pH effects of the addition of three biochars to acidic Indonesian mineral soils

Abstract

Soil acidity may severely reduce crop production. Biochar (BC) may increase soil pH and cation exchange capacity (CEC) but reported effects differ substantially. In a systematic approach, using a standardized protocol on a uniquely large number set of 31 acidic soils, we quantified the effect of increasing amounts (0–30%; weight:weight) of three types of field-produced BCs (from cacao (Theobroma cacao. L.) shell, oil palm (Elaeis guineensis. Jacq.) shell and rice (Oryza sativa. L.) husk) on soil pH and CEC. Soils were sampled from croplands at Java, Sumatra and Kalimantan, Indonesia. All BCs caused a significant increase in mean soil pH with a stronger response and a greater maximum increase for the cacao shell BC addition, due to a greater acid neutralizing capacity (ANC) and larger amounts of extractable base cations. At 1% BC addition, corresponding to about 30 tons ha^?1, the estimated increase in soil pH from the initial mean pH of 4.7 was about 0.5 units for the cacao shell BC, whereas this was only 0.05 and 0.04 units for the oil palm shell and rice husk BC, respectively. Besides depending on BC type, the increase in soil pH upon the addition of each of the three BCs was mainly dependent on soil CEC (low CEC resulting in stronger pH increase), and to a lesser extent on initial soil pH (higher initial pH resulting in stronger pH increase). Addition of BC also increased the amount of exchangeable base cations (cacao shell ? oil palm and rice husk) and CEC. Through this systematic screening of the effect of BC on pH and CEC of acidic soils, we show that a small addition of BC, in particular if made of cacao shell, to acidic agricultural soils increases soil pH and CEC. However, the response is highly dependent on the type, quality and amount of the added BC as well as on intrinsic soil properties, mainly CEC.     

Ursachen kleinräumiger Ertragsschwankungen im bayerischen Tertiärhügelland und Folgerungen für eine teilschlagbezogene Düngung

Site effects of small-scale yield variation in the Tertiary hills north of Munich (Germany) and conclusions for site specific farming The effect of numerous soil factors on small-scale yield variation of winter wheat and spring barley were examined: soil structure and soil texture, soil nitrate content and soil water at different times, P_CAL-, K_CAL-, N_t- and C_t-content, pH, soil microbiology characteristics, relief, root growth and important plant diseases. The varying annual influence of soil parameters on crop yield was interrelated with climatic factors. In soils with low sand content soil productivity was largely influenced by soil structure. This effect was less pronounced on soils with medium sand content. On sandy soils, however, yield was reduced by available water capacity. Yield potential was also lowered by frequent cereal growing associated with take-all root desease of winter wheat. High yield variation from year to year confirmed that a site-specific crop management should consider annual variability of yield in addition to soil conditions and yield measurement. Site-specific N fertilization should be adapted to the actual progress of plant growth.     

Benefits of Biochars and NPK Fertilizers for Soil Quality and Growth of Cowpea (Vigna unguiculata L. Walp.) in an Acid Arenosol

Fertilization is required for optimum plant growth, particularly in unfertile soils, while optimizing nutrient use efficiency is an alternative to reduce inorganic fertilizer needs and reduce environmental problems caused by nutrient leaching. This study investigated soil properties and cowpea yield responses to biochars (BCs) made from different feedstocks, baby corn peel biochar (BC1), branches of mango tree biochar (BC2), and rice husk biochar (BC3), applied in combination with nitrogen-phosphorus-potassium (NPK) fertilizers. The experiment was conducted in a greenhouse, using an acid sandy soil (Arenosol) that was submitted for 70 d to the following eight treatments:i) control; ii) full dose of NPK (a commercial compound fertilizer (12-24-12 of N-P₂O₅-K₂O) + urea (46% N)); iii) BC1 + half dose of NPK; iv) BC1 + full dose of NPK; v) BC2 + half dose of NPK; vi) BC2 + full dose of NPK; vii) BC3 + half dose of NPK; and viii) BC3 + full dose of NPK. All biochars were applied at a rate of 0.9% (weight/weight), and each type of biochar was combined with half and full doses of NPK fertilizers. Soil pH increased significantly (P < 0.05) in treatments with BC1 and BC2, while cation exchange capacity (CEC) and available P were higher in the treatments with BC1; BC1 and BC2 also induced higher activity of enzymes related to the P cycle and higher cowpea yield. Similar soil properties and cowpea yield parameters were obtained with the full and half doses of NPK fertilizers for each type of biochar used. In conclusion, biochars in the combination with NPK fertilizers improved soil chemistry and enzymatic activities, allowing reduced fertilizer application and food production costs in the acid soil studied.     

