Long term fertilization effects on soil organic carbon pools in a sandy loam soil of the Indian sub-Himalayas

An understanding of the dynamics of soil organic carbon (SOC) as affected by farming practices is imperative for maintaining soil productivity and mitigating global warming. Results of a long-term (32 years) experiment in the Indian Himalayas under rainfed soybean (Glycine max L.)- wheat (Triticum aestivum L.) rotation was analyzed to determine the effects of mineral fertilizer and farmyard manure (FYM) application at 10 Mg?ha^-1 on SOC stocks and depth distribution of the labile and recalcitrant pools of SOC. Results indicate all treatments increased SOC contents over the control. The annual application of NPK significantly (P?<?0.05) enhanced total SOC, oxidizable soil organic C and its fractions over the control plots. The increase in these SOC fractions was greater with the NPK + FYM treatment. Nearly 16% (mean of all treatments) of the estimated added C was stabilized into SOC both in the labile and recalcitrant pools, preferentially in the 0?C30 cm soil layer. However, the labile:recalcitrant SOC ratios of applied C stabilized was largest in the 15?C30 cm soil layer. About 62% of total SOC was present in the labile pool. Plots under the N + FYM and NPK + FYM treatments contained a larger proportion of total SOC in the recalcitrant pool than the plots with mineral or no fertilizer, indicating that FYM application promoted SOC stabilization.     

Impact of long-term additions of chemical fertilizers and farm yard manure on carbon and nitrogen sequestration under rice-cowpea cropping system in semi-arid tropics

Restoration of soil organic carbon (SOC) in arable lands represents potential sink for atmospheric CO₂. The strategies for restoration of SOC include the appropriate land use management, cropping sequence, fertilizer and organic manures application. To achieve this goal, the dynamics of SOC and nitrogen (N) in soils needs to be better understood for which the long-term experiments are an important tool. A study was thus conducted to determine SOC and nitrogen dynamics in a long-term experiment in relation to inorganic, integrated and organic fertilizer application in rice-cowpea system on a sandy loam soil (Typic Rhodualf). The fertilizer treatments during rice included (i) 100% N (@ 100 kg N ha^?1), (ii) 100% NP (100 kg N and 50 kg P₂O₅ ha^?1), (iii) 100% NPK (100 kg N, 50 kg P₂O₅ and 50 kg K₂O ha^?1) as inorganic fertilizers, (iv) 50% NPK + 50% farm yard manure (FYM) (@ 5 t ha^?1) and (v) FYM alone @ 10 t ha^?1 compared with (vi) control treatment i.e. without any fertilization. The N alone or N and P did not have any significant effect on soil carbon and nitrogen. The light fraction carbon was 53% higher in NPK + FYM plots and 56% higher in FYM plots than in control plots, in comparison to 30% increase with inorganic fertilizers alone. The microbial biomass carbon and water-soluble carbon were relatively higher both in FYM or NPK + FYM plots. The clay fraction had highest concentration of C and N followed by silt, fine sand and coarse sand fractions in both surface (0–15 cm) and subsurface soil layers (15–30 cm). The C:N ratio was lowest in the clay fraction and increased with increase in particle size. The C and N enrichment ratio was highest for the clay fraction followed by silt and both the sand fractions. Relative decrease in enrichment ratio of clay in treatments receiving NPK and or FYM indicates comparatively greater accumulation of C and N in soil fractions other than clay.     

Effect of inorganic fertilizer and farmyard manure on soil physical properties, root distribution, and water-use efficiency of soybean in Vertisols of central India

