Lime Rates Research Articles

Biomass sorghum hybrids differ in growth and nitrogen use under low bases saturation in sandy soil

Sorghum plants are well cultivated in central region of Brazil, which is originalmente low fertility and rich in aluminum content. These features demand studies to know better hybrids for such environment, mainly regarding the use of nutrients like nitrogen (N). This nutrient is the most limiting to plant growth, development, production and for this reason it is of great concern to understand the effects of low bases saturation on N use in biomass dedicated sorghum plants, that is hybrids used for bioenergy purpouses. With the aim to assess the effect of increasing liming rates on nitrogen use in biomass sorghum hybrids we set a greenhouse quantitative research as a completely randomized factorial experiment by using two sorghum hybrids (PA 5L60 and PA 5D61) under five different bases saturation (V%) – 15, 35, 40, 50 and 60. This experimental design allowed us to study five different concentrations of aluminum in this soil. The growth of both sorghum hybrid was impaired only under at V% 15. Nitrogen concentration, content and the N use efficiency indicators were affected at V% 15 for both sorghum hybrids; however, the hybrid PA 5D61 showed to be less sensitive than PA 5L60 under the studied conditions. The PCA analysis showed that the hybrid PA 5D61 showed to be more tolerant to aluminum and uses N more efficiently than the hybrid PA 5L60 and, therefore, we can argue that this hybrid should be used in marginal, low fertility lands as a feedstock producer for bioenergy.

The extent, significance and amelioration of subsurface acidity in southern New South Wales, Australia

Soil pH is seldom uniform with depth, rather it is stratified in layers. The soil surface (0–0.02 m) commonly exhibits relatively high pH and overlies a layer of acidic soil of 0.05–0.15 m deep, termed an acidic subsurface layer. Commercial and research sampling methods that rely on depth increments of 0.1 m either fail to detect or under report the presence or magnitude of pH stratification. The occurrence of pH stratification and the presence of acidic subsurface layers may cause the extent of acidity in NSW agricultural land to be underestimated. Though the cause of pH stratification in agricultural systems is well understood, the effect on agricultural production is poorly quantified due in part to inadequate sampling depth intervals resulting in poor identification of acidic subsurface layers. Although liming remains the best method to manage acidic soil, current practices of low pH targets (pHCa 5), inadequate application rates and no or ineffective incorporation have resulted in the continued formation of acidic subsurface layers. Regular monitoring in smaller depth increments (0.05 m), higher pH targets (pHCa > 5.5) and calculation of lime rate requirements that account for application method are required to slow or halt soil degradation by subsurface acidification. If higher pH is not maintained in the topsoil, the acidification of subsurface soils will extend further into the profile and require more expensive operations that mechanically place amendments deep in the soil. Although the use of organic amendments has shown promise to enhance soil acidity amelioration with depth, the longevity of their effect is questionable. Consequently, proactive, preventative management of topsoil pH with lime addition remains the most cost-effective solution for growers.

Geostatistics or machine learning for mapping soil attributes and agricultural practices

ABSTRACT Applying the upcoming technologies in agriculture has been a major economic, environmental and social challenge for scientists and farmers. In order to overcome such challenge, this study evaluated the advantages and limitations of using geostatistics and machine learning for soil mapping in agricultural practices and soil surveys. The study occurred in Tocantins State, Brazil, and consisted into seven areas with a total extension of 17.24 km2, 222 meters regular gridded resulting in one-point sampling per 0.0493 km2 of five randomly sampled cores within a 1 m circle radius. It was collected 332 georeferenced soil samples at 0-20 cm depth using an auger and then, soil laboratory analyses performed. Afterward, liming rate maps were originated from the predicted soil attributes clay, cation exchange capacity and base saturation comparing four methods: ordinary kriging, random forest, cubist, support vector machine and the best model results of each soil attribute. Evaluating the methods, the Pearson’s index presented strong results for soil attributes predicted by random forest and ordinary kriging. Machine learning methods can be successfully applied for soil mapping in agricultural practices and soil surveys using less soil samples rather than geostatistical framework.

