Wheat Grain Yield and Yield Stability in a Long-Term Fertilization Experiment on the Loess Plateau

To provide a scientific basis for sustainable land management, a 20-year fertility experiment was conducted in Changwu County, Shaanxi Province, China to investigate the effects of long-term application of chemical fertilizers on wheat grain yield and yield stability on the Loess Plateau using regression and stability analysis. The experiment consisted of 17 fertilizer treatments, containing the combinations of different N and P levels, with three replications arranged in a randomized complete block design. Nitrogen fertilizer was applied as urea, and P was applied as calcium superphosphate. Fertilizer rates had a large effect on the response of wheat yield to fertilization. Phosphorus, combined with N, increased yield significantly （P 〈 0.01）. In the unfertilized control and the N or P sole application treatments, wheat yield had a declining trend although it was not statistically significant. Stability analysis combined with the trend analysis indicated that integrated use of fertilizer N and P was better than their sole application in increasing and sustaining the productivity of rainfed winter wheat.

Steel Slag as an Iron Fertilizer for Corn Growth and Soil Improvement in a Pot Experiment

The feasibility of steel slag used as an iron fertilizer was studied in a pot experiment with corn. Slag alone or acidified slag was added to two Fe-deficient calcareous soils at different rates. Results showed that moderate rates (10 and 20 g kg-1) of slag or acidified slag substantially increased corn dry matter yield and Fe uptake. Application of steel slag increased the residual concentration of ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA) extractable Fe in the soils. The increase of extractable Fe was usually proportional to the application rate, and enhanced by the acidification of slag. Steel slag appeared to be a promising and inexpensive source of Fe to alleviate crop Fe chlorosis in Fe-deficient calcareous soils.

Crop yields and soil organic carbon dynamics in a long-term fertilization experiment in an extremely arid region of northern Xinjiang, China

A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon （SOC） from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control （CK） and six different combinations of phosphorus （P）, potassium （K）, nitrogen （N）, straw （S） and animal manure （M）. The balanced fertilization treatments had significantly （P〈0.05） higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate （NPK） and 1/3 N from farmyard manure （NPKM） had a higher average yield than the other treatments. The average yields （over the 23 years） in the treatments of NPK, and urea, calcium superphosphate （NP） did not differ significantly （P〉0.05） but were higher than that in the treatment with urea and potassium sulfate （NK; P〈0.05）. The results also show that the highest increases in SOC （P〈0.05） occurred in NPKM with a potential increase of 1.2 t C/（hm2.a）. The increase in SOC was only 0.31, 0.30 and 0.12 t C/（hm2.a） for NPKS （9/10 N from NPK and 1/10 N from straw）, NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.

Effect of slow-release iron fertilizer on iron-deficiency chlorosis, yield and quality of Lilium davidii var.unicolor in a two-year field experiment

Iron deficiency chlorosis of Lilium davidii var. unicolor is often the case in practice in alkaline soils of northwest region of China. It is difficult to control iron chlorosis because of high cost and short effective work time of conventional iron fertilizers. In this study, a 2-year field experiment was conducted to evaluate the effects of two slow-release fertilizers on the suppression of iron deficiency chlorosis, soil chemical properties, and the yield and quality of L. davidii var. unicolor. Results show that both coated slow-release iron fertilizers and embedded slow-release iron fertilizer effectively controlled iron-deficiency chlorosis. The application of slow-release iron fertilizers significantly increased plant height and chlorophyll content of L. davidii var. unicolor at different growth stages. Furthermore, coated iron fertilizer application significantly increased starch, protein, soluble sugar and vitamin C content of L. davidii var. unicolor, and it also significantly improved total amino acid content, with increases in essential amino acids(Trp, Leu, Lys, Phe, Val, and Thr contents) and in nonessential amino acids(Asp, Glu, Cit, Ihs, Acc, Ala, Pro, and Cys contents). It was concluded that application of coated slow-release iron fertilizer could be a promising option for suppression of iron deficiency chlorosis and deserves further study.

