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1.
Abstract

An incubation study was conducted for 30 days in Taloka (fine, mixed, thermic mollic Albaqualf) and Leadvale (fine, silty, siliceous, thermic typic Fragiudult) silt loam soils to evaluate carbon (C) and nitrogen (N) mineralization from soybean [Glycine max (L.) Merr.], corn (Zea mays L.), and wheat (Triticum aestivum L.) residues. Corn and soybean residues were collected at the tasseling and late vegetative stages, respectively. Wheat straw was collected after harvest. Carbon dioxide (CO2) evolution and inorganic N accumulation were measured. Carbon mineralization was described by a sequential decomposition model with a rapid and slow phase, each described by first‐order kinetics. Rapid and slow fraction rate constants and percent rapid were determined. Decomposition ranged from 39% for wheat to 67% for soybean. Carbon dioxide evolution peaked on the third day, and 30 to 50% of residue C was decomposed during the first six days of incubation. Decomposition and N mineralization were higher in the Taloka compared to the Leadvale soil, and generally followed the sequence soybean > corn > wheat residues as did percent rapid fraction, and rapid and slow fraction rate constants. Rapid fraction rate constants ranged from 0.039±0.005 to 0.115±0.005 per day. Slow fraction rate constants ranged from 0.013±0.002 to 0.030±0.002 per day. Percent rapid fraction ranged from 13±2% to 38±2%. The half‐lives of the slow fraction ranged from 23.4±3.5 to 51.8±3.5 days. Nitrogen mineralization, as estimated by ammonium (NH4) and nitrate (NO3) formation occurred only with the soybean residue, whereas the corn and wheat residues were characterized by N immobilization throughout the study.  相似文献   

2.
Abstract

Chloride (Cl) toxicity was suspected in corn (Zea mays L.) growing in a poorly‐drained Atlantic Coast Flatwoods soil where Cl toxicity of soybean {Glycine max (L.) Merr.} was a problem. Field and greenhouse research was conducted with rates of applied Cl in an effort to induce Cl toxicity in corn.

‘Trojan 114’ corn was grown in the greenhouse with Cl rates (KCl) of 0, 364, and 728 ug/g and in the field with rates of 0, 85, 170, and 340 kg/ha. Potassium sulfate (K2SO4) treatments were included to supply equivalent amounts of K as that in KCl.

Phytotoxicity of corn did not occur in greenhouse or field experiments with any fertilizer treatment. In the greenhouse Cl concentrations in 26‐day old corn plants grown in a poorly‐drained Flatwoods soil (Leefield sand ‐ arenic Plinthaquic Paleudult) for the 0 and 728 ug Cl/g treatments were 5.0 and 32.7 g/kg in shoots, 1.6 and 14.9 g/kg in ear leaves, and 1.3 and 16.5 g/kg in stalks, respectively. In the field, Cl treatments applied to corn grown in a poorly‐drained Flatwoods soil (Alapaha sand ‐ arenic Plinthic Paleaquults) were not as effective in increasing Cl concentrations in shoots and ear leaves as that for corn grown in a well‐drained soil (Tifton loamy sand ‐ thermic Plinthic Paleudult) apparently because of the greater amount of residual soil Cl in the poorly‐drained soil. Concentrations of Cl in shoots of corn receiving O and 340 kg Cl/ha were 3.8 and 18.0 g Cl/kg, respectively, for corn grown in the well‐drained soil and 16.1 and 18.0 g Cl/kg, respectively, for corn grown in the poorly‐drained soil. Grain yields were not affected by fertilizer treatments on either soil and Cl concentration in grain for corn grown in the Tifton soil was not different among treatments. These data indicate that corn is not very susceptible to high levels of soil Cl.  相似文献   

