Soil cultivation effects on sediment and phosphorus mobilization in surface runoff from three contrasting soil types in England

To encourage the adoption of best management practices in a priority catchment (Hampshire Avon) in south-west England suffering from diffuse pollution, field demonstration areas were established over a 2-year period on three major soil types (a Chalk soil with an 8° slope, a Greensand soil on a 5° slope and an underdrained Clay soil with a 1° slope). Within each demonstration area, three replicate runoff plots measuring 15 m long and 2 m wide and each containing a tramline were established to monitor the effectiveness of cultivation date (early versus late) and cultivation method (traditional versus reduced) on suspended sediment and P mobilization in surface runoff. Reduced cultivation consisted of heavy discing (5–8 cm depth) instead of ploughing (20–25 cm depth). Soil cultivation effects were variable and site specific depending on weather, inherent soil susceptibility to structural degradation and management. Surface sealing of the Greensand soil, tramline compaction on the Chalk soil and direction of drilling on the Clay soil were key contributing factors. Late cultivation increased surface runoff up to 5-fold and mobilization of sediment and P by up to an order of magnitude compared to early drilling using traditional cultivation techniques. Concentrations of sediment and P in runoff from the Greensand and Chalk soils were consistently lower when the soil was minimally tilled than ploughed, even though a range of soil physical measurements indicated greater soil consolidation where the soil was not inverted. The benefits of reduced cultivation were attributed to better surface cover and a firmer surface for tractor wheelings. Early drilling, timeliness of cultivation to avoid soil compaction, better tramline management and reduced cultivation techniques would help reduce agriculture's impact on water quality in the catchment area.     

Earthworm surface casts affect soil erosion by runoff water and phosphorus transfer in a temperate maize crop

To test the hypothesis that earthworm surface casts contribute to soil erosion and nutrient transfers in a temperate maize crop, two rainfall experiments were set up. One was focused on the erodibility of earthworm casts, the second examined in how casts affect water runoff and nutrient transfers. Casts produced from anecic and endogeic earthworm species were both analyzed. Visual observations in the field showed no cast transport but only cast disintegration and transfers of particles. Erodibility of newly deposited casts was high and differed significantly between age groups. Cast erosion was significantly positively related to initial mass when young but not when old. The paradox is that despite a high cast abundance (25% of the area) and obvious cast erosion, amounts of sediment and nutrient losses (C, N and P) in the runoff were at least twice as high without, than in the presence of, surface casts. Earthworm activities were shown to act as a physical brake for soil erosion by (i) creating a surface roughness with the deposition of surface casts and (ii) reducing water runoff by associated enhanced water percolation. Once the breaking-down point of the physical resistance of casts was reached, all surface casts were quickly disintegrated and finally completely washed away. The amount of particulate phosphorus recovered in water runoff was 34.7 mg P m^{− 2}, while 128.5 mg P m^{− 2} was estimated to have been released from casts. The transfers were found to occur over a short-distance through successive deposition/suspension of soil particles in the water runoff.     

植被类型对黄土坡地产流产沙及氮磷流失的影响

植被类型影响黄土坡地径流、土壤侵蚀和和养分迁移过程。该研究通过野外水流冲刷试验,对比分析了6种植被条件下坡面产流产沙及氮磷流失特征。研究结果表明,大黄花拦蓄径流作用最为明显,而大豆最弱;产沙量随时间的变化会出现峰值特征,其中苜蓿控制土壤侵蚀作用要优于其他植被;径流中硝态氮和水溶性磷的浓度在放水初期随时间迅速衰减,而后趋于稳定,幂函数比指数函数能更好的描述径流中硝态氮和水溶性磷浓度变化过程;泥沙中的硝态氮含量随时间迅速衰减,而有效磷的含量则随着时间逐渐波动减小,二者的最高含量均发生在苜蓿地。养分的富集率与土壤侵蚀量成反比;径流硝态氮流失总量的大小关系为谷子苜蓿柠条玉米大豆大黄花,水溶性磷流失总量的大小关系为谷子玉米柠条大豆大黄花苜蓿,谷子、玉米、柠条、大豆、大黄花各自硝态氮和水溶性磷的流失总量基本相同(P0.05);土壤剖面硝态氮含量随着深度增大呈现出峰值特征,且峰值存在的深度不同,土壤有效磷主要积聚在表层5 cm以上,5 cm以下含量极低。综上可知,野外草本植被在拦截径流、减少土壤侵蚀和控制养分流失方面要优于农田作物,在植被恢复中应广泛采用农地撂荒的方式进行恢复。     