Fertilidade de um organossolo e produtividade do feijoeiro influenciados pela calagem e inoculação

O objetivo deste trabalho foi avaliar o efeito da calagem nos atributos químicos de um Organossolo Háplico e a influência da interação da calagem com a inoculação de bactérias fixadoras de N2 atmosférico (Rhizobium tropici), nos teores foliares de nitrogênio, fósforo e potássio e na produtividade de grãos de feijão, cultivar Carioca. O delineamento experimental foi o de blocos ao acaso, com três repetições e esquema de parcelas subdivididas. As parcelas foram constituídas pelas doses de calcário e as subparcelas pela presença e ausência de inoculação. As doses de calcário utilizadas foram 0,0; 4,9; 8,9; 15,0 e 27,2 Mg ha-1, visando elevar respectivamente os níveis de saturação por bases 20; 30; 45 e 75%. Aos 45 dias após a aplicação dos tratamentos, foi realizada uma amostragem do solo para verificar alterações nos atributos químicos do solo. Na fase de florescimento foi realizada a coleta de folhas para avaliação dos teores de nitrogênio, fósforo e potássio. Foi avaliada a produtividade de grãos. A superioridade dos teores de N foliar na interação calagem x inoculação em relação ao controle não inoculado evidência que a calagem favoreceu a simbiose entre o feijoeiro e as estirpes de Rhizobium tropici e, consequentemente, a fixação biológica de N. A calagem associada à inoculação promoveu aumentos nos teores foliares de nitrogênio e na produtividade de grãos.

Phosphorus in an arable coarse sandy soil profile after 74 years with different lime and P fertilizer applications

The distribution of fertilizer phosphorus (P) in the soil profile affects its plant availability and the risk of P loss. We examined the P distribution and sorption in soil profiles of a field experiment initiated in 1942 on coarse sandy soil with four rates of lime (0, 4, 8 or 12 t ha−1 every 5–9 years) and two rates of P (no P or 15.6 kg P ha−1 annually). In 2016, intact soil cores were retrieved to 100 cm depth and divided into five depth intervals (0–20, 20–30, 30–50, 50–70 and 70–100 cm). Soil samples were analyzed for total P, P extracted with sodium bicarbonate (Olsen P) and water (Pw), oxalate-extractable P (Pox), iron (Feox) and aluminum (Alox), pH, carbon (C), and single point sorption index (PSI). Liming raised soil pH significantly at all depths. Addition of P increased total P, Olsen P, Pw and Pox in the upper 30 cm only. In the topsoil the extractability of P in bicarbonate (Olsen P to total P ratio) and water (Pw to total P ratio) declined with liming. Below 30 cm, soil P pools were unaffected by lime and P application. PSI increased with depth until 50–70 cm and related strongly to content of Alox, but not to Feox, Olsen P, soil C and pH. We conclude that Alox plays a dominating role for retention of P in this sandy soil profile, formed by melt-water during the Weichsel glaciation period. The retention of P in soil below 30 cm depth was strong and unaffected by addition of lime.

Base Neutralizing Capacity of Agricultural Soils in a Quaternary Landscape of North-East Germany and Its Relationship to Best Management Practices in Lime Requirement Determination

