Crop rotation and seasonal effects on fatty acid profiles of neutral and phospholipids extracted from no‐till agricultural soils

Analysis of phospholipids (PLFA) and neutral lipids fatty acids (NLFA) was used to characterize no‐till productive agricultural soils associated with different crop rotation levels, replicated across a 400 km transect in the Argentinean pampas, during two sampling seasons, summer and winter. High rotation (HR) management consisted in maize–wheat–soybean intense rotation including cover crops. Low rotation (LR) management trend to soybean monocultures. Soils from nearby natural environments (NEs) were used as references. Fatty acids concentration in soils (nmol/g) decreased c.a. 50% from summer to winter differentially according to soil treatment being the smallest decrease in HR management 35%. Both PLFA and NLFA profiles showed strong potential to discriminate between different land uses. In winter samples, some rare or unknown fatty acids were relevant for the discrimination of agricultural practices while NLFA 20:0 appears to be a good marker of HR soils despite season or location. The PLFA‐based taxonomic biomarkers for total bacteria, Gram‐negative bacteria and arbuscular mycorrhiza showed a significant trend NE>HR>LR in the winter sampling. HR management was also characterized by high levels of NLFA in winter samples as if high crop rotation improves lipids reserves in soil during winter more than in monocropping soil management. In conclusion, PLFA and particularly NLFA profiles appear to provide useful and complementary information to obtain a footprint of different soil use and managements, improving soil biochemistry characterization tools.     

Quantifying farmland shelterbelt impacts on catchment soil erosion and sediment yield for the black soil region,northeastern China

As one part of the ‘Three Norths’ forest protection system, dense farmland shelterbelt networks in northeastern China could greatly modify water and sediment flows. In this paper, catchment soil erosion rate and sediment yield (SY) that are impacted by farmland shelterbelts were estimated using WaTEM/SEDEM model. The shelterbelts reduced catchment soil erosion and SY to some extent. The mean soil erosion rate and specific sediment yield (SSY; defined as the ratio of SY to catchment area; t km^?2 yr^?1) of the 25 reservoir catchments decreased from 351.6 and 93.9 t km^?2 yr^?1 under the supposed scenario without shelterbelts to 331.1 t km^?2 yr^?1 and 86.3% t km^?2 yr^?1 under the current situation with shelterbelts. The sediment trap efficiencies (STEs) varied from 0.01% to 23.6% with an average value of 7.6%. The STEs were significantly correlated with shelterbelt density, catchment perimeter, topographic factors, RUSLEP‐factor and land use patterns including patch density (PD), patch cohesion index (COHESION), Shannon's diversity index (SHDI) and aggregation index (AI). The multiple regression equation involving factors of catchment's topography and morphology and land use pattern has a satisfactory performance, and mean slope gradient (MSG) and AI explained most of the variability of shelterbelts’ STE. This information can help land managers to better design shelterbelts and to reduce water‐derived soil loss at catchment scale.     

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.     

Effects of pepper crop residues and inorganic fertilizers on soil properties relevant to carbon cycling and broccoli production

We conducted a two‐year experiment to evaluate the effects of fresh pepper residues (CR treatment) on soil properties and broccoli yield compared with the application of chemical fertilizers (CF treatment). Soil‐state ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopy was used to characterize the organic composition of added residues and surface soil. We also measured total and soluble organic carbon and different biochemical properties associated with the C cycle. The results show that large application rates of CR increased microbial biomass carbon (MBC) and arylesterase and β‐glucosidase activities compared with the control. There was a significant increase in MBC for the CF treatment only with the greatest application rate. No differences in soil organic carbon composition and structure were found between treatments with soil organic C, soluble C, basal soil respiration, arylesterase and β‐glucosidase activities correlated positively with the soil carboxylic region and negatively with the aromatic region of the spectra. Broccoli yield was significantly more for the second crop cycle with maximum values for the greatest application rates of CF and CR indicating that crop residues with a minimum amount of chemical fertilizers can be used to obtain an adequate yield. The use of pepper residues as an organic amendment improved biochemical properties of the soil with positive effects on broccoli quality and had no negative impact on yield.     

Assessment and monitoring of accelerated water erosion of cultivated land – when will reality be acknowledged?

Soil erosion is a key issue in Europe, and strategies to protect soil need to be developed. Hence, eroding soils or those at risk of erosion need to be identified. Much model‐derived information on rates of erosion and on erosion risk of cultivated land may be of dubious value, and thus, there is need for other ways to assess erosion. Field‐based assessment is one approach for assessing and monitoring erosion and gives information that can be used at a variety of scales. In this review paper, the continuing use of models that predict potential erosion is questioned, and it is argued that there is a need for more field‐based assessment and monitoring of water erosion with monitoring at frequent intervals. Such monitoring allows the magnitude of the erosion problem to be assessed properly, and thus, the physical, social and economic factors that drive erosion can be better analysed and addressed. Field‐based erosion monitoring should be undertaken in all global environments, and then the results can be used to validate those from models of potential erosion.     

Changes in the nitrogen localized in the lamellae systems and stroma of rice chloroplast accompanying the stages of growth

The change in the nitrogen localized in the lamellae systems and stroma region of the rice chloroplast was pursued throughout the stages of growth and, further, the relationship between the composition of the chloroplast and leaf N content was examined. A common trend accompanying the stages of growth is recognized: that in the early stages of growth the amount of nitrogen existing as a form of stroma N is larger than that of lamellae N. Thereafter, stroma N tends to decrease in relation to lamellae N and finally, lamellae N becomes a dominant nitrogenous fraction in the chloroplast. The change in the composition of the chloroplast seems to be brought about by a change in the nitrogen metabolism of the chloroplast by which the distribution of absorbed nitrogen among the nitrogenous fractions of the chloroplast differs.     

畜禽粪便中所含尿囊素在土壤中的动态变化及原因分析

采用室内模拟培养试验,研究了畜禽粪便中尿囊素在土壤中含量的动态变化规律.结果表明,畜禽粪便所含尿囊素在土壤中降解快速,但不同种类和用量处理的变化速度和幅度不同.180 d时,鸡粪和猪粪处理降解率可达95.59%、90.83%.降解率与用量呈负相关,与时间呈正相关,其与时间的关系可以用v=A+BInt回归方程拟合.尿囊素...     

Effects of forage type and gibberellic acid on nitrate leaching losses

Nitrogen (N) leaching from soil into water is a significant concern for intensively grazed forage‐based systems because it can cause a decline in water quality and is a risk to human health. Urine patches from grazing animals are the main source of this N. The objective of this study was to quantify the effect that forage type and gibberellic acid (GA) application had on N leaching and herbage N uptake from urine patches on perennial ryegrass–white clover (RGWC), Italian ryegrass and lucerne. A lysimeter study was conducted over 17 months to measure herbage growth, N uptake and N loss to water beneath each of the three forage types with the following treatments: control, urine (700 kg N/ha) and urine with GA (8 g GA active ingredient/ha). Compared with RGWC (205 kg N/ha), N leaching losses were 35.3% lower from Italian ryegrass (133 kg N/ha) and 98.5% higher from lucerne (407 kg N/ha). These differences in leaching loss are likely to be due to winter plant growth and N uptake. During the winter months, Italian ryegrass had higher N uptake, whereas lucerne had lower N uptake, compared with RGWC. The application of GA had no effect on N leaching losses, DM yield or N uptake of forage treated with 700 kg N/ha urine.