Lime placement on subsoil as a strategy to reduce phosphorus leaching from agricultural soils

Leaching of phosphorus (P) from agricultural land is a major contributor to eutrophication of surface waters in many countries, and effective mitigation options to reduce P in leachate are needed. In this study, intact columns (0.77 m deep) of subsoil from three Swedish agricultural soils (one sand and two clay) were used to examine whether placing quicklime (calcium oxide, CaO) on the subsoil could reduce P leaching over a 3‐yr period. Leaching of particulate P (PP) was significantly less from clay soil columns with lime than from clay soil columns without (P < 0.001 and P < 0.05, respectively), with a relative reduction of 49 and 51% in the two soils. Leaching of dissolved reactive P (DRP) was less from sand columns with lime than from sand columns without, although not significantly so due to large variation in P leaching between columns. These results indicate that placement of lime on subsoil has potential to reduce P leaching, especially of PP from clay soils. However, more studies including both topsoil and subsoil and a range of soil types are needed to assess the full potential of this P mitigation option.     

新罗区黄底灰泥田养分现状与施肥对策

结合2009年新罗区承担农业部测土配方施肥项目,采集473个黄底灰泥田土样进行化验分析,并与1980年第2次全国土壤普查资料对比,结果表明：新罗区黄底灰泥田的有机质、碱解氮、有效磷、速效钾含量分别提高2.17%、52.85%、46.03%、151.2%。分析了黄底灰泥田主要养分变化原因,提出新罗区黄底灰泥田今后因地制宜...     

提高氨化处理秸秆粗蛋白含量的适宜方法研究

为提高秸秆粗蛋白含量,以氢氧化钠、过氧化氢、生石灰、熟石灰、尿素为处理剂,进行不同浓度和不同组合方式处理小麦秸和莜麦秸的试验.结果表明:尿素与氢氧化钠的组合对提高秸秆粗蛋白含量极为有效,5%以上的生石灰与尿素组合提高效率最高,为单纯5%尿素氨化法的4倍.建议生产中根据需要确定尿素剂量.     

砂姜黑土薄荷施肥技术研究

研究了砂姜黑土薄荷施肥技术，结果表明，在薄荷分枝期追施N138kg／hm^2时，基肥施N易使薄荷前期旺长，过早封行，通风透气差，会造成收获期薄荷大量落叶，进而影响薄荷油产量。K肥能显著提高薄荷产量，在低K用量时，氯化钾和硫酸钾增产效果相近，但在高钾用量时，则硫酸钾增产效果明显好于氯化钾，表明高用量的氯对薄荷油有不利的影响，从降低成本和提高产量两方面考虑，硫酸钾和氯化钾配合施用可获得较理想的效果。施用P肥对薄荷生长和产量提高效果不大，且P肥过高会影响薄荷的生长。     

Nature of Soil Acidity in Relation to Properties and Lime Requirement of Some Inceptisols

Some Inceptisols representing the Singla catchment area in Karimgaunge district of Assam, India, were studied for lime requirement as influenced by the nature of soil acidity. The electrostatically bonded (EB)-H+ and EB-Al3+ acidities constituted 33 and 67 percent of exchangeable acidity while EB-H+, EB-Al3+,exchangeable and pH-dependent acidities comprised 6, 14, 20 and 80 percent of total potential acidity. The pH-dependent acidity made a major contribution towards the total potential acidity (67%～84%). Grand mean of lime requirement determined by the laboratory incubation method and estimated by the methods of New Woodruff, Woodruff and Peech as expressed in MgCaCO3 ha-1 was in the order: Woodruff (15.6) ＞ New Woodruff (14.9) ＞ Peech (5.1) ＞ incubation (5.0). Correlations analysis among different forms of acidity and lime requirement methods with selected soil properties showed that pH in three media, namely water, 1 mol L-1 KCl and 0.01 mol L-1 CaCl2, had a significant negative correlation with different forms of acidity and lime requirement methods. Exchangeable Fe and Al showed significant positive correlations with EB-Al3+ acidity, exchangeable acidity, pH-dependent acidity and total potential acidity, and also lime requirement methods. Extractable Al showed positive correlations with different forms of acidity except EB-H+ and EB-Al3+ acidities. The lime requirement by different methods depended upon the extractable aluminium.Significant positive correlations existed between lime requirements and different forms of acidity of the soils except EB-H+ acidity and incubation method. The nature of soil acidity was mostly pH-dependent. Statistically, the Woodruff method did slightly better than the New Woodruff, incubation and Peech methods at estimating lime requirement and hence the Woodruff procedure may be recommended for routine soil testing because of its speed and simplicity.     

长白山地区不同植被下土壤酸度状况

The acidity regimes of representative soils on the north slope of the Changbai Mountains were examined through determinations of pH and pCa of the soil paste as well as in-situ determinations,For soils under broad-leaf forest or broad-leaf-Korean pine forest,the pH decreased from the litte to lower layers gradually until it did not change or decreased further slightly .For soils under coniferous of Erans birch forest,ther was a minimum in pH at a depth of 3-6 cm where the content of humus was high,The pCa increased gradually from the soil surface downward to a constant value.The lime potential(pH-0.5pCa) showed a similar trend as the pH in its distribution.For a given soil,the measured pH value of the thick paste,ranging from 4.5 to 5.5,was lower by about 0.5 units than the value determined by the conventional method with a water to soil ratio of 5:1 ,The pH determined in situ was even lower.It was found that there was a firly close relationship between soil acidity and the type of vegetation.The pH showed a trend of decreasing from soils under broda-leaf forest through broad-leaf-conifer mixed rorest and coniferos forest to Ermans birch forest,and the pCa showed an opposite trend in variation.     