Despite being a natural soil-forming process, soil acidification is a major agronomic challenge under humid climate conditions, as soil acidity influences several yield-relevant soil properties. It can be counterbalanced by the regular application of agricultural lime to maintain or re-establish soil fertility and to optimize plant growth and yield. To avoid underdose as well as overdose, lime rates need to be calculated carefully. The lime rate should be determined by the optimum soil pH (target pH) and the response of the soil to lime, which is described by the base neutralizing capacity (BNC). Several methods exist to determine the lime requirement (LR) to raise the soil pH to its optimum. They range from extremely time-consuming equilibration methods, which mimic the natural processes in the soil, to quick tests, which rely on some approximations and are designed to provide farmers with timely and cost-efficient data. Due to the higher analytical efforts, only limited information is available on the real BNC of particular soils. In the present paper, we report the BNC of 420 topsoil samples from Central Europe (north-east Germany), developed on sediments from the last ice age 10,000 years ago under Holocene conditions. These soils are predominantly sandy and low in humus, but they exhibit a huge spatial variability in soil properties on a small scale. The BNC was determined by adding various concentrations of Ca(OH)2 and fitting an exponential model to derive a titration curve for each sample. The coefficients of the BNC titration curve were well correlated with soil properties affecting soil acidity and pH buffer capacity, i.e., pH, soil texture and soil organic matter (SOM). From the BNC model, the LRs (LRBNC) were derived and compared with LRVDLUFA based on the standard protocol in Germany as established by the Association of German Agricultural Analytic and Research Institutes (VDLUFA). The LRBNC and LRVDLUFA correlated well but the LRVDLUFA were generally by approximately one order of magnitude higher. This is partly due to the VDLUFA concept to recommend a maintenance or conservation liming, even though the pH value is in the optimum range, to keep it there until the next lime application during the following rotation. Furthermore, the VDLUFA method was primarily developed from field experiments where natural soil acidification and management practices depressed the effect of lime treatment. The BNC method, on the other hand, is solely based on laboratory analysis with standardized soil samples. This indicates the demand for further research to develop a sound scientific algorithm that complements LRBNC with realistic values of annual Ca2+ removal and acidification by natural processes and N fertilization.

Effects of lime application on nitrogen and phosphorus availability in humic soils

There is a paucity of information on nitrogen (N) and phosphorus (P) mineralization in humic soils, which are highly weathered and have high carbon (C) (>1.8%). This study was to determine effects of liming on N and P mineralization in humic soils. Lime was applied to reduce acid saturation to 20% of the 0–10 and 10–20 cm depths of soils from Eston and Eshowe. Soils were incubated at field capacity moisture and 25 °C temperature, with destructive sampling after 0, 7, 14, 21, 28, 56, 84 and 112 days. Samples were analysed for pH, ammonium- and nitrate-N and extractable P. Phosphorus pools and soil microbial biomass C and N (SMBC and N) were analysed after 112 days only. Soil pH increased up to day 7 and decreased thereafter in Eston soil but decreased throughout the incubation in Eshowe soil. Ammonium- and nitrate-N increased with lime rate, with ammonium-N peaking after 7 and 14 days for Eston and Eshowe soils, respectively. The 0–10 cm depth had higher ammonium-N than 10–20 cm for both soils. Nitrate-N increased with corresponding decrease in ammonium-N. Extractable P decreased till day 21 and increased thereafter in Eston soil, with slight changes in Eshowe. Higher lime rate decreased Al-P, Fe-P and CBD-P and increased soluble-P, Ca-P, and SMB-C and N for both soils. The findings imply that liming humic soils increase nitrate-N and, to a lesser extent, extractable P, possibly improving productivity and exposing N to leaching.

Soil rehabilitation and growth of pine and eucalyptus in area degraded by coal mining

For rehabilitation of degraded soil by open-pit coal mining it is necessary to correct the acidity and nutrients contents and promote revegetation. We evaluated different rehabilitation methods of a degraded area by coal mining on constructed soil chemical and physical attributes, and on growth of pine and eucalypt. The experiment was established between 2001 and 2004 in southern Brazil using treatments with lime, palisade grass (Urochloa brizantha), and poultry litter. Seedlings of Pinus taeda and Eucalyptus saligna were planted in 2004. In 2010, soil samples were collected at 0-5 and 5-10 cm layers for chemical and physical analysis and height and diameter of the trees were measured. Poultry litter and palisade grass did not affect soil chemical attributes, but palisade grass reduced soil penetration resistance. Lime increased soil pH, calcium and magnesium contents and base saturation and decreased aluminum saturation, however, the difficulty of lime incorporation resulted in overliming in the soil surface layer, however, the difficulty of lime incorporation resulted in overliming in the soil surface layer, which decreased pine growth. The growth of eucalypt decreased with palisade grass and poultry litter but had impaired growth throughout the area due probably to the physical (low porosity) and chemical (low phosphorus) limitations. Therefore, in similar constructed soils the reforestation with Eucalyptus saligna cannot be indicated, while reforestation with Pinus taeda is viable with lower rates of lime.

