A comparison of lime requirements by five methods on grassland mineral soils in Ireland

Liming is necessary for good nutrient availability and crop growth. Lime use in Ireland is now the lowest in half a century. A recent study shows that grassland mineral soils in Ireland has a mean pH of 5.4 and mean lime requirement (LR) of 9.3 t/ha ground limestone. There have been a number of studies in the USA to re-evaluate LR, but little activity in the European Union (EU) in recent years. The primary aim of our research was to compare five methods for estimating LR, which included the Shoemaker–McLean–Pratt (SMP) buffer method currently used in Ireland (IRL), the Sikora buffer method used at the University of Kentucky (UKY), Ca(OH)₂ titration used at University of Georgia (UGA), the modified Mehlich buffer method used at Penn State University (PSU) and the UK RothLime model, using 57 representative grassland mineral soils from Ireland with a pH range from 4.8 to 6.6. The secondary aim was to explore an alternative to the SMP buffer that does not involve the use of toxic chemicals. The results show good agreement between the pH measured by the Irish and three US laboratories and reasonably good agreement in LR estimated by five methods. The main conclusions are: (1) a significant proportion of grassland on mineral soils in Ireland would benefit from liming to increase soil pH, (2) on average, LRs as recommended in Ireland are higher than those advised elsewhere , ( 3) the target pH in Ireland is high compared with that in other countries and should be reduced from pH 6.5 to 6.2, (4) the SMP buffer method should be replaced by a suitable alternative and, in principle, any of the four methods studied would be suitable, (5) to find the most suitable alternative for accurate LR advice it would be necessary to compare the different methods to the actual LR from incubation of representative soils with calcium hydroxide.     

Soil pH Management across Spatially Variable Soils

Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers. The objective of the study was to evaluate in-field spatial variability of soil pH, and compare the efficiency of managing soil pH through site-specific method vs. uniform lime application. The study was conducted on three sites with study sites I and II （23°50＇ S; 29°40＇ E）, and study sites IIl （23°59＇ S; 28°52＇ E） adjacent to each other in the semi-arid regions of the Limpopo Province, South Africa. Soil samples were taken in four replicates from geo-referenced locations on a regular grid of 30 m. Soils were analyzed for pH, and SMP buffer pH. Soil maps were produced with Geographic Information System （GIS） software, and soil pH datasets were interpolated using a geostatistical tool of inverse distance weighing （IDW）. Soil pH in the fields varied from 3.93 to 7.00. An excess amount of lime as high as 30 t/ha under uniform lime application were recorded. These recommendations were in excess on field areas that needed little or no lime applications. Again, there was an under applications of lime as much as 35 t/ha for uniform liming applications. This under- and over-recommendations of lime based on average soil pH values suggests that uniform soil acidity correction and soil pH management strategy is not an appropriate strategy to be adopted in these fields with spatially variable soils. The field can be divided into lime application zones of （1） high rates of lime, （2） low rates of lime and （3） areas that requires no lime at all so that lime rates are applied per zone. A key to site-specific soil acidity correction with lime is to reach ideal soil pH for the crop in all parts of the field.     

Liming and Fertilizer Potentials of Some Underutilized Plant Materials in Southwestern Nigeria

Soil acidification and phosphorus deficiency are a major constraint to crop production in tropical soils.Use of conventional liming materials is associated with some limitations viz:inability to solely improve nitrogen and available phosphorus in soils,loss of soil organic carbon and soil aggregate stability.Liming and fertilizer potentials of leaves from three plant materials(Tithonia diversifolia(TL),Imperata cylindrica(SG)and Gliricidia sepium(GL))widely growing in Ogbomoso,southwest Nigeria,were tested under incubation condition.Each of the plant material was applied at the rate of 10 t·hm~(-2) with and without 50%concentration of NPK 15:15:15-urea mix in 500 g acidic soil.Sole lime applied at 1 t·hm~(-2),sole NPK 15:15:15 applied at 60 kg·hm~(-2) mixed with urea at 60 kg N·hm~(-2) and an unamended soil were compared in completely randomized design in three replicates.The treated soils were incubated for 12 weeks.Thereafter,maize seeds were raised in each pot for a period of 3 weeks.Data collected were subjected to analysis of variance.Regression analysis was used to predict contributions of increased soil p H in plant material treated soils to exchangeable Al,H,dry root weight of maize and available phosphorus.Results indicated that sole plant materials were the order SGTLGL significantly(p0.05)reduced exchangeable acidity compared to unamended and sole NPK.Sole NPK had the highest exchangeable acidity(4.7 cmol·kg~(-1))compared to unamended soil(3.3 cmol·kg~(-1))and sole lime(2.7 cmol·kg~(-1)).Application of sole Tithonia diversifolia increased available phosphorus by 214%and 97%compared to unamended and sole NPK treated soils respectively.Sole plant materials increased maize root weight by 33%compared to sole NPK.Increasing soil p H at harvesting in plant material treated soils significantly reduced exchangeable H and A_1.Soil p H was responsible for up to 33%and 53%reductions in exchangeable Al and H,respectively.This culminated into up to 22%increases in dry root weight of maize seedling.Present results showed ability of the plant materials tested to ameliorate soil acidity and improved soil available phosphorus.The plant materials should be explored for using as green manure and composting feedstock.It will go a long way to reduce high dosage use of conventional liming and fertilizer materials on acidic nutrient degraded soils.     