Effects of Long-Term Combined Application of Organic and Mineral Fertilizers on Microbial Biomass,Soil Enzyme Activities and Soil Fertility

Soil health is important for the sustainable development of terrestrial ecosystem. In this paper, we studied the relationship between soil quality and soil microbial properties such as soil microbial biomass and soil enzyme activities in order to illustrate the function of soil microbial properties as bio-indicators of soil health. In this study, microbial biomass C and N contents （Cmic ＆ Nmic）, soil enzyme activities, and soil fertility with different fertilizer regimes were carried out based on a 15-year long-term fertilizer experiment in Drab Fluvo-aquic soil in Changping County, Beijing, China. At this site, 7 different treatments were established in 1991. They were in a wheat-maize rotation receiving either no fertilizer （CK）, mineral fertilizers （NPK）, mineral fertilizers with wheat straw incorporated （NPKW）, mineral fertilizers with incremental wheat straw incorporated （NPKW＋）, mineral fertilizers plus swine manure （NPKM）, mineral fertilizers plus incremental swine manure （NPKM＋） or mineral fertilizers with maize straw incorporated （NPKS）. In different fertilization treatments Cmic changed from 96.49 to 500.12 mg kg^-1, and Nmic changed from 35.89 to 101.82 mg kg^-1. Compared with CK, the other treatments increased Cmic ＆ Nmic, Cmic/Corg （organic C） ratios, Cmic/Nmic, urease activity, soil organic matter （SOM）, soil total nitrogen （STN）, and soil total phosphorus （STP）. All these properties in treatment with fertilizers input NPKM＋ were the highest. Meantime, long-term combined application of mineral fertilizers with organic manure or crop straw could significantly decrease the soil pH in Fluvo-aquic soil （the pH around 8.00 in this experimental soil）. Some of soil microbial properties （Cmic/Nmic, urease activity） were positively correlated with soil nutrients. Cmic/Nmic was significantly correlated with SOM and STN contents. The correlation between catalase activity and soil nutrients was not significant. In addition, except of catalase activity, the soil pH in this experiment was negatively correlated with soil microbial properties. In conclusion, soil microbial properties reflect changes of soil quality and thus can be used as bio-indicators of soil health.

Effects of a New Long-term Controlled-release Fertilizer on Growth and Development and Yield of Summer Maize

[Objective] The aim was to select the optimal amount of controlled-release fertilizer and provide theoretical references for controlled-release fertilizers use in summer maize. [Method] Long-term controlled-release fertilizers were applied once at sowing summer maize to explore effects on maize growth, yield, economic profits and environment. [Result] Maize yield reduced a little in the treatment group with 60% CRF, and increased in varying degrees in the rest groups in the range of 1.1%-7.4%, and some showed significant differences. [Conclusion] Controlled-release fertilizers can be applied once at the amount of 80% common fertilizer＇s, with con- sideration of maize yield, nitrogen use rate and economic profits, which is beneficial for summer maize application and promotion in North China.

Changes of Organic Matter, N, P and K Content of Soils in Red Soil Areas Under Long-Term Experiment