The effects of minimal tillage and contour cultivation on surface runoff, soil loss and crop yield in the long-term Woburn Erosion Reference Experiment on sandy soil at Woburn, England

Abstract. Over a 10-year period, runoff and soil erosion on the plots of the Woburn Erosion Reference Experiment were concentrated in periods with sparse vegetation cover: in winter after the late planting of cereals; in spring after the planting of beets; or when soils were bare after harvest. The mean event runoff of 1.32 mm from plots cultivated up-and-downslope was significantly greater ( P <0.05) than that from plots cultivated across-slope (0.82 mm). However, mean event soil loss was not significantly different between the two cultivation directions. No significant differences were found between minimal and standard cultivations. Mean event runoff from the across-slope/minimal tillage treatment combination (0.58 mm) was significantly less ( P <0.01) than from the up-and-downslope/minimal tillage (1.41 mm), up-and-downslope/standard tillage (1.24 mm), and across-slope/standard tillage (1.07 mm) treatment combinations. Runoff from the across-slope/standard treatment combination was significantly ( P <0.05) less than from the up-and-downslope/minimal tillage treatment. The across-slope/minimal tillage treatment combination had a significantly smaller ( P <0.05) event soil loss (67 kg ha⁻¹) than the up-and-downslope/standard tillage (278 kg ha⁻¹) and up-and-downslope/minimal tillage (245 kg ha⁻¹) combinations. Crop yields were significantly ( P <0.05) higher on across-slope plots in 1988, 1996 and 1997 than on up-and-downslope plots, and were also higher (but not significantly) on the across-slope plots in 7 of the 8 remaining years. Minimal cultivation decreased yield compared with standard cultivation in one year only. We recommend that across-slope cultivation combined with minimal tillage be investigated at field scale to assess its suitability for incorporation into UK farming systems.     

天然沸石对磷、钾在红壤中迁移影响的室内模拟研究

为了寻求提高磷钾肥利用率的途径，该文采用恒温振荡试验初步研究了天然沸石对水溶性磷、钾在红壤中向无效态转化的影响。结果表明：添加沸石降低了水溶性磷、钾含量，增加了解吸钾量；解吸磷和有效磷在磷酸二氢钾低水平时比对照均降低；在磷酸二氢钾高水平时，前者降低而后者增加了9.6%～32.2%。在富磷的红壤中添加沸石提高了有效磷含量，降低了磷损失的可能性；沸石在红壤中作为钾库和钾源，可调节土壤钾水平。     

Plant‐compositional effects on surface runoff and sediment yield in subalpine grassland

Soil erosion such as sheet erosion is frequently encountered in subalpine grassland in the Urseren Valley (Swiss Central Alps). Erosion damages have increased enormously in this region during the last 50 y, most likely due to changes in land‐use practices and due to the impact of climatic changes. In order to estimate the effect of vegetation characteristics on surface runoff and sediment loss, we irrigated 22 pasture plots of 1 m² during 1 h at an intense rain rate of 50 mm h^–1 in two field campaigns using a portable rain simulator. The rain‐simulation plots differed in plant composition (herb versus grass dominance) and land‐use intensity but not in plant cover (>90%) nor in soil conditions. Prior to the second rain‐simulation campaign, aboveground vegetation was clipped in order to simulate intense grazing. The generated surface runoffs, sediment loss, relative water retention in the aboveground vegetation, and changes in soil moisture were quantified. Runoff coefficient varied between 0.1% and 25%, and sediment loss ranged between 0 and 0.053 g m^–2. Thus, high infiltration rates and full vegetation cover resulted in very low erosion rates even under such extreme rain events. Surface runoff did not differ significantly between herb‐ and grass‐dominated plots. However, clipping had a notable effect on surface runoff in the test plots under different land‐use intensity. In plots without or with intensive use, surface runoff decreased after clipping whereas in extensively used plots, surface runoff increased after the clipping. This opposite effect was mainly explained by higher necromass and litter presence at the extensively used plots after the clipping treatment. The results obtained here contribute to a better understanding of the importance of vegetation characteristics on surface‐runoff formation, thus, on soil‐erosion control. Overall, we delineate vegetation parameters to be crucial in soil‐erosion control which are directly modified by the land‐use management.     

