Stephen J. Herbert

Spatial Variability of Nutrient Properties in Black Soil of Northeast China

A total of 1400 soil samples from the plow layer (0-20cm) at an approximate interval of 5km were collected in the autumn of 2002 over the entire black soil arable crops region to determine the spatial variability of seven variables, such as total organic matter content (OMC), total N, total P, total K, alkali-dissolvable N (AN), available P (AP) and available K (AK), with classical statistics and geostatistical analysis across the entire black soil area in Northeast China. In nonsampled areas ordinary kriging was utilized for interpolation of estimated nutrient determinations. Classical statistics revealed highly significant (P≤0.01) correlations with all seven of the soil properties, except for OMC with AP and total K with AK. In addition, using coefficients of variation, all soil properties, except for total K, were moderately variable. A geostatistical analysis indicated that structural factors, such as parent material, terrain, and water table, were the main causes of the spatial correlations. Strong spatial correlations were noted with OMC, total N, total P, AN, and AP, while they were moderate for total K and AK. The effective spatial autocorrelation of OMC, total N, total P, and AN ranged from 1037 to 1353km, whereas the ranges of total K, AP, and AK were only from 6 to 138km. The fit of the experimental semi-variograms to the theoretical models indicated that except for AN, kriging could successfully interpolate other six variables. Thus, the geostatistical method used on a large scale could accurately evaluate the spatial variability of most black soil nutrient properties in Northeast China.

Sorption of antibiotic sulfamethoxazole varies with biochars produced at different temperatures

Sorption of sulfonamides on biochars is poorly understood, thus sulfamethoxazole (SMX) sorption on biochars produced at 300-600 °C was determined as a function of pH and SMX concentration, as well as the inorganic fractions in the biochars. Neutral SMX molecules (SMX(0)) were dominant for sorption at pH 1.0-6.0. Above pH 7.0, although biochars surfaces were negatively-charged, anionic SMX species sorption increased with pH and is regulated via charge-assisted H-bonds. SMX(0) sorption at pH 5.0 was nonlinear and adsorption-dominant for all the biochars via hydrophobic interaction, π-π electron donor-acceptor interaction and pore-filling. The removal of inorganic fraction reduced SMX sorption by low-temperature biochars (e.g., 300 °C), but enhanced the sorption by high-temperature biochars (e.g., 600 °C) due to the temperature-dependent inorganic fractions in the biochars. These observations are useful for producing designer biochars as engineered sorbents to reduce the bioavailability of antibiotics and/or predict the fate of sulfonamides in biochar-amended soils.

Characteristics and nutrient values of biochars produced from giant reed at different temperatures.

To investigate the effect of pyrolysis temperature on properties and nutrient values, biochars were produced from giant reed (Arundo donax L.) at 300-600°C and their properties such as elemental and mineral compositions, release of N, P and K, and adsorption of N and P were determined. With increasing temperatures, more N was lost and residual N was transformed into heterocyclic-N, whereas no P and K losses were observed. P was transformed to less soluble minerals, resulting in a reduction in available-P in high-temperature biochars. A pH of⩽5 favored release of NH(4)(+), PO(4)(3-) and K(+) into water. Low-temperature biochars (⩽ 400°C) showed appreciable NH(4)(+) adsorption (2102mgkg(-1)). These results indicate that low-temperatures may be optimal for producing biochar from giant reed to improve the nutrient availability.