A field experiment was conducted on a Vertisol for three consecutive years (1998-2000) to study the effects of combined use of inorganic fertilizer (NPK) and organic manure (farmyard manure) on soil physical properties, water-use efficiency, root growth and yield of soybean [Glycine max (L.) Merr.] in a soybean-mustard cropping system. Application of 10 Mg farmyard manure and recommended NPK (NPK+FYM) to soybean for three consecutive years improved the organic carbon content of the surface (0-15 cm) soil from an initial value of 4.4 g kg(-1) to 6.2 g kg(-1) and also increased seed yield and water-use efficiency by 103% and 76%, respectively, over the control. The surface (0-15 cm) soil of the plots receiving both farmyard manure and recommended NPK had larger mean weight diameter (0.50 mm) and a higher percentage of water stable aggregates (55%) than both the inorganically fertilized (NPK) (0.44 mm and 49%) and unfertilized control plots (0.41 mm and 45.4%). The saturated hydraulic conductivity (13.32 x 10(-6) m s(-1)) of the NPK+FYM treatment of the 0-7.5 cm depth was also significantly greater than that of the NPK (10.53 x 10(-6) m s(-1)) and control (8.61 x 10(-6) m s(-1)) treatments. The lowest bulk density (1.18 Mg m(-3)) in the 0-7.5 cm layer was recorded in NPK+FYM whereas it was highest in the control plots (1.30 Mg m(-3)). However, at sub-surface (22.5-30 cm) layer, fertilizer and manure application had little effect on bulk density and saturated hydraulic conductivity. Root length density (RLD) up to the 30 cm depth was highest in the NPK+FYM plots and it was 31.9% and 70.5% more than NPK and control plots. The RLD showed a significant and negative correlation (r=-0.88( * *)) with the penetration resistance.     

不同生育时期增铵营养对小麦生长及氮素利用的影响

通过两年的田间试验,研究了不同生育时期增铵营养(EAN)对小麦生长和氮素利用的影响．结果表明,田间增铵营养促进了小麦植株的生长和氮素吸收．其中基肥、分蘖期、拔节期EAN提高了小麦的干物质积累量、地上部氮积累量、有效穗数、叶面积指数、叶片叶绿素含量以及小麦的籽粒产量;孕穗期EAN效果不明显;全生育期EAN在促进生长方面的效果并无明显优势,但可有效降低土壤NO3^--N的淋溶损失．与对照相比,EAN提高了氮流效率和吸收效率,但以拔节前处理最为明显．拔节期EAN主要在于改善后期的叶片光合性能,并促进同化物向籽粒的再分配,而基肥和分蘖期EAN主要在于提高有效分蘖数．     

Survey of weed composition befor maize sowing in long-term fertilization experiment

The study was carried out in a long-term fertilization field experiment of the Experimental Station of University of Pannonia, Department of Crop Science and Soil Science in 2006. The Long-term fertilization experiment was set up in 1983. In the experiment, the success of the weeds ability to grow under the influence of NPK, NPK + FYM* and NPK + straw treatments was compared, and the effect of increasing Nitrogen dosing on weediness was studied. The bifactorial test was arranged in split plot design with three replications. Treatment A: nutrient: NPK, NPK + 35 t/ha FYM* and NPK + straw manure. Treatment B: N kg/ha(-1) N0-N4 (0, 70, 140, 210, 280), and 100 kg P2O5 ha(-1) & 100 kg K20. The weed survey was made on 2nd of May 2006. There were spraying no herbicide until the survey. For the weed survey the Balázs-Ujvárosi coenological method was applied. Altogether, we have found 23 weed species in the trial. In the NPK treatment there were 20 species, in the treatment NPK+organic manure there were 17 species and in the NPK+ stalk rest treatment there were 16 weed species. The most dominant of the weeds on the NPK and NPK+straw manure treatments was Veronica hederifolia while on the fertilizer + FYM, the A. theophrasti was most dominant. The average weed covering value of the treatment NPK + FYM was 1.36 times higher (10.87%) than that of treatment NPK only (7.97%) and 3.65 times higher than on the NPK + straw manure treatment.     

Long-Term Effect of Manure and Fertilizer on Soil Organic Carbon Pools in Dryland Farming in Northwest China

An understanding of the dynamics of soil organic carbon (SOC) as affected by farming practices is imperative for maintaining soil productivity and mitigating global warming. The objectives of this study were to investigate the effects of long-term fertilization on SOC and SOC fractions for the whole soil profile (0–100 cm) in northwest China. The study was initiated in 1979 in Gansu, China and included six treatments: unfertilized control (CK), nitrogen fertilizer (N), nitrogen and phosphorus (P) fertilizers (NP), straw plus N and P fertilizers (NP+S), farmyard manure (FYM), and farmyard manure plus N and P fertilizers (NP+FYM). Results showed that SOC concentration in the 0–20 cm soil layer increased with time except in the CK and N treatments. Long-term fertilization significantly influenced SOC concentrations and storage to 60 cm depth. Below 60 cm, SOC concentrations and storages were statistically not significant between all treatments. The concentration of SOC at different depths in 0–60 cm soil profile was higher under NP+FYM follow by under NP+S, compared to under CK. The SOC storage in 0–60 cm in NP+FYM, NP+S, FYM and NP treatments were increased by 41.3%, 32.9%, 28.1% and 17.9%, respectively, as compared to the CK treatment. Organic manure plus inorganic fertilizer application also increased labile soil organic carbon pools in 0–60 cm depth. The average concentration of particulate organic carbon (POC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) in organic manure plus inorganic fertilizer treatments (NP+S and NP+FYM) in 0–60 cm depth were increased by 64.9–91.9%, 42.5–56.9%, and 74.7–99.4%, respectively, over the CK treatment. The POC, MBC and DOC concentrations increased linearly with increasing SOC content. These results indicate that long-term additions of organic manure have the most beneficial effects in building carbon pools among the investigated types of fertilization.     