赣北第四纪红壤坡耕地水土及氮磷流失特征

坡耕地水土及养分流失严重,该研究于2011年利用赣北第四纪红壤区野外径流小区定位观测试验数据,分析坡耕地水土及氮、磷、有机质流失特征。结果表明：地表产流产沙为裸露地最高、顺坡耕作和顺坡+植物篱次之,横坡耕作最小,横坡耕作比顺坡耕作减少径流62.71%、减少土壤侵蚀82.9%;坡耕地径流携带的可溶性氮、铵氮、硝态氮、可溶性磷的流失量都表现为裸地最大,横坡耕作最小;坡耕地泥沙携带的全氮、全磷、碱解氮、速效磷的流失量表现为裸地最大,横坡耕作最小;坡耕地可溶性氮中以有机氮流失为主,无机氮中以铵氮流失为主,泥沙中磷的流失主要以泥沙结合态流失。该研究可为坡耕地水土流失和面源污染防治提供科学依据。     

AMF和间作对作物产量和坡耕地土壤径流氮磷流失的影响

坡耕地氮、磷流失是导致河湖污染的主要因子。该文在坡耕地开展田间小区试验,定量研究了丛枝菌根真菌(AMF)与玉米大豆间作系统对径流氮、磷流失的协同削减贡献,可为滇池流域农业面源污染控制提供科学理论依据。结果表明,与单作玉米-抑菌处理相比,间作玉米-未抑菌处理显著提高了玉米的生物量;与单作-抑菌处理相比,玉米大豆间作-未抑菌处理均显著增加了植株茎叶、籽粒磷吸收量及茎叶、根系氮吸收量。与单作玉米-抑菌处理相比,间作玉米-未抑菌处理的土壤全磷、全氮的削减量分别为0.25、0.11 g/kg,径流总磷、总氮浓度的削减量分别为0.13、12.94 mg/L;与单作大豆-抑菌处理相比,间作大豆-未抑菌处理的土壤全磷、全氮的削减量分别为0.07、0.11g/kg,径流总磷、总氮浓度的削减量分别为0.27、24.80mg/L。与单作大豆-抑菌处理相比,玉米大豆间作-未抑菌处理的总磷、总氮流失量分别减少了0.51、19.93 kg/hm~2。经相关分析可知,径流颗粒态磷浓度与植株各部分磷吸收量均呈负相关,且与土壤全磷、速效磷含量也呈负相关性;径流各形态氮浓度与植株各部分氮吸收量、菌丝密度和球囊霉素均呈负相关。可见,丛枝菌根真菌协同玉米大豆间作模式能够通过促进植株对氮、磷养分的吸收而减少土壤氮、磷的残留,进而阻控了氮磷随径流迁移的损失。     

冻融条件下土壤可蚀性对坡面氮磷流失的影响

冻融作用与水力侵蚀的复合作用更容易使土壤发生侵蚀,进而加剧土壤养分的流失,为了揭示冻融作用下土壤可蚀性对坡面养分流失的影响,该文采用室内模拟降雨试验,研究了不同土壤含水率(SWC)下坡面的降雨产流产沙及养分流失特征,并分析了土壤可蚀性对坡面全氮(TN)和全磷(TP)流失的影响。结果表明:产流率与产沙率之间呈现正线性相关关系,相关方程斜率的绝对值可作为土壤可蚀性指标。径流中氮磷的流失主要受径流率控制,受土壤可蚀性影响较小(P0.05);而土壤可蚀性显著影响着泥沙中氮磷和总的氮磷流失(P0.01)。土壤可蚀性对黄土坡面氮素流失的影响与冻融作用有关,而土壤可蚀性对坡面磷素流失的影响与冻融作用无关,磷素的流失随着土壤可蚀性增加而增加。因此,在黄土地区,应当采取一系列的生态建设措施来控制水土流失,降低土壤可蚀性,从而减少坡面养分的流失。该研究结果为冻融条件下黄土坡面水-土和氮磷等养分流失机制提供了有效指导。     