3.
Abstract     
In a greenhouse, radish (Raphanus sativus L.), corn (Zea mays L.), soybean (Glycine max Merr), and wheat (Triticum aestivum L.) were grown in soil‐based medium with captan at 60 mg/kg and truban at 30 mg/kg and with different levels of N from (NH4)2SO4 or NaNO3. Growth of radish, soybean, and corn was restricted by NH4‐N compared with NO3‐N. Captan and truban stunted growth of radish and soybean. As NH4‐N or NO3‐N fertilizer increased, the concentration of Ca and Mg in all plants decreased, and the percentage of K in corn, soybean, and wheat increased. Application of captan and truban increased all cation concentrations in corn, wheat, and soybean but decreased Ca concentration in radish. The amount of residual NH4‐N in the medium supplied with (NH4)2SO4 was increased by application of captan or truban. Captan increased the residual NO3‐N in the medium treated with NaNO3. Chemical names used: captan, (N‐(trichloro)methylthio)‐4‐cyclo‐hexene‐l, 2‐dicarboximide); truban, (5‐ethoxy‐3‐trichloromethyl‐l, 2, 4,‐thiadiazole).  相似文献   

4.
Abstract

The effect of nitrapyrin on the fate of fertilizer nitrogen (N) applied to soil needs further investigation. Our objective was to determine the effect of nitrapyrin under two different leaching regimes on the fate of ammonium sulfate‐nitrogen [(NH4)2SO4‐N] added to the soil, namely corn N uptake, denitrification, nitrate leaching and soil residual N. A Nunn sandy clay loam soil (fine, montmorillonitic, mesic, aridic, argiustoll), low in residual inorganic N was used. Nitrogen‐15 enriched (NH4)2SO4 (5 atom% N‐15) was applied at five rates (0, 50, 100, 200, and 400 mg/kg), nitrapyrin at three rates 0, 1.3, and 2.6 μL/kg (0, 2.36, and 4.72 L/ha) and leaching at two rates (0 and 1000 mL over field capacity in two 500‐mL increments at 3 and 6 weeks after planting) in a complete factorial arrangement with three replications. Corn (Zea mays L.) seeds were planted in pots (2 kg soil/pot) and allowed to grow for 80 days in a greenhouse. The atom% N‐15 values were determined in plant tops, leachates and soil samples using a mass spectrometer. The results showed that N fertilizer increased dry matter production, plant N concentration, leaching of nitrates and denitrification significantly. The effect of nitrapyrin on yield was not statistically significant, but, it at a rate equivalent to 4.72 L/ha reduced denitrification and nitrate (NO3) leaching and increased N uptake efficiency. Application of 4.72 L/ha of nitrapyrin versus control showed the following results respectively, N uptake: 46.3 versus 39.6%, denitrification: 26.3 versus 35.3% and NO3 leaching: 2.7 vesus 6.7% of fertilizer N‐15. Nitrapyrin increased soil residual fertilizer N‐15 in organic matter and roots. The result of this study show that application of nitrapyrin at an adequate rate decreases denitrification and NO3 leaching and increases N uptake efficiency.  相似文献   

5.
Emissions of N2O were measured following addition of 15N‐labelled residues of tropical plant species [Vigna unguiculata (cowpea), Mucuna pruriens and Leucaena leucocephala] to a Ferric Luvisol from Ghana at a rate of 100 mg N/kg soil under controlled environment conditions. Residues were also applied in different ratio combinations with inorganic N fertilizer, at a total rate of 100 mg N/kg soil. N2O emissions were increased after addition of residues, and further increased with combined (ratio) applications of residues and inorganic N fertilizer. However, 15N‐N2O production was low and short‐lived in all treatments, suggesting that most of the measured N2O‐N was derived from the applied fertilizer or native soil mineral N pools. There was no consistent trend in magnitude of emissions with increasing proportion of inorganic fertilizer in the application. The positive interactive effect between residue‐ and fertilizer‐N sources was most pronounced in the 25:75 Leucaena:fertilizer and cowpea:fertilizer treatments where 1082 and 1130 mg N2O‐N/g residue were emitted over 30 days. N2O (loge) emission from all residue amended treatments was positively correlated with the residue C:N ratio, and negatively correlated with residue polyphenol content, polyphenol:N ratio and (lignin + polyphenol):N ratio, indicating the role of residue chemical composition in regulating emissions even when combined with inorganic fertilizer. The positive interactive effect in our treatments suggests that it is unlikely that combined applications of residues and inorganic fertilizer can lower N2O emissions unless the residue is of very low quality promoting strong immobilisation of soil mineral N.  相似文献   