The content of organic matter （OM）, nitrogen （N）, phosphorus （P）, and potassium （K） in the three selected soils, including Calcaric Purpli-Orthic Primosols （purple sand-shale parent material）, Dystric Turbi-Anthric Primosols （quaternary red clay parent material） and Typic Udi-Sandic Primosols （granite parent material） were studied under a long-term experiment by using crop straw and inorganic fertilizers at the Hunan Red Soil Experiment Station of Chinese Academy of Agricultural Sciences. The results showed that the contents of OM, N, P and K in the three selected soils increased after 23 years application of crop straw and inorganic fertilizers, but the contents increased much less when crop straw or inorganic fertilizers was applied alone. The nutrient contents in the three soils developed from granite changed more remarkably than those in the soil derived from quaternary red clay and purple sand-shale. It was also found that the contents of OM, N, and P increased slightly in the treatments without applying fertilizers or returning the crop straw to the root bed. Combined application of inorganic fertilizers and crop straw could remarkably increase the contents of OM, alkalihydrolyzable N and available K, the positive correlation between application of organic fertilizers and increase of OM in soil did not always happened, it provided evidence for the relation between appropriate C/N ratio and accumulation of OM in soil. The increase of nutrient content was influenced by the soil properties. By comparing the contents of nutrient in 0-20 cm depth in the three different soils, it was concluded that the most increases of OM, alkali-hydrolyzable N, and available P were observed in Typic Udi-Sandic Primosols with the average increase by 3.03, 27.38, and 21.73 mg kg^-1, respectively. The available K increased in Dystric Turbi-Anthric Primosols with the average increase by 25.82 mg kg^-1, while it decreased in Calcaric Purpli-Orthic Primosols and Typic Udi-Sandic Primosols. It was concluded that the application of inorganic fertilizer and crop straw was important to improve the soil fertility for all of three selected soils. The straw return to the field had played a significant role for enhancement of the soil quality in the study areas. The application of inorganic fertilizer combined with the straw return to the fields could remarkably improve the soil fertility.

Long-Term Effect of Fertilizer and Rice Straw on Mineral Composition and Potassium Adsorption in a Reddish Paddy Soil

Increasing K＋ adsorption can be an effective alternative in building an available K pool in soils to optimize crop recovery and minimize losses into the environment. We hypothesized that long-term fertilization might change K＋ adsorption because of changes in the chemical and mineralogical properties of a rice （Oryza sativa L.）. The aims of this study were （i） to determine clay minerals in paddy soil clay size fractions using X-ray diffraction methods and a numerical diagramdecomposition method; （ii） to measure K＋ adsorption isotherms before and after H202 oxidation of organic matter, and （iii） to investigate whether K＋ adsorption is correlated with changes in soil chemical and mineral properties. The 30-yr longterm fertilization treatments caused little change in soil organic C （SOC） but a large variation in soil mineral composition. The whole-clay fraction （〈5 Jam） corresponded more to the fertilization treatment than the fine-clay fraction （〈1 gin） in terms of percentage of illite peak area. The total percentage of vermiculite-chlorite peak area was significantly negatively correlated with the total percentage ofillite peak area in the 〈5 lam soil particles （R=-0.946, P〈0.0006）. Different fertilization treatments gave significantly different results in K＋ adsorption. The SOC oxidation test showed positive effects of SOC on K＋ adsorption at lower K＋ concentration （≤120 mg L-0 and negative effects at higher K＋ concentration （240 mg L-l）. The K＋ adsorption by soil clay minerals after SOC oxidization accounted for 60-158% of that by unoxidized soils, suggesting a more important role of soil minerals than SOC on K＋ adsorption. The K＋ adsorption potential was significantly correlated to the amount of poorly crystallized illite present （R--0.879, P=0.012）. The availability of adsorbed K＋ for plant growth needs further study.

Effect of Long-Term Application of K Fertilizer and Wheat Straw to Soil on Crop Yield and Soil K Under Different Planting Systems

Effect of application of K fertilizer and wheat straw to soil on crop yield and status of soil K in the plough layer under different planting systems was studied. The experiments on long-term application of K fertilizer and wheat straw to soil in Hebei fluvo aquic soil and Shanxi brown soil in northern China were begun in 1992. The results showed that K fertilizer and straw could improve the yields of wheat and maize with the order of NPK ＋ St 〉 NPK 〉 NP ＋ St 〉 NP, and treatment of K fertilizer made a significant difference to NP, and the efficiency of K fertilizer in maize was higher than in wheat under rotation system of Hebei. In contrast with Shanxi, the wastage of soil potassium was a more serious issue in the rotation system in Hebei, only treatment of NPK ＋ St showed a surplus of potassium and the others showed a wane. K fertilizer and straw could improve the content of water-soluble K, nonspecifically adsorbed K, non-exchangeable K, mineral K, and total K in contrast to NP; however, K fertilizer and straw reduce the proportion of mineral K and improve proportion of other forms of potassium in the two locating sites. Compared with the beginning of orientation, temporal variability character of soil K content and proportion showed a difference between the two soil types; furthermore, there was a decrease in the content of mineral K and total K simultaneously in the two locating sites. As a whole, the effect of K fertilizer applied to soil directly excelled to wheat straw to soil. Wheat straw to soil was an effective measure to complement potassium to increase crop yield and retard the decrease of soil K.