甘薯淀粉白度的研究

用石灰水调整磨浆液ｐＨ值至７．５～８．５，（３０００－４０００ｒ／ｍｉｎ）离心分离和沉淀，能有效改善甘薯淀粉白度。     

Soil tillage systems and forms of lime application on soil attribute enhancements in ratoon sugarcane

Combining deep tillage (DT) with lime application at greater depths may improve sugarcane yield. The objective of this study was to evaluate the impact of conventional tillage (CT) and DT systems and liming on sugarcane productivity and soil physical attributes. The experiment was conducted in a clayey-textured Rhodic Hapludox soil cultivated with sugarcane for two growing seasons (first and third ratoons) using a randomized block design with four treatments and four repetitions. The treatments consisted of DT without liming (DT0), DT with liming (DT2), CT without liming (CT0) and CT with liming (CT2). In addition to sugarcane stalk and sugar yields, macroporosity (MA), microporosity (MI), total soil porosity (TP), weighted average diameter (WAD), aggregate stability index (ASI), soil penetration resistance (SPR), pH, potential acidity (H + Al), total soil organic carbon (SOC), particulate organic carbon (POC), mineral-associated organic carbon (MOC), calcium (Ca) and magnesium (Mg) were analysed. DT2 promoted the best soil conservation effect on sugarcane. In general, DT, regardless of lime application, reduced SOC and POC in soil surface layer. Nevertheless, in the long term, localized lime addition resulted in significant reductions in compaction, reaching values below 2 MPa. The soil fertility improvement provided by DT2 promoted increased sucrose concentrations and stalks yield. Considering that there was an improvement in the physical quality and fertility of soil for better plant development, the deep tillage with localized lime addition can be considered an effective alternative for sugarcane cultivation.     

Effects of application of lime nitrogen and dicyandiamide on nitrous oxide emissions from green tea fields

Abstract

The aim of this study was to assess the mitigating effects of lime nitrogen (calcium cyanamide) and dicyandiamide (DCD) application on nitrous oxide (N₂O) emissions from fields of green tea [Camellia sinensis (L.) Kuntze]. The study was conducted in experimental tea fields in which the fertilizer application rate was 544 kg nitrogen (N) ha^?1 yr^?1 for 2 years. The mean cumulative N₂O flux from the soil between the canopies of tea plants for 2 years was 7.1 ± 0.9 kg N ha^?1 yr^?1 in control plots. The cumulative N₂O flux in the plots supplemented with lime nitrogen was 3.5 ± 0.1 kgN ha^?1, approximately 51% lower than that in control plots. This reduction was due to the inhibition of nitrification by DCD, which was produced from the lime nitrogen. In addition, the increase in soil pH by lime in the lime nitrogen may also be another reason for the decreased N₂O emissions from soil in LN plots. Meanwhile, the cumulative N₂O flux in DCD plots was not significantly different from that in control plots. The seasonal variability in N₂O emissions in DCD plots differed from that in control plots and application of DCD sometimes increased N₂O emissions from tea field soil. The nitrification inhibition effect of lime nitrogen and DCD helped to delay nitrification of ammonium-nitrogen (NH₄⁺-N), leading to high NH₄⁺-N concentrations and a high ratio of NH₄⁺-N /nitrate-nitrogen (NO₃^–-N) in the soil. The inhibitors delayed the formation of NO₃^–-N in soil. N uptake by tea plants was almost the same among all three treatments.     

A rapid procedure to calculate lime requirements based on single titration with base

The lime requirement (LR) in 39 surface acid soil samples (0–30 cm) from western Greece was calculated using a single-addition titration of successive 3-mL 0.022 M calcium hydroxide [Ca(OH)₂]. Soil pH measurements and titrations were performed in soil/water (1:2) and in a soil/0.01 M CaCl₂ (1:2) suspension while being stirred. The results were referred to as ‘pH data group I’ and ‘pH data group II’, respectively. In each ‘pH data group’, the samples were separated into ‘pH data subgroups’, according to the total volume (mL) of 0.022 M Ca(OH)₂ added to increase the initial pH (pH_a) to a target value of 6.5 (pH_t). The fitted linear regression equation pH_t = b × volume + pH_a was used for each ‘pH data group’ to determine the slope b. The b-weighted mean for each ‘pH data group’ was calculated. The LR was then calculated as follows: Mg CaCO₃ ha^?1 = 0.495 (pH_t – pH_a)/b, where b is the average weighted mean from the two ‘pH data groups’ and is equal to 0.227. The validity of the above equation was confirmed after incubation with Ca(OH)₂ for 72 h. This procedure is simple and gives a rapid and accurate estimation of LR with respect to the environment.