6.
Abstract

The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have been developed to assess residual soil nitrogen (N) sufficiency for corn (Zea mays L.) in the humid eastern U.S. We conducted field studies at 47 sites during 1990 and 1991 to evaluate the use of the PSNT and PTNT for corn in Coastal Plain, Piedmont, and Appalachian Ridge and Valley regions of Virginia. Seven rates of fertilizer N (0, 45, 90, 135, 180, 225, and 270 kg/ha) were applied at corn height of 0.40 to 0.50 m and replicated four times in a randomized complete block design. Whole corn plants and soil to a depth of 0.30 m were sampled when corn height was 0.15 to 0.30 m to estimate available soil N prior to the application of fertilizer N treatments. Corn grain yield response to fertilizer N was used to assess residual soil N availability. Nitrogen concentration of whole corn plants at 0.15 to 0.30 m height was not an accurate indicator of plant‐available soil N. Corn yields were maximized without sidedress N at the 19 sites where soil NO3‐N was at least 18 mg‐kg‐1 and at the 17 sites where soil (NO3+NH4)‐N was at least 22 mg‐kg‐1. The PSNT predicted corn N sufficiency regardless of soil physiographic region or surface texture; however, the critical values for NO3‐N and (NO3+NH4)‐N were 3 to 5 mg‐kg‐1 lower than those established in Pennsylvania and Maryland, where cooler soil temperatures may permit greater residence time of inorganic N.  相似文献   

7.
Notice     
Abstract

Interest is increasing in alternative, reduced input cropping systems. Potential interactive effects of input additions or eliminations on crop yield must be delineated to develop the most resource‐efficient cropping systems. Information of this type is especially lacking in the southern United States. The principal objective of this field study was to determine the main and interactive effects of nitrogen (N) fertilization, herbicide, and insecticide on grain yields in a corn (Zea mays L.)‐soybean [(Glycine max (L.) Merr.)] rotation. Dryland studies were conducted for four years (1990–1993) on a Weswood silt loam soil (fine, mixed, thermic Fluventic Ustochrept). Variables included none or “optimal”; applications of N fertilizer, herbicide, and insecticide. Mean corn grain yield was increased 156% by N fertilization compared to the no N control. Herbicide significantly increased corn grain yield two of four years, while soil‐applied insecticide had no effect. Johnsongrass [Sorghum halepense (L.) Pers.] was identified as the primary competitive weed species in corn. No interactions of inputs were observed for corn grain yield. Nitrogen fertilization and herbicide did not affect soybean yield, but insecticide increased average soybean yield by 29%. Interactions of N fertilization and insecticide and herbicide and insecticide were significant for soybean yield.  相似文献   

8.
Summary The dynamics of basally applied 15N-labeled ammonium sulfate in inorganic and organic soil fractions of five wetland rice soils of the Philippines was studied in a greenhouse experiment. Soil and plant samples were collected and analyzed for 15N at various growth stages. Exchangeable NH4 + depletion continued after 40 days after transplanting (DAT) and corresponded with increased nitrogen uptake by rice plants. Part of the applied fertilizer was fixed by 2:1 clay minerals, especially in Maligaya silty clay loam, which contained beidellite as the dominant clay mineral. After the initial fixation, nonexchangeable 15N was released from 20 DAT in Maligaya silty clay loam, but fixation delayed fertilizer N uptake from the soil. Part of the applied N was immobilized into the organic fraction. In Guadalupe clay and Maligaya silty clay loam, immobilization increased with time while the three other soils showed significant release of fertilizer N from the organic fraction during crop growth. Most of the immobilized fertilizer N was recovered in the nondistillable acid soluble (alpha-amino acid + hydrolyzable unknown-N) fraction at crop maturity. Between 61% and 66% of applied N was recovered from the plant in four soils while 52% of fertilizer N was recovered from the plant in Maligaya silty loam. Only 20% – 30% of the total N uptake at maturity was derived from fertilizer N. Nmin (mineral N) content of the soil before transplanting significantly correlated with N uptake. Twenty-two to 34% of applied N was unaccounted for possibly due to denitrification and ammonia volatilization.  相似文献   