Effects of 42-year long-term fertilizer management on soil phosphorus availability, fractionation,adsorption–desorption isotherm and plant uptake in flooded tropical rice

Soil phosphorus(P) fractionation, adsorption, and desorption isotherm, and rice yield and P uptake were investigated in flooded tropical rice(Oryza sativa L.) following 42-year fertilizer and manure application. The treatments included low-input [unfertilized control without N, P, or K(C0N0)], farmyard manure(FYM)(C1N0), NP(C0NP), NPK(C0NPK), FYM + NP(C1NP), and high-input treatment, FYM + NPK(C1NPK). Grain yield was increased significantly by 74%over the control under the combined application of FYM + NPK. However, under low- and high-input treatments, yield as well as P uptake was maintained at constant levels for 35 years.During the same period, high yield levels and P uptake were maintained under the C0 NP, C0 NPK,and C1 NPK treatments. These are unique characteristics of a tropical flooded ecosystem, which is a self-sustaining system for rice production. The Fe–P fraction was highest compared to the Ca–P and Al–P fractions after 42 years of fertilizer application and was significantly higher under FYM + NPK treatment. The P adsorption capacity of soil was highest under the low-input treatment and lowest under long-term balanced fertilization(FYM + NPK). In contrast, P desorption capacity was highest under NPK and lowest in the control treatment. Long-term balanced fertilization in the form of FYM + NPK for 42 years lowered the bonding energy and adsorption capacity for P in soil but increased its desorption potential, increasing P availability to the plant and leading to higher P uptake and yield maintenance.

Effects of Long-Term Application of Sulfur-Containing and Chloride-Containing Chemical Fertilizers on Rice Yield and Its Components

Impacts of 33-yr of application of S-containing and Cl-containing chemical fertilizers on rice （Oryza sativa L.） yield and its components were investigated in a red paddy field experiment,south China.The treatments included：1） adding 302 kg SO42--S ha-1 yr-1 with application of （NH4）2SO4-,K2SO4,and calcium superphosphate （SO42-）;2） adding 56 kg SO42--S and 176 kg Cl ha-1 yr-1 with application of urea,calcium superphosphate,and KCl （Cl-＋SO42-）;3） adding 516 kg Cl ha-1 yr-1 with application of NH4Cl,KCl,and KH2PO4 （Cl-）.Under each treatment,the applied N,P,and K nutrients were controlled at conventional rates of 150 kg N ha-1 yr-1,75 kg P2O5 ha-1 yr-1,225 kg K2O ha-1 yr-1,respectively.Under the S-containing fertilizer application,soil SO42--S content showed a first increasing then decreasing trend with years,and was significantly negatively correlated with annual rice yield.Average annual yield significantly declined in an order of Cl-,Cl-＋SO42-,and SO42-.Under the Cl-treatment,soil SO42--S content was maintained at about 26.5 mg kg-1,not showing deficiency.From 1990 to 2000,rice yield declined rapidly under the SO42- treatment,and was significantly lower than that under the Cltreatment.After then,there was no significant difference in yield among the treatments.Our results demonstrated that long-term application of S- containing fertilizer could result in excessive accumulation of SO42--S in the red paddy soils of south China,therefore producing a certain threat to rice growth.The Cl- containing fertilizer could be relatively safe.

