Corn response to potassium placement in conservation tillage

Improvements in the yield potential of corn (Zea mays L.) grown using conservation-tillage may depend, in part, on K fertility management. Field research was conducted in 1997 and 1998 on a field which had been in continuous no-tillage (NT) for the previous 12 years near Paris, Ont., Canada to evaluate potassium (KCl) placement effects on corn growth and yields in NT, spring zone-tillage (ZT) and spring mulch-tillage (MT) systems. Soils were classified as moderately well drained and had low soil-test K levels. Potassium was spring-applied (1 day prior to corn planting) at either 0 or 100 kg K ha⁻¹. Potassium was either broadcast applied, deep in-row banded (15 cm deep), or half broadcast applied and half shallow-banded (5 cm beside the row, 5 cm below seeding depth). Early season and mid-season corn ear-leaf K concentrations indicated that spring-applied K fertilizer was available for uptake by corn in conservation-tillage systems. Potassium application sometimes significantly increased corn yields compared to the zero K control in the NT and ZT systems. However, MT corn yields did not show any response to K fertilization in either season despite the low soil-test K levels. There were no significant corn yield increases with deep banding of K fertilizer relative to shallow placement in any tillage system. This study suggests that, for similar low-testing K soils, alternate K placements will have greater impacts on corn plant nutritional status than on final yields. Surface broadcasting of K fertilizer is appropriate for continuous NT corn despite evident K stratification present after long-term NT. MT may improve corn K nutrition after long-term NT.     

茶树钾营养特性的研究

本文对我国主要茶区茶园土壤的含钾状况，茶树品种和土壤水分对茶树吸收钾的影响和茶园施肥钾肥的增产效果进行了系统研究。结果表明，我国有近６０％的茶园土壤处于罐钾状态，这已成为限制茶叶高产优质的主要障碍因子之一。不同品种茶树对钾的吸收具有明显差异，它们对钻的最大速率Ｖｍａｘ为龙井４３＞碧云＞苹云＞碧峰＞菊花春，米氏亲和常数Ｋｍ为碧峰＞碧云＞龙井４３＞苹云＞菊花春。干旱处理的茶树体内累积的钾和叶片的含钾量     

Effect of Catch Cropping on Phosphorus Bioavailability in Comparison to Organic and Inorganic Fertilization

ABSTRACT

Phosphorus (P) is a limited resource and its efficient use is a main task in sustainable agriculture. In a 3-year field experiment the effects of catch cropping [oil radish (Raphanus sativus), buckwheat (Fagopyrum esculentum), serradella (Ornithopus sativus), ryegrass (Lolium westerwoldicum), and phacelia (Phacelia tanacetifolia)] of organic fertilization (cattle manure and biowaste compost) and of inorganic fertilization (Triple-Superphosphate) on plant and soil parameters were investigated on a P-poor loamy sand in Northeast Germany. The catch crops were sown in September and remained on the plots until next spring. Then the main crops oilseed rape (Brassica napus), spring barley (Hordeum vulgare), or spring wheat (Triticum aestivum) were cultivated. The yield and P uptake of the main crops were determined. Furthermore, in the soil the organic matter content, pH, phosphorus (P) in soil solution (Psol), double-lactate and oxalate P content, P sorption capacity, and degree of P saturation were measured. All applied forms of fertilizer affected the P contents in soil and the yields and P uptakes of main crops. For green fertilization especially phacelia was found to contribute to the P supply of the main crops, since it increased the P uptake as well as the P contents in soil significantly. The cultivation of ryegrass led to a reduction of the P availability in soil. For example, in average of the three years the Psol content was 0.35 mg L^{? 1}when phacelia was cultivated and 0.22 mg L^{? 1} when ryegrass was cultivated. The cultivation of phacelia had a comparable effect on soil and plant parameters as the organic and mineral fertilization. An improved P availability and P utilization by catch cropping can reduce the need for external P input which may help to save the limited P resources worldwide.     