9.
Abstract

Tillage, cropping system, and cover crops have seasonal and long‐term effects on the nitrogen (N) cycle and total soil organic carbon (C), which in turn affects soil quality. This study evaluated the effects of crop, cover crop, and tillage practices on inorganic N levels and total soil N, the timing of inorganic N release from hairy vetch and soybean, and the capacity for C sequestration. Cropping systems included continuous corn (Zea mays L.) and stalk residue, continuous corn and hairy vetch (Vicia villosa Roth), continuous soybeans (Glycine max L.) plus residue, and two corn/soybean rotations in corn alternate years with hairy vetch and ammonium nitrate (0, 85, and 170 kg N ha?1). Subplot treatments were moldboard plow and no tillage. Legumes coupled with no tillage reduced the N fertilizer requirement of corn, increased plant‐available N, and augmented total soil C and N stores.  相似文献   

10.
Abstract

The effects of liming (7 500 kg CaCO3/ha) and rate of urea application (0,50,100, and 200 kg N/ha) and its placement at the surface or at 5 cm depth on grain yield and nutrient uptake by corn grown on an acidic tropical soil (Fluventic Eutropept) were studied. Liming significantly increased grain yield, N uptake, and P and K uptake although Ca and Mg uptake, generally, were unaffected. Sub‐surface application of urea increased N uptake only. Yield response to applied N was observed up to 50 kg N/ha when limed but at all rates in the absence of liming. It therefore, reduced the fertilizer N requirement for optimum grain yield. Liming the acidic soil also reduced exchangeable Al but increased nitrification rate and available P in the soil profile (at least up to 0.6 m depth).  相似文献   

11.
Abstract

The volume of soil treated with P fertilizer affects P uptake by the crop. Earlier studies have shown that the stimulation of root growth in P‐fertilized soil was similar for both corn (Zea mays L.) and soybean (Glycine max L. Merr). The objective of this research was to determine the effect of fertilizer P placement on P uptake and shoot and root growth of spring wheat (Triticum vulgare L.). Wheat was grown for 34 days in Raub silt loam (Aquic Argiudolls) in a controlled climate chamber. One rate of phosphate per pot, 150 mg P per three kg of soil, was mixed with 2, 5, 10, 20, 40 and 100% of the soil in the pot. The P was equilibrated with moist soil for 5 days at 70°C followed by 21 days at 25° C before transplanting 8‐day‐old wheat plants into each 3 L pot. The P stimulation of root growth in the P‐treated soil was similar to that for corn and soybeans. The effect could be described by the equation y = x0.7 where y is the fraction of the root system in the P‐fertilized soil where P is mixed with x fraction of the soil. The greatest P uptake and plant growth occurred when added P was mixed with 20% of the soil.  相似文献   

12.
Subsoil acidity restricts root growth and reduces crop yields in many parts of the world. More than half of the fertilizer nitrogen(N) applied in crop production is currently lost to the environment. This study aimed to investigate the effect of gypsum application on the efficiency of N fertilizer in no-till corn(Zea mays L.) production in southern Brazil. A field experiment examined the effects of surface-applied gypsum(0, 5, 10, and 15 Mg ha~(-1)) and top-dressed ammonium nitrate(NH_4NO_3)(60, 120, and 180 kg N ha~(-1)) on corn root length, N uptake, and grain yield. A greenhouse experiment was conducted using undisturbed soil columns collected from the field experiment site to evaluate NO_3-N leaching, N uptake, and root length with surface-applied gypsum(0 and 10 Mg ha~(-1)) and top-dressed NH_4NO_3(0 and 180 kg N ha~(-1)). Amelioration of subsoil acidity due to gypsum application increased corn root growth,N uptake, grain yield, and N use efficiency. Applying gypsum to the soil surface increased corn grain yield by 19%–38% and partial factor productivity of N(PFPN) by 27%–38%, depending on the N application rate. Results of the undisturbed soil column greenhouse experiment showed that improvement of N use efficiency by gypsum application was due to the higher N uptake from NO_3-N in the subsoil as a result of increased corn root length. Our results suggest that ameliorating subsoil acidity with gypsum in a no-till corn system could increase N use efficiency, improve grain yield, and reduce environmental risks due to NO_3-N leaching.  相似文献   