Soil phosphorus dynamic, balance and critical P values in longterm fertilization experiment in Taihu Lake region, China

Phosphorus（P） is an important macronutrient for plant but can also cause potential environmental risk. In this paper, we studied the long-term fertilizer experiment（started 1980） to assess the soil P dynamic, balance, critical P value and the crop yield response in Taihu Lake region, China. To avoid the effect of nitrogen（N） and potassium（K）, only the following treatments were chosen for subsequent discussion, including： C0（control treatment without any fertilizer or organic manure）, CNK treatment（mineral N and K only）, CNPK（balanced fertilization with mineral N, P and K）, MNK（integrated organic manure and mineral N and K）, and MNPK（organic manure plus balanced fertilization）. The results revealed that the response of wheat yield was more sensitive than rice, and no significant differences of crop yield had been detected among MNK, CNPK and MNPK until 2013. Dynamic and balance of soil total P（TP） and Olsen-P showed soil TP pool was enlarged significantly over consistent fertilization. However, the diminishing marginal utility of soil Olsen-P was also found, indicating that high-level P application in the present condition could not increase soil Olsen-P contents anymore. Linear-linear and Mitscherlich models were used to estimate the critical value of Olsen-P for crops. The average critical P value for rice and wheat was 3.40 and 4.08 mg kg^（–1）, respectively. The smaller critical P value than in uplands indicated a stronger ability of P supply for crops in this paddy soil. We concluded that no more mineral P should be applied in rice-wheat system in Taihu Lake region if soil Olsen-P is higher than the critical P value. The agricultural technique and management referring to activate the plant-available P pool are also considerable, such as integrated use of low-P organic manure with mineral N and K.

Improvement of soil fertility and rice yield after long-term application of cow manure combined with inorganic fertilizers

Fertilization is an effective technique to improve soil fertility and increase crop yield.The long-term effects of different fertilizers on soil considerably vary.Over 38 consecutive years of different fertilization positioning experiments in a double cropping rice field of Qiyang Red Soil Experimental Station,seven different fertilization treatments including CK(no fertilization),NPK(nitrogen,phosphorus,and potassium fertilizer),M(cow manure),NPKM(nitrogen,phosphorus,and potassium with cow manure),NPM(nitrogen and phosphorus with cow manure),NKM(nitrogen and potassium with cow manure),and PKM(phosphorus and potassium with cow manure)were applied to study the effects on rice yield,soil fertility,and nutrient apparent balance in a paddy field.The results showed that the annual average yields of rice in NPKM,NPM,NKM,PKM,M,NPK and CK treatments ranged from 6214 to 11562 kg ha-1.Yields under long-term organic and inorganic treatments(NPKM,NPM,NKM and PKM)were 22.58,15.35,10.53 and 4.41%,respectively,greater than under the NPK treatment.Soil organic carbon(SOC),total nitrogen(TN),available nitrogen(AN)and available potassium(AK)concentration with long-term organic and inorganic treatment(NPKM,NPM,NKM and PKM)were significantly higher than in inorganic fertilizer(NPK)treatments.Soil total phosphorus(TP)and available phosphorus(AP)contentration with organic fertilizer combined with inorganic N and P fertilizer treatment(NPKM,NPM and PKM)were significantly higher than with inorganic fertilizer alone(NPK treatments).The average annual rice yield(11562 kg ha-1),SOC(20.88 g kg-1),TN(2.30 g kg-1),TP(0.95 g kg-1),TK(22.50 g kg-1)and AP(38.94 mg kg-1)concentrations were the highest in the NPKM treatment.The soil AN concentration(152.40 mg kg-1)and AK contentration(151.00 mg kg-1)were the highest in the NKM treatment.N and P application led to a surplus of nitrogen and phosphorus in the soil,but NPKM treatment effectively reduced the surplus compared with other treatments.Soils under all treatments were deficient in potassium.Correlation analysis showed that SOC,TN,AN,TP,and AP contentration was significantly correlated with rice yield;the correlation coefficients were 0.428,0.496,0.518,0.501,and 0.438,respectively.This study showed that the combined application of N,P,and K with cow manure had important effects on rice yield and soil fertility,but balanced application of N,P,and K with cow manure was required.

