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1.

Aims

This study aims to evaluate the effects of wood ash application on nutrient dynamics and soil properties of an acidic forest soil (Arenosol).

Methods

Treatments were loose and pelleted ash application (11?Mg?ha?1), alone or together with N fertiliser, and control treatment in a lysimeter experiment. Nutrient leaching was followed during a 2-year period and soil chemical and biological properties were evaluated at the end of the experiment.

Results

Wood ash increased leaching of total N, NH 4 + -N, base cations and P, mainly during the first months, the effect being more pronounced for the loose formulation. At the end of the study period, a positive effect on soil nutrient availability and soil acidity reduction was seen. The application of loose and pelleted ash alone decreased N leaching and increased N microbial biomass at the end of the experiment. The C dynamics was weakly affected.

Conclusion

Wood ash can be used to improve nutrient availability and balance nutrient exported by tree harvesting in acid forest soils, the effects at short-term being stronger for loose than for pelleted ash. However, their application should be carried out when vegetation is established to minimise nutrient losses at short-term and reduce the potential risk for water bodies. In N-limited soils, wood ash should be applied with N fertilisers to counteract N immobilisation.  相似文献   

2.
The effects of wood ash or wood ash plus nitrogen (N) fertilization on soil chemical properties, needle nutrient concentrations and tree growth were studied in five coniferous stands, aged 31–75 yrs, after 5 and 10 yrs. In each experiment 3 t ha?1 of loose wood ash was applied to three replicated plots (30×30 m). In three of the experiments 120–150 kg N ha?1 was applied together with the same wood ash (WAN). These three experiments also included a stand-specific fertilization (SSF) treatment, which consisted of 120, 150 or 180 kg N ha?1. Five years after wood ash or WAN application the pH increase in the humus layer was 1–1.7 pH-units and in the 0–5 cm mineral soil layer 0.3–0.4 pH-units. The increase was approximately the same 10 yrs after application, and was also associated with an increase in pH in the 5–10 cm mineral soil layer. Wood ash or WAN significantly increased both the total and extractable calcium and magnesium concentrations in the humus layer on all the sites. Wood ash or WAN had an increasing effect on the boron concentrations, but a decreasing effect on the manganese concentrations in the needles. Wood ash had no significant effect on the volume growth. The trees on the WAN plots grew as well as or slightly better than those on the SSF plots.  相似文献   

3.

Nitrogen (N) is the only nutrient that promotes forest growth when given individually. An extra stem growth of 15 m 3 ha -1 is obtained during a 10 yr period following an application of 150 kg N ha -1 . Larger growth increases have often been the result of more intensive N fertilization. Lime or wood ash give a minor growth stimulation on sites with a carbon (C) to N ratio below 30 in the humus layer, while the opposite effect prevails on N-poor sites. Nutrients given as soluble fertilizers are readily taken up by trees. Boron deficiency may be induced in northern Sweden after N fertilization or liming. The ground vegetation may be altered by single-shot N fertilization, but long-term effects occur only for intensive regimes. Lime or wood ash may modify the flora if soil pH is significantly altered: the change will be in response to N availability. Fruit-body production of mycorrhizal fungi is disfavoured by chronic N input, but also by lime or ash. However, the mycorrhizal structures on root tips are less affected. Faunistic studies are not common and those present are mostly devoted to soil fauna. A practical N dose of 150 kg N ha -1 has no clear effect, but higher doses may reduce the abundance in some groups. Hardened wood ash does not significantly affect the soil fauna. Lime favours snails and earthworms, while other groups are often disfavoured. The response of aquatic fauna to terrestrial treatments has hardly been studied. N fertilization generally results in insignificant effects on fish and benthic fauna. Lime and wood ash reduce the acidity of the topsoil, but practical doses (2-3 t ha -1 ) are too low to raise the alkalinity of runoff unless outflow areas are treated. N fertilizer use in forestry and N-free fertilizers lack effects on acidification. N fertilization may, however, be strongly acidifying if nitrification is induced and followed by nitrate leaching. N fertilization often results in increased long-term C retention in trees and soil, but does not promote significant N 2 O losses. N may temporarily reduce CH 4 oxidation in soil, but there are indications of a long-term opposite effect. Lime and poorly hardened wood ash may cause losses of C from N-rich soils. Only a few per cent of added N are leached to surface water following practical N fertilization, while N-free fertilizers do not induce N leaching. Soil incubations and soil-water studies suggest an increased risk for nitrate formation and leaching where lime or wood have been added to N-rich soils, but increased leaching to surface water has not been observed. Wood ash causes a temporal increase in bioavailability of cadmium (Cd). Other fertilizers may indirectly increase the availability of heavy metals. Wood ash may contain radioactive caesium 137Cs, but addition of such ash does not increase radioactivity in plants and soil.  相似文献   