13.
Abstract

Fertilization and harvest frequency affect yield and quality of forages. The purposes of this experiment were to determine (i) the effects of fertilization and frequent harvesting on yield and quality of tall fescue (Festuca arundinacea Schreb.) and smooth bromegrass (Bromus inermis Leyss.) and (ii) the efficiency of N in animal waste as compared with inorganic N fertilizer for forage production of these cool season grasses. ‘Fawn’ tall fescue and ‘Southland’ smooth bromegrass were grown in the greenhouse on Pullman clay loam topsoil (fine, mixed thermic Torrertic Paleustoll) under eleven fertilizer treatments and two harvest regimes. Nitrogen fertilizer increased yields, N and K concentrations and K/(Ca + Mg) ratios and decreased P, Ca, and Mg concentrations. Phosphorus and K fertilizers did not affect yields but applied P increased P and tended to decrease N and Ca concentrations. Applied K tended to increase Ca concentrations. Recovery of N from feedlot manure ranged from 0.8 to 14%, whereas, recovery from NH4NO3 averaged 64%. Harvesting at 3‐week rather than at 6‐week intervals reduced yields 25%; however, N and P removal were higher under the 3‐week harvest regime. Even though forage production was reduced under heavy utilization, the grasses required more N fertilizer under heavy than under lighter utilization. The two grasses produced similar yields under the 3‐week cutting regime and at N rates through 340 kg/ha under the 6‐week cutting regime. Tall fescue yields were higher with the higher N rates under the 6‐week cutting regime. Smooth bromegrass forage was higher than tall fescue forage in N, K, and Ca, whereas tall fescue forage was higher in P and Mg.  相似文献   

14.
Abstract

A significant portion of chemical zinc (Zn) fertilizers applied to calcareous soils is not absorbed by the first crop and may, therefore, affect the growth and chemical composition of the subsequent crops. This is called the residual effect of Zn. Soil tests may be used to predict such effects. The present experiment was conducted to study the residual effects of zinc sulfate (ZnSO4) on the second crop of corn (Zea mays L.) grown on selected highly calcareous soils of Iran and to compare the suitability of three soil tests for prediction of the effects. Twenty highly calcareous soils of southern Iran (16–58% calcium carbonate equivalent; pH 7.9–8.5), previously treated with three levels of Zn (0, 10, and 20 mg Zn/kg as ZnSO4) and under one crop of corn, was used in greenhouse to grow a second crop of corn without additional Zn fertilizer but with uniform application of nitrogen (N), phosphorus (P), and iron (Fe). Soils were sampled before the second crop and extracted with three Zn extradants, DTPA, EDTA‐(NH4)2CO3, and EDTA. Dry weight of plant tops and Zn concentration and uptake after eight weeks under the greenhouse conditions were used as the plant responses to residual Zn. Statistical analyses including F‐test and multiple regression equations showed that the overall effect of previously‐applied Zn on dry matter was nonsignificant, but Zn concentration and uptake were significantly increased. The three soil tests predicted the Zn concentration and uptake equally well. Moreover, DTPA and EDTA soil tests could predict the dry matter of plants at the highest level of previuosly‐applied Zn (20 mg Zn/kg), especially when selected chemical properties of soil, namely, calcium carbonate equivalent or organic matter content, were considered in the regression equations.  相似文献   