Nutrient removal by corn grain harvest

for crop nutrient removal are an important component of nutrient management planning and crop production. Effective nutrient management requires an accurate accounting of Although state agronomy guides and other sources nutrients removed from soils in the harvested portion of a crop. Because the typical crop nutrient values that have historically been used often publish values for crop nutrient removal, the origimay be different under current production practices, a study was nal studies on which those values are based are seldom conducted to measure nutrient uptake in grain harvested in 1998 and cited. Also, the values that were established in the past 1999 from 23 site-years in the Mid-Atlantic region of the USA. There may not be correct for current agronomic technologies were 10 hybrids included in the study, but each site grew only one such as hybrid, higher plant population, yield potential, hybrid each year. Corn (Zea mays L.) production practices followed fertilizer practice, and soil conditions. Furthermore, local state extension recommendations. Minimum, maximum, and there is a need to re-evaluate crop nutrient removal mean corn grain yields were 4.9, 16.7, and 10.3 Mg ha 1. Nutrient values for corn as several states in the Mid-Atlantic concentrations were determined on grain samples oven-dried at 70 C USA now mandate the development of comprehensive for 24 h. Minimum, maximum, and median nutrient concentration nutrient management plans (Simpson, 1998; Sims, 1999; values were as follows: 10.2, 15.0, and 12.9 g N kg 1; 2.2, 5.4, and 3.8 g P kg 1; 3.1, 6.2, and 4.8 g K kg 1; 0.13, 0.45, and 0.28 g Ca kg 1; 0.88, Pennsylvania State Conservation Commission, 1997). 2.18, and 1.45 g Mg kg 1; 0.9, 1.4, and 1.0 g S kg 1; 9.0, 89.5, and Nutrient removal values are a key component of nutri33.6 mg Fe kg 1; 15.0, 34.5, and 26.8 mg Zn kg 1; 1.0, 9.8, and 5.3 mg ent management planning because manure nutrient apMn kg 1; 1.0, 5.8, and 3.0 mg Cu kg 1; and 2.3, 10.0, and 5.5 mg B plications are being limited to the expected level of crop kg 1. Median nutrient uptake values found in this study are similar nutrient removal. to commonly used book values, but there was considerable variation The large volume of manure generated by concenamong samples of corn grain. Concentrations of P and K in grain trated animal-feeding operations in the Mid-Atlantic were positively associated with yield level, and concentrations of grain region and the environmental concerns associated with P were positively correlated with Mehlich-3 soil test P. The variability accumulation of soil P to excessive levels (Sims, 1998) in nutrient removal values seen in this study, even for the same hybrid, have focused much attention on P in nutrient manageraises questions about the usefulness of average values for estimating crop nutrient removal across a range of cropping conditions. Research ment planning. Until recently, manure application recomis needed to identify or develop a means to correct for the sources mendations were designed to match the N requirements of variability. of the crop, often leading to manure P applications in excess of crop removal. While at present, there is emphasis on P-based nutrient management planning, other F the viewpoint of sustainable agriculture, nutrinutrients may receive greater attention in the future. ent management ideally should provide a balance The objective of this study was to measure nutrient between nutrient inputs and outputs over the long term (N, P, K, S, Ca, Mg, Zn, Mn, Cu, B, and Fe) removal (Bacon et al., 1990). In the establishment of a sustainable by corn grain over a range of growing conditions in system, soil nutrient levels that are deficient are built the Mid-Atlantic region and to determine if nutrient up to levels that will support economic crop yields. To concentrations in grain were related to crop yield. The sustain soil fertility levels, nutrients that are removed study was conducted as part of a larger regional project by crop harvest or other losses from the system must on P fertility research. This allowed us to also examine be replaced annually or at least within the longer crop the relationship between soil test level and crop removal rotation cycle. When nutrient inputs as fertilizer, maof P. nure, or waste materials exceed crop removal over a period of years, soils become oversupplied and nutrient MATERIALS AND METHODS leaching and runoff become an environmental concern We grew corn in five states (Delaware, Massachusetts, (Daniel et al., 1998; Sims et al., 1998). Accurate values Maryland, New Jersey, and Pennsylvania) in 1998 and 1999 for a total of 23 site-years (Table 1). Sites were selected to J.R. Heckman, Dep. of Plant Biol. and Pathology, 59 Dudley Rd., represent the wide range of soils (Alfisols and Ultisols) and Foran Hall, Cook College, New Brunswick, NJ 08901-8520; J.T. Sims, P fertility levels within the Mid-Atlantic region. They included Dep. of Plant Sci., Univ. of Delaware, Newark, DE 19717-1303; D.B. both on-farm and research station land. Local recommendaBeegle, Dep. of Crop and Soil Sci., 116 Agric. Sci. Bldg., University tions guided cultural practices. Starter fertilizer at all sites Park, PA 16082; F.J. Coale, Nat. Resour. Sci. and Landscape Architecsupplied 15 kg P ha 1 in the form of monoammonium phosture, Univ. of Maryland, 214 H J Patterson Hall, College Park, MD phate. Spacing between rows was 0.76 m. We measured yields 20742; S.J. Herbert, Dep. of Plant and Soil Sci., Univ. of Massachusetts, from a harvested area of two 6-m rows in the middle of each Amherst, MA 01003; T.W. Bruulsema, Potash and Phosphate Inst., 18 of four replicated plots. Harris Laboratory, Lincoln, NE, anaMaplewood Drive, Guelph, ON, Canada N1G 1L8; and W.J. Bamka, Rutgers Coop. Ext. of Burlington County, 49 Rancocas St., Mount lyzed grain samples that were collected from each plot. They Holly, NJ 08060-1317. Received 2 May 2002. *Corresponding author were oven-dried at 70 C and ground in a Wiley mill to pass (heckman@aesop.rutgers.edu). Abbreviations: M3P, Mehlich-3 phosphorus. Published in Agron. J. 95:587–591 (2003).

