Tillage, Crop Rotation, and Cultural Practice Effects on Dryland Soil Carbon Fractions

Information is needed on novel management practices to increase dryland C sequestration and soil quality in the northern Great Plains, USA. We evaluated the effects of tillage, crop rotation, and cultural practice on dryland crop biomass (stems and leaves) yield, surface residue, and soil C fractions at the 0-20 cm depth from 2004 to 2008 in a Williams loam in eastern Montana, USA. Treatments were two tillage (no-tillage [NT] and conventional tillage [CT]), two crop rotations (continuous spring wheat [Triticum aestivum L.] [CW] and spring wheat-barley [Hordeum vulgaris L.] hay-corn [Zea mays L.]-pea [Pisum sativum L.] [W-B-C-P]), and two cultural practices (regular [conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height] and ecological [variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height]). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop biomass was 24% to 39% greater in W-B-C-P than in CW in 2004 and 2005. Surface residue C was 36% greater in NT than in CT in the regular practice. At 5 - 20 cm, SOC was 14% greater in NT with W-B-C-P and the regular practice than in CT with CW and the ecological practice. In 2007, POC and PCM at 0 - 20 cm were 23 to 54% greater in NT with CW or the regular practice than in CT with CW or the ecological practice. Similarly, MBC at 10 - 20 cm was 70% greater with the regular than with the ecological practice in NT with CW. Surface residue, PCM, and MBC declined from autumn 2007 to spring 2008. No-tillage with the regular cultural practice increased surface residue and soil C storage and microbial biomass and activity compared to conventional tillage with the ecological practice. Mineralization reduced surface residue and soil labile C fractions from autumn to spring.

Land Use and Soil Texture Effects on Organic Carbon Change in Dryland Soils, Senegal

Soil organic carbon (SOC) losses due to poor soil management in dryland are now well documented. However, the influence of soil properties on organic carbon change is not well known. The groundnut plant (Arachis hypogaea L.), and the dominant crop system in the Senegal’s Soudanian zone, have been compared with semi-natural savanna. Leaves, stems and roots biomass were measured, and soil characteristics were analysed. The total leaves and stems biomass was 1.7 and 2.7 Mg ha-1 dry matter in groundnut fields and savanna respectively. Total SOC stocks were low (8 to 20 Mg C·ha-1 within upper 0.2 m depth, 20 to 64 Mg C·ha-1 within upper 1 m depth) and were significantly lower (P δ13C values show that SOC quality is transformed from the savanna plants (C4/C3 mixed-pools) to C3-pools in groundnut cultivated zone, with the organic matter signature more preserved in the clayey soils. This study confirms that converting woodland to groundnut fields provokes texture transformation and SOC loss. The results call for the extreme necessity to regenerate the wooded zone or encourage practices that favour SOC restitution.

Effect of Fertilization on Soil Fertility and Wheat Yield of Dryland in the Loess Plateau

Long-term fertility experiments have become an important tool for investigating the sustainability of cropping systems.Therefore, a long-term (18-year) fertilization experiment was conducted in Changwu County, Shaanxi Province, China,to ascertain the effect of the long-term application of chemical fertilizers and manure on wheat yield and soil fertility in the Loess Plateau, so as to provide a scientific basis for sustainable land management. The experiment consisted of nine fertilizer treatments with three replicates arranged in a completely randomized design: 1) CK (no fertilizer); 2) N (N 120 kg ha-i); 3) P (P 26.2 kg ha-1); 4) NP (N 120, P 26.2 kg ha-1); 5) M (manure 75 t ha-1); 6) NM (N 120 kg ha-1,manure 75 t ha-1); 7) PM (P 26.2 kg ha-1, manure 75 t ha-1); 8) NPM (N 120, P 26.2 kg ha-1, manure 75 t ha-1);and 9) fallow (no fertilizer, no crop). N fertilizer was applied in the form of urea and P was applied as calcium super phosphate. The results showed that precipitation had a large effect on the response of wheat yield to fertilization. Manure (M), NP, PM, NM, and NPM treatments significantly increased (P ＜ 0.05) average yield. In the NP, PM, NM and NPM treatments, the percentage increases in yield due to fertilization were highest in normal years, and lowest in the drought years. Long-term P application enhanced soil available P markedly, and manure applications contributed more to soil fertility than chemical fertilizers alone. Chemical fertilizers applied together with manure distinctly improved soil fertility.The results also showed that the soil nutrient concentration changed mainly in the 0-60 cm layers and fertilization and planting only slightly affected soil nutrients below the 100 cm layers.