Cover crops and residual effect of lime and gypsum on soil subsurface physical attributes

The use of lime, gypsum, and different cover crops may influence the soil physical attributes, the formation of soil coverage before the crop implantation is crucial for the consolidation of the No-Tillage System. This work aimed to evaluate the alterations in the subsoil physical attributes, influenced by different cover crops combined with the application of lime and gypsum, in a no-tillage system in the Cerrado region, the soil of the experiment area was classified as Dystrophic Red Latosol. The experiment was carried out in Chapadão do Sul, state of Mato Grosso do Sul, Brazil, in a complete randomized block design, in a split-plot scheme. Plots consisted of cover crops (Urochloa ruziziensis and Pennisetum glaucum) and fallow; the subplots were formed by gypsum rates (0, 2.3, and 4.6 Mg ha-1); and the sub-sub-plots consisted of lime rates (0, 2, 4, and 6 Mg ha-1), with three replications. The cover crops, Uruchloa ruziziensis, Pennisetum glaucum and the rates of limestone and gypsum do not interfere with the density of the soil. The Uruchloa ruziziensis cover crop provides increased microporosity and total soil porosity. The cover crops Uruchloa ruziziensis and Pennisetum glaucum were not efficient in decompressing the soil in the layers of 0.20 - 0.30 and 0.30 - 0.40 m in depth. The residual effect of the lime rate of 2 Mg ha-1 without gypsum application provided higher total porosity the 0.30 - 0.40 m layer.

Effects of Liming on Dithionate and Oxalate Extractable Aluminium in Acid Soils

Liming and phosphorus (P) applications are recommended practices for improving crop production in acid soils of the tropics. Although considerable work has been done to establish liming rates for acid soils in many parts of the world, information on the effects of lime on the forms of aluminium which actively sorb P in such soils is minimal. A greenhouse pot experiment was conducted at Waruhiu Farmers Training Centre, Githunguri to evaluate the effect of liming on oxalate and dithionate extractable aluminium in acid soils. Extremely (pH 4.48) and strongly (pH 4.59) acidic soils were evaluated. Four liming (CaO) rates namely 0, 2.2, 5.2 and 7.4 tonnes ha-1 for extremely acidic and 0, 1.4, 3.2, and 4.5 tonnes ha-1 for strongly acidic soils were evaluated. The experiment was laid out in a Randomized Complete Block Design (RCBD) and replicated three times. Data collected included: initial soil chemical properties, oxalate (Alo) and dithionate (Ald) aluminium levels. The tested soils had high exchangeable Al (> 2 cmol Al kg-1), Al saturation of (> 20% Al) and low extractable P values (< 15 mg P kg-1 soil). Liming significantly (p=.05) reduced Alo by 70% and 68% in extremely and strongly acidic soils respectively and Ald by 78% in both extremely and strongly acidic soils compared to control. Use of 7.4 tonnes ha-1 of lime in extremely acidic soils and 4.5 tonnes ha-1 of lime in strongly acidic soils significantly (p=.05) reduced both Alo and Ald by > 68% compared to no lime. It was, therefore, concluded that liming contributes to the reduction of soluble Alo and Ald in acid soils of the Kenya highlands leading to increased soluble P availability. Studies are required to provide short and long term optimal liming rates that reduce Alo and Ald without distabilizing availability of other nutrients in field conditions under wide range of acid soils.

Effects of lime, phosphorus and stocking rate on an extensively managed permanent pasture: botanical composition and groundcover

