Long-term application of animal slurries to grassland alters soil cation balance

Abstract. Soil samples from a 32-year grassland field experiment were taken from 0–5, 5–10, and 10–15 cm soil depths in February 2002. Plots received annual treatments of unamended control, mineral fertilizer, three rates of pig slurry and three rates of cow slurry, each with six replicates. Samples were analysed for cation exchange capacity (CEC), exchangeable cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), pH and Olsen P. Exchangeable sodium percentage (ESP) was calculated as a sodicity indicator. Mean ESP was generally greater for slurry treatments than the control, with a trend of increasing ESP with application rate. This was particularly marked for cow slurry. At 0–5 cm depth ESP increased from 1.18 in the control to 1.75 at the highest rate of pig slurry and 5.60 at the highest rate of cow slurry. Similar trends were shown for CEC, exchangeable Na⁺, K⁺ and Mg²⁺, Ca²⁺ and Olsen P. The build-up of soil P due to slurry applications, together with this combination of physical and chemical factors, may increase the risk of P loss to surface waters, particularly from soils receiving high rates of cow slurry.     

Mass balanced based LCA of a common carp-lettuce aquaponics system

An aquaponics system (AS) is an integrated system that combines a recirculating aquaculture system and a hydroponics system (HS). It is designed to recover nutrients released from fish and transfer them to plants to provide a system more environmentally-friendly than the two systems working separately. As a result, several AS are under development, but little information is available about their overall performances. The aim of this study was to assess nutrient-use efficiency and environmental impacts of an AS, specifically a common carp-lettuce AS located in a greenhouse. Nutrient budgets of nitrogen (N) and phosphorus (P) were calculated and Life Cycle Assessment (LCA) was performed for the AS and for a lettuce Individual Hydroponics System (IHS), similar to the HS of the AS, operating in the greenhouse at the same time. The experiment was performed over a 52-day cycle, which corresponds to the growing time required to harvest marketable lettuce. The nutrient budgets were well balanced, with 24.6% of the N unaccounted-for, most likely due to N2 gas emission, and 6.6% of the P unaccounted-for, most likely due to having underestimated the quantity of sediment. At the beginning of the experiment, N represented 55.9%, 37.1% and 0.1% of the total N input in the formulated feed, stocked fish and lettuce seedlings, respectively. At the end of the experiment, N represented 47.6% and 0.4% of the total N input in the harvested fish and lettuce, respectively. At the beginning of the experiment, P represented 56.94%, 40.20% and 0.03% of the total P input in the formulated feed, stocked fish and lettuce seedlings, respectively. At the end of the experiment, P represented 51.52% and 0.42% of the total P input in the harvested fish and lettuce, respectively. LCA clearly indicated two environmental impact hotspots: the origin of nutrients and energy use. One kg of lettuce growth in the AS clearly had lower environmental impacts than that in the IHS for climate change, acidification, eutrophication, land competition and cumulative energy demand; however, a decrease in water dependence was not observed. The indicator for net primary production use highlighted the dependence of the AS on natural resources, especially fish meal and fish oil. Compared to the use of chemical nutrients in the IHS, the use of nutrients from formulated feed in the AS decreased climate change impact but increased the use of natural resources.     

5个竹种林下土壤营养元素含量比较

[目的]比较不同竹种林下土壤的营养元素含量。[方法]在福建农林大学百竹园内选取大明竹、牡竹、角竹、花巨竹和大木竹5个竹种,分别于春、夏、秋、冬4个季节对其林下土壤进行"S"型多点采样,对其氮、磷、钾含量进行测定。[结果]大明竹、牡竹、角竹、花巨竹和大木竹5个竹种林下土壤的营养元素含量皆较高,但各竹种之间的营养元素含量有显著差异,且各竹种在不同季节的营养元素含量也有明显差异。其中大明竹林下土壤的营养元素含量最高,且最为稳定,牡竹相对较差。[结论]在福建地区,大明竹对营养元素的产生及维系稳定具有良好的能力,可成为该地区城市观赏用竹及发展林下经济的优良竹种。     

Predicting the degree of phosphorus saturation using the ammonium acetate–EDTA soil test

As a result of the important role played by phosphorus (P) in surface water eutrophication, the susceptibility of soils to release P requires evaluation. The degree of phosphorus saturation, assessed by oxalate extraction (DPS_ox), has been used as an indicator. However, most laboratories do not include DPS_ox in routine soil tests because of cost and time. This study evaluates the suitability of the ammonium acetate extraction in the presence of EDTA (AAEDTA), the standard soil test P (STP) in Wallonia (Southern Belgium), to predict DPS_ox; we also compared it with the Mehlich 3 extraction. Ninety‐three topsoil samples were collected in agricultural soils throughout Wallonia. Good correlations were found between the AAEDTA and the Mehlich 3 methods for P, Fe and Al (r = 0.85, 0.77 and 0.86, respectively). An exponential relationship was found between P_AAEDTA and DPS_ox. Results of principal component analysis and regression demonstrated that STP can be used to predict DPS_ox (r = 0.93) after logarithmic transformation. Soil test Al was also a good indicator of the P sorption capacity (PSC_ox) of soils (r = 0.86). Including the clay fraction in regression equations only slightly improved the prediction of PSC_ox (r = 0.90), while other readily available data (such as pH or organic carbon) did not significantly improve either DPS_ox or PSC_ox predictions.     