Distribution of soil aggregates and organic carbon in deep soil under long-term conservation tillage with residual retention in dryland

To ascertain the effects of long-term conservation tillage and residue retention on soil organic carbon(SOC) content and aggregate distribution in a deep soil(>20-cm depth) in a dryland environment,this paper analyzed the SOC and aggregate distribution in soil, and the aggregate-associated organic carbon(OC) and SOC physical fractions. Conservation tillage(reduced tillage with residue incorporated(RT) and no-tillage with residue mulch(NT)) significantly increased SOC sequestration and soil aggregation in deep soil compared with conventional tillage with residue removal(CT). Compared with CT, RT significantly increased the proportion of small macroaggregates by 23%–81% in the 10–80 cm layer, and the OC content in small macroaggregates by 1%–58% in the 0–80 cm layer. RT significantly increased(by 24%–90%) the OC content in mineral-SOC within small macroaggregates in the 0–60 cm layer, while there was a 23%–80% increase in the 0–40 cm layer with NT. These results indicated that:(1) conservation tillage treatments are beneficial for soil aggregation and SOC sequestration in a deep soil in a dryland environment; and(2)the SOC in mineral-associated OC plays important roles in soil aggregation and SOC sequestration. In conclusion, RT with NT is recommended as an agricultural management tool in dryland soils because of its role in improving soil aggregation and SOC sequestration.

Zai Pit Effects on Selected Soil Properties and Cowpea (<i>Vigna unguiculata</i>) Growth and Grain Yield in Two Selected Dryland Regions of Kenya

Erratic rainfall and temperature regimes, strongly affect agricultural productivity. To address the reduction in production, this study assessed the effect of Zai pit depths on selected soil properties and cowpea growth and grain yield. “Zai” pit technology was tested in two locations falling under Agroecological Zone IV (relatively dry areas) i.e. Katumani in Machakos County and Naivasha in Nakuru County, Kenya, aiming to determine the combined effect of four “Zai” pit depths and two levels of manure (plots with manure and plots without manure) on selected soil properties, growth and yield of cowpea. Experiment was laid out in split plot arrangement, with manure levels as the main plot factor and “Zai” pit depths (Flat: Z0, 30 cm: Z30, 45 cm: Z45 and 60 cm: Z60) as subplot factor, replicated four times. Cowpea (M66 variety) was used as the test crop. Inorganic N and extractable P were significantly (P < 0.05) higher, at 1.37 mg⋅kg−1 for Nin and 80.4 mg⋅kg−1 for Pex in Zai pits compared to flat plots which were at 0.91 mg⋅kg−1 for Nin and 47.1 mg⋅kg−1 for Pex. The values of Nin and Pex also varied depending on depths, with Z45 having highest Nin at 1.17 against the least, at 0.89 in the Z0, while Pex was highest in Z30 at 102.3 mg⋅kg−1 while Z0 having the least Pex of 89.7 mg⋅kg−1. Generally, crops in “Zai” pitted plots were larger in diameter at 0.46 cm than crops in flat plots at 0.42 cm. Better performance was observed in yield, with Z30 yielding 30.5% against 18.2% Flat plots in Machakos while 27.9% in Z30 against 22.5% from Flat plots in Naivasha. This study demonstrated great potential of “Zai” pit technology on crop production, as reflected on improved growth and yield of cowpeas. Combining “Zai” pits with manure increases soil Nin, Pex and is a guarantee of great crop performance in terms of high final yields.

