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1.
《Journal of plant nutrition》2013,36(7):1383-1402
Abstract

Narrow‐row soybean [Glycine max (L.) Merr.] production in corn [Zea mays L.]–soybean rotations results in various distances of soybean rows from previous corn rows, yet little is known about soybean responses to proximity to prior corn rows in no‐till systems. The objective of this study was to evaluate the impacts of preceding corn rows on potassium (K) nutrition and yield of subsequent no‐till soybeans. Four field experiments involving a corn–soybean rotation were conducted on long‐term no‐till fields with low to medium K levels from 1998 to 2000 near Paris and Kirkton, Ontario, Canada. In the corn year, treatments included K application rate and placement in conjunction with tillage systems or corn hybrids. Before soybean flowering, soil exchangeable K concentrations (0–20 cm depth) in previous corn rows were significantly higher than those between corn rows. At the initial flowering stage, trifoliate leaf K concentrations of soybeans in preceding corn rows were 2.0 to 5.3 g kg?1 higher than those from corresponding plants between corn rows. Yield of no‐till soybeans in previous corn rows increased 10 to 44% compared to those between previous corn rows. Positive impacts of prior corn rows on soil K fertility, soybean leaf K, and soybean yield occurred even when K fertilizer was not applied in the prior corn season. Deep banding of K fertilizer tended to accentuate row vs. between‐row effects on soybean leaf K concentrations in low‐testing soils. Corn row effects on soybeans were generally not affected by either tillage system or corn hybrid employed in the prior corn crop. Potassium management strategies for narrow‐row no‐till soybeans should take the potential preceding corn row impacts on soil K distribution into account; adjustments to current soil sampling protocols may be warranted when narrow‐row no‐till soybeans follow corn on soils with low to medium levels of exchangeable K.  相似文献   

2.
Abstract

A maximum crop yield depends upon a balanced supply of the 16 essential elements throughout the growth cycle. Achieving this balance can often be achieved by plant analysis guided fertilizer treatments. Sampling is the first step when conducting a plant analysis. An extensive survey of the literature revealed a lack of published research that statistically determined what number of plants must be sampled in order to obtain a representative sample. In our study, we utilized three field research sites in South Dakota, two locations planted to soybean (Glycine max L.) [Experiments 1 and 2] and the other to corn (Zea mays L.) [Experiment 3]. Ninety six plants were sampled at each site, collecting leaf tissue. After the leaf samples were collected, dried, and ground, they were analyzed for their N, P, K, Ca, Mg, S, Mn, and Zn content. Stein's equation, n = t2s2/d2, was used to estimate the number of plants required to be sampled in order to obtain a given level of precision and accuracy for each element. Our results indicate that the number of plants to be sampled in order to estimate the population mean for the elements assayed are 16 and 34 for soybean and corn, respectively.  相似文献   

3.
The objective of the present study was to provide experimental evidence on the active role of plant roots in rock weathering and the importance of the proximity of roots to rock in the weathering process. The analysis was based on the release of different elements from basalt rock particles by three crop species: rice, soybean and maize. Quantitative results were obtained by chemical analyses. We designed two types of hydroponic crop pots, in which fine roots were allowed (or not allowed) to make contact with rock particles by using coarse (or fine) net bags. Experiments were carried out in a controlled glasshouse during a 42 d period. The release of elements in the presence of the plants was calculated by subtracting the decrease in the amounts of elements in the media from the amounts absorbed by the plants. We observed the positive effect of plants on the release of elements from the rock particles and the highest amounts were released in the soybean pots. The amounts of Si, Ca, Mg, Mn and Al released increased by a factor of 2–5, 2–7, 16–112, 3–19 and 6–60, respectively. The amount of Fe released by soybean plants from the rock particles was 4–6 times higher than that by other plants. Between the coarse and fine net pots, the amount of released elements differed significantly only for soybean (Si, Mg and Mn at p < 0.01 level and Fe at p < 0.05 level), which displayed the most vigorous growth. Our results imply that weathering may be caused partially by the absorption of nutrient elements directly through the interface of fine roots and rock particles, and is most likely associated with alterations of the local rhizosphere conditions surrounding the roots.  相似文献   

