Dolomitic Lime Research Articles

Martin Marietta Materials, Inc.

AbstractEarth & Rock Mining (MIC: SIC: 1481 NAIC: 213115)Martin Marietta Materials is a producer of aggregates for the construction industry, including infrastructure, commercial, agricultural, and residential. As of Dec 31 2007, Co.'s aggregates, asphalt products, and ready mixed concrete are sold and shipped from a network of approximately 287 quarries, underground mines, distribution facilities, and plants in 28 states, Canada, and the Bahamas. Co. operates through four reportable business segments: the Mideast Group, Southeast Group, and West Group, comprising the Aggregates business, and the Specialty Products segment, which manufactures and markets magnesia‐based chemical products, dolomitic lime, and structural composite products.

Efeito da calagem superficial em plantio direto na concentração de cátions hidrossolúveis na parte aérea de culturas anuais

A acidez do solo no sistema plantio direto pode ser minimizada com aplicação superficial de calcário. Tal prática é favorecida pela permanência de restos vegetais na superfície do solo, pela liberação de compostos orgânicos hidrossolúveis, que variam de planta para planta. Por isso foi instalado um experimento em Latossolo Vermelho distrófico (V = 41 %) em Botucatu (SP), objetivando avaliar os efeitos da aplicação superficial de calcário dolomítico na concentração de cátions solúveis nos resíduos vegetais das culturas de milheto, feijão e aveia preta em dois anos agrícolas (2002/2003 e 2003/2004). No caso do feijoeiro, o delineamento experimental utilizado foi o de blocos casualizados em esquema de parcelas subdivididas, com quatro repetições. As parcelas foram representadas por cultivares de feijão (Carioca, IAC Carioca Eté, Pérola, IAPAR 81 e Campeão 2), enquanto as subparcelas foram formadas por doses de calcário dolomítico (sem aplicação, 1,8; 3,6 e 5,4 t ha-1). Para o milheto e aveia preta foram consideradas apenas as doses como fator. Foram avaliados os teores de Ca, Mg, K e Mn na parte aérea de todas as culturas, bem como a condutividade elétrica no extrato. Os resultados evidenciaram que os teores de Ca, K e Mg solúveis na parte aérea das culturas anuais avaliadas não foram alterados com a aplicação superficial de doses de calcário dolomítico. As culturas do milheto e feijão apresentaram maior teor de cátions solúveis na parte aérea, quando comparado ao da aveia preta.

Sulfation of calcitic and dolomitic lime mortars in the presence of diesel particulate matter

The sulfation of four types of calcitic and dolomitic lime mortars exposed to SO2 in the presence of particulate matter from diesel vehicle exhaust emissions has been investigated. The binders mineralogy and mortars texture are the main factors influencing the formation of deleterious sulfate salts. The type of binder also influences the pore size distribution and the total porosity of the mortars: for equal aggregate (quartz or dolomite), dolomitic lime mortars have smaller pores and higher porosity than calcitic ones. During the first 24 h exposure to SO2, calcitic lime mortars undergo a higher weight increase than dolomitic ones due to rapid formation of gypsum on their surface. However, at the end of the sulfation test (10 days), dolomitic mortars show a higher weight increase due to massive formation of epsomite and gypsum, which is facilitated by their higher porosity and the high reactivity of Mg phases in the porous and partially carbonated binder. Control samples (not covered with diesel particulate matter) also develop calcium and magnesium sulfates upon long term exposure to SO2. This is due to the presence of uncarbonated Ca and Mg hydroxides that promote SO2 fixation as sulfates. However, the amount and size of sulfate crystals are significantly smaller than those observed on samples covered with diesel particulate matter. These results show that diesel particulate matter enhances the sulfation of lime mortars and demonstrate that sulfation of dolomitic lime is an important mechanism for the in situ formation of highly soluble and deleterious hydrated magnesium sulfates (epsomite and hexahydrite). The use of dolomitic limes in the conservation of monuments exposed to air pollution in urban environments may therefore pose a significant risk.