Organic amendments as a source of phosphorus: agronomic and environmental impact of different animal manures applied to an acid soil

Phosphorus (P) is a non-renewable resource highlighting the significance of developing and using alternative P sources for a sustainable agriculture. The work aims to compare the effects of different organic amendments (OA) and a mineral P fertiliser as reference on P use efficiency by the crop, and on P losses to runoff waters and eroded sediments. A two-year field trial was conducted in a Dystric Regosol with Lolium sp. Treatments were: cattle manure compost (CM), solid fraction of swine (SS) and duck (DS) slurries and triple superphosphate (TSP), each applied at 50 kg P ha^?1 year^?1. Olsen P (mg P kg^?1) increased from ≈ 19 at the beginning to ≈ 30 (TSP, CM), 45 (SS) and 62 (DS) after the experiment. Most of applied P remained in soil, between 92% (SS) and 96% (TSP), plant uptake ranged from 5% (CM) to 3.5% (TSP) and total P loss in runoff and sediments ranged between 0.2% (CM) and 4% (SS). OA increased P-use efficiency by the ryegrass crop compared with mineral P fertilizer. Composted cattle manure showed the best agronomic and environmental behaviour, simultaneously increasing P-use efficiency and decreasing P losses by runoff and erosion.     

Conservation management decreases surface runoff and soil erosion

Conservation management practices – including agroforestry, cover cropping, no-till, reduced tillage, and residue return – have been applied for decades to control surface runoff and soil erosion, yet results have not been integrated and evaluated across cropping systems. In this study we collected data comparing agricultural production with and without conservation management strategies. We used a bootstrap resampling analysis to explore interactions between practice type, soil texture, surface runoff, and soil erosion. We then used a correlation analysis to relate changes in surface runoff and soil erosion to 13 other soil health and agronomic indicators, including soil organic carbon, soil aggregation, infiltration, porosity, subsurface leaching, and cash crop yield. Across all conservation management practices, surface runoff and erosion had respective mean decreases of 67% and 80% compared with controls. Use of cover cropping provided the largest decreases in erosion and surface runoff, thus emphasizing the importance of maintaining continuous vegetative cover on soils. Coarse- and medium-textured soils had greater decreases in both erosion and runoff than fine-textured soils. Changes in surface runoff and soil erosion under conservation management were highly correlated with soil organic carbon, aggregation, porosity, infiltration, leaching, and yield, showing that conservation practices help drive important interactions between these different facets of soil health. This study offers the first large-scale comparison of how different conservation agriculture practices reduce surface runoff and soil erosion, and at the same time provides new insight into how these interactions influence the improvement or loss of soil health.     

长期施肥对塿土磷素状况的影响

利用塿土12年长期肥料定位试验,研究了不同施肥方式对耕层土壤全磷(TP)、有机磷(OP)与有效磷（Olsen-P）的影响。结果表明,施用化学磷肥提高了耕层土壤TP、Olsen-P含量,但并未提高OP含量;对照与磷钾处理的OP含量有降低趋势。当基于含氮量施有机肥时,土壤TP和Olsen-P含量大幅度提高,也提高了OP含量,但OP/TP比率在降低到一定程度后维持在一个较为稳定的水平;即使施用有机肥的处理,磷素也主要以无机形态累积。土壤Olsen-P与TP或两者的增加量都呈显著的线性相关,塿土TP每提高100 mg/kg,Olsen-P增加量约为20.8 mg/kg,且单位土壤全磷增加带来的Olsen-P增加有随施肥时间降低的趋势。在土壤Olsen-P含量达到一定水平时应考虑减少磷肥用量。基于有机肥中磷素含量来推荐有机肥施用或延长其施用的时间间隔,将有助于减少由于有机肥施用带来的磷素大量快速累积。     

