In-field management of corn cob and residue mix: Effect on soil greenhouse gas emissions

In-field management practices of corn cob and residue mix (CRM) as a feedstock source for ethanol production can have potential effects on soil greenhouse gas (GHG) emissions. The objective of this study was to investigate the effects of CRM piles, storage in-field, and subsequent removal on soil CO₂ and N₂O emissions. The study was conducted in 2010–2012 at the Iowa State University, Agronomy Research Farm located near Ames, Iowa (42.0°′N; 93.8°′W). The soil type at the site is Canisteo silty clay loam (fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquolls). The treatments for CRM consisted of control (no CRM applied and no residue removed after harvest), early spring complete removal (CR) of CRM after application of 7.5 cm depth of CRM in the fall, 2.5 cm, and 7.5 cm depth of CRM over two tillage systems of no-till (NT) and conventional tillage (CT) and three N rates (0, 180, and 270 kg N ha⁻¹) of 32% liquid UAN (NH₄NO₃) in a randomized complete block design with split–split arrangements. The findings of the study suggest that soil CO₂ and N₂O emissions were affected by tillage, CRM treatments, and N rates. Most N₂O and CO₂ emissions peaks occurred as soil moisture or temperature increased with increase precipitation or air temperature. However, soil CO₂ emissions were increased as the CRM amount increased. On the other hand, soil N₂O emissions increased with high level of CRM as N rate increased. Also, it was observed that NT with 7.5 cm CRM produced higher CO₂ emissions in drought condition as compared to CT. Additionally, no differences in N₂O emissions were observed due to tillage system. In general, dry soil conditions caused a reduction in both CO₂ and N₂O emissions across all tillage, CRM treatments, and N rates.     

稻田土壤养分特性对不同耕作方式的生态响应

为深入了解耕作措施对稻田耕层土壤的作用效果,笔者在前人研究结果的基础上综述了免耕、翻耕等不同耕作方式对稻田土壤物理性质包括容重、孔隙度、团聚体、水分、温度,土壤化学性质如氮、磷、钾、有机质和微量元素含量以及土壤生物学特性包括微生物、酶活性的影响,分析了不同稻作措施的优缺点。最后对稻田耕层的合理调控提出因地制宜,依据当地的气候、土壤条件、栽培模式选择合理的耕作方式;合理轮耕,免耕、翻耕和旋耕交替运作;配施绿肥和有机肥;推行节水稻作模式等建议。     

有机培肥与耕作方式对稻麦轮作土壤团聚体和有机碳组分的影响

为了明确不同外源有机物和耕作方式对土壤地力培育的影响,以水稻-小麦轮作系统为对象,通过2个年度(2016—2018年)大田试验研究了外源有机物(秸秆和有机肥)和耕作方式及其交互作用[稻麦秸秆还田配合旋耕(SR),稻麦秸秆还田配合翻耕(SP),秸秆不还田、增施有机肥配合旋耕(MR),秸秆不还田、增施有机肥配合翻耕(MP),秸秆不还田、不施用有机肥、旋耕深度15 cm(CKR)]对土壤团聚体和有机碳组成的短期影响。结果表明:SR处理能够降低水稻季土壤容重并增加总孔隙度。相比CKR,小麦季SR处理显著增加0.05mm水稳性团聚体含量,增加量为7.2%。此外,外源有机物和耕作对土壤有机碳活性组分具有显著影响。其中,易氧化有机碳(EOC)主要受耕作与有机物交互作用影响,酸水解有机碳(LPIc和LPII_c)主要受耕作措施的影响, SR处理的土壤EOC和LPI_c含量比CKR提高0.3～2.6 g·kg~(-1)。颗粒有机碳(POC)主要受外源有机物的影响,并且秸秆还田处理POC平均含量高于增施有机肥处理,增加量为0.75g·kg~(-1)。短期内,外源有机物和耕作及其交互作用对稳定性有机碳(黑碳和矿物结合态有机碳)的影响较小。综上,秸秆还田配合旋耕有助于提高土壤水稳性团聚体和活性有机碳的含量(EOC、LPI_c和POC)。     

The use of remote sensing to detect the consequences of erosion in gypsiferous soils