夏闲期耕作下旱地土壤有机碳库与温度和含水量季节变化及关系研究

为明确夏闲期耕作下土壤有机碳(SOC)库与温度和含水量的季节变化及其相互关系,设置夏闲期免耕、翻耕和深松3种耕作处理,分析了黄土高原旱地麦田SOC和易氧化有机碳(POxC)含量的季节变化、土壤含水量和温度的季节变化、以及碳库与温度和含水量变化的关系。结果表明,在冬小麦生育期内,随着生育进程的推进,翻耕和深松处理0~5和5~10 cm土层SOC含量呈先升高后降低的变化趋势,而POxC含量呈“降低—升高—再降低”的变化趋势;土壤质量含水量变化均呈“增加—降低—再增加”的变化趋势,而土壤温度呈先降低后升高的变化趋势。回归分析发现,5~10 cm土层土壤质量含水量与SOC含量呈线性关系(P<0.05),与POxC含量呈二次多项式关系(P<0.05),尤其与免耕和深松处理相比,翻耕处理拟合效果更佳。此外,0~5和5~10 cm土层土壤温度变化与SOC含量无显著相关性,而日最高温度、日平均温度和日最低温度与POxC含量呈显著负相关。综上所述,不同夏闲期耕作下旱地麦田0~10 cm土层POxC含量季节变化与土壤质量含水量和温度变化密切相关,而SOC含量变化对土壤温度变化的敏感性较弱。本研究结果为旱地麦田碳库管理提供了理论依据。

不同施肥年限对红壤细菌多样性及群落结构演替的影响

为探讨不同年限施肥处理对旱地红壤细菌多样性和群落结构演替的影响,基于中国科学院红壤生态实验站设置的不同秸秆还田方式长期定位试验,采集种植玉米后第1年(Y2011)、第3年(Y2013)和第7年(Y2017)的土样进行分析。试验处理分为不施肥(CK)、化肥(N)和化肥+秸秆猪粪配施(NSM)3个处理,通过高通量测序技术研究旱地红壤细菌多样性和群落结构差异。结果表明:(1)施肥处理显著提高了土壤有机碳、全氮、全磷和有效磷养分含量,NSM处理对土壤肥力的提升效果比N处理好,且随着施肥年限的延长,提升效果越显著;(2)与Y2011相比,Y2013和Y2017下CK、N和NSM处理的细菌α多样性均显著提高,且N和NSM处理细菌多样性显著高于CK处理;(3)主坐标分析和聚类分析表明,土壤细菌群落主要通过施肥年限聚类在一起,但同一施肥年限下不同施肥处理之间细菌群落结构没有显著差异;(4)土壤全磷是驱动细菌多样性和群落结构变异的最关键因子。本研究从细菌多样性增加的角度,为探索有机培肥下红壤肥力提升和生态系统健康管护提供了科学依据。

不同施肥方式对旱地玉米土壤质量及产量的影响

针对宁夏南部山区耕地地力条件薄弱、农田生产力水平低、水分利用效率低等问题,选择典型的旱地玉米农田,跟踪监测在不同施肥方式下旱地玉米的主要农艺性状、土壤含水量、土壤养分、产量等指标,探究不同施肥方式对旱地土壤质量及玉米产量的影响。结果表明,常规化肥减量1/3+有机肥50 kg·hm^(-2)的施肥方式使0~40 cm土壤的耗水量最低;施用有机肥和常规化肥减量1/2+有机肥50 kg·hm^(-2)的施肥方式使深层土壤的耗水量最高。常规化肥减量1/3+有机肥50 kg·hm^(-2)的施肥方式使土壤有机质含量显著高于其他施肥方式;常规化肥减量1/3+有机肥50 kg·hm^(-2)和常规化肥减量1/2+有机肥50 kg·hm^(-2)这2种施肥方式土壤全氮、全磷和全钾的平均含量均高于其他处理。减N+有机肥的施肥方式能有效提升土壤养分。施有机肥和常规化肥减量1/2+有机肥50 kg·hm^(-2)的施肥方式可在一定程度上提高作物的产量。