施肥对麦田土壤可溶性有机氮的影响

利用长期定位试验,研究施肥和小麦生长对土壤可溶性有机氮(EON)的影响。长期不同施肥土壤包括不施肥(No-F)、施用化肥(NPK)和有机肥与化肥配施(MNPK)3种。EON含量范围为7.5—29.3 kg/hm~2,No-F、NPK和MNPK土壤中EON分别占可溶性总氮的40%、56%和56%。长期有机肥与化肥配施显著提高0—15 cm土层EON含量,但对30 cm以下土层EON含量无影响。在小麦开花期,可溶性有机氮的含量及其相对含量显著高于拔节期和收获期。虽然施用氮肥对当季EON含量无显著影响,但同位素示踪微区试验表明,土壤耕层(0—15 cm)中仍有0.4%—2.8%的可溶性有机氮来源于当季施入的肥料氮。可见,化学氮肥向可溶性有机氮的转化缓慢,但农田土壤中可溶性有机氮含量与矿质态氮含量相当,发生淋溶损失的风险大。     

Effect of distillery effluents on some physiological aspects in maize

A field experiment was conducted for two years to study the effect of application of different distillery effluents: raw spent wash (RSW), biomethanated spent wash (BSW), lagoon sludge (LS), recommended NPK + FYM (farm yard manure) and control (no fertilizer and effluent) on some physiological aspects in maize. The study revealed that the application of distillery effluents resulted in increased leaf area, chlorophyll content, nitrate reductase activity total dry weight and grain yield. Among the effluents, the highest grain yield (36.9 qha(-1)) was obtained in BSW followed by RSW (32.2 qha(-1)) and LS (28.3 qha(-1)). Overall, NPK + FYM treatment recorded the highest grain yield (51.8 qha(-1)). However, to achieve the full manurial potential of the effluents, some amount of fertilizer should be supplemented.     

Effect of organic and mineral fertilizers on N-use by wheat under different irrigation frequencies

A field trial was established in Errachidia, southern Morocco, to investigate the interaction between wheat residue management and mineral 15N-labelled ammonium sulphate, under different irrigation treatments, applied to wheat (Triticum durum var. Karim). In treatments I1, I2, I3 and I4, plots were irrigated every 10, 15, 21 and 30 days. Each plot contained three sub-plots that received three fertilization treatments: T1 received 42 kg N ha-1 of ammonium sulphate before seedling, 42 kg N ha-1 of ammonium sulphate labelled with 9.764 at % 15N excess at tillering and 84 N kg ha-1 of ammonium sulphate at flowering; T2 received 42 kg N ha-1 of ammonium sulphate labelled with 9.764 at % 15N excess at seedling, 42 kg N ha-1 at tillering and 42 kg N ha-1 at flowering; T3 received 4800 kg ha-1 of wheat residue labelled with 1.504 at % 15N excess and 42 kg N ha-1 of ammonium sulphate before seedling and 42 kg N ha-1 of ammonium sulphate at flowering. Nitrogen fertilization with 168 kg N ha-1 did no significantly increase grain and straw yields in comparison to the 126 kg N ha-1 application. The combination of the organic input and supplementary application of mineral fertilizer N has been found as a more attractive management option. For all irrigation treatments, the % recovery of N in the whole plant was higher in plants that received 15N at tillering (63%, 49% respectively for irrigation intervals between 10 and 30 d) than in plants that received 15N just after seeding (28% for irrigation each 10- and 30-d intervals). For the irrigation treatment each 10 and 15 days, the 15N was mainly recovered by the grain for all fertilization treatments, whereas for irrigation treatment each 30 days, the grain and straw recovered nearly equal amounts of fertilizer. For grain and straw of wheat, nitrogen in the plant derived from the fertilizer was low, while most of the N was derived from the soil for all irrigation and fertilization treatments. The % nitrogen in the plant derived from the fertilizer values showed no significant difference between the different plant parts. The results suggested a dominant influence of moisture availability on the fertilizer N uptake by wheat. Under dry conditions the losses of N can be allotted to denitrification and volatilisation.     