Tolerance of forage legumes to lime‐stabilized sludge

Abstract

Lime‐stabilized sludge (LSS) from dairy processing waste‐water treatment plants is a desirable product for land application. The material contains lime, which neutralizes soil acidity, and P, which is useful as a plant nutrient. The fineness of the lime and the solubility of P make LSS especially desirable in establishing forage legumes. This greenhouse study had two objectives: to determine a reasonable quantity of LSS for establishing forage legumes such as alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) and to prevent adverse effects on seedlings. Sludge was applied at 0, 2.5, 5.0, 7.5 g kg^‐1 to an acid, low P soil in pots, and alfalfa and red clover seeds were sown. All treatments received 123 μg g^‐1 potassium as KCl. A completely randomized design with four replications was used. Each species was handled as a separate study. Dry matter production was measured at one‐tenth bloom stage. Plant samples were analyzed for P, K, Ca, and Mg content. Soil samples taken at the end of the study were analyzed for pH, organic matter, Bray P, K, Ca, Mg, exchangeable Al, EC, and CEC. The higher quantities of LSS (7.5 g kg^‐1 for alfalfa and 5.0 g kg^‐1 for red clover) had negative effects on seedling germination and establishment. Lime‐stabilized sludge resulted in an increase in total nutrient uptake of Ca, Mg, K, and P up to 5.0 and 2.5 g kg^‐1 in alfalfa and red clover, respectively. In both species significant dry matter yield increases were obtained with LSS up to 5.0 g kg^‐1; however, 7.5 g kg^‐1 caused a reduction in dry matter yield. Based on these results, applications of LSS at 5.0 for alfalfa and 2.5 g kg^‐1 for red clover had positive effects in seedling establishment, nutrient uptake, and dry matter production. Lime‐stabilized sludge application resulted in significant increases in soil pH, available P, Ca, Mg, EC, and CEC; decreases were seen in neutralizable acidity and exchangeable Al levels in soil. This study indicates that LSS is appropriate for the acidic, low P soils of Southern Missouri for alfalfa and red clover establishment and production, if applied in appropriate quantities.     

Application of Dolostone Powder as Industrial Residual on Magnesium‐Deficient Arable Soils in Estonia

About 60% (678,000 ha) of Estonian arable soils have a deficiency of plant‐available magnesium (Mg). The soils formed from dolostone (or dolomite rock) till are considerably richer in Mg than those formed from limestone‐rich and noncalcareous tills. Formerly, ground dolostone rock with a high content of mineral dolomite was used only as a soil liming material. Later, dolostone powder (DSP), received in the course of industrial manufacturing of dolostone rubble, was also applied for the mitigation of Mg deficiency in soil. The easily accessible resources of DSP as an industrial waste may also qualify as an Mg fertilizer. It soon became apparent, however, that with the application of DSP to the soil, an excessive quantity of Mg could be accumulated. This Mg surplus in soil destroys the equilibrium in plants' assimilation of nutrition elements and inhibits the normal development of agricultural crops. In our research, the influence of different DSP doses on the yield of red clover (Trifolium pratense L.), lucerne (Medicago sativa L.), barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), and oil rape (Brassica napus L. var. Oleifera subvar. Annua) was studied on arable soils formed from different parent materials. We elucidated from the 2‐year experiment the high efficiency of DSP application in increasing the yields of Mg‐philic crops such as clover, lucerne, and oil rape. The negative influence of excessive Mg application on crop yields, especially in the first year of DSP application, is more clearly visible on soils that are calcium deficient for plant production. For the amendment of deficiency in Mg acid arable soils, 1–1.5 t ha^?1 of DSP should be used every 2 to 3 years. The broad application of industrial‐origin DSP is useful from at least three points of view: (1) industrially produced Mg fertilizers may be replaced by a readily available local industrial (mining) by‐product, (2) managing costs and territories for the disposal of industrial wastes will be reduced, and (3) it will be possible to attain complex and environmentally friendly utilization of local mineral resources.     