全球旱地饱和水汽压差和根区土壤水分变化对植被生产力的影响及其成因

旱地约占全球陆地面积的40%,而水分是旱地植被生长的一大限制要素。尽管土壤水分与饱和水汽压差对植被生长的重要性已经得到了广泛证实,然而目前二者对植被生产力影响的空间异质性及其形成因素仍未得到深入研究,这对研究旱地生态系统对气候变化的响应带来了挑战。为了填补这一认知空白,研究收集了多源气象、根区土壤含水率和总初级生产力产品,基于随机森林算法量化了植被总初级生产力对根区土壤含水率和饱和水汽压差的敏感性,结合土地覆盖数据和分档平均方法分析了敏感性空间异质性的形成机制。结果表明:全球旱地饱和水汽压差与植被生产力总体呈显著上升趋势;根区土壤水分对植被生长的影响以正效应主导,饱和水汽压差对植被生长的影响以负效应主导;相较于森林和灌木,饱和水汽压差对植被生长的负效应及根区土壤含水率对植被生长的正效应在农田、草地和苔原及半干旱区更为强烈;植被生产力对饱和水汽压差和根区土壤水分的敏感性在数量上总体呈显著的线性负相关性。综上,植被种类和气候条件是导致全球旱地植被生产力对土壤水分和饱和水汽压差敏感性空间异质性的重要因素。

3种不同土类对狭叶方竹实生苗生长的影响

为探索狭叶方竹实生苗生长的合适土类,为人工种植狭叶方竹提供借鉴和数据支撑,本研究开展了林下土、旱地土和稻田土3种土类4次重复种子繁殖试验,并对实生苗的生长进行了观察和记录。结果表明:3种不同土类对狭叶方竹实生苗的苗高和地径影响明显,其中稻田土为狭叶方竹实生苗生长的最优土类,苗高平均值达24.19 cm,地径平均值达2.72 mm。

Scenario Analysis of Tillage, Residue and Fertilization Management Effects on Soil Organic Carbon Dynamics

Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model’s parameters, and the applicability of the model to propose soil organic carbon (SOC) management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified via scenario analysis. Results between simulations and actual measurements were in close agreement when appropriate applications of stover, manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50% residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited.

Response of yield increase for dryland winter wheat to tillage practice during summer fallow and sowing method in the Loess Plateau of China

Soil moisture is the most critical limiting factor impacting yields of dryland winter wheat(Triticum aestivum L.) and it is strongly affected by tillage practice and sowing methods. This study was to assess the link between sowing method and tillage practice during summer fallow and their subsequent effect on soil moisture and grain yield. Furthermore, we sought to identify a more appropriate farming management practice for winter wheat production in Loess Plateau region of China. The experiment was conducted from 2011 to 2013, using a two-factor split plot design, including subsoiling(SS) or no tillage(NT) during summer fallow for main plots, and conventional drill sowing(DS) or plastic film drill sowing(FM) for subplots. Results showed that the maximum soil water storage(SWS) was under SS×FM treatment with values of 649.1 mm(2011–2012) and 499.4 mm(2012–2013). The SWS during the 2011–2012 growing season were 149.7 mm higher than that in the 2012–2013 growing season. And adoption of SS×FM significantly increased precipitation use efficiency(PUE) and water use efficiency(WUE) compared to other treatments for both seasons. Moreover, adoption of SS×FM significantly increased yield by 13.1, 14.4, 47.3% and 25.9, 39.1, 35.7% than other three treatments during the two growing seasons, respectively. In summary, combining subsoiling during summer fallow with plastic film drill sowing(SS×FM) increased SWS at sowing and effectively improved WUE, thus representing a feasible technology to improve grain yield of dryland winter wheat in the Loess Plateau of China.

Study on micro-water-collecting technique in dryland field of spring maize

This paper analyses the effect of water storage and soil moisture conservation by means of micro water collecting technique in the dryland field of spring maize. The results indicate that the rainfall infiltration depth is deeper by means of micro water collecting treatment than that of the control. In micro water collecting treatment, the amount of soil water storage within 0～200 cm of soil layers increases by 50.5 mm, 13.5～58.6 mm, and 24.5 mm respectively during seedling stage, the critical stage of water requirement and the ripening and harvesting stage compared with the control. The micro water collecting technique not only has the function of regulating and adjusting the amount and distribution of field evapotranspiration, but also can raise the water use efficiency, which results in an obvious effect of increasing crop yield, especially in the dry years.