Soil properties and maple–beech regeneration a decade after liming in a northern hardwood stand

Soil properties, regeneration, sugar maple (SM, Acer saccharum Marsh.) crown dieback, and light interception were evaluated following dolomitic lime application (CaMg(CO 3) 2; 0, 2, 5, 10 and 20 t ha −1) in a base-poor and declining northern hardwood stand of Quebec (Canada). Ten years after liming, soil pH, cation exchange capacity and base saturation increased with the lime rate. Meanwhile, concentrations of exchangeable K, Na, and acidity (0–20 cm) decreased. Concentrations and content of total carbon, organic matter, and total N decreased in the top sampled soil layer, mainly for the highest lime rate. Mean crown dieback of SM ranked from 0 to 3.4% among lime treatments, while it ranked 18.4% for the unlimed controls. Light interception by the canopy responded with an opposite pattern to crown dieback, with higher interception in lime treatments and lower in control. Proportion and diameter of SM regeneration stems increased with lime rate while proportion of American beech (AB, Fagus grandifolia Ehrh.) regeneration stems decreased in the understory. Height and stem diameter of the three taller regeneration stems (mainly AB) in each plot were inversely correlated with lime rate. Overall, the results suggest that the increase in soil fertility following liming had a beneficial effect on SM regeneration within 10 years, even if light availability was lower under treated SM than under control, and had an overall negative impact on AB regeneration.

Liming and Ionic speciation of an Oxisol under no-till system

The chemical speciation of the soil solution is an important tool for evaluating nutrient availability and aluminum phytotoxicity. The effect of liming in the composition of the soil solution under the no-till (NT) system is still not well known. We evaluated the chemical speciation of Al and nutrients in the soil solution (water extract 1:1), five years after liming at the moment of the establishment of NT in a native pasture, in Ponta Grossa, Paraná State, Brazil. Dolomitic lime was applied at a rate of 4.5 t ha-1 (either incorporated or surface-applied), or split in three annual rates of 1.5 t ha-1. Soil samples from a dystrophic clayey Rhodic Hapludox were collected at the 0 - 0.05; 0.05 - 0.1; 0.1 - 0.2; 0.2 - 0.4; 0.4 - 0.6; and 0.6 - 0.8 m layers, in May, 2003. Aluminum was mainly complexed to dissolved organic carbon (DOC) and fluoride, while the free form Al3+ was present in fewer amounts even under acidic conditions. Calcium and magnesium were found as free forms (Ca2+, Mg2+) and complexed by organic anions. Phosphorus was found as free forms (HPO4(2-), H2PO4-) and complexed with aluminum (ionic pair Al-HxPO4x) up to 0.1 m. Complexation of Al by DOC was not influenced by surface-applied or incorporated liming. Liming did not change Ca and Mg speciation in the soil solution under NT system. The presence of free forms HPO4(2-) and H2PO4-, however, was influenced by liming, because of the increase in cation associated forms.

Influência da adição de alumina na microestrutura da espuma vítrea

No presente trabalho estudou-se a influência da adição de alumina nas propriedades da espuma vítrea. A alumina foi empregada com a finalidade de proporcionar uma maior refratariedade para os corpos cerâmicos. Foram investigados corpos cerâmicos à base de vidro sodo-cálcico moído, oriundo de embalagens de vidro transparente, calcário dolomítico e alumina. Os corpos cerâmicos foram formulados com teores de 3% e 5% em peso de calcário dolomítico, ambos sem e com 4% em peso de alumina, conformados por prensagem uniaxial e queimados entre 600 ºC e 1000 ºC, com uma taxa de aquecimento de 150 K/h. A caracterização tecnológica dos corpos cerâmicos envolveu a determinação da expansão volumétrica. A microestrutura foi avaliada por meio de microscopia óptica e eletrônica de varredura. Os resultados experimentais mostraram que a adição de alumina influencia a expansão volumétrica dos corpos cerâmicos, reduzindo a espumação significativamente.

Martin Marietta Materials, Inc.

AbstractEarth & Rock Mining (MIC: 14.5 SIC: 1481 NAIC: 213115)Martin Marietta Materials is a producer of aggregates for the construction industry, including infrastructure, commercial, agricultural, and residential. As of Dec 31 2007, Co.'s aggregates, asphalt products, and ready mixed concrete are sold and shipped from a network of approximately 287 quarries, underground mines, distribution facilities, and plants in 28 states, Canada, and the Bahamas. Co. operates through four reportable business segments: the Mideast Group, Southeast Group, and West Group, comprising the Aggregates business, and the Specialty Products segment, which manufactures and markets magnesia‐based chemical products, dolomitic lime, and structural composite products.