Low phosphorus (P) constrains productivity of many of the permanent pastures of south-eastern Australia where wool and meat production are important. Whereas the need for fertilisation with P is indisputable for many soils, the benefits of liming to ameliorate soil acidification are not always clear in terms of forage production or quality. This experiment, by measuring botanical composition and groundcover over 10 years, aimed to address the issue of forage composition and groundcover. Merino wethers were continuously grazed on a permanent pasture under two stocking rates (low and high) following treatments with three rates of surface-applied lime and two rates of P. The lime rates were: nil, and sufficient to raise the pHCaCl2 of the 0–10 cm soil layer to 5.0 and to 5.5. Phosphorus was added as two rates of single superphosphate: 125 kg ha–1 every 2–3 years, and 250 kg ha–1 every year. Two hypotheses were proposed: (i) as lime application rate increased, it would lead to the pasture swards having a higher percentage of species favourable for grazing animal production, and a higher level of sward groundcover would be maintained; and (ii) legume presence would be favoured by a higher level of applied P over the long term. The Millennium Drought (1997–2008), which coincided with this experiment (1998–2008), tended to mask or reduce lime effects; nevertheless, the higher legume content in the sward, as well as the superior groundcover found in the high lime–high P treatments at various times throughout the experiment and at its completion compared with the nil-lime control, indicated positive forage effects of lime application. Moreover, by the termination of the experiment in 2008, groundcover generally tended to be lower under nil lime than in treatments that had received lime. The higher proportion of legume in the sward was closely linked to greater applied P, although this did not occur at the low stocking rate in the absence of lime. By contrast, similar high P–low stocking rate treatments but with applied lime had the highest clover contents. It is proposed that the poor persistence of the treatment without lime may be due to a combination of poor legume seedset, because of excessive competition from accompanying grasses, and aluminium toxicity adversely affecting legume growth.

Assessment and Mapping of Soil pH and Available Phosphorus Status in Wuchale District, North Shewa Zone, Oromia

The lack of site specific fertilizer recommendation to replenish declining soil fertility has been the major challenge to boost crop production in Ethiopia. Therefore, an investigation was conducted on soil pH and Av. P status assessment and mapping at wuchale district. About One hundred sixty one (161) geo–referenced soil samples were collected by using grid survey method. For both soil parameter analysis standard laboratory analysis were followed. In order to predict values for not sampled locations the Ordinary Kriging interpolation was used by ArcGIS10.3 software. The pH of the soil samples ranged from 4.84 to 6.67 and about 98.13% of all agricultural soils were acidic in reaction. The district has three categories of soil pH but the majority of the area falls in moderately acidic, strongly acidic and neutral soil pH which account area share of 51.55%, 46.58% and 1.87% respectively. Available P ranged from 2 to 64.79 ppm. The available phosphorus level is categorized as low, medium and high which is 26.70%, 52.80% and 20.50% respectively. The dominating class is medium i.e. (5 to 15ppm). Appropriate rate of lime needs to be applied or cultivating acid tolerant crops is recommended for both strongly acidic and moderately acidic soils of the study district to obtain optimum crop yields. The areas which are low in available soil phosphorus level need to be improved by adding organic manures (FYM/Compost) and inorganic fertilizers to boost the agricultural productivity of the study areas.

Amelioration of Acidic Soil to Increase Tef (<i>Eragrostis tef</i> (Zucc) Trotter) Yield on Smallholder Farmer Fields in Ethiopian Highlands

Crop productivity of Ethiopian highlands has been declining mainly due to high intensity of acidic soil thus amelioration is vital to improve soil properties and crop yield. Unfortunately, most farmers in Ethiopian highlands in general and in Gozamin district in particular are characterized by economically poor. This study was designed to investigate the effects integrated effects of commercial lime and low cost materials on tef yield. It was conducted under rain fed conditions of 2017 & 2018 seasons. The factorial combination of three levels lime (0, 1.5 and 3 t/ha), kitchen ash (0, 1 and 2 t/ha) and manure (0, 2.5 and 5 t/ha) treatments were laid out in randomized complete block design and replicated three times. Days to maturity were prolonged by highest application rates of lime and manure meanwhile early maturity of the crop recorded at zero application rates. Maximum number of tillers and the longest plant height were obtained at 1.5 t/ha lime and 5 t/ha manure applications. Crop yields (grain, straw and biomass) were increased linearly with manure rates meanwhile in quadratic function with application of lime. Maximum grain yield (2.12 t/ha) was obtained from combined 1.5 t lime + 0.5 t kitchen ash+ 5 t/ha manure treatment and followed by 1.97 t/ha yield through the treatment that received same rate of lime and manure with 1 t kitchen ash. These treatments were increased grain yield by more than one tone over the control. Besides, the economic analysis result confirmed that combined 1.5 t lime, 0.5 t kitchen ash and 5 t/ha manure application gave maximum net profit of 27,629 Birr/ha with acceptable MRR of 18%, thus, this application rate is optimum to increase tef production on small scale farmer fields. However, comprehensive recommendation will be drawn in future by using further findings rather than rely on a single study.