Water Availability for Winter Wheat Affected by Summer Fallow Tillage Practices in Slope Dryland

The tillage experiments for winter wheat were conducted on the slope farmland in Luoyang, Henan Province in the semihumid to arid loess plateau areas of North China. Different tillage methods including reduced tillage(RT), no-till(NT), 2 crops/year(2C), subsoiling(SS), and conventional tillage(CT)were compared to determine the effects of tillage methods on soil water conservation, water availability, and wheat yields in a search for better farming systems in the areas. The NT and SS showed good effects on water conservation. The soil water storage increased 12 - 33 mm with NT and 9-24 mm with SS at the end of summer fallow periods. The soil evaporation with NT and SS decreased 7-8 mm and 34 - 36 mm during the fallow periods of 1999 and 2001, respectively. Evapotranspiration(ET)with NT and SS increased about 47 mm during wheat growth periods of 2000 to 2001. Treatment RT and 2C had low water storage and high water losses during the fallow periods. The winter wheat yields with conservation tillage practices were improved in the 2nd year, increased by 3, 5 and 8% with RT, NT and SS, respectively, compared with CT. The highest wheat yields were obtained with subsoiling, and the maximum economic benefits from no-till. All conservation tillage practices provided great benefits to saving energy and labors, reducing operation inputs, and increasing economic returns. No-till and subsoiling have shown promise in increasing water storage, reducing water loss, enhancing water availability, and saving energy, as well as increasing wheat yield.

高砷煤矿周围旱作土壤重金属污染特征及农作物健康风险评价

为了掌握高砷煤矿周边旱作农田重金属污染状况,运用单因子污染指数法、内梅罗综合污染指数法和地积累指数法对高砷煤矿周边旱作土壤重金属(As、Cd、Hg、Cu、Zn)进行污染风险评价,并采用富集系数法、目标危害商数法和致癌风险指数法对农作物和人体健康风险进行评价。结果表明:调查区域土壤综合污染指数均值为2.12,属中度污染水平;土壤中As、Cd、Hg、Zn、Cu的含量均值分别为全国土壤背景值的7.91、2.57、5.26、1.53、3.44倍;As和Hg的污染等级高且范围广,Cu污染等级低但污染范围广,Cd的污染等级较低且范围较小,Zn基本无污染。富集系数法评价结果显示,作物对5种重金属的吸收能力表现为Cd>Zn>Cu>Hg>As。农作物健康风险评价结果显示,5种农作物的健康风险主要为非致癌风险,As是可食用农作物(除玉米外)的主要致癌风险因子和非致癌风险因子,Cd是烟草的主要致癌风险因子和非致癌风险因子。食用本地农作物对人体造成的健康风险依次为As>Cd>Hg>Cu>Zn。研究表明:研究区域土壤处于中度污染水平,As的风险较高;可食农作物中重金属的潜在健康风险主要源于As,且对儿童造成的健康风险明显高于成人;烟草的健康风险主要源于Cd;农作物中辣椒和烟草的健康风险最高。

垄沟种植对旱地玉-麦轮作体系生产力和土壤硝态氮累积量的影响

【目的】探究不同垄沟种植模式对旱地玉-麦轮作体系作物生产力、土壤性状及土壤硝态氮累积量的影响,为改善旱地土壤肥力,提高作物产量和效率,降低环境风险提供科学依据。【方法】基于中国农业科学院洛阳旱农试验基地始于2004年的长期定位试验,设置6行固定道垄沟种植(6RPRF)、6行每年起垄垄沟种植(6REYRF)、4行固定道垄沟种植(4RPRF)、4行每年起垄垄沟种植(4REYRF)和传统平作(CF)5个处理,分析了2015—2021年度玉米、小麦及其周年的产量、水分利用效率,2020年玉米收获期0—40 cm不同土层的容重、养分含量和酶活性,以及2019—2020年度小麦收获期0—380 cm土层土壤硝态氮累积量。【结果】与CF相比,4种垄沟种植下玉米、小麦、周年的6年平均产量分别显著提高8.6%—32.1%、12.5%—25.6%、11.3%—29.6%,水分利用效率分别显著提高8.6%—31.4%、12.5%—31.1%、12.8%—30.3%;0—5 cm和20—40cm土层的容重分别显著降低7.3%—11.3%和4.9%—11.5%;0—40 cm土层平均有机质、全氮、有效磷和速效钾含量及脲酶活性分别提高6.0%—19.8%、80.8%—100.0%、28.5%—80.9%、58.5%—141.2%和24.0%—46.9%,0—100 cm土层的硝态氮累积量显著提高38.8%—116.0%,其中,总体以4RPRF处理效果最优,其还可以在硝态氮累积量总量维持在CF水平的同时使0—100cm土层显著提高38.8%、200—380 cm土层显著降低15.0%,具有提高根层、降低深层土壤硝态氮累积量的作用。固定道垄作模式(PRF)与每年起垄模式(EYRF)相比,玉米和周年的6年平均产量分别显著提高10.6%和9.1%,垄面种植6行模式(6R)下玉米、垄面种植4行模式(4R)下小麦和周年的6年平均水分利用效率分别显著提高21.1%、15.2%和8.2%,土壤养分含量表层提高、下层降低,0—380 cm土层的硝态氮累积量显著降低4.9%—30.2%。4行模式较6行模式,玉米和周年的6年平均产量分别显著提高9.9%和6.8%,EYRF下玉米、PRE下小麦和周年的6年平均水分利用效率分别显著提高7.4%、16.5%和6.7%,土壤特性有改善趋势,但其效应因指标而异,且在不同起垄模式和不同土层表现不同。【结论】4行固定道垄沟种植(4RPRF)既可降低土壤容重,提高土壤有机质、全氮和速效钾含量,又可使玉米、小麦、周年的产量和水分利用效率在多数条件下表现最优,还可以有效降低200—380 cm土层的硝态氮累积量,是协同实现旱地雨养玉-麦轮作区作物高产高效和环境友好生产的种植模式。