The principles and guidelines for designing long-term agronomic experiments

Many of the important questions facing farming systems in the world today require long-term studies to provide meaningful information and answers. A long-term agronomic experiment (LTAE) should (1) have long-term objectives; (2) study important soil processes or ecological processes; and (3) be related to the productivity and sustainability of systems. A well established LTAE can provide both insights into how the system operates and foresight into where the system goes. The prerequisites for setting up a LTAE are the secured land, continuous funding and dedicated scientists. A number of principles must be considered carefully when establishing a LTAE, (1) the site must be representative of large areas; (2) the treatments should be simple, but focusing on the big questions; (3) the plots should be large enough to allow subsequent modification of the experiment if this becomes necessary; (4) crop rotations should minimise, wherever possible, the risk of build-up of pests and diseases, and rotational phase should be considered in a rotational experiment; (5) a clearly defined experimental protocol should be developed to ensure data collected is scientifically valid and statistically analysable, but with flexibility to allow essential changes; (6) soil samples, possibly plant samples, should be achieved to provide better answer to the original questions when new, perhaps more accurate analytical techniques are developed, or answer new research questions that were not considered in the original design. The MASTER experiment in Australia was used as a case study to demonstrate how these principles are implemented in practice.

Approach for improving precision of regression analysis of single-replication fertilization experiments in rice

The field experiment designs with single replication were frequently used for factorial experiments in which the numbers of field plots were limited, but the experimental error was difficult to be estimated. To study a new statistical method for improving precision of regression analysis of such experiments in rice, 84 fertilizer experiments were conducted in 15 provinces of China, including Zhejiang, Jiangsu, Anhui, Hunan, Sichuan, Heilongjiang, etc. Three factors with 14 treatments (N: 0—225kg/ha, P: 0 —112. 5kg/ha, K: 0—150kg/ha) and two replications were employed using approaching optimun design. There were 2352 (84×14×2=2352) Yield deviations (d) between the individual treatment yields and its arithmetic mean. The results indicated that:

Effects of Long-term Fertilization on Micro-morphological Features in Purple Soil

[Objective] The study aimed to better understand the effect of different fertilizer treatments on micro-morphological characteristics of a purple soil at the 0-20 cm topsoil in a long-term fertilizer experiment. [Method] Soil micro-morphology was observed and analyzed under a single polarizing microscope. [Result] For the CK （no fertilizer） treatment, soil structure was dense with little porosity developed. Its soil microstructure was poor, sandy fabric-granular fabric. After continuously applied chemical fertilizers only for more than two decades, the soil particles did not evolve into soil structures and formed little porosity. The microstructures of soil in N, NP and NPK treatments were porphyroskelic fabric-fine sandy granular fabric, better than that of the soil in CK treatment. Adding manure obviously improved the quantity of groundmass and endowed the soil a loose structure and plenty porosity, enriched animal and plant residues, and well-formed iron-manganese nodules and humus ma- terials, all resulting in better micro-aggregates development. The type of soil microstructures in MNPK treatment was pectized-compacted takyric fabric-intertextic fabric, the best among all the treatments. [Conclusion] Combined application of both or- ganic and inorganic fertilizers can significantly improve the structure of the purple soil, enhance soil fertility and achieve soil sustainable development.