节水灌溉减施磷肥对黑土稻作产量及土壤磷利用与平衡的影响

为探寻节水灌溉减施磷肥对黑土稻作磷利用及土壤磷平衡的影响,于2020年和2021年开展大田试验,以常规淹灌+常规施磷肥(CK,45 kg/hm2)作对照,节水灌溉模式下设置5个磷肥施用梯度：0（CP0,不施磷肥）、18 kg/hm2（CP1,减磷60%）、27 kg/hm2（CP2,减磷40%）、36 kg/hm2（CP3,减磷20%）、45 kg/hm2（CP4,常规施磷）。分析节水灌溉模式下减施不同程度磷肥对稻田产量、地上部植株吸磷量和土壤剖面各土层有效磷含量的影响,并计算土壤磷素表观平衡量和磷肥利用率。结果表明：2020年水稻收获后节水灌溉减施磷肥各处理表层土壤有效磷含量均显著低于CK处理的土壤有效磷含量（P<0.05）;2021年水稻收获后CP3处理表层土壤有效磷含量显著高于CK处理（P<0.05）。CP3处理2020年和2021年的地上部植株磷素积累量显著高于常规施肥CP4处理和CK处理,分别为14.64和15.86 kg/hm2（P<0.05）。地上部植株各器官磷素积累量由大到小为籽粒、茎鞘、叶。与常规施肥相比,2 a年CP3处理均显著提高了磷肥的吸收利用效率、农学利用率,显著降低土壤磷素盈余量（P<0.05）。综合考虑,节水灌溉下减施常规磷肥用量20%为黑土区适宜的磷肥施用量,2 a均提高水稻产量和磷肥利用率,且土壤磷素盈余量低。研究可为黑土区磷肥施用提供理论依据。     

基于水文和土壤侵蚀模型评估植被过滤带净化径流中氮磷的效果

为了方便快速地评估单次径流条件下植被过滤带对污染物氮、磷的净化效果,该文设计了地表径流的模拟放水试验,分析了泥沙与颗粒态污染物的相关性,依据土壤混合层概念简化了土壤污染物的输移,建立了植被过滤带对污染物作用效果的估算模型。结果表明:径流中颗粒态氮、磷含量与泥沙含量有显著相关性(P0.05),据此建立线性相关方程,估算出植被过滤带对颗粒态污染物的净化效果,其86%以上样本的颗粒态氮、磷质量浓度模拟偏差均在±20%之内;溶解态氮、磷的迁移分两部分,即发生于坡面地表径流中和土壤混合层中,分别根据质量平衡原理建立方程对溶解态污染物的迁移进行了模拟,验证得到83%以上样本的溶解态氮质量浓度模拟偏差在±20%之内,67%以上样本的溶解态磷质量浓度模拟偏差也在±20%之内,研究表明,可以基于土壤混合层概念和水文及土壤侵蚀模型对植被过滤带净化效果进行评估。     

Performance of soil and water conservation practices in the erosion evolution process,runoff dynamics and surface roughness

Soil and water conservation practices are used widely to prevent soil erosion and protect soil and water resources, which is significant for ecological restoration and food security. However, rill evolution processes, erosion and deposition characteristics and critical hydrodynamic parameters need more research. In order to investigate the effect of soil and water conservation practices on soil erosion dynamics, simulated rainfall experiments were undertaken in a laboratory on 15° loess slopes with engineering measures (fish-scale pits, FSPs), tillage measures (artificial digging, AD; contour ploughing, CP) and bare slope (CK). The results showed that: (1) during rill erosion, hillslopes with FSPs, CP and AD were more likely to develop wide and shallow rills, while a bare slope (CK) was more likely to develop narrow and deep rills. At the end of the experiment (cumulative rainfall was about 150 mm), headward retreat erosion dominated the AD slope (maximum rill length: 3.27 m), side-wall expansion erosion dominated the CP slope (maximum rill width: 0.522 m) and bed incision erosion dominated the CK (maximum rill depth: 0.09 m); (2) soil and water conservation practices reduced surface erosion and sediment transport and runoff velocity. However, the positive effects disappeared when rainfall amounts exceeded 82.5, 105 and 127.5 mm for FSPs, CP and AD, respectively; (3) for runoff kinetic energy and runoff shear strength of 3 J and 1.5 N/m², respectively, soil and water conservation measures had greater anti-erosion abilities than CK; (4) as rainfall duration increased, surface roughness, runoff rate and sediment concentration increased on the CK and FSP treatments, but decreased on the CP and AD treatments. This study has important implications for managing different soil and water conservation measures based on rainfall conditions and offers a deeper understanding of soil erosion processes.     