Tillage practices on sloping ground often result in unsustainable soil losses impairing soil functions such as crop productivity, water and nutrients storage, and soil organic carbon (SOC) sequestration. A sloping olive grove (10%) was planted in shallow gypsiferous soils in 2004. It was managed by minimum tillage; the most frequent management practice in central Spain. The consequences of erosion were studied in soil samples (at 0–10, 10–20, and 20–30 cm depths) by analyzing SOC, available water and gypsum content, and by detecting spectral signatures using an ASD FieldSpecPro® VIS/NIR-spectroradiometer. The Brightness index (BI), Shape index (FI), and Normalized Difference Vegetation Index (NDVI) were derived from the ASD spectral signatures and from remote sensing (Sentinel-2 image) data. The development of these young olive trees was estimated from the measured diameter of the trunks (17 ± 18 cm diameter). In 20–30 cm of the soil, the carbon stock (38 ± 18 Mg ha⁻¹) as well as the available water content (12 ± 6%) was scarce, affecting the productivity of the olive grove. The above-mentioned indices obtained from the laboratory samples and the pixels of the Sentinel-2 image were significantly (p < 0.01) correlated, with a correlation coefficient of around 0.4. The BI was related to the gypsum content and the slope of the plot. The FI was related to the carbon and water contents. The NDVI derived from the satellite image identified the influence of soil degradation on the trees and the carbon content. The spatial-temporal changes of the indices might help in tracking soil changes over time.     

不同耕作方式对辽西褐土物理性状及玉米根系分布的影响

通过连续3年大田试验，对旋耕、翻耕、深松3种耕作方式下的土壤物理性质、玉米根系分布和产量进行测定。结果表明，与翻耕和旋耕相比，深松显著增加了玉米田土壤耕层厚度和降低了犁底层厚度。在中下层土壤，深松还降低了土壤紧实度和容重，改善了土壤的孔隙状况，有利于玉米根系向下生长，使得中下层土壤的玉米根系不仅更丰富，而且占总根系量的比例也更高，最终提高了玉米产量。本研究表明，深松耕作有利于改善辽西褐土区土壤结构和促进玉米生长。     

Impact of different crop rotations and tillage systems on weed infestation and productivity of bread wheat

Crop rotation and tillage systems have important implications for weed infestation and crop productivity. In this study, five tillage systems viz. zero tillage (ZT), conventional tillage (CT), deep tillage (DT), bed sowing (60/30 cm with four rows; BS₁) and bed sowing (90/45 cm with six rows; BS₂) were evaluated in five different crop rotations viz. fallow-wheat (FW), rice-wheat (RW), cotton-wheat (CW), mungbean-wheat (MW) and sorghum-wheat (SW) for their effect on weed infestation and productivity of bread wheat. Interaction between different tillage practices and cropping systems had significant effect on density and dry biomass of total, broadleaved and grass weeds, agronomic and yield-related traits, and grain yield of bread wheat. The un-disturbed soils (ZT) under fallow-wheat or mungbean-wheat rotations favoured the weed prevalence (a total weed dry biomass of 72.4–109.6 and 105.6–112.1 g m⁻² in first and second year, respectively). Contrary to this, the disturbed soils (CT, DT, BS₁ and BS₂) had less weed infestation with either of the rotations (a total weed biomass of 0.4–7.1 and 1.1–5.4 g m⁻² in first and second year, respectively). Sorghum-wheat rotation had strong suppressive effect on weed infestation in all tillage systems. The impact of crop rotation was more visible during second year of experimentation. Bed sown wheat (BS₁ and BS₂) in mungbean-wheat rotation had the highest wheat grain yield (6.30–6.47 t ha⁻¹) compared to other tillage systems in different crop rotation combinations.     

Effects of different soil conservation tillage approaches on soil nutrients,water use and wheat-maize yield in rainfed dry-land regions of North China

Excessive tillage compromises soil quality by causing severe water shortages that can lead to crop failure. Reports on the effects of conservation tillage on major soil nutrients, water use efficiency and gain yield in wheat (Triticum aestivum L.) and maize (Zea mays L.) in rainfed regions in the North China Plain are relatively scarce. In this work, four tillage approaches were tested from 2004 to 2012 in a randomized study performed in triplicate: one conventional tillage and three conservation tillage experiments with straw mulching (no tillage during wheat and maize seasons, subsoiling during the maize season but no tillage during the wheat season, and ridge planting during both wheat and maize seasons). Compared with conventional tillage, by 2012, eight years of conservation tillage treatments (no tillage, subsoiling and ridge planting) resulted in a significant increase in available phosphorus in topsoil (0–0.20 m), by 3.8%, 37.8% and 36.9%, respectively. Soil available potassium was also increased following conservation tillage, by 13.6%, 37.5% and 25.0%, and soil organic matter by 0.17%, 5.65% and 4.77%, while soil total nitrogen was altered by −2.33%, 4.21% and 1.74%, respectively. Meanwhile, all three conservation tillage approaches increased water use efficiency, by 19.1–28.4% (average 24.6%), 10.1–23.8% (average 15.9%) and 11.2–20.7% (average 15.7%) in wheat, maize and annual, respectively. Additionally, wheat yield was increased by 7.9–12.0% (average 10.3%), maize yield by 13.4–24.6% (average 17.4%) and rotation annual yield by 12.3–16.9% (average 14.1%). Overall, our findings demonstrate that subsoiling and ridge planting with straw mulching performed better than conventional tillage for enhancing major soil nutrients and improving grain yield and water use efficiency in rainfed regions in the North China Plain.     

