Long-term effect of tillage, crop rotation and N fertilization to wheat on gaseous emissions under rainfed Mediterranean conditions

A field study was conducted to assess the effect of N fertilizer application to wheat (Triticum aestivum L.), tillage system and crop rotation on total denitrification N losses, N₂O and CO₂ emissions under Mediterranean conditions in a long-term trial started 18 years ago on a Vertisol soil. The tillage system consisted of conventional tillage vs. no-tillage and the crop rotation system consisted of two different 2-years rotations: wheat–sunflower (Helianthus annuus L.) (WS) and wheat–faba bean (Vicia faba L.) (WF). Fertilizer rates were 0 and 100 kg N ha⁻¹ applied to wheat splitted in two amendments of 50 kg N ha⁻¹ each. Two different fertilization systems were studied. In the old fertilized plots system fertilizer had been applied for 18 years since the beginning of the trial, and in the new fertilized plots system fertilizer was applied for the first time when this experiment was started. Measurements were carried out after fertilizer applications.

In the long term, continued fertilizer application produced a higher soil total N content. Nevertheless, no increase in denitrification potential, N₂O + N₂ production by denitrification, N₂O or CO₂ emissions was observed either by the recent application of N or by the continued application during 18 years. The soil presented a higher potential to denitrify up to N₂ than up to N₂O. So, denitrification was probably occurring mainly in the form of N₂, while N₂O emissions were occurring in a great manner by nitrification, both denitrification and nitrification occurring simultaneously at soil field capacity (60–70%) expressed as water filled pore space (WFPS). Conventional tillage induced an increase in soil total N content and in the potential to denitrify up to N₂ with respect to no-tillage. This higher potential was translated into higher N₂O + N₂ production by denitrification presumably stimulated in the short time by the higher available carbon provided by decomposing roots and by the subsequent creation of soil anaerobic microsites. Contrarily, no effect of tillage was observed on N₂O emissions because of being produced in an important manner by nitrification, which does not depend on carbon availability. The wheat–faba bean rotation induced higher soil nitrate contents than the wheat–sunflower, although the effect in the long time was not observed regarding soil total N content. The same as for the fertilizer effect, this increase in nitrate content was not followed by a higher denitrification potential or higher N₂O + N₂ production by denitrification because of the lack of organic matter, while an increase was observed in N₂O emissions.     

Medium-term effects of a single application of mustard residues on soil microbiota and C content of vertisols

 A study of the effects of different qualities (fresh and composted) and rates (equivalent to 120, 240, and 360 kg N ha^–1) of mustard meal application on wheat yields on humid tropical vertisol was started in 1990 at Ginchi Research Station in Ethiopia. After continuous wheat cropping for 7 years and without any further fertilisation, soil microbial parameters (basal respiration, microbial biomass-C and N, organic-C, and ecophysiological quotients) were studied during one growth period. After 7 years of application, mustard meal still exerted a significant positive effect on microbial biomass, basal respiration, organic-C, C_mic : N_mic ratio, and metabolic quotient (qCO₂). Organic-C, qCO₂ and C_mic : N_mic ratios were higher for the compost-amended plots than plots amended with fresh mustard meal. Basal respiration, C_mic, and C_mic : N_mic ratio showed a clear seasonality, but only in manured plots. The data indicate shifts in microbial community structure (from bacteria to fungi and from r to K strategists) and suggest positive medium-term effects of mustard meal on humid tropical vertisol biological qualities. Received: 25 May 1999     

Impact of nodule damage by Rivellia angulata on N2-fixation,growth, and yield of pigeonpea (Cajanus cajan L. Millsp.) grown in a Vertisol

Summary Damage caused by Rivellia angulata larvae to pigeonpea root nodules at the ICRISAT center in India was greater in the crop grown on Vertisols (up to 86%) compared to that on Alfisols (20%). Attempts to quantify the field effects of nodule damage on growth and yield of pigeonpea in a Vertisol, involving many heavy applications of soil insecticides (aldrin and hexachlorocyclohexane) failed because the insecticides did not control the pest and adversely affected the growth of the pigeonpea and the subsequent crop of sorghum (Sorgorum bicolor L. Moench). The impact of nodule damage on pigeonpea growth, yield and nutrient uptake was successfully studied in greenhouse-grown plants at three N levels. In this pot study, artificial inoculation with Rivellia sp. led to substantial nodule damage (70%). The results of this damage were a significant overall reduction in nodule dry weight (46%), acetylene reduction activity (31%), total leaf area (36%), chlorophyll content of leaves (39%) and shoot dry weight (23%) 68 days after sowing. At maturity, Rivellia sp. infestation caused significant reductions in top dry weight (22%), root and nodule dry weight (27%), seed dry weight (14%), and total N (29%) and P uptake (19%). The problems and prospects of manipulating nodule damage so as to reduce N losses in pigeonpea are discussed.Submitted as JA No. 756 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