Optimal lime rates for soil acidity mitigation: impacts of crop choice and nitrogen fertiliser in Western Australia

Many agricultural soils are naturally acidic, and agricultural production can acidify soil through processes such as nitrogen (N) fixation by legumes and application of N fertiliser. This means that decisions about mitigation of soil acidity (e.g. through application of lime), crop rotation and N fertiliser application are interdependent. This paper presents a dynamic model to determine jointly the optimal lime application strategies and N application rates in a rainfed cropping system in Western Australia. The model accounts for two crop rotations (with and without a legume break crop), for the acid tolerance of different crop types, and for differences in the acidifying effect of different N fertilisers. Results show that liming is a profitable strategy to treat acidic soils in the study region, but that there are interactions between N and acidity management. Choice of fertiliser affects optimal lime rates substantially, with the use of a more acidifying ammonium-based fertiliser leading to higher lime rates. The optimal liming strategy is also sensitive to inclusion of a legume crop in the rotation, because its fixed N can be less acidifying than fertiliser, and it allows a reduction in fertiliser rates. Higher rainfall zones have greater N leaching, which contributes to a higher optimal rate of lime. We find that injection of lime into the subsoil increases profit. Optimal lime rates in the absence of subsoil incorporation are higher than usual current practice, although the economic gains from increasing rates are small.

Alleviating Soil Acidity: Optimization of Lime and Zinc Use in Maize (Zea mays L.) Grown on Alfisols

ABSTRACTSoil acidity, one of the causes of soil degradation, adversely affects phytoavailability of soil nutrients and crop growth in 50% of arable land of the world. There is a persistent need for alleviating the effect of soil acidity for adequate nutrient availability and proper crop growth. Addition of ameliorants like farmyard manure (FYM) and lime to acid soils affects the crop growth and nutrient availability, especially zinc (Zn) availability, by moderating soil acidity. However, the information regarding optimum quantities of lime and zinc requirement for alleviating soil acidity, proper crop growth, and Zn nutrition in acid soil is limited. Therefore, the present greenhouse pot experiments were carried out at ICAR-Indian Institute of Soil Science, Bhopal, India, in kharif season of 2015 using two acid soils (representing Alfisol order) to optimize lime and Zn application and to understand the impact of FYM and lime application on soil properties, phytoavailable Zn, biomass yield of maize, and Zn uptake, for better growth and Zn nutrition of maize. Maize was raised for 60 days with two levels of FYM (0 and 4,500 mg kg−1), five levels of lime requirement (LR) (0, 1/10th, 1/3rd, 2/3rd, and 1.0), and three Zn levels (0, 2.5, and 5.0 mg kg−1). Results revealed that FYM and lime addition significantly influenced soil properties, biomass yield, and postharvest soil extractable Zn. Lime addition at 1/3rd LR was found optimum as biomass yield enhanced up to this level of liming. FYM addition augmented biomass yield. A higher amount of lime (2/3rd and 1.0 LR) led to a reduction in crop Zn concentration and its uptake. The phytoavailable Zn extracted by different extractants in soils declined with increasing lime rates. Zn addition enhanced biomass yield and crop Zn concentration. The lowest and the highest amount of Zn were extracted from the soil at all levels of lime addition by diethylenetriaminepentaaceticacid (DTPA) and 0.1 M HCl, respectively. The extractable Zn was correlated significantly with biomass yield, crop Zn concentration, and its uptake. Ammonium bicarbonate DTPA (ABDTPA) proved promising extractant for estimation of Zn availability in these acid soils. This knowledge will be of use for alleviation of acid soils by the addition of the required quantity of lime and effective Zn management in acid soils for proper Zn nutrition and crop growth.