4.
Liming and phosphorus (P) applications are common practices for improving crop production in acid soils of the tropical as well as temperate regions. Four greenhouse experiments were conducted on an Oxisol (clayey, kaolinitic, isothermic, Typic Haplustox) to evaluate response of liming (0,2, and 4 g/kg) and P application (0, 50, and 175 mg P/kg) in a factorial combination on growth and nutrient uptake by upland rice (Oryza sativa L.), wheat (Triticum aestivum L.), common bean (Phaseolus vulgaris L.), and corn (Zea mays L.). Phosphorus application significantly (P<0.01) increased dry weight of tops of all the four crop species as well as dry weight of roots of wheat and corn. Liming significantly (P<0.01) improved growth of common bean and corn but had significant negative effects on rice growth. Maximum dry weight of tops of rice and wheat was obtained at 175 mg P/kg without lime. Maximum dry weight of tops in common bean was obtained at 4 g lime/kg with 175 mg P/kg of soil. In all the crops, increasing levels of applied P significantly increased nutrient uptake. With some exceptions, increasing levels of lime tend to reduce uptake of P, zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) and increase the uptake of calcium (Ca) and magnesium (Mg) in all the crop species. Decrease in potassium (K) uptake, due to high lime, is probably due to antagonistic effects of Ca and Mg and reduced micronutrients uptake is probably due to increased soil pH resulting in decreased availability of these elements to plants. Therefore, in these types of acid soils, one should avoid over liming.  相似文献   

5.
ABSTRACT

Winter camelina [WC, Camelina sativa (L.) Crantz] and field pennycress (FP, Thlaspi arvense L.) are emerging oilseed crops in corn–soybean rotations, but little is known about their cover crop potential. A 2-year study was conducted in Minnesota, USA to evaluate the effect of winter oilseed crops on nitrogen (N) use, growth and yield of corn and soybean. Treatments included WC, FP, winter rye (WR, Secale cereale L.), and a no cover crop (NC) control. Oilseed crops produced 40–50% less spring biomass and accumulated less N compared to WR. The tissue-N of WC and FP was 39.0% and 6.6% higher than WR, respectively. The C:N ratio of cover crops was lower than 20:1, suggesting rapid decomposition. Compared with NC, cover crops lowered soil nitrate before major crops planting, but the post-harvest N profile following corn and soybean was not affected. Compared with NC, cover crops significantly decreased corn yield, with 8.7%, 9.5% and 9.8% reduction following WC, FP and WR, respectively. Cover crops did not affect growth, yield and N uptake of soybean. Oilseed crops showed potential to improve N cycling in the rotation, but more research of their impact on major crops is needed.  相似文献   

6.
The soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is a major pest of soybeans (Glycine max L. Merrill) in the central and southern United States. Soybean cyst nematode causes stunted top growth, root pruning and symptoms of mineral element deficiency in soybeans. The objective of this study was to determine the effect of two selections of SCN (I selected on PI209332 and IV selected on PI 89772) on macronutrient uptake, translocation, and tissue concentrations of soybean and to determine the elemental composition of cysts isolated from roots. Soybeans were grown in plastic tubes in the greenhouse where the middle one‐third of the Hodge fine sand (Typic Udipsamment) contained 0, 25,000, or 50,000 SCN eggs. After 35 days, plants were harvested and tissue nutrient element concentrations were determined. Plants infested with both SCN selections were smaller and had much less root volume than controls. Dry weight of each plant tissue decreased as SCN population was increased. Root concentration of potassium (K) and magnesium (Mg) was decreased, whereas root calcium (Ca) and phosphorus (P) concentrations were increased with SCN treatments. Leaf Mg and Ca concentrations increased with SCN treatment. Magnesium uptake per unit root volume was decreased, but Mg translocation (% of total plant content in aerial portion) was increased with SCN treatment. Calcium uptake per unit of root volume was increased, but translocation was unchanged by SCN treatment. The Ca and P concentration of cysts isolated from the soybean roots was high. This high concentration of Ca in cysts is interesting based on the greater root Ca concentration and uptake per unit of root volume in SCN infested plants. Since total uptake and root concentrations of both K and Mg were decreased by SCN treatment, infested soybeans might require very high levels of K and Mg fertilization. These results indicate that K and Mg fertility should be followed closely in SCM‐infested soybean fields.  相似文献   