Effects of Long-term Fertilization on Fertility of Lateritic Red Loam Paddy

The change rules of the fertility of red soil paddy under the long-term different fertilization were investigated, and the reasonable fertilization mode to improve the fertility of red soil paddy was discussed. There were eight treatments in the experiment, which were CK （no fertilizer）, N1 （N of 60 kg/hm2）, N2 （N of 120 kg/hm2）, N1P1 （P2O5 of 30 kg/hm2）, N2P1 and N2P2 （P2O5 of 60 kg/hm2）, N2P2K1 （K2O of 45 kg/hm2） and N2P2K2 （K2O of 90 kg/hm2）. All treatments were applied with composted cow dung as the base fertilizer, and each season 50% of the straws were returned to the field. The content of organic matter, nitrogen, phosphorous and potassium in red soil paddy was observed continuously for ten years and their correlation was also analyzed. Under cow manure and straw return to field, organic matter content of different treatments was positively correlated to year. After ten years, organic matter content of surface soil rose by 2.5 g/kg averagely with an annual increase of 0.25 g/kg. Total nitrogen content and organic matter content of different treatments presented similar variation trend. Total nitrogen content rose by 0.35 g/kg averagely with an annual increase of 0.035 g/kg. Among all the treatments, N2P2K1 and N2P2K2 showed the biggest increase, which went up by 0.052 and 0.48 g/kg, respectively. Phosphorous-free treatments （CK, N1, N2） had steady phosphorous content with irregular changes of different years. Total phosphorous content of phosphorous treatments increased year by year. Total phosphorous content of N1P1 and N2P1 rose by 0.008 g/kg every year. The increment range of total phosphorous content of N2P2, N2P2K1 and N2P2K2 was 0.012 -0.013 g/kg annually. Available phosphorous content varied vastly among different treatments. Available phosphorous content of organic fertilizer treatments basically remained stable with irregular changes of different years. Available phosphorous content of organic fertilizer with phosphate fertilizer treatments rose year by year. Available phosphorous content of N1P1 and N2P1 rose approximately by 0.8 mg/kg. Available phosphorous content of N2P2, N2P2K1 and N2P2K2 rose approximately by 1.4 -1.6 mg/kg annually. Potassium fertilizer amount greatly affected total potassium content. Total potassium content of no-potassium treatments （CK, N1, N2, N1P1, N2P1 and N2P2） remained the same. Total potassium content of N2P2K markedly increased year by year, which was 0.014 g/kg annually. Rapid available potassium content of no-potassium treatments （CK, N1, N2, N1P1, N2P1 and N2P2） showed a decreasing trend. With phosphate fertilizer, rapid available potassium content of N2P2K1 and N2P2K2 remained the same or increased year by year. The change trend of slow available potassium content and rapid available potassium content resembled. Rational allocation of organic fertilizer, nitrogenous fertilizer, phosphate fertilizer and potassium fertilizer can significantly improve soil fertility and economic benefits. Balanced fertilization is an effective measure for soil fertility improvement as it＇s shown that nutrients of surface soil accumulate annually.

Effects of Long-term Located Fertilization on Wheat Yield and Soil Nutrients of Three Types of Soils in Shandong Province

[Objective] This study aimed to investigate the effects of long-term differ- ent fertilization in three types of soils on wheat yield and soil nutrient variation in Shandong Province. [Method] A 30-year located experiment in Jinan of Shandong Province was selected and the results of soil nutrient and crop yield in 1984, 1987, 1988, 1989, 1990, 2001, 2005, 2006, 2007 and 2010 were measured and collected. In this study, five treatments： CK, NP, NK, PK and NPK of the located experiment were selected. [Result] The three types of soils in wheat yields decreased signifi- cantly in the first several years and in 2006. Wheat yields of the treatments with P fertilizers were obviously higher than those without P fertilizers; it was shown that phosphorus is the primary nutritional factor for high-yielding of wheat. The highest yield is from cinnamon soil, followed by that from brown soil, and the lowest pro- duction is from fluvo-aquic soil. Under the same fertilization, the influence of other factors on wheat yield of brown soil is the smallest, while cinnamon soil is vulnera- ble to the influence of external conditions, resulting in larger fluctuation of annual wheat yield. The alkali-hydro nitrogen contents of three kinds of soils first de- creased, then raised, and at last reduced apparently. Since 2007, the change of al- kali-hydro nitrogen content appeared rebounded. The available P contents of no- phosphorus treatments decreased over time while those of the treatments with P fertilizers increased at first, then decreased, and after that kept relatively stable. The available K contents of no K treatments decreased slowly. The treatments of PK and NK had higher available K content than NPK treatment. [Conclusion] Thus, it is an effective fertilization measure to improve the wheat yield by supplying reasonable phosphate fertilizer and nitrogen fertilizer and making up potassium fertilizer.