15.
A computational exercise was undertaken to quantify the percent N derived from atmosphere %Ndfa) in soybean and consequent N benefit from biological N2‐fixation process annually accrued to the soil by the soybean crop using average annual N‐input/‐output balance sheet from a 7 yr old soybean‐wheat continuous rotational experiment on a Typic Haplustert. The experiment was conducted with 16 treatments comprised of combinations of four annual rates of farmyard manure (FYM ? 0, 4, 8, and 16 t ha–1) and four annual rates of fertilizer N (? 0, 72.5, 145, and 230 kg N ha–1) applications. The estimated N contributed through residual biomass of soybean (RBNS) consisting of leaf fall, root, nodules, and rhizodeposition varied in the ranges of 7.02–16.94, 11.65–28.83, 3.31–8.91, and 11.3–23.8 kg N ha–1 yr–1, respectively. A linear relationship was observed between RBNS and harvested biomass N (HBNS) of soybean in the form of RBNS = 0.461 × HBNS – 20.67 (r = 0.989, P < 0.01), indicating that for each 100 kg N assimilated by the harvested biomass of soybean, 25.4 kg N was added to the soil through residual biomass. The Ndfa values ranged between 13% and 81% depending upon the annual rates of application of fertilizer N and FYM. As per the main effects, the %Ndfa declined from 76.4 to 26.0 with the increase in annual fertilizer‐N application from 0 to 230 kg N ha–1, whereas %Ndfa increased from 40.8 to 65.8 with the increase in FYM rates from 0 to 16 t ha–1, respectively. The N benefit from biological N2 fixation accrued to the soil through residual biomass of soybean ranged from 7.6 to 53.7 kg N ha–1 yr–1. The treatments having %Ndfa values higher than 78 showed considerable annual contribution of N from N2 fixation to the soil which were sufficient enough to offset the quantity of N removed from the soil (i.e., native soil N / FYM‐N / fertilizer‐N) with harvested biomass of soybean.  相似文献   

16.
Abstract

Long‐term tillage and crop management studies may be useful for determining crop production practices that are conducive to securing a sustainable agriculture. Objectives of this field study were to evaluate the combined effects of crop rotation and tillage practices on yield and changes in soil chemical properties after 12 years of research on the Clyde‐Kenyon‐Floyd soil association in northeastern Iowa. Continuous corn (Zea mays L.) and a corn‐soybean [Glycine max L. (Herr.)] rotation were grown using moldboard plowing, chisel plowing, ridge‐tillage, or no‐tillage methods. Tillage and crop rotation effects on soil pH, Bray P1, 1M NH4OAc exchangeable K, Ca, and Mg, total C, and total N in the top 200 mm were evaluated. Profile NO3‐N concentrations were also measured in spring and autumn of 1988. Crop yields and N use efficiencies were used to assess sustainability. Bray P1 levels increased, but exchangeable K decreased for all cropping and tillage methods. Nutrient stratification was evident for no‐tillage and ridge‐tillage methods, while the moldboard plowing treatment had the most uniform soil test levels within the 200 mm management zone. Chisel plowing incorporated fertilizer to a depth of 100 mm. Soil pH was lower with continuous corn than with crop rotation because of greater and more frequent N applications. Profile NO3‐N concentrations were significantly different for sampling depth and among tillage methods in spring 1988. In autumn the concentrations were significantly different for sampling depth and for a rotation by tillage interaction. Estimated N use efficiencies were 40 and 50 kg grain per kg N for continuous corn, and 48 and 69 kg grain per kg N for rotated corn in 1988 and 1989, respectively. The results suggest that P fertilizer rates can be reduced, but K rates should probably be increased to maintain soil‐test levels for this soil association. Crop rotation and reduced tillage methods such as ridge‐tillage or chisel plowing appear to meet the criteria for sustainable agriculture on these soils.  相似文献   