7.
Abstract

The objective of this study was to provide agronomic, nematode, and economic analysis of alternative production rotation systems for soybeans (Glycine max L. Merr.) on a silt loam soil association in Arkansas. Monocropped soybeans and soybeans double‐cropped with wheat (Triocum aestivam L.) was included as well as grain sorghum (Sorghum bicolor L. Moench) under dryland conditions in order to reduce soybean cyst nematode (SCN, Heteroderaglycine Ichinohe) populations. A total of seven crop rotations and eleven treatments that included alternative tillage conditions and wheat stubble management practices were analyzed using data from 1980–1984 experiments conducted at the Arkansas Cotton Branch Experiment Station on a silt loam Loring‐Calloway‐Henry Association (Alfisols). Although crop rotation was effective for nematode suppression, yields for double‐cropped soybeans were comparable to soybean yields under monocropped’ continuous management practices. Economic results indicated that average net returns of $338.50 per hectare (about $ 137 per acre) were highest for the continuous double‐cropped wheat‐soybean production management systems which combine the conventional tillage method with burning of wheat stubble. For the conditions analyzed and level of SCN present, this research provides evidence that control of the soybean cyst nematode through rotation practices that utilize grain sorghum is not economically efficient where continuous double‐cropped wheat‐soybeans systems can be incorporated.  相似文献   

8.
Abstract

Greenhouse‐pot experiments were conducted to compare wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merrill] in terms of their potassium (K) and magnesium (Mg) uptake. Previously, a field study indicated that various rates of K and Mg fertilization did not produce a significant wheat‐yield response. However, a yield increase with residual K and Mg was measured for the subsequent soybean crop. The 0 to 15 cm layer of Norfolk loamy fine sand (fine loamy, siliceous, thermic Typic Kandiudult) from two different sites was used for the pot experiments. Soil from both sites had a pH of 5.1. Potassium as potassium sulfate (K2SO4) was mixed into the soil from the K‐deficient site and Mg as magnesium sulfate (MgSO4) was mixed into the soil from the Mg‐deficient site. ‘Florida 301’ wheat and ‘Cobb’ soybean were grown in winter and summer, respectively.

Soybean and wheat were similar in K uptake/g of roots on the first and second sampling dates. However, by the third sampling date, K uptake/g of wheat roots was about twice as high as for soybean. Potassium uptake/cm of soybean roots was two to five times that of wheat at each sampling date. Magnesium uptake/g of soybean roots was about four to five times as high as wheat on each sampling date. Similarly, Mg uptake/cm of soybean roots was 10 to 30 times higher than for wheat. Soybean showed higher total K and Mg content than wheat, suggesting that soybean has a higher demand for both K and Mg. The higher demand for K and Mg by soybeans than by wheat suggests that wheat could meet its demand for K and Mg at much lower soil levels than that for soybean. This would also explain a grain‐yield response to K and Mg by soybeans in the previously reported field study, despite a lack of yield response by wheat grown on the same site.  相似文献   

9.
Crop rotation adoption in no‐tillage systems (NTS) has been recommended to increase the biological activity and soil aggregation, suppress soil and plant pathogens, and increase the productivity aiming at the sustainability of agricultural areas. In this context, this study aimed to assess the effect of crop rotation on the arbuscular mycorrhizal fungi (AMF) community and soil aggregation in a soil cultivated for nine years under NTS. Treatments consisted of combinations of three summer crop sequences and seven winter crops. Summer crop sequences consisted of corn (Zea mays L.) monoculture, soybean (Glycine max L. Merrill) monoculture, and soybean–corn rotation. Winter crops consisted of corn, sorghum (Sorghum bicolor (L.) Moench), sunflower (Helianthus annuus L.), sunn hemp (Crotalaria juncea L.), pigeon pea (Cajanus cajan (L.) Millsp.), oilseed radish (Raphanus sativus L.), and millet (Pennisetum americanum (L.) Leeke). Soil samples were collected at a depth of 0–0.10 m for analyses of soil chemical, physical, and biological attributes. Spore abundance, total glomalin, and soil aggregate stability index were higher in the soil under corn monoculture. The highest values of aggregate mean weight diameter were observed in the soybean–corn rotation (3.78 mm) and corn monoculture (3.70 mm), both differing from soybean monoculture (3.15 mm), while winter crops showed significant differences only between sorghum (3.96 mm) and pigeon pea (3.25 mm). Two processes were identified in the soil under summer crop sequences. The first process was observed in PC1 (spore abundance, total glomalin, easily extractable glomalin, pH, P, and Mg2+) and was related to AMF; the second process occurred in PC2 (aggregate mean weight diameter, soil aggregate stability index, K+, and organic matter) and was related to soil aggregation. The nine‐year no‐tillage system under the same crop rotation adoption influenced AMF abundance in the soil, especially with corn cultivation in the summer crop sequence, which promoted an increased total external mycelium length and number of spores of AMF. In addition, it favored an increased soil organic matter content, which is directly related to the formation and stability of soil aggregates in these managements.  相似文献   