Responses of Acer saccharum canopy trees and saplings to P, K and lime additions under high N deposition

Heavy atmospheric nitrogen (N) deposition has been associated with altered nutrient cycling, and even N saturation, in forest ecosystems previously thought to be N-limited. This observation has prompted application to such forests of non-N mineral nutrients as a mitigation measure. We examined leaf gas-exchange, leaf chemistry and leaf and shoot morphological responses of Acer saccharum Marsh. saplings and mature trees to experimental additions of non-nitrogenous mineral nutrients (dolomitic lime, phosphorus + potassium (P + K) and lime plus P + K) over 2 years in the Haliburton region of central Ontario, which receives some of the largest annual N inputs in North America. Nutrients were adsorbed in the mineral soil and taken up by A. saccharum trees within 1 year of fertilizer application; however, contrary to expectation, liming had no effect on soil P availability. Saplings and canopy trees showed significant responses to both P + K fertilization and liming, including increased foliar nutrient concentration, leaf size and shoot extension growth; however, no treatment effects on leaf gas-exchange parameters were detected. Increases in shoot extension preceded increases in diameter growth in saplings and canopy trees. Vector analysis of shoot extension growth and nutrient content was consistent with sufficiency of N but marked limitation of P, with co-limitation by calcium (Ca) in saplings and by Ca, Mg and K in canopy trees.

Severe and Widespread Clubroot Epidemics in Nepal.

Cultivation of brassica vegetables has the highest potential for generating income among more traditional rice and maize farmers in Nepal. Among brassica vegetables, the most important are cauliflower (Brassica oleracea var. botrytis L.) and cabbage (B. oleracea var. capitata L.). Although clubroot disease, caused by Plasmodiophora brassicae Woronin, has been observed in Nepal since 1993, severe and widespread epidemics have been observed since 2004 in the Bhaktapur, Kathmandu, Lalitpur, and Palung Valley production areas. Typical disease symptoms (1) are widespread, and disease severity has been particularly severe in the Kathmandu Valley and Palung/Daman area of the Makwanpur District. Many cauliflower fields in these areas have had as much as 100% yield loss between 2004 and 2006 with an estimated 40% overall loss from clubroot. Estimates from interviews with growers in the Palung production area during an intensive farmers' interaction program indicated that cauliflower production was reduced from 5 to 6 metric tons per household (1,500 m2) prior to 2004 to <300 kg per household in 2004 and beyond. The economic loss in this area alone was estimated at $1.4 million in 2004 and 2005. Examination of transplant nurseries indicated that frequently >80% of the seedlings have symptoms of clubroot at the time of transplanting. Soil samples from throughout the production areas indicated that the sandy loam soils were predominately acidic (pH range of 4.2 to 7.2 with >90% below 6.0). Several management practices are being employed to reduce disease severity, including the use of clubroot resistant cultivars, raising the soil pH to >7.0 by using dolomitic lime, testing of the fungicide flusulfamide (Nebijin) and biopesticide Sanjeevani (Trichoderma viride), and biofumigation and solarization of the nursery beds in an effort to reduce disease pressure on transplant material.

Martin Marietta Materials, Inc.

AbstractEarth &amp; Rock Mining (MIC: 14.5 SIC: 1481 NAIC: 213115)Martin Marietta Materials is a producer of aggregates for the construction industry, including infrastructure, commercial, agricultural, and residential. As of Dec 31 2006, Co.'s aggregates, asphalt products, and ready mixed concrete are sold and shipped from a network of approximately 307 quarries, underground mines, distribution facilities, and plants in 28 states, Canada, and the Bahamas. Co. operates through four reportable business segments: the Mideast Group, Southeast Group, and West Group, comprising the Aggregates business, and the Specialty Products segment, which manufactures and markets magnesia‐based chemical products, dolomitic lime, and structural composite products.