黄壤稻田土壤微生物生物量碳磷对长期不同施肥的响应

本研究以进行了22年的黄壤稻田长期定位试验为依托,分析了不同施肥模式下土壤碳(C)、磷(P)与微生物生物量C(MBC)、P(MBP)的变化及其耦合特征,旨在探讨黄壤地区合理培肥模式以提高土壤磷素有效性.试验包括10个处理,分别为不施肥(CK)、单施氮肥(N)、磷钾配合(PK)、氮钾配合(NK)、氮磷配合(NP)、氮磷钾配合(NPK)、单施有机肥(M)、3种有机无机肥配施(1/4M+3/4NP、0.5MNP、MNPK).结果表明:与不施肥相比,N和NK处理土壤有机碳(TOC)、全磷(TP)、MBC、MBP均有不同程度的降低,施磷处理(PK、NP、NPK)则有不同程度的提升;与不施肥和施用无机肥相比,施用有机肥各处理TOC、MBC、MBP及MBP/TP均显著增加,其中M和MNPK处理增幅最大.MBC/MBP、TOC/MBP、MBC/TP以施用有机肥处理最低,N处理最高.土壤MBC、MBP及其耦合关系与土壤TOC和有效磷均呈极显著相关,TOC是影响MBC、MBP、MBP/TP的直接因素,而有效磷则是影响MBC/MBP、TOC/MBP、MBC/TP的直接因素.土壤MBP及碳、磷耦合关系各指标可以有效区分单施化肥和施用有机肥的不同施肥方式,可作为评价黄壤稻田磷素肥力的生物学指标.配施有机肥是增加黄壤稻田磷有效性、提高土壤供磷潜力和保持土壤生物健康的有效途径.     

不同生育时期增铵营养对小麦生长及氮素利用的影响

通过两年的田间试验,研究了不同生育时期增铵营养(EAN)对小麦生长和氮素利用的影响.结果表明,田间增铵营养促进了小麦植株的生长和氮素吸收.其中基肥、分蘖期、拔节期EAN提高了小麦的干物质积累量、地上部氮积累量、有效穗数、叶面积指数、叶片叶绿素含量以及小麦的籽粒产量;孕穗期EAN效果不明显;全生育期EAN在促进生长方面的效果并无明显优势,但可有效降低土壤N₃^--N的淋溶损失.与对照相比,EAN提高了氮流效率和吸收效率,但以拔节前处理最为明显.拔节期EAN主要在于改善后期的叶片光合性能,并促进同化物向籽粒的再分配,而基肥和分蘖期EAN主要在于提高有效分蘖数.     

The effects of mineral fertilizer and organic manure on soil microbial community and diversity

The effects of mineral fertilizer (NPK) and organic manure on phospholipid fatty acid profiles and microbial functional diversity were investigated in a long-term (21-year) fertilizer experiment. The experiment included nine treatments: organic manure (OM), organic manure plus fertilizer NPK (OM + NPK), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer N (N), fertilizer P (P), fertilizer K (K), and the control (CK, without fertilization). The original soil was extremely eroded, characterized by low pH and deficiencies of nutrients, particularly N and P. The application of OM and OM + NPK greatly increased crop yields, soil pH, organic C, total N, P and K, available N, P and K content. Crop yields, soil pH, organic C, total N and available N were also clearly increased by the application of mineral NPK fertilizer. The amounts of total PLFAs, bacterial, Gram-negative and actinobacterial PLFAs were highest in the OM + NPK treatment, followed by the OM treatment, whilst least in the N treatment. The amounts of Gram-positive and anaerobic PLFAs were highest in the OM treatment whilst least in the P treatment and the control, respectively. The amounts of aerobic and fungal PLFAs were highest in the NPK treatment whilst least in the N and P treatment, respectively. The average well color development (AWCD) was significantly increased by the application of OM and OM + NPK, and the functional diversity indices including Shannon index (H ^′ ), Simpson index (D) and McIntosh index (U) were also significantly increased by the application of OM and OM + NPK. Principal component analysis (PCA) of PLFA profiles and C source utilization patterns were used to describe changes in microbial biomass and metabolic fingerprints from nine fertilizer treatments. The PLFA profiles from OM, OM + NPK, NP and NPK were significantly different from that of CK, N, P, K and NK, and C source utilization patterns from OM and OM + NPK were clearly different from organic manure deficient treatments (CK, N, P, K, NP, NK 6 and NPK). Stepwise multiple regression analysis showed that total N, available P and soil pH significantly affected PLFA profiles and microbial functional diversity. Our results could provide a better understanding of the importance of organic manure plus balanced fertilization with N, P and K in promoting the soil microbial biomass, activity and diversity and thus enhancing crop growth and production.     