10.
Abstract

Environmental regulations and limited storage space compel processors to remove spent limestone and not stockpile it on site. This material is often used as a liming material to control pH on acid soils, but in some cases may have to be applied to alkaline soils. This study was undertaken to evaluate the effect of applying sugar beet processing lime on soils with an alkaline solum. Studies were conducted at seven sites representing four soil series. Lime was applied at rates of 0,1.4, 2.8, and 5.6 magnesium (Mg) ha‐1. Sugar beet (Beta vulgaris L.), soybean (Glycine max L.), cora (Zea mays L.), field bean (Phaseolus vulgaris L.), and wheat (Triticum aestivum L.) were used as test crops. Yield of sucrose and roots of sugar beet as well as yield of soybean, corn, field bean, and wheat were not affected by lime application. Manganese (Mn) and zinc (Zn) concentration in leaves of sugar beet and soybean, and whole field bean plants decreased with increasing lime rates. These results show this lime may be applied at rates up to 5 Mg ha‐1 once every three years on these alkaline soils without negatively affecting the yield of sugar beet, soybean, corn, field bean, and wheat. Nutritional status of these crops should be carefully monitored after lime application.  相似文献   

11.
Increased crop diversity and length of rotation may improve corn (Zea mays L.) yield and water- and nitrogen-use efficiency (WUE and NUE). The objectives of this study were to determine effects of crop rotation on corn yield, water use, and nitrogen (N) use. No-tillage (NT) crop rotations were started in 1997 on a Barnes clay loam (fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, S.D. Rotations were continuous corn (CC), corn–soybean [Glycine max (L.) Merr.] (CS), a 3-year rotation of corn–soybean–oat/pea (Avena sativa L. and Pisum sativum L.) hay (CSH), a 3-year rotation of corn–soybean–spring wheat (Triticum aestivum L.) (CSW), and a 5-year rotation of corn–soybean–oat/pea hay companion seeded with alfalfa (Medicago sativa L.)–alfalfa–alfalfa (CSHAA). Fertilizer N was applied to corn on all rotations at planting (16 kg N ha?1) and side-dressed (64 kg N ha?1). Average corn grain yields (1998–2007) were greatest under CSW (7.38 Mg ha?1) and least under CC (4.66 Mg ha?1). Yields were not different among CSH, CSW, and CSHAA rotations. Water-use efficiency of rotation was ordered as CSW > CSH > CSHAA > CS > CC. Nitrogen-use efficiency was greatest under CSW and least under CC. There were no differences in yield advantage (YA) among crop rotations during years with plentiful early-season rainfall (May 1–July 31). In years with low spring rainfall, YA was greatest under CSW (54%) and least under CSHAA (33%). Corn yields under extended rotations (CSH, CSW, and CSHAA) were greater than under CC and CS, but lack of rainfall may result in reduced yields under CSHAA.  相似文献   