Short and long‐term distribution with depth of soil organic carbon and nutrients under traditional and conservation tillage in a Mediterranean environment (southwest Spain)

The impacts of tillage and cropping sequences on soil organic matter and nutrients have been frequently reported to affect the uppermost soil layers, but there is little published information concerning effects at greater depth. This article reports results on the distribution of soil organic carbon (SOC), active carbon (AC), N, Olsen‐P and extractable K within 100 cm in short (4 yr) and long (16 yr) term experiments under different tillage systems. Short (TT₄) and long (TT₁₆) traditional tillage are compared with conservation tillage, reduced (RT₁₆) and non‐tillage (NT₄). The results show more accumulation of SOC in the near‐surface under RT₁₆ and NT₄ in both experiments compared with traditional tillage. Moreover, greater C content occurs to 40 cm depth in the long‐term experiment. The results demonstrate the importance of time on C accumulation, not only in near‐surface layers but also at greater depths. Active C is an indicator of the increase in soil quality in the long‐term experiment. This trend is only apparent for the first 10 cm in the short‐term experiment. Patterns in N, Olsen‐P and extractable K are similar to that of SOC. However, only extractable K is significantly greater in soil under conservation tillage (RT₁₆ and NT₄) after short and long periods. Potassium availability is a good indicator of the changes caused by tillage. Our results indicate that studies of soils at depth could be very useful in long‐term experiments to demonstrate the effect of conservation tillage on C and nutrient distribution.     

Combined use of optical and radar satellite data for the detection of tillage and irrigation operations: Case study in Central Morocco

The objective of this study is to present a new application of optical and radar remote sensing with high spatial (∼10 m) and temporal (a few days) resolutions for the detection of tillage and irrigation operations. The analysis was performed for irrigated wheat crops in the semi-arid Tensift/Marrakech plain (Central Morocco) using three FORMOSAT-2 images and two ASAR images acquired within one week at the beginning of the 2005/2006 agricultural season.The approach we developed uses simple mapping algorithms (band thresholding and decision tree) for the characterisation of soil surface states. The first images acquired by FORMOSAT and ASAR were processed to classify fields into three main categories: ploughed (in depth), prepared to be sown (harrowed), and not ploughed-not harrowed. This information was combined with a change detection analysis based on multitemporal images to identify harrowing and irrigation operations which occurred between two satellite observations.The performance of the algorithm was evaluated using data related to land use and agricultural practices collected on 124 fields. The analysis shows that drastic changes of surface states caused by ploughing or irrigation are detected without ambiguity (consistency index of 96%). This study provided evidence that optical and radar data contain complementary information for the detection of agricultural operations at the beginning of agricultural season. This information could be useful in regional decision support systems to refine crop calendars and to improve prediction of crop water needs over large areas.     

Application of the Soil and Water Assessment Tool (SWAT) to predict the impact of alternative management practices on water quality and quantity

Alternative land management practices such as conservation or no-tillage, contour farming, terraces, and buffer strips are increasingly used to reduce nonpoint source and water pollution resulting from agricultural activities. Models are useful tools to investigate effects of such management practice alternatives on the watershed level. However, there is a lack of knowledge about the sensitivity of such models to parameters used to represent these conservation practices. Knowledge about the sensitivity to these parameters would help models better simulate the effects of land management. Hence, this paper presents in the first step a sensitivity analysis for conservation management parameters (specifically tillage depth, mechanical soil mixing efficiency, biological soil mixing efficiency, curve number, Manning's roughness coefficient for overland flow, USLE support practice factor, and filter strip width) in the Soil and Water Assessment Tool (SWAT). With this analysis we aimed to improve model parameterisation and calibration efficiency. In contrast to less sensitive parameters such as tillage depth and mixing efficiency we parameterised sensitive parameters such as curve number values in detail.In the second step the analysis consisted of varying management practices (conventional tillage, conservation tillage, and no-tillage) for different crops (spring barley, winter barley, and sugar beet) and varying operation dates. Results showed that the model is very sensitive to applied crop rotations and in some cases even to small variations of management practices. But the different settings do not have the same sensitivity. Duration of vegetation period and soil cover over time was most sensitive followed by soil cover characteristics of applied crops.