Soil acidity, liming and soybean performance under no-till

The effects of soil chemical changes on soybean root growth, mineral nutrition and grain yield, as a result of surface application of lime under no-till (NT), are still under discussion. A field trial was carried out on a loamy dystrophic Typic Hapludox at Ponta Grossa, Paraná State, Brazil, using a completely randomized block design with three replicates, in a split-plot experiment. The main plots received four dolomitic lime rates applied on the surface (0, 2, 4, and 6 Mg ha-1) in July 1993. In the subplots, two dolomitic lime rates were reapplied on the surface (0 and 3 Mg ha-1) in June 2000. After nine years, liming increased pH, exchangeable Ca2+ and reduced exchangeable Al3+ as well as soil Al3+ saturation down to a 60 cm depth. Re-liming, after two years, also provided soil acidity amelioration to a 60 cm depth. Soybean total root length per soil surface area (0-60 cm) decreased with the surface lime application under NT. The reduction in soil exchangeable Al3+ with liming did not change Al concentrations in the soybean roots and leaves. Surface-applied dolomitic lime under NT brought an increase in Ca and Mg concentrations and a decrease in the Mn level in both soybean roots and leaves. Soybean grain yield was not influenced by surface liming because of the decreased Al toxicity and because root growth was stimulated by soil acidity stress under NT.

EFEITOS QUALITATIVO E QUANTITATIVO DA APLICAÇÃO DE FÓSFORO NO CAPIM TANZÂNIA-1

The amendment of phosphorus shortage is indispensable to elevate the capacity of animal support capacity of a pasture. To improve P status of these soils and to know the qualitative and quantitative effect of phosphorus fertilizer on the forage Tanzânia-1, an experiment was conducted in one dark red latosol , at Santo Antonio de Goias - GO. The soil was prepared by using a harrow and one ploughing, and sowing was done after a week. The plots were fertilized by using 0; 50 and 100 kg of P ha-1 of commercial thermo-phosphate in previously amended soil with 3 t ha-1 of dolomite lime. The mean values of plant height, budding, green mass and dry matter increased but decreased the gross protein and increased the fiber contents. The phosphorus fertilizer didn’t influence potassium, calcium, zinc and manganese contents in the leaf tissue of plants. However, it reduced phosphorus, copper and iron contents but increased the magnesium contents. KEY-WORDS: Savanah; mineral nutricion; Panicum maximum; pasture.

AVALIAÇÃO DA CALAGEM SOBRE OS PARÂMETROS QUANTITATIVOS, QUALITATIVOS E NUTRICIONAIS DA FORRAGEIRA TANZÂNIA-1

The soils of cerrado are acid and chemically poor, and the liming can increase the availability of most of the soil nutrients and mainly those supplied by the fertilizers through the soil fertilization, when reducing the surface soil acidity of the labor layer. In this experiment, three levels of liming were tested (0,3 and 6 t ha -1 of dolomite lime) in Dark Red Latosol. The grass production didn’t increase by the lime application, however the largest concentrations of K, Ca, Fe and Mn were observed in plant tissue developed in the limed areas. Detergent Neutral Fiber and Zn presented decreasing tendency while the Cu and P tended to increase with the increment of the liming. The plant height, the number of buds and the productions of dry matter and green mass decreased significantly in response to lime application. In terms of bromatologic aspect, the quality of the forage was improved with the correction of the soil; the largest amounts of gross protein were observed in plants developed in the areas where 3 t ha -1 were applied. KEY-WORDS: Forage; liming; savannal soil.

Mobilidade de cátions e correção da acidez de um Cambissolo em função da aplicação superficial de calcário combinado com sais de potássio

A menor reatividade do calcário abaixo dos locais de aplicação deve-se principalmente à sua baixa solubilidade, ao aumento das cargas negativas nas camadas aplicadas devido ao aumento do pH e à pequena permanência dos ânions adicionados na solução do solo. O presente trabalho teve por objetivo avaliar o efeito da adição de ânions a partir de sais de K sobre a superfície do solo, no incremento da reatividade do calcário e na mobilidade de seus cátions em um Cambissolo Húmico. O experimento foi realizado em 2005, em solo com 360 g kg-1 de argila, 60 g kg-1 de matéria orgânica e pH 4,1. Foram utilizadas três doses de calcário dolomítico (0, 0,74 e 1,48 kg m-2), combinadas com 40 g m-2 de K, na forma de KCl ou de KNO3, e com uma testemunha sem K, todos incorporados no primeiro centímetro da coluna do solo. As unidades experimentais (colunas de PVC com 10 x 30 cm, contendo 1,5 kg de solo) foram percoladas 21 vezes, a cada sete dias, com 300 mL de água destilada por semana, totalizando o equivalente a 800 mm de chuva. Os sais potássicos lixiviaram muito mais Ca e Mg do que o calcário. Na média dos três tratamentos de calagem, a adição dos sais aumentou a lixiviação total de Ca, Mg e K, respectivamente de 36 para 132 mg, de 5,8 para 26 mg e de 25 para 51 mg/coluna, relativamente ao tratamento sem adição de sal. Na ausência dos sais, a aplicação da maior dose de calcário dolomítico lixiviou apenas 5 mg de Ca e 1,2 mg/coluna de Mg, em relação ao tratamento sem calcário. A calagem superficial afetou o pH do solo e a concentração de Ca, Mg e Al trocável até a profundidade máxima de 5,0 cm, cujas alterações foram quase sempre proporcionais à dose aplicada, porém não foram influenciadas pela adição dos sais. A aplicação dos fertilizantes potássicos não influenciou a capacidade reativa do calcário aplicado na superfície do solo.