12.
Abstract

Research is needed to compare the different techniques for developing site‐specific phosphorus (P) recommendations on a field‐wide basis. The objective of this study was to determine the impact different techniques for developing site‐specific P recommendation maps on yield and profitability. Enterprise analysis combined with a crop simulation model and detailed field characterization was used to estimate the value of spatial P information in a system where N was not limiting. The systems evaluated were continuous corn (Zea mays) and corn and soybean (Gfycine max) rotations where sampling and fertilizer applications were applied annually and semi‐annually, respectively. The sampling techniques tested were: (i) an unfertilized P control; (ii) whole field; (iii) whole field plus historic information (feedlot); (iv) landscape positions; (v) soil type; (vi) soil type plus historic information (feedlot); and (vii) 90‐m grid sampling. The finding of this study were based on soil samples collected from a 30 by 30‐m grid. The value of the spatial information was dependent on the crops response to P, the accuracy of the different sampling techniques, crop rotation, and the length of time between sampling dates. All of the sampling techniques produced different application maps. The recommendation map based on a single composite sample under fertilized 56.5% of the field. Increasing the sampling density reduced the percentage of under‐fertilized land. If corn had a low P response, then simulation/enterprise analysis indicated that applying P did not increased profits. For all scenarios tested: (i) the soil type + historic sampling approach had higher potential profits than the 90 m grid sampling approach; and (ii) there was no economic benefit associated with the 90‐m grid sampling. However, if research shows that amortization of sampling and analysis costs over 3 or 4 years is appropriate, then it may be possible to derive economic benefit from a 90‐m grid sampling. For a corn/soybean rotation, where fertilizer was applied when corn was planted and N and P was not applied to soybeans, enterprise/ simulation analysis (2.8 Mg ha‐1 soybean yield goal and a moderate P model) showed that soil + historic sampling approach increased profitability $3.74 ha‐1 when compared to the uniform P treatment.  相似文献   

13.
Residual effects on soybeans (Glycine max L.) from phosphrous (P) fertilizer bands applied 5 cm to the side and 5 cm below the seeds of a preceding corn (Zea mays L.) crop on a Brandt silt loam soil (fine‐silty, mixed Udic Haploboroll) were studied after an intervening no‐till fallow period. The P rates applied were 0, 12, 24, and 49 kg P ha‐1. Soybean rows were planted as close as possible to the preceding corn rows. Soybean tissue was sampled at the early bloom stage in each row of the paired‐row design. Twenty soil column (2.5x3 cm) samples were collected from the 0–15 cm depth along a 50‐cm‐long trench that bisected a soybean row. The distance of the previous P band (column with the highest extractable Bray‐I P level) from the soybean row became a variable in this experiment with category range distances of <6 cm, 6–9 cm, and >9 cm from band to row. Residual P from all application rates increased shoot dry matter weight, shoot P uptake, and to a lesser extent grain yield in comparison to the unfertilized soybeans. Distance of the P band from the row was more important than the P concentration in the band. Shoot P uptake and grain yield were significantly larger for fertilized compared to unfertilized soybeans when the band distance was less than 9 cm from the row. Residual P band distance of greater than 9 cm from the row had little effect on soybean growth and yield.  相似文献   

14.
Effect of Fine Root Contact on Plant-Induced Weathering of Basalt   总被引：1，自引：0，他引：1  
The objective of the present study was to provide experimental evidence on the active role of plant roots in rock weathering and the importance of the proximity of roots to rock in the weathering process. The analysis was based on the release of different elements from basalt rock particles by three crop species: rice, soybean and maize. Quantitative results were obtained by chemical analyses. We designed two types of hydroponic crop pots, in which fine roots were allowed (or not allowed) to make contact with rock particles by using coarse (or fine) net bags. Experiments were carried out in a controlled glasshouse during a 42 d period. The release of elements in the presence of the plants was calculated by subtracting the decrease in the amounts of elements in the media from the amounts absorbed by the plants. We observed the positive effect of plants on the release of elements from the rock particles and the highest amounts were released in the soybean pots. The amounts of Si, Ca, Mg, Mn and Al released increased by a factor of 2–5, 2–7, 16–112, 3–19 and 6–60, respectively. The amount of Fe released by soybean plants from the rock particles was 4–6 times higher than that by other plants. Between the coarse and fine net pots, the amount of released elements differed significantly only for soybean (Si, Mg and Mn at p < 0.01 level and Fe at p < 0.05 level), which displayed the most vigorous growth. Our results imply that weathering may be caused partially by the absorption of nutrient elements directly through the interface of fine roots and rock particles, and is most likely associated with alterations of the local rhizosphere conditions surrounding the roots.  相似文献   