Soil Organic Carbon Dynamics in Black Soils of China Under Different Agricultural Management Systems

Cultivation can reduce soil organic carbon (SOC) content and lead to soil deterioration, but some agricultural management systems may increase SOC content and soil productivity. This research examined the SOC dynamics during a 50-year cultivation and how long-term agricultural management practices influenced SOC content in a typical black soil (Mollisol) region of P.R. China. The experiments selected four areas with different cultivation periods: uncultivated, five years, fourteen years, and fifty years. In addition, four long-term agricultural managements were initiated in 1992: conventional wheat–soybean rotation, wheat–sweet clover rotation, wheat–soybean rotation with addition of pig manure, and wheat–soybean rotation with addition of wheat straw. The SOC content declined rapidly at early years of cultivation and gradually afterwards. Wheat–soybean rotation with addition of wheat straw or pig manure resulted in a substantial increase in SOC content in 9 years. Thus, proper soil management can improve soil quality and health by increasing SOM content, and mitigate the greenhouse effect by sequestrating carbon dioxide from the atmosphere as indicated by the significant increase of organic carbon content in soil.

Fifteen years of research examining cultivation of continuous soybean in northeast China: A review

This paper reviews aspects of research on continuous soybean for the last 15 years in northeast China. Growth and development including changes of root nodule number and LAI are described, and reduction in yield and seed quality are discussed. The effects on physiological and biochemical processes, soil rhizosphere microbes, and soil properties are reviewed; and roles of root diseases, insect pests, and root exudates or plant residuals are discussed. Farm practices for alleviating effects on yield reduction are provided, and a diagram of the interaction among factors involved in continuous soybean yield reduction is presented.

Characterization and influence of biochars on nitrous oxide emission from agricultural soil

Extensive use of biochar to mitigate N(2)O emission is limited by the lack of understanding on the exact mechanisms altering N(2)O emissions from biochar-amended soils. Biochars produced from giant reed were characterized and used to investigate their influence on N(2)O emission. Responses of N(2)O emission varied with pyrolysis temperature, and the reduction order of N(2)O emission by biochar (BC) was: BC200 ≈ BC600 > BC500 ≈ BC300 ≈ BC350 > BC400. The reduced emission was attributed to enhanced N immobilization and decreased denitrification in the biochar-amended soils. The remaining polycyclic aromatic hydrocarbons (PAHs) in low-temperature biochars (300-400 °C) played a major role in reducing N(2)O emission, but not for high-temperature biochars (500-600 °C). Removal of phenolic compounds from low-temperature (200-400 °C) biochars resulted in a surprising reduction of N(2)O emission, but the mechanism is still unknown. Overall, adding giant reed biochars could reduce N(2)O evolution from agricultural soil, thus possibly mitigating global warming.

