Transformation of Phosphorus in Forest and Savannah Agro-Ecological Alfisols incubated with Different Phosphorus Fertilizers,in Ekiti state,Southwestern Nigeria

Experiments on incubation with phosphorus (P) changes in two Nigerian Alfisols, were evaluated on the effectiveness of P sources (ground phosphate rock, GRP-9% P, Pace-setter Organo-Mineral Fertilizer (PR-fortified P-S-OM, 11% P and single superphosphate, SSP-7.7% P, for reference). All samples were adjusted to water tension measured at M Ψ w = 0.03 MPa. Changes in applied P were evaluated at 2, 6, 12 and 24 weeks after which data were analyzed using analysis of variance and correlations. Over 24 weeks of incubation, SSP transformed mostly into iron (Fe)-bound P and GPR produced the highest inorganic phosphate ions and transformed largely into the soluble and more chemically stable residual P, in both soils. This fraction, had high and positive correlations (r = 0.69, p < 0.05) with soil properties and constituted a major source and sinks of plant available P. Thus, GPR contributing beneficial effects of residual phosphates.     

张家界植烟土壤的有机无机复合状况及其与土壤养分的关系

用傅积平改进法测定了张家界植烟土壤的有机无机复合状况,并分析了其与土壤养分的关系.结果表明:腐殖质的结合形态主要以松结态和紧结态为主,稳结态腐殖质含量最少;土壤复合量与松结态腐殖质、紧结态腐殖质和有机质均呈极显著正相关,有机无机复合度仅与有机质呈显著负相关.3种结合态腐殖质中,松结态与土壤养分(全氮、全磷和有机质)的相关性最高,土壤全钾与腐殖质没有明显的相关性.松结态腐殖质主要是铁、铝键结合的腐殖质,稳结态腐殖质则主要是钙键结合的腐殖质.腐殖质不同形态与土壤pH值、阳离子交换量(CEC)、交换性钙、交换性镁、有效硫和有效铁之间都有着密不可分的联系.     

以水稻为主的种植系统对土壤有机质状况的影响

A long-term simulation experiment was carried out to study the effect of rice-based cropping system, green manure and ground-water level on soil organic matter. Soil organic matter content increased when upland soil was puddled and cropped under submerged conditions. Among all treatments, soil organic matter contents in the treatments of rice-rice-flooded fallow in winter (WF) were the highest, those in the treatments of rice-rice-astragalus (WG) came the second, and those in the treatments of rice-rice-rape (WR) were the lowest. At the same rate of green manure application, the degrees of organo-mineral complexing in soils of treatments WG and WR were higher than those of treatment WF. After 9-year rice cultivation, the state of combination of humus in heavy fraction varied with treatments. The relative content of loosely bonded humus decreased in the order of WR > WG > WF, and it correlated significantly with Se availability.     

菜园土肥力特征及蔬菜硝酸盐污染的调控技术Ⅳ.有机无机肥配合施用对小白菜硝酸盐和亚硝酸盐含量的影响

通过田问小区试验，研究有机肥与化肥配合施用对小白菜硝酸盐和亚硝酸盐含量的影响．结果表明：有机肥与化肥配施，可以明显地降低蔬菜硝酸盐含量，尤以有机肥与化肥施用比例为1：1时产量较高和硝酸盐含量较低，达到了高产优质．     

紫色土发育成的水稻土微团粒结构中有机－无机复合体的性质

This paper deals with characteristics of organo-mineral complexing of microaggregates in the paddy soils developed from purple soils in Sichuan, China. Results show that the contents of organic matter in microaggregates are in the order of 1-0.25 mm > smaller than 0.05 mm > 0.05-0.25 mm. But the organic matter in 1-0.01 mm microaggregates accounts for 68.1%-78.7% of that in soil. The organic matter in < 0.05 mm microaggregates is complexed humus on the whole, of which the degree of organo-mineral complexing varies between 96.1% and 99.5%, which is higher than that of the soil or > 0.05 mm microaggregates. The contents of loosely combined humus and the ratios of loosely and tightly combined humus markedly decline with the size of microaggregates. Flesh soil humus formed from semi-decomposed organic material or organic manure added is combined first with < 0.001 mm clay, and then aggregated with other organic and mineral particles to form larger microaggregates, in which the aging of humus happens at the same time; whereas organic matter of the light fraction is mainly involved in the formation of > 0.05 mm microaggregates.     