不同施肥处理对土壤活性有机碳和甲烷排放的影响

通过采集田间试验区连续3a施入有机肥的稻田耕层土壤,分析土壤中微生物量碳(MBC)、水溶性有机碳(DOC)、易氧化有机碳(ROC)和可矿化有机碳(readily mineralizable carbon,RMC)等活性有机碳的含量,稻田甲烷(CH_4)的排放通量,探讨施用有机肥的土壤活性有机碳变化及与CH_4排放的关系。研究结果显示:(1)施有机肥对土壤中的活性有机碳均有一定的促进作用。3a不同施肥处理土壤中DOC、ROC、MBC和RMC的平均含量分别为383.6、2501.2、640.4 mg/kg和291.7 mg/kg。3a施猪粪(猪粪+化肥,PM)、鸡粪(鸡粪+化肥,CM)和稻草(稻草+化肥,RS)的DOC的含量分别比化肥(CF)处理增加5.6%、6.7%和19.3%,ROC的含量分别比CF增加6.6%、8.4%和9.8%;MBC含量分别比CF增加5.1%、14.8%和21.5%,RMC增加6.8%、22.0%和33.9%。不同施肥处理的稻田土壤活性有机碳为分蘖期高于成熟期。(2)施肥处理显著增加稻田CH_4排放,CH_4分蘖期的排放通量是成熟期的143倍,3a PM、CM和RS处理的CH_4排放分别比CF处理增加37.0%(P0.05)、92.7%(P0.05)和99.4%(P0.05)。(3)不同施肥处理的DOC、ROC、MBC和RMC含量与CH_4排放通量均存在显著正相关关系,ROC与CH_4排放的相关系数最高,为0.754(P0.01),且4种有机碳间关系密切。稻田分蘖期土壤中的活性有机碳与稻田CH_4排放呈显著正相关关系。(4)综合分析,在4种有机碳中,土壤中ROC和MBC的含量直接影响CH_4排放。     

Relative efficacy of different distillery effluents on growth, nitrogen fixation and yield of groundnut.

A field experiment with groundnut as test crop was conducted to evaluate the manurial potential of three distillery effluents: raw spent wash (RSW), biomethanated spent wash (BSW) and lagoon sludge (LS) vis-à-vis recommended fertilizers (NPK + farm yard manure (FYM)) and a control (no fertilizer or distillery effluent). It was found that all the three distillery effluents increased total chlorophyll content, crop growth rate (CGR), total dry matter, nutrient uptake (N, P and K) and finally seed yield compared to the control but inhibited nodulation and decreased nitrogen fixation. Among the three distillery effluents, BSW produced the highest seed yield (619 kg ha(-1)) twice that of control (3.10 kg ha(-1)), followed by RSW (557 kg ha(-1)) and LS (472 kg ha(-1)). However, the distillery effluents did not influence protein and oil contents. It was concluded that these distillery effluents because of their high manurial potential could supply nutrients, particularly potassium, nitrogen and sulphur, to the crops and thus reduce the fertilizer requirement of crops. Nevertheless, the crop performance and yield with three distillery effluents were overall less than that produced by recommended NPK + FYM probably on account of failure of the effluents to supply balanced nutrition to the plants for achieving their potential growth capacity.     