A STUDY ON FIELD WATER CIRCULATION PATTERN IN THE DRYLAND OF NORTHERN CHINA

Based on the observed data of soil moisture from locating experiments from 1986 to 1990, the pattern of field water circulation in dryland of northern China, where the mean annual precipitation is 300 600 mm, is studied in this paper using the method of water balance. The results show that water satisfying ratio of spring seeding crops is 83.7 90.8 percent and that of winter wheat is about 70 percent in these areas; about 80 90 percent of water consumption of spring seeding crops and about 60 70 percent of water consumption of winter wheat comes from precipitation during the growing period, the rest comes from the soil water storage before the seeding period. But the available soil water is not used thoroughly, about 30 70 percent of available soil water remains unused when the crops are harvested. At the fallow period, the amount of soil water lost by evaporation is very important, which takes up 57 68 percent of precipitation in winter wheat field and 73 244 percent in field of spring seeding crops. Thus restraining soil evaporation, raising the storage ratio of natural precipitation and the soil water utilization efficiency of crops, strengthening the circulation ability of soil water by adopting efficient measures of agricultural techniques, are the main ways for exploiting and developing the potential productivity of natural precipitation in these areas.

耕作方式对旱地麦田土壤团聚体及其碳氮组分分布的影响

为明确蓄水保墒耕作方式下旱地麦田土壤团聚体稳定性、有机碳及碳组分和全氮及氮组分在不同粒径团聚体组分中的分布特征,深入了解不同耕作方式下土壤碳氮固持机制,以连续3 a(2017—2020年)实施不同耕作方式(免耕、深松、深翻)后冬小麦收获期0~20 cm土壤为研究对象,采用湿筛法测算土壤团聚体的构成与稳定性(R_(0.25),>0.25 mm团聚体含量;MWD,平均重量直径;GMD,几何平均直径),并测定各粒径团聚体有机碳(SOC)和碳组分(重组有机碳,HFOC;轻组有机碳,LFOC;易氧化有机碳,EOC;可溶性有机碳,DOC;颗粒有机碳,POC)含量、全氮(TN)和氮组分(硝态氮,NO^(-)_(3)-N;铵态氮,NH^(+)_(4)-N;可溶性有机氮,SON)含量,分析了碳氮组分的相关关系。结果显示:(1)免耕和深松处理>2 mm团聚体土壤比例较深翻处理分别提高8.8%和22.1%,免耕有利于增加<0.053 mm粉黏粒比例,较深松和深翻处理分别提高46.4%和27.7%。深松处理较深翻处理的R_(0.25)、MWD、GMD分别提高了2.8%、6.3%和9.0%;(2)免耕和深松处理较深翻提高土壤各粒径团聚体SOC、LFOC、EOC、DOC和POC含量。深松处理各粒径团聚体HFOC含量均高于深翻处理,免耕处理仅<0.053 mm团聚体HFOC含量比深翻高24.7%;(3)与深翻处理相比,免耕处理有利于提高>2 mm、0.25~2 mm、0.053~0.25 mm土壤团聚体TN、NO^(-)_(3)-N和NH^(+)_(4)-N含量;深松处理有利于增加土壤各粒径团聚体TN含量以及>2 mm和0.25~2 mm团聚体NO^(-)_(3)-N含量,各粒径团聚体NH^(+)_(4)-N含量低于深翻处理。免耕和深松处理各粒径团聚体SON含量均高于深翻处理。碳氮比(C/N)在不同粒径团聚体均表现为深松>免耕>深翻;(4)免耕和深松处理的0~20 cm土壤碳储量分别比深翻高85.4%和86.3%,土壤氮储量分别比深翻高48.1%和32.5%,而秸秆碳还田量分别比深翻低30.9%和16.4%;(5)通过结构方程模型分析发现,DOC和POC通过协同EOC变化,是影响SOC变化的主导因子。SON是协同TN提升的主导因子。因此,黄土高原旱地麦田实施深松技术可改善土壤团聚体结构,实现土壤固碳保氮的协同效应。

