouldboard, chisel and harrow passes, on soil translocation and tillage erosion was studied during a period of 3 years. Soil translocation in excess of 10 m was observed while the average net translocation rates ranged between 0 and 0.9 m. The results suggest that the annual tillage transport coefficient, associated with mechanized agriculture, is in the order of 781 kg m⁻¹ yr⁻¹. The experimental results also show that the tillage transport coefficient of a sequence of tillage operations can be reasonably well predicted from information provided by the farmer and by summing the transport coefficients obtained from controlled, single pass experiments. However, a Monte Carlo simulation showed that a relatively high number of tillage operations are required to obtain accurate estimates of the tillage transport coefficients in multiple pass experiments.     

A method for estimating coefficients of soil organic matter dynamics based on long-term experiments

The one-compartment C model C_t=C₀e^−k₂t+k₁A/k₂(1−e^−k₂t) is being long used to simulate soil organic C (SOC) stocks. C_t is the SOC stock at the time t; C₀, the initial SOC stock; k₂, the annual rate of SOC loss (mainly mineralization and erosion); k₁, the annual rate to which the added C is incorporated into SOC; and A, the annual C addition. The component C₀e^−k₂t expresses the decay of C₀ and, for a time t, corresponds to the remains of C₀ (C_0 remains). The component k₁A/k₂(1−e^−k₂t) refers, at time t, to the stock of SOC derived from C crops (C_crop). We herein propose a simple method to estimate k₁ and k₂ coefficients for tillage systems conducted in long-term experiments under several cropping systems with a wide range of annual C additions (A) and SOC stocks. We estimated k₁ and k₂ for conventional tillage (CT) and no-till (NT), which has been conducted under three cropping systems (oat/maize −O/M, vetch/maize −V/M and oat + vetch/maize + cowpea −OV/MC) and two N-urea rates (0 kg N ha⁻¹ −0 N and 180 kg N ha⁻¹ −180 N) in a long-term experiment established in a subtropical Acrisol with C₀ = 32.55 Mg C ha⁻¹ in the 0–17.5 cm layer. A linear equation (C_t = a + bA) between the SOC stocks measured at the 13th year (0–17.5 cm) and the mean annual C additions was fitted for CT and NT. This equation is equivalent to the equation of the model C_t=C₀e^−k₂t+k₁A/k₂(1−e^−k₂t), so that a=C₀e^−k₂t and bA=k₁A/k₂(1−e^−k₂t). Such equivalences thus allow the calculation of k₁ and k₂. NT soil had a lower rate of C loss (k₂ = 0.019 year⁻¹) than CT soil (k₂ = 0.040 year⁻¹), while k₁ was not affected by tillage (0.148 year⁻¹ under CT and 0.146 year⁻¹ under NT). Despite that only three treatments had lack of fit (LOFIT) value lower than the critical 5% F value, all treatments showed root mean square error (RMSE) lower than RMSE 95% indicating that simulated values fall within 95% confidence interval of the measurements. The estimated SOC stocks at steady state (C_e) in the 0–17.5 cm layer ranged from 15.65 Mg ha⁻¹ in CT O/M 0 N to 60.17 Mg ha⁻¹ in NT OV/MC 180 N. The SOC half-life (t_1/2 = ln 2/k₂) was 36 years in NT and 17 years in CT, reflecting the slower C turnover in NT. The effects of NT on the SOC stocks relates to the maintenance of the initial C stocks (higher C_0 remais), while increments in C_crop are imparted mainly by crop additions.     

半干旱地区坡耕地渗水孔耕作法试验研究

定西地区属半干旱黄土丘陵沟壑区,农业生产发展缓慢的主要原因是干旱缺水和水土流失。经坡地田间聚流技术试验研究表明:渗水孔耕作法,不仅能增强天然降雨入渗,而且还能增加入渗深度,减少地表蒸发,提高了降雨利用率和水分利用效率,达到了保土、增收及合理利用水土资源的目的。     