15.
The possibility of using composted pulp fiber residues (CPFR) in a potato rotation in eastern Canada was tested. Three rates of CPFR (0, 45, and 90 Mg C ha?1) with or without supplementary irrigation were applied. Pea (Pisum sativum L.), corn (Zea mays L.), and potato (Solanum tuberosum L.) were cultivated in 2002, 2003, and 2004, respectively. Soil total carbon (C) and nitrogen (N), bulk density, and water-holding capacity were improved by CPFR. Pea and corn yields and total dry matter were increased using CPFR. Supplemental irrigation increased pea yield compared with the rain-fed system. Total tuber yield was increased by CPFR in the irrigated but not in the rain-fed system. The CPFR application increased plant-available phosphorus (P) and potassium (K) in all rotation crops. Nitrogen accumulation in all rotation crops except potato was increased by CPFR. The CPFR application successfully enhanced soil fertility and crop productivity without any adverse effects.  相似文献   

16.
Abstract

Knowledge of crop response to temporary waterlogging is important in the development of effective water management practices. A field study was conducted to determine the response of soybean [Glvcine max. (L.) Merr] grown on a poorly drained, clayey soil to temporary flooding at three growth stages. The four treatments were soybean flooded for seven consecutive days at either VI, V4 or R2 growth stages at a flood height of 0.03 m above the soil surface and a well‐watered control. Flooding for seven consecutive days wetted but did not saturate the lower parts of the soil profile. This was attributed to the swelling by the montmorillonitic clay and subsequent sealing of the soil near the surface. In general, Eh and ODR decreased gradually during the flood, but increased as the soil dried upon removal of the flood. Canopy heights and dry weights of the flooded soybeans were dependent on plant growth stage at flooding and time of measurement but were lower than the control. When flooded at the VI or V4 growth stages, concentrations of N and K in the above‐ground plants were lower than the control after the flood. Three weeks after the flood was removed higher concentrations of these elements were found. When flooded at R2, concentrations of N and K were lower than in the control. Few differences were found in the plant concentrations of Ca, Mg, Mn, Fe, Al, and Na in the plant due to the flood, but by the end of the growing season, concentrations of Mn, Fe and Al were higher in the R2 flooded soybeans than in the other treatments. Seed yield response of the soybeans depended upon plant growth stage at flooding. The soybeans were particularly sensitive to the seven days of continuous flood at the R2 growth stage. Values of relative seed yield were 88, 83, and 44 % of the well watered‐control for the VI, V4 and R2 growth stages, respectively. Differences in seed yield were found with cultivar and with cultivar?flood treatment.  相似文献   

17.
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   

18.
Manganese (Mn) deficiency is reported worldwide and often decreases crop yield. However, plant species differ in their susceptibility to Mn deficiency. Poaceae are often inefficient, whereas Brassicaceae seem to be efficient in Mn uptake. The objective of this paper was to determine the relevance of Mn‐uptake kinetics, root‐system size, and Mn mobilization for differences in Mn efficiency of wheat, oat, and raya. To determine Mn‐uptake kinetics, wheat (Triticum aestivum L. cv. PBW 343), raya (Brassica juncea L. cv. RLM 619), and oat (Avena sativa L. cv. Aragon) were grown in a growth chamber together in complete nutrient solution having an average Mn concentration of 90, 180, 360, 910, and 2270 nmol L–1. For determining Mn efficiency of the three species in soil, the plants were grown for 22 d in pots filled with 3 kg of a loamy soil low in Mn availability (pH (CaCl2) 7.4; DTPA‐extractable Mn: 3.5 mg (kg soil)–1). The soil was fertilized with 0, 1, 2, 4, and 8 mmol Mn (kg soil)–1 resulting in Mn soil‐solution concentrations ranging from 40 to 90 nmol L–1, hence lower than in the solution experiment. In order to determine Mn soil‐solution concentration close to the root surface, the root length density was increased by growing two plants of raya and four plants of wheat in only 250 mL soil columns for 25 d. In solution culture at high concentrations, raya showed a higher Mn uptake compared to wheat and oat. However, at low Mn supply, all three species were comparably Mn‐efficient, i.e., plant growth was similar, and also the uptake was similar. In soil, the highest yield was achieved for raya in the unfertilized treatment whereas the Poaceae needed at least a fertilization of 1 mmol Mn (kg soil)–1. The Poaceae showed a yield reduction of about 40% in the unfertilized treatment. Manganese concentration in the shoot dry weight was always higher in raya than in wheat or oat. This was due to a higher Mn uptake whereas relative shoot‐growth rate and root‐to‐shoot ratio were similar among the species. The higher Mn uptake of raya in soil was in contradiction to the comparable Mn‐uptake kinetics of the three crops at low Mn concentration in solution. This points to plant differences in their ability to affect Mn availability in the rhizosphere. In the bulk soil, all the crops decreased Mn solution concentration, but this effect was somewhat less for raya. But in the rhizosphere, raya increased Mn soil‐solution concentration significantly to 58 nmol L–1, as compared to 37 nmol L–1 of the unplanted control soil. In contrast, wheat showed a Mn solution concentration of 25 nmol L–1 which was not significantly different from the control. The results indicate that differences in Mn efficiency among the crops studied are related to their ability to affect the solubility of Mn in the rhizosphere.  相似文献   