Indicators and trade-offs of ecosystem services in agricultural soils along a landscape heterogeneity gradient

Soil functions can be classified as supporting (nutrient cycling) and provisioning (crop production) ecosystem services (ES). These services consist of multiple and dynamic functions and are typically assessed using indicators, e.g. microbial biomass as an indicator of supporting services. Agricultural intensification negatively affects indicators of soil functions and is therefore considered to deplete soil ES. It has been suggested that incorporating leys into crop rotations can enhance soil ES. We examined this by comparing indicators of supporting soil services – organic carbon, nitrogen, water holding capacity and available phosphorous (carbon storage and nutrient retention); net nitrogen mineralisation rate and microbial biomass (nutrient cycling and retention) – in barley fields, leys and permanent pastures along a landscape heterogeneity gradient (100, 500 and 1000 m radii). In addition, barley yields (provisioning service) were analysed against these indicators to identify trade-offs among soil services. Levels of most indicators did not differ between barley and ley fields and were consistently lower than in permanent pastures. Leys supported greater microbial biomass than barley fields. Landscape heterogeneity had no effect on the indicators or microbial community composition. However, landscape heterogeneity correlated negatively with yield and soil pH, suggesting that soils in heterogeneous landscapes are less fertile and therefore have lower yields. No trade-offs were found between increasing barley yield and the soil indicators. The results suggest that soil ES are determined at the field level, with little influence from the surrounding landscape, and that greater crop yields do not necessarily come at the expense of supporting soil services.     

Compost,Manure and Synthetic Fertilizer Influences Crop Yields,Soil Properties,Nitrate Leaching and Crop Nutrient Content

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input. From 1993 to 1998, red clover (Trifolium pratense L.) and crimson clover (Trifolium incarnatum L.) were used as an annual winter legume cover crop prior to maize production. From 1999 to 2001, hairy vetch (Vicia villosa Roth.) served as the legume green manure nitrogen (N) source for maize. In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production. Vegetables received either compost, manure, or fertilizer N inputs. Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre). This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001. When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 10-24 bu/a). Hairy vetch cover cropping also resulted in a 9-25 % increase in wheat yields in the compost treatments compared to clover cover cropping. Hairy vetch cover crops increased both maize and wheat grain protein contents about 16 to 20% compared to the clover cover crop. Compost was superior to conventional synthetic fertilizer and raw dairy manure in 1) building soil nutrient levels, 2) providing residual nutrient support to wheat production, and 3) reducing nutrient losses to ground and surface waters. After 9 years, soil carbon (C) and soil N remained unchanged or declined slightly in the synthetic fertilizer treatment, but increased with use of compost amendments by 16-27% for C and by 13-16% for N. However, with hairy vetch cover crops, N leaching increased 4 times when compared to clover cover crops. September was the highest month for nitrate leaching, combining high rainfall with a lack of active cash crop or cover crop growth to use residual N. Broiler litter leaf compost (BLLC) showed the lowest nitrate leaching of all the nutrient amendments tested (P= 0.05).     

Incorporation of catch crop residues does not increase phosphorus leaching: a soil column experiment in unsaturated conditions