TERRESTRIAL LIMING BENEFITS BIRDS IN AN ACIDIFIED FOREST IN THE NORTHEAST

Studies in Europe have reported negative effects of acid deposition on forest birds, and research in North America has identified links between forest bird abundance and rates of acid deposition. We examined the bird community in an acidified forest in central Pennsylvania (USA) and evaluated the effects of terrestrial lime application on birds. We used a before-after control-impact (BACI) study design, with one year of observation before (2003) and three years after lime application (2004, 2005, and 2006). Between the 2003 and 2004 field seasons, 4500 kg/ha of dolomitic lime were applied to two of four 100-ha watersheds. Each year, we monitored bird abundance and Ovenbird (Seiurus aurocapilla) eggshell thickness and territory size. Soil and snail abundance data were also collected. The bird community and territory size results indicated that the study area may be providing low-quality habitat for forest birds, perhaps as a result of acid deposition. We found lower forest bird abundances than have been found in less acidified areas of Pennsylvania, and larger Ovenbird territory sizes than have been found in other studies. We found a significant positive relationship between soil calcium and bird abundance, indicating that soil calcium may affect bird abundance. Liming increased soil calcium and pH and led to increased snail and bird abundances. After liming, bird abundance was positively related to snail abundance. No significant changes occurred in Ovenbird territory size or eggshell thickness. Our results suggest that acid deposition could be responsible for reduced bird abundance, and that liming is a potential mitigation technique.

Cattle manure and grass residues as liming materials in a semi-subsistence farming system

A field experiment was conducted on an acid soil in a semi-subsistence farming area of KwaZulu-Natal, South Africa to investigate the possibility of using organic amendments as liming materials within a minimum tillage (strip cultivation) system to produce maize. Amendments (cattle manure, grass residues and dolomitic lime) were incorporated to a depth of 20 cm in bands 15 cm wide down plant rows at rates of 10 and 20 t ha −1 (in the amended area) for organic materials and 2.5 and 5.0 t ha −1 for lime. The remainder of the field remained untilled. Additions of cattle manure rapidly increased soil pH, and concentrations of exchangeable K, Ca and Mg and extractable P were also greatly elevated. Grass residue additions increased pH progressively and increased exchangeable K and Mg and those of dolomitic lime increased pH, exchangeable Ca and Mg. Addition of each of the amendments decreased concentrations of exchangeable Al; the effect was greatest for animal manure after 6 weeks and for lime and grass residues at harvest. At harvest, addition of all three amendments had significantly reduced concentrations of both phytotoxic monomeric and total Al in soil solution. The system not only resulted in an increase in pH and extractable nutrients in row soil compared to that in the inter-row but also an increase in the size and activity of the soil microbial community. Maize yields were increased by additions of amendments under both unfertilised and fertilised conditions and yields were generally greatest at the higher rate of addition. Under unfertilised conditions, cattle manure treatments gave the greatest yields. Fertiliser additions increased yields greatly particularly in the control, grass residue and lime treatments. It was concluded that the strip tillage system used is a practicable way of applying high rates of organic materials to soils, that cattle manure has a rapid liming effect as well as being a nutrient source and that grass residues from rangeland decompose slowly and, therefore, have a slow liming effect.

Martin Marietta Materials, Inc.