Short-term immobilisation and crop uptake of fertiliser nitrogen applied to winter wheat: effect of date of application in spring

Previous studies on the fate of fertiliser nitrogen applied to winter wheat in temperate climates have shown that nitrogen (N) applied early, at tillering for wheat, was less efficiently taken up than N applied later in the growth cycle. We examined the extent to which the soil microbial N immobilisation varied during the wheat spring growth cycle and how microbial immobilisation and plant uptake competed for nitrogen. We set up a pulse-15N labelled field experiment in which N was applied at eight development stages from tillering (beginning of March) to anthesis (mid-June). Each application was 50 kg N ha-1 as 15N labelled urea except for the first application which was 25 kg N ha-1. The distribution of fertiliser 15N in shoots, roots, mineral and organic soil N was examined by destructive sampling 7 and 14 days after each 15N pulse. The inorganic 15N pool was almost depleted by day 14. The N uptake efficiency increased with later applications from 45% at tillering to 65% at flowering. N immobilisation was rather constant at 13–16% of N applied, whatever the date of application. The increase in plant 15N uptake resulted in an increase in the total 15N recovery in the plant-soil system (15N in soil +15N in plant), suggesting that gaseous losses were lower at the later application dates.     

Sustaining productivity of wheat–soybean cropping system through integrated nutrient management practices on the Vertisols of central India

Wheat–soybean is one of the most dominant cropping systems on the Vertisols of central India. Cultivation of durum wheat in winter season (November to April) has a considerable potential due to congenial climate, while soybean in rainy season (June to October) has witnessed a phenomenal growth in the last two decades in the region. Beside including a legume (soybean) in sequence with a cereal crop (wheat), combined use of available organic sources along with chemical fertilizers may prove beneficial for long-term productivity and sustainability of the system. A long-term experiment was conducted during 1995–2000 on the fine-textured Vertisols at Indore, India to study the effect of combined use of farmyard manure (FYM), poultry manure, vermicompost and biofertilizers (Azotobacter + phosphate solubilizing bacteria) with 0.5 and 1.0 NPK (120 kg N + 26.2 kg P + 33.3 kg K ha⁻¹) on wheat, and residual effect on following soybean. Grain yield of aestivum wheat in the initial 2 years and durum wheat in the later 3 years was significantly increased with 0.5 NPK + poultry manure at 2.5 t ha⁻¹ or FYM at 10 t ha⁻¹ compared with 0.5 NPK alone, and was on par with 1.0 NPK. However, the highest productivity was obtained when these organic sources were applied along with 1.0 NPK. Quality parameters of durum wheat viz protein content, hectolitre weight and sedimentation value showed improvement, and yellow berry content was significantly lower with combined use of NPK + organic sources compared with NPK alone and control. Soybean did not show much response to residual effect of nutrient management treatments applied to wheat. Wheat gave higher profit than soybean, particularly in the later years due to lower grain yields and market price of soybean. However, the superiority of FYM as well as poultry manure along with 1.0 NPK was evident on the overall profitability of the system. Various soil fertility parameters including chemical and biological properties showed conspicuous improvement over the initial status under the treatments of FYM and poultry manure. Sustainability yield index was maximum under 1.0 NPK, followed by 1.0 NPK + poultry manure or FYM. It was concluded that application of available organic sources, particularly FYM and poultry manure along with full recommended dose of NPK fertilizers to wheat was essential for improving productivity, grain quality, profitability, soil health and sustainability of wheat–soybean system.     

不同施肥黑土微生物量氮变化特征及相关因素

研究长期施用两种不同量有机肥(M2、M4)和化肥(NPK)的黑土微生物量N在作物生长季的变化特征．结果表明,施用有机肥黑土微生物量N显著高于施用化肥(NPK)和不施肥(CK),微生物量N季节波动小．微生物量N为M4 25．52～239．12mg·kg^-1,M2 10．40～94．31mg·kg^-1．NPK6．27～87．04mg·kg^-1,CK9．15～69．81mg·kg^-1,同一处理最大值与最小值相差7～14倍．M2、NPK处理微生物量N最大值出现在抽雄吐丝期,M4处理最大值出现在拔节期,CK处理最大值出现在播种期;不同处理微生物量N的差异并未因季节变化及玉米生育时期影响而明显改变．微生物量N的动态变化与极少数黑土生物、理化特性指标动态变化显著相关;微生物量N与黑土生物、理化特性,植物氮、磷、钾有极显著的正相关关系,与土壤含水量、籽粒粗蛋白含量呈显著正相关关系．     