Inconsistent effects of limestone on rice cadmium uptake: Results from multi-scale field trials and large-scale investigation

Adding limestone into acidic paddy soils might reduce cadmium (Cd) accumulation in rice plants and the harvested grains but with inconsistent results in the field practice. We conducted three experiments of different field scales, including small-plots, multi-location trial, and large-scale field samplings of rice grown in a major production region of southern China, to investigate whether liming could sustainably limit the Cd phytoavailability to rice. Forty-eight physical, chemical, and biological attributes associated with paired soils and plants were collectively analyzed. Rice Cd uptake was significantly reduced when moderate dosage (2.25–3 t ha−1) of liming was present in the soils. The limes decreased rice Cd uptake by reducing the Cd concentrations of soil solution phase and regulating Ca2+ and Cd2+ competitions for absorption sites at root surfaces. Soil Zn hardly any effect on rice Cd uptake. Rice Cd uptake was suppressed at the higher rates of liming (4.5–9 t ha−1) due to the heavy loss of soil labile Mn. The tendencies of over compensating were soil-, plant-, and climate-dependent and were estimated by a transfer function and the risks were characterized using probabilistic analysis. The sustainable doses of limestone that reduced grain Cd accumulation, but did not compromise yield, or disrupt the rice rhizosphere was 3 t ha−1 annually incorporated two weeks before the seedlings were transplanted.

Response of Calceolaria ×herbeohybrida Cultivars to Substrate pH and Corresponding Leaf Tissue Nutrient Concentration Effects

Calceolaria (Calceolaria ×herbeohybrida) is a flowering potted greenhouse crop that often develops upper-leaf chlorosis, interveinal chlorosis, and marginal and leaf-tip necrosis (death) caused by cultural practices. The objectives of this research were to 1) determine the optimal incorporation rate of dolomitic and/or hydrated lime to increase substrate pH; 2) determine the influence of the liming material on substrate pH, plant growth, and leaf tissue nutrient concentrations; and 3) determine the optimal substrate pH to grow and maintain during calceolaria production. Sphagnum peatmoss was amended with 20% (by volume) perlite and incorporated with pulverized dolomitic carbonate limestone (DL) and/or hydrated limestone (HL) at the following concentrations: 48.1 kg·m−3 or 144.2 kg·m−3 DL, 17.6 kg·m−3 DL + 5.3 kg·m−3 HL, or 17.6 kg·m−3 DL + 10.6 kg·m−3 HL to achieve a target substrate pH of 4.5, 5.5, 6.5, and 7.5, respectively. Calceolaria ‘Orange’, ‘Orange Red Eye’, ‘Yellow’, and ‘Yellow Red Eye’ were grown in each of the prepared substrates. For all cultivars, substrate solution pH increased as limestone incorporation concentration and weeks after transplant (WAT) increased, although to different magnitudes. For example, as limestone incorporation increased from 48.1 kg·m−3 DL to 17.6 kg·m−3 DL + 10.6 kg·m−3 HL, substrate solution pH for ‘Orange’ calceolaria increased from 4.1 to 6.9 to 4.8 to 7.2 at 2 and 6 WAT, respectively. Substrate solution electrical conductivity (EC) and growth indices were not influenced by limestone incorporation, but total plant dry mass increased. Few macronutrients and most micronutrients were influenced by limestone incorporation. Leaf tissue iron concentrations for ‘Orange’, ‘Orange Red Eye’, ‘Yellow’, and ‘Yellow Red Eye’ calceolaria decreased by 146%, 91%, 71%, and 84%, respectively, when plants were grown in substrates incorporated with increasing limestone concentrations from 144.2 kg·m−3 DL to 17.6 kg·m−3 DL + 10.6 kg·m−3 HL (pH 6.5–6.9). Therefore, incorporating 144.2 kg·m−3 DL into peat-based substrates and maintaining a pH <6.5 will avoid high pH–induced Fe deficiency and prevent upper-leaf and interveinal chlorosis.