秸秆还田对砂姜黑土理化性质与锰、锌、铜有效性的影响

采用田间试验与实验室培育试验研究作物秸秆还田对砂姜黑土理化性质及Cu、Zn、Mn有效性的影响,结果表明,秸秆还田可降低土壤容重,增大土壤总孔隙度,特别是毛管孔隙度显著增加。土壤中胡敏酸和富里酸含量显著增加,胡敏酸含量的增加对提高土壤有机质活性和改善土壤肥力具有良好效应。与单施化肥比较,秸秆配施化肥土壤中交换态锰、锌、铜含量分别增加11%、21%和41%,有机结合态锰、铜分别增加19%和103%。培育试验表明,加入粉碎的作物秸秆培育90d后,土壤中有效锰、有效铜含量分别增加21%和27%。     

Effect of added nitrogen on plant litter decomposition depends on initial soil carbon and nitrogen stoichiometry

Increasing organic carbon inputs to agricultural soils through the use of pastures or crop residues has been suggested as a means of restoring soil organic carbon lost via anthropogenic activities, such as land use change. However, the decomposition and retention of different plant residues in soil, and how these processes are affected by soil properties and nitrogen fertiliser application, is not fully understood. We evaluated the rate and extent of decomposition of ¹³C-pulse labelled plant material in response to nitrogen addition in four pasture soils of varying physico-chemical characteristics. Microbial respiration of buffel grass (Cenchrus ciliaris L.), wheat (Triticum aestivum L.) and lucerne (Medicago sativa L.) residues was monitored over 365-days. A double exponential model fitted to the data suggested that microbial respiration occurred as an early rapid and a late slow stage. A weighted three-compartment mixing model estimated the decomposition of both soluble and insoluble plant ¹³C (mg C kg⁻¹ soil). Total plant material decomposition followed the alkyl C: O-alkyl C ratio of plant material, as determined by solid-state ¹³C nuclear magnetic resonance spectroscopy. Urea-N addition increased the decomposition of insoluble plant ¹³C in some soils (≤0.1% total nitrogen) but not others (0.3% total nitrogen). Principal components regression analysis indicated that 26% of the variability of plant material decomposition was explained by soil physico-chemical characteristics (P = 0.001), which was primarily described by the C:N ratio. We conclude that plant species with increasing alkyl C: O-alkyl C ratio are better retained as soil organic matter, and that the C:N stoichiometry of soils determines whether N addition leads to increases in soil organic carbon stocks.     

Short-term phosphorus sorption and desorption in contrasting cropped Vertisols

Vertisols are important cropping soils in tropical and subtropical areas, but in many regions, decades of cropping has substantially reduced concentrations of plant-available phosphorus (P), especially in the subsoil layers. Phosphorus behaviour in P-depleted Vertisols has received comparatively little attention, and the availability of P following the addition of inorganic P fertilisers at different concentrations is poorly understood. In this study, we evaluated short-term P sorption and desorption behaviour in cropped Vertisols in relation to specific soil physical and chemical properties. We collected the surface and subsurface of 15 Australian soils with a broad range of physical and chemical properties, comprising nine Vertisols, three Ferralsols, two Lixisols and one Calcisol. For each soil, we generated sorption and desorption curves (fitted with a Freundlich equation), determined soil physical and chemical properties likely to influence P sorption and evaluated the relationships between the measured soil properties and the Freundlich equation sorption coefficients. The P sorption curves differed drastically between soils, with the sorption equation coefficients (a_S × b) significantly correlated with the P buffering index (PBI) and clay content. Clay content itself was correlated with citrate-extractable Fe and Al oxides and BET surface area. Vertisols formed on basaltic parent materials had greater Fe and Al oxide concentrations, resulting in an overall greater P sorption capacity. Sorption and desorption hysteresis were mostly small. The reacting materials in these soils probably had limited ability to continue to react with P. The Vertisols differed in their capacity to replenish P in the soil solution by desorbing different proportions of previously sorbed P, although the proportion of desorbable P generally increased with greater concentrations of sorbed P. These results suggest that for fertiliser management in these soils, smaller volumes of P enrichment combined with higher P concentrations may result in a greater P recovery by the crop.     