耕作方式对黑土有机碳及有机无机复合状况的影响

[目的]研究耕作方式对黑土有机碳数量的变化、有机无机复合度及腐殖质结合形态的影响。[方法]采用设置休闲、玉米连作和玉米—大豆轮作3种耕作方式进行长期定位试验。[结果]不同耕作方式对黑土有机无机复合状况有明显的影响。休闲、连作及轮作均能增加土壤有机碳及其各组分、重组有机碳含量以及原土复合量,提高土壤活性有机碳含量,降低土壤有机碳的氧化稳定性及原土复合度。连作和轮作增加黑土土壤追加复合量和追加复合度,以轮作效果最好。不同耕作方式中各种结合形态的腐殖质在绝对含量上均有明显提高,以松结合态腐殖质增加较多。[结论]轮作更有利于提高土壤HA/FA比值、HA的E4/E6比值、土壤松结合态腐殖质含量及土壤重组腐殖质碳的松/稳和松/紧比值。     

土壤中钙结合和铁铝结合腐殖质的组成及结构特征

Calcium-bound and iron- and aluminium-bound humus extracted from different soils collected from north to south of China were characterized by chemical and spectroscopic methods. Meaningful differences in the composition and structure between them were revealed by ¹³C NMR, visible spectroscopy and elemental analysis. Results showed that the contents of carbon, hydrogen and nitrogen were higher in iron- and aluminium-bound humus than in calcium-bound humus while oxygen content in calcium-bound humus was shown to be higher. The calcium-bound humus had higher C/N and O/C ratios than iron- and aluminium-bound humus. The calcium-bound humic acid (HA1) showed higher E₄/E₆ ratios than iron- and aluminum-bound humic acid (HA2) while iron- and aluminum-bound fulvic acid (FA2) showed higher E₄/E₆ ratios than calcium-bound fulvic acid (FA1). An inverse relationship between E₄/E₆ ratios and aromaticity as determined by ¹³C NMR spectra was observed for HA and FA from black soil. The ¹³C NMR spectroscopy revealed that HA2 was more aromatic than HA1. On the other hand, FA1 exhibited a higher aromaticity than FA2.     

Alkaline hydrolyzable nitrogen and properties that dictate its distribution in paddy soil profiles

Nitrogen (N) is a key nutrient for rice production, and its bioavailability in paddy soils is strongly coupled to soil organic matter (SOM) cycling. A better understanding of potentially available N forms in soil, such as alkaline hydrolyzable N (AH-N), and their depth distribution will support the development of best management practices to improve the N use efficiency of rice while minimizing adverse environmental effects. Fifteen rice (Oryza sativa L.) fields from Southern Brazil were selected, and stratified soil samples were taken to a depth of 60 cm before crop establishment. Selected soil physical and chemical properties were analyzed to evaluate their relationships with AH-N contents in the soil profile. The AH-N contents below 20 cm varied extensively (increased, reduced, or constant) compared with that above 20 cm. Although clay and clay + silt contents were highly correlated to AH-N for some soils, the major property dictating AH-N distribution by depth was total N (TN), as the correlation between TN and AH-N was mainly by direct effect. The proportion of TN recovered as AH-N across sites and depths presented high amplitude, and thus AH-N was not a constant N pool across depths, indicating that AH-N can be affected by soil management practices even when TN showed no major changes. The distinct distribution of AH-N across soil sampling sites and depths indicates that depths greater than 20 cm should be considered when calibrating the AH-N index for N fertilizer recommendations for flooded rice in Southern Brazil.