Lime movement through highly weathered soil profiles

Applying lime is a fundamental practice for abating acidity in highly weathered soil, but better management strategies for no-till systems are needed to prevent surface pH elevation with little to no subsurface effects. This study was conducted to quantify chemical changes within the soil profile in response to lime and straw applications under both greenhouse and field conditions. Four controlled environment experiments (soil columns) and one field study were conducted on soils classified as Rhodic Hapludox and Rhodic Eutrodox. The soil column experiments evaluated four lime rates (0, 3.9, 7.8, or 15.6 Mg ha−1) and four straw rates (0, 4, 12 and 16 Mg ha−1) either individually or in combination. Lime treatments were surface applied or incorporated in the top 5-cm, while straw treatments were incorporated in the top 5-cm. In the field, lime rates of 0, 8.3 and 33.2 Mg ha−1 were incorporated into the 0 to 10-cm depth in both a soybean [Glycine max] monoculture and diversified cropping system with white oat (Avena sativa), soybean, black oats (Avena strigosa), corn (Zea mays) and wheat (Triticum aestivum). Both field and soil columns studies showed minimal lime movement into the soil profile with chemical changes being limited to 2.5-cm below where it was applied or incorporated regardless of cropping system. Surface application of high lime rates promoted chemical stratification resulting in dramatic increases in topsoil pH and exchangeable Ca and Mg levels with minimal mitigation of subsurface soil acidity. Other studies also suggest that lime movement into the soil profile can vary depending on the experimental condition. Therefore, additional investigations across a wider geographic area, greater range of weather and climatic conditions, methods and rates of lime application need to be conducted to improve lime recommendation for high weathered soil managed using no-till practices.

Exploration of Heavy Metal(loid)s Immobilizing Agents Available for Agricultural Lands and Their Combination Effects

Heavy metal(loid)s contamination in Korean agricultural lands is mostly caused by tailing wastes, debris, and leachate from abandoned mines. For safe agricultural production, immobilizing agents have been actively studied to reduce phytoavailability of heavy metal(loid)s. However, more various immobilizing materials need to be explored to achieve a practical application of this technique. This study aims to examine and compare the effects of known and unknown immobilizing agents on decrease plant-available heavy metal(loid)s. Lime, gypsum, guano, and bone meal were applied in metal contaminated soils in isolation or in combination. After the treatment, changes in soil pH and dissolved organic carbon were analyzed. Lettuce was grown for 7 weeks in each soil, and heavy metal(loid)s concentration in lettuce was determined. The mixed immobilizing agents reduced phytoavailability of heavy metal(loid)s more effectively than the isolate treatments. A mixture of lime, gypsum, and guano was the most effective combination, followed by a mixture of lime, gypsum, and bone meal. Future study on a practical application of the immobilizing agents is required to increase both safety and productivity of agricultural crops. Cumulated heavy metal(loid) immobilizing rates of gypsum, lime, guano, and bone meal, treated either alone or in selected combinations

Liming and Nitrogen Effects on Maize Yield and Nitrogen Use Efficiency

ABSTRACTThe study was aimed to determine the appropriate nitrogen (N) rate to combine with liming for enhanced maize yield and nitrogen use efficiency (NUE). Two maize varieties [Ikom White (IKW) and Obatanpa-98 (Oba-98)], two lime rates (0 kg ha−1 and 500 kg ha−1) and three N rates (0, 90 and 180 kg ha−1) were used. The treatments were laid as a split-split plot in a randomized complete block design with three replications. The growth attributes, photosynthetically active radiation (PAR), harvest index, dry matter, and grain yield increased (P ≤ 0.05) with increases in N rates, especially in plots amended with lime. Oba-98 was better yielding (2.12 versus (vs) 1.88 t ha−1) and absorbed more (P ≤ 0.05) radiation (442.06 vs 409.54 μmol m−2s−1) than IKW. The efficiency indices and partial factor productivity were best optimized at the 90 kg ha−1 N rate with Oba-98 having higher values than IKW. Therefore, liming (500 kg ha−1) plus N at 180 kg ha−1produced the best yield of the hybrid maize, Oba-98.