产ACC脱氨酶植物根际促生菌的筛选及其对修复植物高羊茅生长的影响

以1-氨基环丙烷-1-羧酸(ACC)为唯一氮源,从石油污染的土壤中分离得到一株具有ACC脱氨酶活性的菌株D5A.该菌在以ACC为唯一氮源条件下,其ACC脱氨酶比活力为0.084 U/mg.另外,D5A还具有产生吲哚乙酸(IAA)、耐盐以及溶磷的特性.在液体培养条件下该菌株产IAA高达112 mg/L,在90 g/kg盐含量的培养基中仍能够正常生长且具有较强的溶解矿物磷能力.同时该菌对酸碱具有良好的适应性,在初始pH4～10的LB培养基中生长良好.种子发芽试验表明在3 g/kg和6 g/kg浓度NaC1的逆境条件下,该菌株能显著提高高羊茅种子的发芽率和芽长.最后,通过对其进行生理生化特性和16S rDNA序列分析,该菌株初步鉴定为克雷伯氏菌(Klebsiellasp.).     

Modeling soil metabolic processes using isotopologue pairs of position-specific C-labeled glucose and pyruvate

Most organic carbon (C) in soils eventually turns into CO₂ after passing through microbial metabolic pathways, while providing cells with energy and biosynthetic precursors. Therefore, detailed insight into these metabolic processes may help elucidate mechanisms of soil C cycling processes. Here, we describe a modeling approach to quantify the C flux through metabolic pathways by adding 1-¹³C and 2,3-¹³C pyruvate and 1-¹³C and U-¹³C glucose as metabolic tracers to intact soil microbial communities. The model calculates, assuming steady-state conditions and glucose as the only substrate, the reaction rates through glycolysis, Krebs cycle, pentose phosphate pathway, anaplerotic activity through pyruvate carboxylase, and various biosynthesis reactions. The model assumes a known and constant microbial proportional precursor demand, estimated from literature data. The model is parameterized with experimentally determined ratios of ¹³CO₂ production from pyruvate and glucose isotopologue pairs. Model sensitivity analysis shows that metabolic flux patterns are especially responsive to changes in experimentally determined ¹³CO₂ ratios from pyruvate and glucose. Calculated fluxes are far less sensitive to assumptions concerning microbial chemical and community composition. The calculated metabolic flux pattern for a young volcanic soil indicates significant pentose phosphate pathway activity in excess of pentose precursor demand and significant anaplerotic activity. These C flux patterns can be used to calculate C use efficiency, energy production and consumption for growth and maintenance purposes, substrate consumption, nitrogen demand, oxygen consumption, and microbial C isotope composition. The metabolic labeling and modeling methods may improve our ability to study the biochemistry and ecophysiology of intact and undisturbed soil microbial communities.     

厩肥、秸秆和绿肥的含钾状况及其对土壤和作物钾素的供应能力

以常用有机肥料牛厩肥、猪厩肥、鸡粪及作物秸秆、油菜绿肥为材料，研究了这些有机物的全钾、速效钾和缓效钾的含量状况，以及它们对土壤钾及作物吸钾的供应能力。结果表明：（１）三种有机烘肥及作物秸秆、绿肥中含钾量为０．８５％～４．５０％，其中有３２．７％～６９．７％为速效态钾，１．７％～２５．０％为缓效态钾；（２）肥料与土壤共同培养１５０ｄ后，约有５０％～８０％的速效态钾和缓效态钾仍以两种形态存在于土壤之中     

钾对小麦旗叶蛋白水解酶活性和籽粒品质的影响

利用强筋冬小麦品种烟农15研究了钾素对小麦旗叶蛋白质含量和籽粒品质及有关酶活性的影响. 结果表明, 钾素有利于提高灌浆前期和中期小麦旗叶中可溶性蛋白质和游离氨基酸的含量, 增强内肽酶和羧肽酶的活性, 促进籽粒中游离氨基酸转化为蛋白质, 提高籽粒中清蛋白、球蛋白、醇溶蛋白和谷蛋白的含量, 改善籽粒营养品质和加工品质     

固氮肺炎克氏杆菌的产酸和解磷能力

本文报道了549、258属于肺炎克氏杆菌的这一类联合固氮细菌具有产酸解磷的能力.549在培养过程中能产生多种有机酸成分,使无机磷的有效性提高.它还能利用卵磷脂这种有机磷作为自己的磷源,在其培养过程中产酸量有一定限度,达到一定酸度时,培养环境中的酸基本上就不再增加,维持在一个相对稳定的水平.549、258产酸解磷的结果能够改善植物的磷素营养,从非豆科植物根际联合固氮的研究角度考虑,可以认为产酸的联合固氮细菌具有固氮和解磷的双重性.     