磷素水平对不同大豆品种钾素吸收效率的影响

通过原子吸收分光光度计法研究了施磷量对不同大豆品种各器官及全株吸收钾素营养的影响,结果表明:施磷量对不同大豆品种植株及各器官钾素含量有较大影响.不同品种不同处理全株及各器官钾素含量从分枝期逐渐增加,开花期达到高峰,随后下降至成熟期;同一品种不同处理间钾素含量三个品种都是P10处理全株及各器官钾素含量最高,整个生育期高磷或不施磷都会影响钾素含量,只有适宜的施磷才能促进钾素含量达到最高峰.同一处理不同品种全株及各器官钾素含量在品种间没有明显的变化规律.     

两种形态氮源条件下磷对大豆结瘤固氮的影响

用营养液培养大豆7周,研究两种氮源条件下,磷对大豆结瘤固氮的影响.在本试验的各取样时期,随营养液中磷水平的增加,生物固氮植株的根瘤数增加较多,尤其是处理后第6周,磷对根瘤形成的影响最大.磷对硝态氮处理根瘤数的影响不大,但本试验条件下,在16μmol/L磷水平,根瘤数较多.硝态氮处理根瘤数远没有生物固氮处理多,表现出氮素对大豆结瘤的抑制作用,导致根瘤固定的氮量减少.因此,硝态氮植株体内含氮量随磷水平的增加而降低,而生物固氮植株增加.生物固氮处理根中N/P与根瘤数之间存在显著的负相关关系,r=-0.5816*,硝态氮处理根中N/P与根瘤数之间不相关.     

Phosphorus saturation in soils and groundwaters

On average, crops require about 30 kg ha⁻¹ y⁻¹ of P in humid regions. in some regions fertilizer and manure are applied in amounts that exceed this. the surplus of P in agricultural areas is about 20-45 kg ha⁻¹ y⁻¹. This implies an accumulation of P. the surplus of P estimated from the balance of agricultural soils of industrialized countries in Europe in the last four decades is between 800 and more than 1500 kg ha⁻¹ although this distribution is not even. Phosphorus accumulation is more than one order of magnitude higher than average in areas with intensive livestock farming. Consequently, The application of high levels of manure exceed the capacity of the soil to store P. This implies that P saturation May, pose a problem. Indeed, about half of the Dutch sandy soils (approximately 300 000 ha) are currently considered to be saturated with P, meaning that there is a hazard of P leaching to groundwaters in the future. Assuming current phosphate application rates, phosphate leaching is a distinct possibility over a period of decades to a century. Vulnerable areas are soils with high inputs, low sorption capacities for P, high water-tables and a low retention time for water. the possible consequence is a time-delayed increase of eutrophication of surface waters (lakes, rivers and the sea) caused by a diffuse load of P in the few next decades. Modelling the influence of different agricultural strategies shows that accumulation of P would not increase further only if the use of P increases by an amount that compensates for the increased inputs. It is proposed to change the current support system of agriculture by installing a system of financial incentives and taxes which seek to promote nutrient balances for each farm.     

杨树根际土壤磷吸附特性的研究

对滨海脱盐土壤上11年生1-69杨根际、非根际土壤磷吸附特性进行了研究。结果表明,I-69杨根系活动能抑制根际土壤对磷的吸附,抑制能力与培养溶液起始磷浓度相关,当培养溶液起始磷浓度为30 mg／L时,抑制能力最大,根际、非根际土壤磷吸附量之差为-15．57 mg／kg;I-69杨根际、非根际土壤磷恒温吸附数据都能很好地用一元 Langmuir方程、Freundich方程和Temkin方程拟合,其中一元Langmuir方程拟合最好;根际土壤磷吸附容量参数Xm,k, k1,k2的值明显低于非根际土壤,相关分析表明,它们与土壤有效磷含量呈显著负相关。     

淡水养殖对长江氮磷输出的贡献及其河口环境效应

本研究利用集成式环境评估模式—营养盐模型(IMAGE-GNM),计算了2003—2018年长江流经主要省份淡水养殖引起的总氮(TN)和总磷(TP)年排放量。结果显示,长江流域淡水养殖产生的TN和TP释放量具有一致的空间分布,由湖北、湖南和江西省组成的中游占淡水养殖TN和TP总排放量的60%以上;2003—2018年长江流经的主要省份淡水养殖的TN和TP负荷均呈增长趋势,且TP的增长幅度略高于TN;长江流域淡水养殖TN和TP的年排放量分别占2010年长江N、P输送量的7.93%和13.65%,是长江水体N、P营养盐重要的来源;淡水养殖污染的N/P介于6.35～12.53之间(质量比),也对长江水体N/P失衡起到了一定的缓解作用。本研究估算与观测结果一致性较高,相关估算在一定程度上反映了长江流域养殖污染的现状;随着淡水养殖过程中N、P释放通量的增加,河流—河口富营养化的程度可能会加剧,值得进一步的关注。