Some studies suggest that incorporation of catch crop residues leads to increased availability of P to plants. However, little information is available on how this affects P leaching in soils with a high P load. We tested the effect of catch‐crop residue incorporation at the end of winter on the P leaching potential in a soil column experiment under unsaturated conditions using a typical sandy loam soil of NW Europe characterized by a high P load. We sampled the catch crops white mustard (Sinapis alba L.), Italian ryegrass (Lolium multiflorum L.), black oats (Avena strigosa L.) and a perennial ryegrass‐white clover mix (Lolium perenne L.‐Trifolium repens L.) from a field trial on catch crops and soil from the plots where they were grown. Plant biomass was incorporated taking account of the differences in conditions of the plant material at the end of winter and the biomass yield of each catch crop. Incorporation of catch‐crop residues decreased P leaching compared to the fallow treatment probably through immobilization of soil P during catch crop residue decomposition. The exception was black oats, where the leaching of P was the same as for fallow soil. We observed clear differences in C/N, C/P, water soluble and total P concentration, and biodegradability between the tested catch crops, which seemed to affect the P leaching. We conclude that the incorporation of catch crop residues under typical soil and weather conditions and agricultural practices of NW Europe does not increase the potential P leaching losses.     

Why short‐term biochar application has no yield benefits: evidence from three field‐grown crops

This study determines the impact of biochar, as a supplement, on soil nutrient availability and yields for three crops within commercial management systems in a temperate environment. Central to the suggestion of biochar benefits is an increase in soil nutrient availability, and here, we test this idea by examining crop nutrient uptake, growth and yields of field‐grown spring barley, strawberry and potato. Biochar produced from Castanea sativa wood was incorporated into a sandy loam soil at 0, 20 and 50 t/ha as a supplement to standard crop management practice. Fertilizer was applied normally for each of the three crops. The biochar contained substantial concentrations of Ca, Mg, K, P, but only K occurred at high concentration in water‐soluble analysis. The large concentration of extractable K resulted in a significant increase of extractable K in soil. The increased availability of K in biochar‐treated soil, with the exception of spring barley grain and the leaves of strawberry during the second year, did not induce greater tissue concentrations. In general, biochar application rate had little influence on the tissue concentration of any nutrient, irrespective of crop or sampling date. There was, however, evidence of a biochar‐induced increase in tissue Mo and a decrease in Mn, in strawberry, which could be linked to soil alkalinization as could the reduction in extractable soil P. These experiments show a single rotational application of biochar to soil had no effect on the growth or harvest yield of any of these field‐grown crops. Heavy metal analysis revealed small concentrations in the biochar (i.e. <10 μg/g biochar), with the largest levels for Ni, V and Cu.     

Soil‐test values after eight years of tillage research on a Norfolk loamy sand

Abstract

Long‐term effects of alternate tillage systems on soil‐test values for Coastal Plain soils were unknown. Therefore, soil pH, organic carbon, and Mehlich I extractable P, K, Ca, and Mg concentrations measured during an eight‐year tillage study on Norfolk loamy sand (fine‐loamy, silicious, thermic, Typic Paleudults) have been summarized. Yields for corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] are also summarized to provide an indication of nutrient removal by the crops. Soil‐test measurements after six years showed no significant differences in Mehlich I extractable nutrient concentrations for the 0‐ to 20‐cm depth between disked (conventional) and nondlsked (conservation) tillage treatments, but for pH, P, Ca, and Mg, the tillage by depth of sampling interaction was significant at P‐0.05. Stratification did not appear to affect crop yield. Soil organic matter concentration in the Ap horizon nearly doubled after eight years of research at this site. This change occurred within both tillage treatments, apparently because high levels of management produced good crop yields, residues were not removed, and even for the disked treatment, surface tillage was not excessive. These results show that long‐term average yields for corn and soybean on Norfolk soil will not be reduced by adopting reduced or conservation tillage practices. They also show that nutrient levels can be maintained at adequate levels for crop production on Coastal Plain soils by using current soil‐test procedures and recommendations for lime and fertilizer application.     

The effect of Ca and K levels on the herbage yield and nutrient composition of barley plants grown in high Mg soils

Abstract

The effects of Ca and K levels on barley (cv. Johnston) yield were studied in soil media containing high levels of Mg. The dry matter yield of barley decreased with increasing concentrations of Mg in soils, but the decrease was small. Dry matter yield was positively related to concentration of K in the soil. However, additions of fertilizer Ca or K did not increase dry matter yield, indicating that depressed yield associated with high Mg levels was not due to reduced availability of Ca or K. In commercial agriculture, applications of either Ca or K to such soils are unlikely to prove beneficial in increasing crop yields.