提升雨养夏玉米-冬小麦两熟体系生产力和土壤硝态氮累积的最优耕作模式

【目的】研究耕作模式对旱地雨养夏玉米–冬小麦(以下简称玉–麦)两熟体系生产力的影响,并对深松、翻耕在轮耕模式中的作用进行评价。【方法】定位试验于2015—2021年在中国农业科学院洛阳旱农试验基地进行。设置夏免耕秋免耕(SNAN)、夏深松秋免耕(SSAN)、夏免耕秋3年免耕1年翻耕(SNA3N1P)、夏深松秋3年免耕1年翻耕(SSA3N1P)和传统夏秋季均翻耕(CT)5种耕作模式,调查了玉米、小麦的产量和水分利用效率,2020年测定了玉米收获期0—40 cm土层土壤容重、养分含量和酶活性,以及2019—2020年度小麦收获期0—380 cm土层的硝态氮累积量。【结果】1)与CT处理相比,SNAN、SSAN、SNA3N1P和SSA3N1P处理的玉米、小麦和周年产量分别显著提高了28.4%~33.5%、23.7%~25.0%和27.1%~30.3%,水分利用效率分别显著提高了19.6%~39.2%、20.2%~29.3%和29.5%~34.5%,0—5 cm和20—40 cm土层土壤容重显著降低,0—5 cm土层的有机质含量以及0—40 cm多数土层的全氮、有效磷、速效钾含量和脲酶、蔗糖酶活性均显著提高;0—80 cm土层硝态氮累积量显著提高了44.3%~104.8%,120—380 cm土层硝态氮累积量显著降低了22.1%~34.1%。2)与夏免耕(SN)处理相比,夏深松(SS)处理对玉米和小麦产量没有显著影响,但显著降低了玉米水分利用效率,提高了10—20 cm土层有机质含量、0—20 cm土层全氮含量、0—5 cm和10—20 cm土层有效磷含量、10—20 cm土层速效钾含量、5—40 cm土层脲酶活性、0—40 cm土层蔗糖酶活性,也提高了20—40 cm土层容重和0—380 cm土层硝态氮累积量。3)与秋免耕(AN)处理相比,秋3年免耕1年翻耕(A3N1P)处理降低了0—5 cm土层的土壤养分含量,增加了5—20 cm各土层有机质含量、5—40 cm各土层速效钾含量、0—40 cm各土层脲酶和蔗糖酶活性;SN处理下的小麦水分利用效率6年均值显著提高了7.1%,SS处理下0—380 cm土层的硝态氮累积量显著降低了12.4%。4)虽然SSA3N1P处理的产量和水分利用效率与其他轮耕模式无显著差异,但其改善土壤性状和提高根层(0—80 cm)、降低深层(120—380 cm)土壤硝态氮累积量的效果最优。【结论】夏深松相比夏免耕、秋季3年免耕1年翻耕相比秋免耕均可改善土壤性状。夏深松秋3年免耕1年翻耕的改土、增产增效和优化土壤硝态氮分布的效果总体最优,是适宜雨养玉–麦两熟体系的耕作模式。