氯化钾肥对淮北地区砂姜黑土油菜产量和品质的影响

淮北砂姜黑土上连续三年的试验结果表明,施用氯化钾肥可提高油菜籽粒产量和含油率,但对油菜籽粒蛋白质含量影响不明显。施用氯化钾肥提高了油菜中期茎叶氯、钾离子浓度及成熟期茎叶和籽粒的钾离子浓度,同时增加了油菜对N、P、K养分的吸收总量。对于中等钾含量水平的土壤,施钾(K2O)80kghm-2难以维持土壤钾素养分平衡,当其用量达到160kghm-2以上时,基本能满足作物高产对钾素的需求,并且土壤速效钾含量水平缓慢提高。     

Soil tillage and crop productivity on a Vertisol in Ethiopian highlands

Soil quality deterioration and consequent reduced productivity characterize the Vertisols in the highlands of Ethiopia. The problem is exacerbated by lack of appropriate land preparation alternatives for the major crops in the area. A field experiment was carried out for 6 years (1998–2003) at Caffee Doonsa in the central highlands of Ethiopia to evaluate alternative land preparation methods on the performance of wheat (Triticum durum Desf.), lentil (Lens culinaries Medik L) and tef (Eragrostis tef L) grown in rotation. Four methods of land preparation (broad bed and furrow, green manure, ridge and furrow and reduced tillage) were arranged in a randomized complete block design with three replications on permanent plots of 22 m by 6 m. Broad bed and furrow significantly increased the grain yield of lentils by 59% (from 1029 to 1632 kg ha⁻¹) as compared to the control. On the other hand, reduced tillage resulted in the highest grain yield of wheat (1862 kg ha⁻¹) and tef (1378 kg ha⁻¹) as compared to 1698 kg ha⁻¹ of wheat and 1274 kg ha⁻¹ of tef for the control although the increase was not statistically significant. A gross margin analysis showed that BBF is the most profitable option for lentil with 65% increase in total gross margin. On the other hand, RT resulted in 11 and 8% increase in gross margin of wheat and tef, respectively as compared to the control. Based on the agronomic and economic performances best combinations of crop and land preparation method were: lentil sown on broad bed and furrow, and wheat and tef sown after reduced tillage.     

Yield and Zinc,Copper, Manganese and Iron Concentration in Maize (Zea mays L.) Grown on Vertisol as Influenced by Zinc Application from Various Zinc Fertilizers

Zinc (Zn) deficiency in soils and field crops is widespread across the world, including India, resulting in severe reduction in yield. Hence, soil application of Zn fertilizers is recommended for ameliorating Zn deficiency in soil and for obtaining higher crop yield and better crop quality. Zinc sulfate is commonly used Zn fertilizer in India because of its solubility and less cost. However, good quality and adequate quantity of zinc sulfate is not available in the market round the year for farmers' use. Field experiments were therefore conducted during rainy season of 2010 and 2011 at research farm of Indian Institute of Soil Science, Bhopal, India to assess the influence of Zn application through zinc sulfate monohydrate (33% Zn), zinc polyphosphate (21% Zn) and Zn ethylenediaminetetraacetate (EDTA) (12% Zn) on yield and micronutrient concentration and uptake by maize (Zea mays L.). In both the years, grain and vegetative tissue (stover) yield of maize increased significantly with successive application of Zn up to 1 kg ha^?1 added through zinc sulfate monohydrate and zinc polyphosphate. Addition of 2.5 kg Zn ha^?1 did not increase yield further but resulted in highest stover Zn concentration. Zinc, copper (Cu), manganese (Mn), and iron (Fe) concentration in maize grain varied from 22.2 to 27.6, 1.6 to 2.5, 3.5 to 4.7 and 19.9 to 24.5 mg kg^?1 respectively in both the years. Maize stover had 25.9 to 36.2, 7.9 to 9.8, 36.7 to 44.9 and 174 to 212 mg kg^?1 Zn, Cu, Mn, and Fe, respectively. Zinc application did not influence Cu, Mn and Fe concentration in both grain and stover of maize. Transfer coefficients (TCs) of micronutrients varied from 0.72 to 0.95, 0.18 to 0.30, 0.08 to 0.13 and 0.10 to 0.15 for Zn, Cu, Mn, and Fe respectively. Total Zn uptake significantly increased with Zn application from 0.5 to 2.5 kg ha^?1 supplied through zinc sulfate monohydrate and zinc polyphosphate. Recovery efficiency of Zn declined with increased Zn rates.     

基于集成学习的砂姜黑土含水量高光谱反演研究

为提高砂姜黑土土壤水分的估测精度,本研究以河南省西平县砂姜黑土为研究对象,通过配制不同含水率土壤样本并在室内进行高光谱测量,对土壤样本高光谱数据平滑(SR)、倒对数[LOG(1/R)]、一阶微分(FD)、多元散射校正(MSC)、去包络线(CR)光谱变换后,结合连续投影算法(SPA)识别最佳特征波段,采用偏最小二乘回归(PLSR)、支持向量机回归(SVR)的机器学习方法和堆叠(Stacking)集成学习方法分别构建土壤含水率反演模型。结果表明：经MSC变换后光谱中土壤含水率相关信息增强最多;SPA算法能对砂姜黑土含水率光谱数据进行降维和特征信息提取;经反射光谱MSC变换后由PLSR和SVR集成的Stacking集成模型决定系数最高(R²=0.963)、均方根误差最小(RMSE=1.7)。研究表明,Stacking集成学习模型有效提升了模型的精度和泛化能力,是砂姜黑土含水率最佳反演模型。