木炭和磷矿石改良堆肥作为玉簪栽培基质研究

为了减少我国花卉无土栽培领域对泥炭资源的依赖,提高园林废弃物的资源化再利用率,以园林废弃物堆肥基质为原材料,木炭和磷矿石为堆肥基质改良剂,选取9种不同混合比例的木炭和磷矿石,添加于园林废弃物堆肥基质中,探讨木炭和磷矿石作为堆肥基质改良剂的协同增效作用以及改良后的堆肥基质作为玉簪栽培基质的可行性。通过对不同处理的堆肥基质理化性质、养分含量和发芽试验,以及对玉簪生物量、叶片光合色素含量和其他生长指标的测定与分析,得出木炭和磷矿石改良园林废弃物堆肥基质的效果显著,最优处理为添加10%木炭和25%磷矿石的园林废弃物堆肥基质。其中,与未添加改良剂的堆肥基质相比,最优处理的堆肥基质容重、pH、电导率分别从0.581g/cm~3、7.64、0.70 mS/cm降低至0.321g/cm~3、6.21、0.38mS/cm,总孔隙度、饱和含水量、阳离子交换量分别从55.32%、56.45%、65.83cmol/kg升高至86.54%、83.95%、131.98cmol/kg,氮、磷、钾含量分别从1.11%、0.03%、0.21%升高至3.02%、0.42%、0.84%;同时,最优处理的堆肥基质栽培下的玉簪总鲜重、总干重、总叶绿素含量分别从349g、76g、7.62 mg/g升高至620g、208g、13.73mg/g。由此可知,木炭和磷矿石作为堆肥基质改良剂不仅可以调节堆肥基质理化性质,增加其养分含量,还可以提高花卉品质和产量。     

Recycled iron phosphate as a fertilizer raw material for tree stands on drained boreal peatlands

Fertilization of drained peatland forests with easily soluble or slow-release apatite fertilizers can increase phosphorus (P) export to water courses, especially when the soil is low in aluminum (Al) and iron (Fe) hydroxides and oxides. Application of Al and Fe together with P increases P adsorption to the soil and decreases the risk of leaching. The aim of this study was to investigate the use of recycled iron phosphate (rFePO₄) as forest fertilizer raw material from environmental and forest production perspectives. Trial fertilizers with different mixtures of rFePO₄ and Russian Kola apatite (Kap) were applied on 15 mini-catchments (area 100 m²), where the discharge at the outlet was collected, sampled and analyzed throughout the about 4-year measurement period. The foliage P content and height growth of the trees on the mini-catchments were measured. The biomass growth of the extramatrical mycorrhizal mycelia (EMM) was studied with a separate in-growth mesh bag experiment conducted on the same site. The results indicated no increase in phosphorus export to surface waters after application of rFePO₄ and 25/75 and 50/50 mixtures of rFePO₄ and Kap. In contrast to earlier studies showing a relatively high P export with different types of apatite fertilizers, the Kap fertilizer showed only minor phosphorus export. The height growth measurements and needle analyses of the juvenile Scots pine stands indicated poor P availability from pure rFePO₄, but the P availability from the 50/50 and 25/75 mixtures of rFePO₄ and Kap was similar to pure Kap. The mixtures of Kap and rFePO₄ enhanced the EMM biomass by 2- to 3-fold, whereas Kap and rFePO₄ alone, and high P availability (superphosphate) had no significant effect compared to non-P controls. The increase in EMM biomass as induced by concurrent application of Kap and rFePO₄ was not clearly reflected in tree growth and P acquisition. However, longer follow-up studies than in this one may be needed in order to verify the effect of increased EMM biomass on mycorrhizal mycelia mediated nutrient uptake and tree growth.