不同施肥措施对白土腐殖质组成的影响

以白土稻区4年大田定位试验为基础,设置2种翻耕深度(10 cm、20 cm,分别标记为T10、T20)和4种施肥措施(单施化肥、化肥+畜禽粪肥、化肥+秸秆还田、化肥+绿肥,分别标记为F、F+M、F+S、F+G),通过腐殖质组成修改法分别提取表层土壤水溶性物质、胡敏酸、富里酸和胡敏素,研究不同施肥措施对白土腐殖质各组分碳含量的影响。结果表明:单施化肥措施下,翻耕20 cm处理(T20+F)土壤总有机碳和腐殖质各组分碳含量均低于翻耕10 cm处理(T10+F),但差异未达显著水平。在翻耕20 cm的基础上增施有机肥能显著提高土壤总有机碳和腐殖质各组分碳含量,增施畜禽粪(T20+F+M)、秸秆还田(T20+F+S)和增施绿肥(T20+F+G)3处理的土壤总有机碳、胡敏酸、富里酸和水溶性物质碳含量较T20+F处理分别提高14.57%~30.64%、10.36%~30.57%、0.74%~12.31%和14.25%~26.80%。增施有机肥显著提高胡敏素碳含量,T20+F+M、T20+F+S和T20+F+G处理较T20+F处理提高18.87%~35.78%。4年不同翻耕与施肥措施对白土腐殖质性质未产生显著影响。增施有机肥能一定程度上提高土壤PQ值、胡富比、E4/E6值和色调系数。相关性分析表明,胡敏素、胡敏酸、富里酸碳含量与总有机碳含量间均存在显著或极显著正相关,与水溶性物质碳含量间无明显相关性。     

Tillage and mulch effects on soil physical environment, root growth, nutrient uptake and yield of maize and wheat on an Alfisol in north-west India

Field experiments were conducted for 6 years on a silty clay loam to study the effect of soil management on soil physical properties, root growth, nutrient uptake and yield of rainfed maize (Zea mays L.) and wheat (Triticum aestivum L.) grown in a sequence. Treatments were: no-tillage (NT), NT+pine needle mulch at a rate of 10 t ha⁻¹ (NT+M), conventional tillage (CT), CT+pine needle mulch at a rate of 10 t ha⁻¹ (CT+M) and deep tillage (DT). The soil is classified as a Typic Hapludalf and has compact sub-surface layers. The NT treatment increased the bulk density of the surface layer but this problem was not observed in the no-tilled treatment having mulch at the surface (NT+M). The CT+M and NT+M treatments favourably moderated the hydro-theregime resulting in greater root growth, nutrient uptake and grain yields of maize and wheat. The DT treatment, imposed only once, at the beginning of the study, also enhanced root growth and grain yields. The yields were similar to the mulched treatments for maize and somewhat less than the mulched treatments for wheat. Mulched treatments generally showed significantly greater total uptake of N, P and K than corresponding unmulched ones. Since NT+M was comparable to CT for maize and superior for wheat, the latter is preferable since it does not require ellaborate tillage.     

Influence of tillage and crop residue on soil physical properties and yields of rice and wheat under shallow water table conditions

An experiment was conducted to evaluate the effects of tillage and residue incorporation on soil properties and yields of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) in rotation for 4 years on a silty clay loam of an Aquic Hapludoll with natural water table fluctuating between 0.05 and 0.97 m depth The rice experiment was laid out in split plot design with four levels of tillage, viz. conventional puddling (CP), puddling by four passes of rotavator (PR), reduced puddling by two passes of rotavator (ReP), and direct seeding without puddling (DSWP) and two levels of residue, viz. residue incorporation (RI) and residue removal (RR) in four replications. The treatments for wheat were zero tillage (ZT) and conventional tillage (CT) with RI and RR superimposed over the plots of rice. Tillage for rice increased puddling index and bulk density (BD) over the years. The increase was significantly higher in CP and PR than in ReP. In wheat season, BD was higher under ZT than under CT but the differences were not significant. Puddling decreased saturated hydraulic conductivity with time, which became significantly lower in CP and PR in the fourth year than in ReP in the first year. Infiltration rate (IR) also decreased with time and was lowest in CP and PR. In wheat season, IR was at par under ZT and CT. Rice yield in PR was maximum and at par with that in ReP. But wheat yield was lowest in PR and highest in DSWP, and was at par in DSWP and ReP. Thus, rice yields were optimum under ReP, in which changes in soil properties were least, and wheat yields were optimum both under ZT and CT in the DSWP and ReP plots of rice under shallow water table conditions of the silty clay loam.