17.
Peanut (Arachis hypoaaea L.) is a major cash crop in Georgia. Corn (Zea mays L.) is the preferred rotation crop, but is often not profitable because of large inputs costs. Fertilizer comprises approximately 50% of the variable production costs of irrigated corn. There is interest in reducing fertilizer inputs, in particular N, to reduce variable costs and decrease nitrate leaching to groundwater, but yields may suffer. Our objective was to investigate the effect of N, P, and K fertilizer rates on the yield of N‐fertigated corn in a corn/peanut rotation. Field experiments were conducted during 1987 and 1988 on a Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudult) at Tifton, GA. Treatments were three rates each of N, P, and K fertilizer in a complete factorial. Nitrogen, P, and K rates were 168, 252, 336 kg N ha‐1 yr‐1; 44, 73, 103 kg P ha‐1 yr‐1; and 84, 223, and 363 kg K ha‐1 yr‐1, respectively. Grain yields were large, 12.6 and 10.4 Mg ha‐1 in 1987 and 1988, respectively, but not affected by N, P, or K rate. Since the lower rates of N, P, and K were less than recommended, fertilizer use efficiency for fertigated corn can be improved, for at least one year, by reducing N, P, and K fertilizer rates to less than current recommendations. Rates of N, P, and K did not result in a substantial difference in the concentration of essential nutrients. Stalk rot was limited (< 15%), but decreased with increasing K fertilizer rate.  相似文献   

18.
Abstract

Crop response to fertilizer nitrogen (N) is dependent upon tillage management. This study was conducted to determine how tillage rotation influences non‐irrigated crop growth, N uptake and yield. The effects of tillage rotation, N rate and N timing schedule on early season dry matter production and N uptake, ear leaf N concentration at silking, and yield of corn [Zea mays (L.) Pioneer 3378] were investigated at Painter, VA, on an Altavista loam (fine‐loamy, mixed, thermic Aquic Hapludult). In 1986, maximum yields achieved in the 6‐year continuous no till (NT) [5.82 Mg/ha] and first year no till (AT) [5.64 Mg/ha] were significantly greater than that of the 6‐year continuous conventional till (CT) [3.67 Mg/ha], but no yield differences were obtained in the drier 1987 season. A higher rate of N fertilizer was required to obtain maximum yield in the first year no till (168 kg N/ha) than in the NT (112 kg N/ha) during 1986. Early 1986 N uptake and growth response with and without N at planting increased in the order CT < AT = NT and AT < CT < NT, respectively, indicating greatest immobilization of soil N occurred in the newly established no till soil. Lack of differences in critical ear leaf N values developed for NT and CT in each year imply that plant norms developed for one tillage system may accurately assess N status of corn grown under different tillage practices.  相似文献   

19.
We did a pot experiment with three different fertilized soils (no fertilizer (No-F), inorganic fertilizer nitrogen, phosphorus and potassium (NPK), manure plus inorganic fertilizer (MNPK)) from a 19-year fertilizer trial. Three N treatments, (1) no N, (2) 100 mg/kg urea-15N (N), (3) 50 mg/kg urea-15N + 50 mg/kg corn straw-N (1/2N + 1/2S), were applied to each soil. The residual soil from the same treatments was used to grow second wheat crop. The MNPK soil had significantly higher nitrogen use efficiency (NUE) in the first growing season, and lower N loss than the NPK, and No-F soils. The 1/2N + 1/2S treatment decreased NUE on each soil, even though the MNPK soil still had highest NUE and lowest N loss. The residual 15N use efficiency (RNUE) in 1/2N + 1/2S treatment of MNPK soil was higher than NPK and No-F soils. We concluded that long-term application of manure plus inorganic fertilizer increased NUE and decreased N loss.  相似文献   

20.
A greenhouse experiment was conducted in which four varieties of soybean (Glycine max L.) and three varieties of sorghum (Sorghum bicolor L. Moench) were grown in a calcareous soil with and without soil applied FeEDDHA (0 and 2 mg Fe/kg soil). Soil applications of FeEDDHA increased Fe concentrations and reduced Mn concentrations in all varieties of soybean and eliminated Mn toxicity symptoms in Corsoy soybeans. Soil applications of FeEDDHA did not increase Fe uptake or affect Mn uptake into sorghum leaves. This study tends to support the hypothesis that there are distinct plant mechanisms between dicots and graminaceous species for the uptake of Fe, and that these mechanisms have a direct effect on Mn availability for plant uptake.  相似文献   

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