Comparison of effects of phosphorus sources on soil acidity,available phosphorus and maize yields at two sites in western Kenya

The effects of farmyard manure (FYM), Tithonia diversifolia (tithonia) and urea when applied alone or in combination with Minjingu phosphate rock (MPR), Busumbu phosphate rock (BPR) or triple superphosphate (TSP) on soil acidity, P availability, maize yields and financial benefits were evaluated at Bukura and Kakamega in western Kenya. A reduction in exchangeable acidity and Al was observed in most tithonia- and FYM-treated soils, but not with inorganic P sources when applied in combination with urea. The effectiveness in increasing available soil P followed the order; TSP > MPR > BPR among inorganic P sources, and FYM > tithonia among organic materials at both sites. At Bukura, a site higher in both available P and Al saturation compared with Kakamega, maize did not respond to inorganic P sources applied in combination with urea. Maize, however, responded when inorganic P sources were applied in combination with FYM or tithonia at this site. At Kakamega, maize responded to TSP but not to MPR or BPR when applied with urea. Application of TSP in combination with tithonia gave the highest maize yields at both sites. Of the tested technologies, only FYM when applied alone at Bukura was economically attractive.     

植物篱埂垄向区田技术对坡耕地水土和氮磷流失控制研究

针对松干流域农田面源污染控制需求,该文开展了植物篱埂垄向区田技术在坡耕地上的水土及氮磷流失控制效应研究。田间设置8个试验处理,包括两个对照即传统顺垄种植(CK1)与横垄种植(CK2)、3个间距的顺垄种植植物篱埂(1 m间距,T1;3 m间距,T2;5 m间距,T3)和3个间距的土埂(1 m间距,T4;3 m间距,T5;5 m间距,T6)。选择三叶草为植物篱材料。结果表明:1)与传统顺垄种植相比,横垄种植泥沙量减少46.9%,径流量减少52.9%;植物篱埂T1、T2与T3泥沙量分别减少44.6%、44.1%和42.1%,径流量分别减少50.6%、49.8%和49.2%;T4、T5和T6也能降低水土流失量,但与T1、T2与T3相比,泥沙流失量分别增加16.3%、12.6%和29.5%,径流量分别增加29.6%、46.8和76.9%;植物篱埂垄向区田技术的泥沙量与径流量控制效果相对接近横垄种植。2)与传统顺垄种植相比,各处理泥沙与径流TN浓度增大,TP浓度无变化;各处理的径流TN与TP浓度增大,其中各处理间的TN浓度有较大差异,TP浓度无明显差异;径流液TN浓度增加并没有引起农田氮流失增加,农田氮流失平均降低19.7%。3)考虑到经济投入问题,推荐植物篱埂间距3～5 m,较大坡度和坡上坡中采用较小间距,较小坡度和坡底采用较大间距;植物篱埂垄向区田技术能够提高玉米产量,平均增产5%～5.6%。     

Predicting environmental soil phosphorus limits for dissolved reactive phosphorus loss

The dependence of runoff dissolved reactive phosphorus (DRP) loss on soil test P or rapid estimations of degree of P saturation (DPS) often varies with soil types. It is not clear whether the soil‐specific nature of runoff DRP versus DPS is due to the different sorption characteristics of individual soils or the inability of these rapid DPS estimates to accurately reflect the actual soil P saturation status. This study aimed to assess environmental measures of soil P that could serve as reliable predictors of runoff DRP concentration by using soils collected from Ontario, Canada, that cover a range of chemical and physical properties. A P sorption study was conducted using the Langmuir equation  to describe amount of P sorbed or desorbed by the soil (Q_s, mg/kg) versus equilibrium P concentration (C, mg/L) in solution, where Q_max is P sorption maximum (mg/kg), k represents P sorption strength (L/mg), and Q₀ (mg/kg) is the P sorbed to soil prior to analysis. Runoff DRP concentration increased linearly with increasing DPS_sorp (i.e. the ratio of (Q₀ + Q_D)/Q_max) following a common slope value amongst soil types, while the P buffering capacity (PBC₀) at C = C₀ yielded a common change point, below which runoff DRP concentration decreased greatly with increasing PBC₀ compared to that above the change point, where C₀ and Q_D represent the equilibrium P concentration and amount of P desorbed, respectively. Both DPS_sorp and PBC₀ showed great promises as indicators of runoff DRP concentration.