AbstractGeneral Construction Supplies &amp; Services (MIC: 3.3 SIC: 1481 NAIC:213115)Martin Marietta Materials is a producer of aggregates for the construction industry, including infrastructure, commercial, agricultural, and residential. As of Dec 31 2006, Co.'s aggregates, asphalt products, and ready mixed concrete are sold and shipped from a network of approximately 307 quarries, underground mines, distribution facilities, and plants in 28 states, Canada, and the Bahamas. Co. operates through four reportable business segments: the Mideast Group, Southeast Group, and West Group, comprising the Aggregates business, and the Specialty Products segment, which manufactures and markets magnesia‐based chemical products, dolomitic lime, and structural composite products.

Martin Marietta Materials, Inc.

AbstractGeneral Construction Supplies &amp; Services (MIC: 3.3 SIC: 1481 NAIC:213115)Martin Marietta Materials is a producer of aggregates for the construction industry, including infrastructure, commercial, agricultural, and residential. As of Dec 31 2006, Co.'s aggregates, asphalt products, and ready mixed concrete are sold and shipped from a network of approximately 307 quarries, underground mines, distribution facilities, and plants in 28 states, Canada, and the Bahamas. Co. operates through four reportable business segments: the Mideast Group, Southeast Group, and West Group, comprising the Aggregates business, and the Specialty Products segment, which manufactures and markets magnesia‐based chemical products, dolomitic lime, and structural composite products.

Martin Marietta Materials, Inc.

AbstractGeneral Construction Supplies &amp; Services (MIC: 3.3 SIC: 1481 NAIC:213115)Martin Marietta Materials is a producer of aggregates for the construction industry, including infrastructure, commercial, agricultural, and residential. As of Dec 31 2006, Co.'s aggregates, asphalt products, and ready mixed concrete are sold and shipped from a network of approximately 307 quarries, underground mines, distribution facilities, and plants in 28 states, Canada, and the Bahamas. Co. operates through four reportable business segments: the Mideast Group, Southeast Group, and West Group, comprising the Aggregates business, and the Specialty Products segment, which manufactures and markets magnesia‐based chemical products, dolomitic lime, and structural composite products.

Soil type, management history and current resource allocation: Three dimensions regulating variability in crop productivity on African smallholder farms

Soil fertility varies markedly within and between African smallholder farms, both as a consequence of inherent factors and differential management. Fields closest to homesteads (homefields) typically receive most nutrients and are more fertile than outlying fields (outfields), with implications for crop production and nutrient use efficiencies. Maize yields following application of 100 kg N ha −1 and different rates and sources of P were assessed on homefields and outfields of smallholder farms in Zimbabwe. Soil organic carbon, available P and exchangeable bases were greater on the homefields than outfields. In each of three experimental seasons, maize yields in homefield control plots were greater than in the outfields of farms on a granitic sandy and a red-clay soil. Application of mineral N significantly increased maize yields on homefields in the first season (2.1–3.0 t ha −1 on the clay soil and 1.0–1.5 t ha −1 on the sandy soil) but the effects of N alone were not significant on the outfields due to other yield-limiting factors. Greatest yields of about 6 t ha −1 were achieved on the clayey homefield with 100 kg N ha −1 and 30 kg P ha −1 applied as single super phosphate (SSP). Manure application gave greater yields (3–4 t ha −1) than SSP (2–3 t ha −1) in the sandy homefield and in the clayey outfield. Maize did not respond significantly to N, dolomitic lime, manure and P on the sandy outfield in the first and second seasons. In the third season, manure application (∼17 t manure ha −1 year −1) on the sandy outfield did result in a significant response in grain yields. Apparent P recovery in the first season was 55–65% when P was applied at 10 kg ha −1 on the clayey homefield (SSP), clayey outfield (SSP and manure) and sandy homefield (manure) with apparent P recovery less than 40% when P was applied at 30 kg ha −1. On the sandy outfield, P recovery was initially poor (<20%), but increased in the successive seasons with manure application. In a second experiment, less than 60 kg N ha −1 was required to attain at least 90% of the maximum yields of 2–3 t ha −1 on the sandy homefield and clayey outfield. N use efficiency varied from >50 kg grain kg −1 N on the infields, to less than 5 kg grain kg −1 N on the sandy outfields. Apparent N recovery efficiency by maize was greatest at small N application rates with P applied. We conclude that blanket fertilizer recommendations are of limited relevance for heterogeneous smallholder farms. Targeted application of mineral fertilizers and manure according to soil type and past management of fields is imperative for improving crop yields and nutrient use efficiencies.