Assessment of herbicide sorption by biochars and organic matter associated with soil and sediment

Sorption of two herbicides, fluridone (FLUN) and norflurazon (NORO), by two types of biochars, whole sediment, and various soil/sediment organic matter (OM) fractions including nonhydrolyzable carbon (NHC), black carbon (BC) and humic acid (HA) was examined. The single-point organic carbon (OC)-normalized distribution coefficients (K(OC)) of FLUN and NORO at low solution concentration (C(e)=0.01S(W), solubility) for HA, NHC, and BC were about 3, 14, and 24 times and 3, 16, and 36 times larger than their bulk sediments, respectively, indicating the importance of different OM fractions in herbicide sorption. This study revealed that aliphatic moieties of the hydrothermal biochars and aromatic moieties of NHC samples, respectively, were possibly responsible for herbicide sorption. The hydrothermal biochar and condensed OM (i.e., NHC and BC) showed relatively high or similar herbicide sorption efficiency compared to the thermal biochar, suggesting that the hydrothermal biochar may serve as an amendment for minimizing off-site herbicide movement.

Using ground-penetrating radar to detect layers in a sandy field soil

Abstract Pollutant transport in sandy soils can be very complex due to the presence of coarse sand lenses. Water flows laterally over the coarse material and, subsequently, breakthrough occurs in concentrated pathways, called fingers. This (funneled) flow process is a form of preferential flow reducing solute travel time and degradation of organic chemicals. In this paper, we test ground-penetrating radar (GPR) as a tool for detecting layers in the soil. Several GPR transects were established on a fine sandy loam soil throughout the growing season and subsequent fall period to find the best time to reveal layer structures. The effect of the spatially varying moisture content on the radar velocity was determined from actual measurements with soil samples and by using the Common Mid-Point (CMP) technique. The optimal time to find coarse layers with GPR in this soil was at the end of the fall season when the soil was wetted and evaporation had decreased. The depth of layers, as indicated by GPR, was highly sensitive to the soil moisture content and could be in error by as much as ±0.4 m on a depth scale of 1.5 to 2 m if an average propagation velocity was used. A satisfactory depth prediction of textural interfaces was obtained non-destructively by collecting data in both reflection and CMP mode.

Effects of Long‐Term Continuous Cropping, Tillage, and Fertilization on Soil Organic Carbon and Nitrogen of Black Soils in China

Abstract Cultivation and tillage practices alter soil properties and often lead to decline of soil quality. Adoption of appropriate agricultural management systems, however, may maintain soil productivity. This research examined the effects of long‐term continuous cropping, tillage, and fertilization on soil organic carbon (C) and nitrogen (N) contents of black soils in China. Soil samples from 11‐year tillage, 11‐year continuous cropping, and 16‐year fertilization experiments were analyzed. Soil organic carbon (SOC) and N declined with depth in all treatments. Compared with a wheat‐corn‐soybean rotation, continuous cropping of wheat, corn, or soybean reduced SOC and N contents, particularly SOC content. Continuous cropping of corn reduced SOC more than that of soybean or wheat in topsoil layers. Moldboard plowing significantly reduced SOC and N contents, whereas integrated tillage (i.e., moldboard plow for wheat, deep tillage (subsoiling) for soybean, and rotary tillage for corn) increased SOC and N relative to conventional tillage. Use of chemical fertilizers [N, phosphorus (P), and potassium (K)] along with return of crop residues resulted in a substantial increase in SOC and N in topsoil layers. It is proposed that the best management for maintaining soil productivity in the study area would be crop rotation along with the integrated tillage and addition of crop residues and chemical fertilizers.