19.
Effects of local green manure (GM) and lime on soil productivity in a low-input agricultural system were evaluated by growing three successive crops of sweet corn (Zea mays) on an acid Oxisol (Typic acrorthox, Togitogiga series) in Western Samoa. The soil was amended with coral lime at 0, 5, and 10Mgha–1 and with cowpea GM at 0, 7.5, and 15Mgha–1. Commercial NPK fertilizers at 50kgha–1 each of N, P, and K were included for comparison. The amendments were applied only once prior to planting of the first crop. Response parameters measured included nutrient composition of leaves at tasseling and grain yield of each crop, and selected soil chemical properties at each planting. Yields of the first crop were nearly tripled with GM additions and doubled with lime additions. Such yield increases were caused mainly by better K nutrition and to a lesser extent by enhanced P nutrition. Yields of subsequent crops were much lower than those of the first, and the declines were much steeper for the GM treatments than for the lime treatments. Thus, the enhancement effect on K nutrition did not last beyond one crop. Poor growth of the second and third crops was caused by K deficiency; probably coupled with Mn toxicity. Significant yield reductions were found when Mn-to-K ratios in leaves exceeded 0.010. As for effects on soil, soil pH was increased significantly by lime but only slightly by GM. Given the variable charge property of this Oxisol, each unit pH increase corresponds to a cation exchange capacity (CEC) increase of 5cmolckg–1. Having greater CEC, the amended soil retained K more effectively, thereby causing yield increases, especially of the first corn crop, which required at least 0.75cmolckg–1 of exchangeable soil K or 7% of CEC for adequate growth. Received: 15 April 1996  相似文献   

20.
Yard trimmings from sources rich in grass clippings have the potential to supply nutrients for crop production. Our objectives were to estimate N availability from yard trimmings and determine their effects on crop production, soil nutrients, and organic matter levels. We conducted a field experiment, comparing three consecutive years of yard trimmings applications (22, 44, or 66 Mg ha?1 yr?1 dry weight) with inorganic N (112 kg N ha?1 yr?1) and zero-N controls in a silage corn (Zea mays L.) - winter triticale (Triticosecale spp.) rotation. The yard trimmings were screened and ground, and allowed to heat for a short period. They were incorporated each spring before planting corn. We measured crop yield and N uptake, and estimated apparent N recovery (ANR). We measured soil inorganic N two weeks after yard trimmings application and after corn harvest. In a one-year on-farm demonstration, we compared three sources of yard trimmings applied at a single rate. Yard trimmings applied at 44 Mg ha?1 dry weight provided sufficient available N to replace inorganic N. For silage corn grown with summer irrigation, estimated ANR in the crop was 7% in Year 1, 19% in Year 2, and 18% in Year 3 at the 44 Mg ha?1 yard trimmings rate, compared with a mean ANR of 65% for the inorganic N treatment. Postharvest soil nitrate residual (0-to 120-cm depth) was similar for the 44 Mg ha?1 treatment and inorganic N treatment. We observed variation in N availability with year and source of material. Yard trimmings also increased soil test K and organic matter.  相似文献   

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