Phosphorus Availability in Lolium perenne L. in Acidic and Limed Soils

Soil liming may increase phosphorus (P) availability, but this increase may also be achieved with generous P applications. However, it is not well known which practice has longer-term effects. Thus, in a pot experiment, an acidic soil (pH 4.57), limed to pH 6.5, was added with P and sown with Lolium perenne L. We conducted three cuttings (on Days 40, 80, and 120) in order to evaluate P dynamics in each of the treatments. As expected, biomass increased significantly with liming. We also found that plant P concentration increased in the liming treatment, but not in the P-added treatment, although the difference was reduced on Day 120. This shows that in severely acidic soils, liming should be preferred over P addition, although the beneficial effects may not last for a very long time, since in this experiment, they only lasted for 4 months. Similar conclusions were drawn from soil P extraction results.     

Variability in the solubility of agricultural limestone from different sources and its pertinence for aquaculture

Samples of agricultural limestone were obtained from quarries in the USA as follows: Talking Rock, GA; Whitestone, GA; Austinville, VA; Bonham, TX; and Thomasville, PA, referred as GA‐1, GA‐2, VA, TX and PA respectively. The limestone products were tested initially for non‐equilibrium pH, concentrations of calcium and magnesium, neutralizing value (NV) and fineness rate. Laboratory solubility test of the products was conducted in which pH, specific conductance (SC), total alkalinity (TA), total and calcium hardness were measured weekly for 9 weeks. It was found that the agricultural limestone samples had comparable chemical compositions, that is NV (97–108%), Ca (19.8–32.1%), Mg (3.2–12.2%), pH of slurry (8.1–9.7), but somewhat different solubilities in water. Total alkalinity concentrations at equilibrium ranged from 30 to 60 mg L^?1. It was possible to quickly estimate the relative solubility of different agricultural limestone samples by comparing their specific conductance under standardized conditions (2.0 g samples w/0.15–0.25 mm fineness; 3.5 L distilled water; 24 h). This procedure might be helpful in achieving better results when liming aquaculture ponds, that is choosing the agricultural limestones with the highest solubilities in water.     

Decomposition in a peaty soil improved for pastoral agriculture

Abstract. The rates of CO₂ production and decomposition of ¹³C-enriched Lolium perenne leaves and roots in soil from the surface five cm of two upland stagnohumic gley soils were measured in laboratory experiments. One of the soils had been limed (pH 6.8) 13 years earlier. The other was unlimed (pH 3.7). Liming increased the rate of CO₂ release from soil to which no L. perenne had been added. About 30% of the ¹³C in L. perenne leaves remained in both limed and unlimed soil after 224 days. By contrast, less ¹³C-remained in the limed soil amended with L. perenne roots (44%) than in the limed soils (55%). Although the daily rate of CO₂ from the plant material-amended soils was initially greater in the improved than in the unimproved soil, it subsequently declined more rapidly.     

Reduction of resting spore density of Plasmodiophora brassicae and clubroot disease severity by liming

Abstract

Relationships between the disease severity of clubroot caused by Plasmodiophora brassicae, the soil pH value and the concentration of exchangeable calcium associated with liming were investigated under controlled density of resting spores. Disease indices were lower in the plots treated with lime than in the control plots without lime application. The disease index was significantly lower when lime materials were mixed two weeks before sowing compared with four weeks before sowing. The reduction rate of the disease index was larger for a concentration of 2.0 g kg^?1 than 1.0 g kg^?1 of lime in soil. The density of the resting spores in soil at the time of sowing was significantly reduced by liming. The reduction rate was 17–31 % for calcium cyanamide, 12–29% for dolomite, and 20–39% for calcium carbonate compared with the control plot. It was suggested that the disease severity was influenced by both the soil pH and the content of exchangeable calcium in soil based on the analysis of covariance.     

Effects of stopping liming on abandoned agricultural land

It is suggested that stopping liming on agricultural land could lead to a potential chemical time bomb (CTB). the sequence of interrelated events leading to the CTB include the end of liming, perhaps caused by a change in land use, a progressive decrease in soil pH and increased solubility of potentially toxic contaminants that accumulate in soils as a result of agricultural practices. Data are presented on rates of long-term soil acidification and modelled changes in the solubility of some trace metals in soil as a result of acidification. Soil acidification rates depend primarily on acid input rates and the soil's acid neutralizing capacity, possibly limited by neutralization kinetics. Experimental data illustrating this point show that the pH decreased rapidly in a field soil receiving ammonium rather than nitrate fertilizer treatment. on a limed agricultural field that was later abandoned and converted to deciduous woodland, The pH of the 0-23 cm soil layers decreased over 100 years from pH 7 to 4.2. Deeper layers acidified at a slower rate. Thermodynamic model calculations simulating the solubilities of metals in a sandy topsoil showed zinc, cadmium and aluminium solubilities increasing exponentially with decreasing pH, resulting in several-fold solubility increases between pH 5 and 4. These results suggest how metal solubility increases after liming stops. the model pH-solubility relationships depended on the type of metal, The solid phase controlling the solubility, and the amount of metal in the soil if adsorption controlled the solubility. Decreasing pH and the resultant increase in metal solubility expected on abandoned farmland might be managed through techniques such as liming or planting forests of selected tree species.