Concentrations of Mg in soil solutions of unfertilized soils were lower than levels which were previously shown to reduce crop yield. Additions of N fertilizer increased Mg concentrations to levels which could reduce barley yield     

Catch crop strategy and nitrate leaching following grazed grass-clover

Cultivation of grassland presents a high risk of nitrate leaching. This study aimed to determine if leaching could be reduced by growing spring barley (Hordeum vulgare L.) as a green crop for silage with undersown Italian ryegrass (Lolium multiflorum Lam.) compared with barley grown to maturity with or without an undersown conventional catch crop of perennial ryegrass (Lolium perenne L.). All treatments received 0, 60 or 120 kg of ammonium‐N ha^?1 in cattle slurry. In spring 2003, two grass‐clover fields (3 and 5 years old, respectively, with different management histories) were ploughed. The effects of the treatments on yield and nitrate leaching were determined in the first year, while the residual effects of the treatments were determined in the second year in a crop of spring barley/perennial ryegrass. Nitrate leaching was estimated in selected treatments using soil water samples from ceramic cups. The experiment showed that compared with treatments without catch crop, green barley/Italian ryegrass reduced leaching by 163–320 kg N ha^?1, corresponding to 95–99%, and the perennial ryegrass reduced leaching to between 34 and 86 kg N ha^?1, corresponding to a reduction of 80 and 66%. Also, in the second growing season, leaching following catch crops was reduced compared with the bare soil treatment. It was concluded that the green barley/Italian ryegrass offers advantages not only for the environment but also for farmers, for whom it provides a fodder high in roughage and avoids the difficulties with clover fatigue increasingly experienced by Danish farmers.     

Different leguminous pre-crops increased yield of succeeding cereals in two consecutive years

Leguminous pre-crops are an important source of green manure in organic crop rotations for improving soil fertility and achieving high yields of cereals. We aimed to study the potential of various leguminous species, other than the traditionally cultivated red clover (Trifolium pratense L.), as green manure pre-crops for subsequent cereals. The use of different legume species enables to exploit advantages of specific legumes in organic cereal production. In order to test the legumes as pre-crops for cereals, we carried out trials located in the temperate climate zone of northeast Europe (58°44′59.41″ N, 26°24′54.02″ E). We sowed the following perennial legumes as pre-crops: red clover, alsike clover (Trifolium hybridum L.) and Washington lupine (Lupinus polyphyllus Lindl.), biennial white sweet clover (Melilotus albus Medik.) and annual Alexandria clover (Trifolium alexandrinum L.), and crimson clover (Trifolium incarnatum L.). Timothy (Phleum pratense L.) was used as a control. The leguminous pre-crops were followed by three spring cereals (barley, oat and spring wheat) and two winter cereals (rye and winter wheat). We tested the first-year after-effect (all cereals) and second-year after-effect (only barley and oat) of pre-crops on the grain yield of cereals. Perennial and biennial legume species produced the highest dry matter yield and contained the highest amount of nutrients, especially nitrogen, compared to annual species. All subsequent cereals produced significant extra yields after each leguminous pre-crop in the following two years, although the effect was smaller in the second year. The most suitable pre-crops for spring cereals were red and alsike clover followed by lupine, whereas the best pre-crops for winter cereals were sweet clover and annual clovers. Our results show the potential of various leguminous pre-crop species as valuable sources of green manure in organic crop rotation.     

Contributions from carbon and nitrogen in roots to closing the yield gap between conventional and organic cropping systems

This study investigates the effect of different crop rotation systems on carbon (C) and nitrogen (N) in root biomass as well as on soil organic carbon (SOC ). Soils under spring barley and spring barley/pea mixture were sampled both in organic and conventional crop rotations. The amounts of root biomass and SOC in fine (250–253 μ m), medium (425–250 μ m) and coarse (>425 μ m) soil particulate organic matter (POM ) were determined. Grain dry matter (DM ) and the amount of N in harvested grain were also quantified. Organic systems with varying use of manure and catch crops had lower spring barley grain DM yield compared to those in conventional systems, whereas barley/pea showed no differences. The largest benefits were observed for grain N yields and grain DM yields for spring barley, where grain N yield was positively correlated with root N. The inclusion of catch crops in organic rotations resulted in higher root N and SOC (g C/m²) in fine POM in soils under barley/pea. Our results suggest that manure application and inclusion of catch crops improve crop N supply and reduce the yield gap between conventional and organic rotations. The observed positive correlation between root N and grain N imply that management practices aimed at increasing grain N could also increase root N and thus enhance N supply for subsequent crops.     