Effects of Long-Term Fertilization on Distribution of Organic Matters and Nitrogen in Cinnamon Soil Macro-Aggregates

Soil samples collected from a 25-year long-term fertilizer experiment carried out on the Earth-cumulic-Orthic Anthrosols in semi-humid farmland ecological system, were used to study the distribution of soil organic matters, total nitrogen, nitrate nitrogen, and ammoniate nitrogen in different grades of soil macro-aggregates in order to study the effects of long-term application of organic manures in combination with chemical fertilizers. It is showed that the percentage of mass of the soil macro-aggregates with long-term application of fertilizers with sizes of 5-2 mm is increased compared with that of the samples with no fertilizer. It is easier to form lager size soil macro-aggregates by the long-term application of organic manures in combination with chemical fertilizers. The contents of organic matters, total nitrogen and nitrate nitrogen are all higher after treatments with different combinations of fertilizers, while there is a little effect on the contents of ammoniate nitrogen. The contents of organic matters, total nitrogen in the grades of soil macro-aggregates from the plough layers of the treated farmland exhibited significant difference. Moreover, the contents of organic matters and total nitrogen in the soil macro-aggregates with the size of 1-0.25 mm is the highest in all treated soil samples. The contents of nitrate nitrogen in soil macro-aggregates increased with the increasing of soil macro-aggregate size except those applied with chemical fertilizer and lower amount of corn stover. The results of correlation analysis revealed that there exists a significantly positive correlation between the percentage of mass of soil macro-aggregates with the size of 5-2 mm and the contents of organic matters, total nitrogen and nitrate nitrogen in the soil samples. However, the correlation between the percentage of mass of soil macro-aggregates with the size of 1-0.25 rnm and the contents of total nitrogen and nitrate nitrogen is significantly negative.The study showed that the highest contributing rates of macro-aggregates fractions to soil fertility is from the soil macro-aggregates fraction with the size of 1-0.25 mm in most of the cases.

Effects of Long-term Located Fertilization on the Contents and Composition of Organic Matter in Paddy Soil

To reveal variation of organic matter content in red paddy soil, Through a 27 years-located fertilization experiment in red paddy soil, the content and composi- tion of organic matter in paddy soil were studied in this paper. The result showed that： the dynamics of soil organic matter of the different fertilization treatments showed significant differences, in the premise of equal nutrient （nitrogen and phos- phorus and potassium）, combining application of organic-inorganic was benefited for the accumulation of organic matter in paddy soil than without fertilizer treatment or chemical fertilizer treatment; the dynamics of soil humic acid, HA and FA of chemi- cal fertilizer only and Combining application of organic-inorganic treatments had basi- cally the same trend, But the contents of humic acid, HA and FA of combining ap- plication of organic-inorganic treatments had been higher than that without fertilizer and chemical fertilizer treatment. Moreover combining application of organic-inorganic treatments was benefited for improving the contents of HA and FA, but decreasing HA/FA ratio as an extension of time. Combining application of organic-inorganic was benefited for improving the contents ol readily oxidizable organic matter. And the contents of soil organic matter in long-term experiment and the contents of readily oxidizable O.M were highly significant positive correlation and the contents of soil total nitrogen, avail nitrogen and potassium were significant positive correlation; the contents of soil readily oxidizable O.M and the contents of soil total nitrogen, avail- able P and rice yield were significant positive correlation. Thereinto, the correlation （r=0.818 1 ） between the rice yield and soil readily oxidizable O.M was higher than the correlation （r=0.802 0） between the rice yield and soil organic matter. It showed the soil readily oxidized organic matter had greater contribution to the rice yield.