长期施肥对玉米生育期土壤微生物量碳氮及酶活性的影响

以小麦-玉米轮作长期肥料定位试验为平台,探讨不同养分管理对玉米生育期塿土微生物量碳、氮和酶活性动态变化的影响。试验包括6个处理,分别为不施肥(CK)、单施氮肥(N)、氮磷配合(NP)、氮磷钾配合(NPK)、NPK+秸秆(SNPK)以及有机肥+NPK(MNPK)。结果表明玉米生育期土壤微生物量碳、氮变化显著。不同施肥管理下土壤微生物量碳、氮的高低显著性分别为MNPK>SNPK、NP、NPK>N、CK。玉米生育期内土壤酶活性也变化显著,蔗糖酶、脲酶和纤维素酶在玉米抽雄期达到活性高峰,而磷酸酶在玉米拔节期出现活性高峰。不同施肥管理对土壤酶活性的影响总体表现为MNPK处理最高,其次为SNPK处理,再次为NPK和NP处理,N和CK处理最低。不同施肥处理间土壤微生物量碳、氮以及酶活性与土壤有机碳、全氮、速效磷水平密切相关。塿土长期施用氮磷或氮磷钾化肥可以提高土壤微生物量碳、氮以及酶活性。一季作物秸秆还田配合氮磷钾化肥与氮磷钾相比有提高土壤微生物量碳、氮以及酶活性的趋势。在等氮量下,有机肥配合化肥与其他施肥模式相比,均显著提升土壤化学肥力因素、微生物量碳氮和酶活性。因此,塿土上建议进行有机无机肥配合以提高土壤肥力,保持土壤生物健康。     

稻草还田对水稻土固氮基因(nifH)组成结构和多样性的影响

以中国科学院桃源农业生态试验站长期定位施肥试验为平台,选取稻草还田(C)、氮磷钾(NPK)、氮磷钾加稻草还田(NPK+C)和不施肥对照(CK)4个处理,在晚稻的分蘖期、孕穗期和成熟期分别采集土样,利用实时定量PCR(Q-PCR)和末端限制性片段多态性(T-RFLP)等分子生物学方法研究长期稻草还田对水稻土含nifH基因固氮微生物群落丰度、组成和多样性的影响.结果表明：与对照相比,稻草还田和单施化肥处理均显著增加nifH基因的丰度(分蘖期除外),NPK+C处理中含nifH基因的微生物数量最高;nifH基因组成也受到长期施肥的影响,其中CK处理nifH基因组成与各施肥处理明显不同,C与NPK处理间nifH基因组成存在一定差异,而NPK与NPK+C处理间无显著差异.长期施肥不会引起含nifH基因微生物群落多样性的显著改变.可见,稻草还田不仅引起nifH基因群落的组成发生变化,而且导致其数量显著增加,因而可增加土壤的固氮能力.     

Variation in Yield Gap Induced by Nitrogen,Phosphorus and Potassium Fertilizer in North China Plain

A field experiment was conducted under a wheat-maize rotation system from 1990 to 2006 in North China Plain (NCP) to determine the effects of N, P and K on yield and yield gap. There were five treatments: NPK, PK, NK, NP and a control. Average wheat and maize yields were the highest in the NPK treatment, followed by those in the NP plots among all treatments. For wheat and maize yield, a significant increasing trend over time was found in the NPK-treated plots and a decreasing trend in the NK-treated plots. In the absence of N or P, wheat and maize yields were significantly lower than those in the NPK treatment. For both crops, the increasing rate of the yield gap was the highest in the P omission plots, i.e., 189.1 kg ha⁻¹ yr⁻¹ for wheat and 560.6 kg ha⁻¹ yr⁻¹ for maize. The cumulative omission of P fertilizer induced a deficit in the soil available N and extractable P concentrations for maize. The P fertilizer was more pivotal in long-term wheat and maize growth and soil fertility conservation in NCP, although the N fertilizer input was important for both crops growth. The crop response to K fertilizers was much lower than that to N or P fertilizers, but for maize, the cumulative omission of K fertilizer decreased the yield by 26% and increased the yield gap at a rate of 322.7 kg ha⁻¹ yr⁻¹. The soil indigenous K supply was not sufficiently high to meet maize K requirement over a long period. The proper application of K fertilizers is necessary for maize production in the region. Thus, the appropriate application of N and P fertilizers for the growth of both crops, while regularly combining K fertilizers for maize growth, is absolutely necessary for sustainable crop production in the NCP.