生物炭和堆肥提高西澳大利亚沙质平原土壤上的作物产量但这种效应是短期的

Sandplain soils on the south coast of Western Australia have low inherent fertility, which is mainly due to poor nutrient retention caused by insufficient clay and organic colloidal material. Previous research has shown the benefits in nutrient levels and retention from adding clay to sandplain soils; however, there is almost no information on the addition of organic amendments. A field experiment was established at the Esperance Downs Research Station, Western Australian, in May 2010, to assess the effects of wheat straw (WS) and chicken manure (CM) biochars and compost with and without phosphorus (P) addition on soil properties and crop production over five growing seasons. The five seasons alternated between winter and summer crops.~The CM and WS biochar and compost treatments significantly increased crop yields and P uptake in 3, 2 and 1 of the five seasons, respectively. The yield increases $(P<0.05)$ were no more than 8\%. By the end of the third season, no differences in crop yields were found that could be attributed to the organic amendments. The addition of P increased crop yields in each winter cropping season. Phosphorus addition explained more than 30\% of the variation in crop yields. Despite marginal P levels and summer drought conditions, arbuscular mycorrhizal root colonisation was not affected by the organic amendments. There were no significant interactions between the organic amendments and P addition in terms of crop yields, P uptake or P uptake efficiency. We conclude that much of the effect of the organic amendments was due to direct nutrient addition which dissipated over time.     

Soil nitrogen and carbon status following clover production in louisiana

Abstract

Field studies were conducted for four to seven years on two soils, Tangi silt loam (Typic Fragiudalf, fine‐silty, mixed, thermic) and Dexter loam (Ultic Hapludalf, fine‐silty, mixed, thermic), to determine the effects of phosphorus (P) applications on growth and nitrogen (N) content of white clover (Trifolium repens L.) and subterranean clover (Trifolium subterranum L.) and on ammonium (NH₄ ⁺)‐ and nitrate (NO₃ ^‐)‐N, total N, and organic carbon (C) levels in the soils at the end of the study. Phosphorus applications consistently and significantly increased forage yields and led to significantly higher N yields by the clovers. Increases in plant yields and N₂‐fixation, however, were not reflected in higher soil N and C levels. On Tangi soil, NH₄ ⁺‐ and NO₃ ^‐‐N levels were lowest where no P was applied but no statistically significant differences (P < 0.05) were found among P rates above 20 kg/ha. On the Dexter soils, no significant differences were found at any P application level. Significant differences due to higher clover yields at increasing P rates were not found in total N or organic C . levels in either soil. Greenhouse evaluations showed no differences in bermuda‐grass yield, N concentration, or total N recovery despite increasing subclover yields in the field during the previous seven years. Harvesting nearly all above ground clover growth caused plant roots to be the major N and C contributor to the soil. It is possible that root production was not increased in proportion to forage production as P applications increased. Perhaps increased microbial activities and some leaching losses also minimized accumulations of N and C released by clover roots.     

Biochar application to soil for climate change mitigation by soil organic carbon sequestration

Pyrogenic carbon (C) is produced by incomplete combustion of fuels including organic matter (OM). Certain ranges in the combustion continuum are termed ‘black carbon' (BC). Because of its assumed persistence, surface soils in large parts of the world contain BC with up to 80% of surface soil organic C (SOC) stocks and up to 32% of subsoil SOC in agricultural soils consisting of BC. High SOC stocks and high levels of soil fertility in some ancient soils containing charcoal (e.g., terra preta de Índio) have recently been used as strategies for soil applications of biochar, an engineered BC material similar to charcoal but with the purposeful use as a soil conditioner (1) to mitigate increases in atmospheric carbon dioxide (CO₂) by SOC sequestration and (2) to enhance soil fertility. However, effects of biochar on soils and crop productivity cannot be generalized as they are biochar‐, plant‐ and site‐specific. For example, the largest potential increases in crop yields were reported in areas with highly weathered soils, such as those characterizing much of the humid tropics. Soils of high inherent fertility, characterizing much of the world's important agricultural areas, appear to be less likely to benefit from biochar. It has been hypothesized that both liming and aggregating/moistening effects of biochar improved crop productivity. Meta‐analyses of biochar effects on SOC sequestration have not yet been reported. To effectively mitigate climate change by SOC sequestration, a net removal of C and storage in soil relative to atmospheric CO₂ must occur and persist for several hundred years to a few millennia. At deeper soil depths, SOC is characterized by long turnover times, enhanced stabilization, and less vulnerability to loss by decomposition and erosion. In fact, some studies have reported preferential long‐term accumulation of BC at deeper depths. Thus, it is hypothesized that surface applied biochar‐C (1) must be translocated to subsoil layers and (2) result in deepening of SOC distribution for a notable contribution to climate change mitigation. Detailed studies are needed to understand how surface‐applied biochar can move to deeper soil depths, and how its application affects organic C input to deeper soil depths. Based on this knowledge, biochar systems for climate change mitigation through SOC sequestration can be designed. It is critically important to identify mechanisms underlying the sometimes observed negative effects of biochar application on biomass, yield and SOC as biochar may persist in soils for long periods of time as well as the impacts on downstream environments and the net climate impact when biochar particles become airborne.     

Changes in Grain Production,Mechanisms for Sale of Grain and Possible Effects on Grain Quality in Lithuania in the Period 1990-1999

The main objective was to compare the response of grain yield to fertiliser N in a winter wheat-white clover intercropping system with the response in wheat alone. Clover was undersown in spring barley and remained established in two consecutive crops of wheat in two field experiments. Clover reduced grain yield in the first crop of wheat and increased it in the second. There was more inorganic N in the soil and a higher concentration of N in the grains in the intercropping system. The grain and N yield response to fertiliser N was equal or less with intercropped than with wheat alone. The reduction of clover biomass with a herbicide increased grain yield of the first crop of wheat without reducing the clover biomass or the positive residual effect in the second wheat crop. It was concluded that in order to produce large grain yields, competition from clover needs to be kept small when wheat is at the tillering stage.     

Sulfuric acid effects on iron and phosphorus availability in two calcareous soils

An attempt was made to study the effects of sulfuric acid additions to iron (Fe)‐ and phosphorus (P)‐deficient calcareous soils. Several greenhouse experiments were conducted with sorghum (Sorghum bicolor L.) grown in two calcareous soils. Addition of sulfuric acid to soils increased soil acidity, salinity, DTPA‐extractable Fe, available P (NaHCO₃‐extractable), and crop yield. The change in soil pH is the primary cause of increased nutrient availability and thus crop yield. Leaching after acid application is highly beneficial in decreasing salinity during germination and seedling stages and therefore has a direct impact on the yield. The beneficial effects of acid carried over for at least two greenhouse cropping seasons (approximately 4.5 months).     

Exchangeable K levels for maximum crop yields on soils of different cation exchange capacities

Abstract

Wide differences in levels of exchangeable K considered adequate for maximum yields in different States are probably a consequence of the acceptance of either a single 200 pp2m rate for 95–987. sufficiency suggested by Bray, or a variable level based on a percentage of the soil cation exchange capacity (CEC) proposed by Bear. It now appears that sufficiency levels should vary with soil CEC, but not merely as a simple percentage of it. Moreover, the relatiorshlp in practice is complicated by such factors as leaching of K from coarse textured soils, and fixation of added K in, and release of native K from, non‐exchangeable forms in soils high in micaceous clay content. Since these influences occur widely in Ohio soils, the need for new field studies was recognized and implemented. Laboratory and growth chamber studies relating K sufficiency to energies of exchange were examined. Also, a new procedure used by the Ohio Soil Testing Laboratory for providing K sufficiency baaed on soil CEC and crop yield and composition is described.