4.
Soil chemistry influences plant health and carbon storage in forest ecosystems. Increasing nitrogen (N) deposition has potential effect on soil chemistry. We studied N deposition effects on soil chemistry in subtropical Pleioblastus amarus bamboo forest ecosystems. An experiment with four N treatment levels (0, 50, 150, and 300 kg N ha?1 a?1, applied monthly, expressed as CK, LN, MN, HN, respectively) in three replicates. After 6 years of N additions, soil base cations, acid-forming cations, exchangeable acidity (EA), organic carbon fractions and nitrogen components were measured in all four seasons. The mean soil pH values in CK, LN, MN and HN were 4.71, 4.62, 4.71, and 4.40, respectively, with a significant difference between CK and HN. Nitrogen additions significantly increased soil exchangeable Al3+, EA, and Al/Ca, and exchangeable Al3+ in HN increased by 70% compared to CK. Soil base cations (Ca2+, Mg2+, K+, and Na+) did not respond to N additions. Nitrogen treatments significantly increased soil NO3?–N but had little effect on soil total nitrogen, particulate organic nitrogen, or NH4+–N. Nitrogen additions did not affect soil total organic carbon, extractable dissolved organic carbon, incorporated organic carbon, or particulate organic carbon. This study suggests that increasing N deposition could increase soil NO3?–N, reduce soil pH, and increase mobilization of Al3+. These changes induced by N deposition can impede root grow and function, further may influence soil carbon storage and nutrient cycles in the future.  相似文献   

5.
Reclamation of post-mining sites is challenged by limiting factors including adverse soil chemical and physical properties, along with weed competition. Fertilization may alleviate nutrient deficiencies, but broadcast fertilization with immediately available fertilizers (IAF) results in generally low rates of nutrient recovery for planted trees. Directed application of controlled-release fertilizer (CRF) to the rhizosphere offers an alternative to extend nutrient longevity while reducing nutrient leaching or uptake by competing vegetation. We evaluated white spruce (Picea glauca (Moench) Voss) and aspen (Populus tremuloides Michx.) development on a mine reclamation site in the Oil Sands Region of northern Alberta in response to IAF and polymer-coated CRF (3–4 and 8–9 month release). IAF and CRF (each NPK plus other macro- and micro-nutrients) were applied at 20 and 40 g N seedling?1 and 2 and 4 g N seedling?1, respectively. No effect on seedling survival occurred. White spruce year-1 height and diameter growth responded positively to both IAF and CRF relative to non-fertilized controls, but in year-2 seedlings treated with CRF (i.e., 8–9 month) outperformed those fertilized with IAF, which were similar to controls. Aspen height growth did not respond strongly to fertilization in either year, but diameter growth showed positive responses to all fertilizer treatments in year-1 and to all CRF treatments and the high IAF rate in year-2. Responses were attributed to a pronounced increase in vegetative competition observed for IAF relative to CRF or controls following the first growing season, and generally higher levels of foliar N in year-1 for CRF compared to IAF or unfertilized trees. Thus, directed root zone application of CRF promoted seedling growth responses similar to or better than those induced by broadcast IAF applications, but at 90–95 % lower N application rates.  相似文献   

6.
To evaluate the characteristics of wood ash as fertilizer, composition of inorganic elements and the leaching behavior were studied. The leaching behavior was evaluated by three leaching methods using different solvents (water, hydrochloric acid, and acetic acid: Japanese leaching test Nos. 18 and 19 and modified toxicity characteristic leaching procedure prescribed by the US Environmental Protection Agency). The ash composition varied according to raw materials for fuel and ash collection systems. Concentration of Na, Al, Si, and V became higher in bark ashes while that of K became higher in wood ashes. Pb, Cd, Se, and Zn were more volatile and enriched in fly ashes. Of the nutrient elements, K showed high water solubility and its phytoavailability also appeared high, although the amount of water-soluble K was low in bark ash. Ca and Mg had intermediate solubility while P was less soluble in both water and acetic acid. The amount of hazardous substances having leached was low for most, but not all the ashes, in terms of Pb, Cr and As. Nevertheless, the phytoavailability of these hazardous substances after their application to the forest appeared low, due to their amphoteric leaching behavior and the acidity of Japanese forest soils.  相似文献   

7.
Plants can assimilate amino acids from soils. This has been demonstrated in controlled environments and soils of various forest ecosystems. However, the role of root-absorbed amino acids in plant nitrogen nutrition is still poorly understood. We investigated the agroecological performance and nutrient use physiology of two conifers (Abies fraseri and Pinus resinosa) and one hardwood species (hybrid poplar) under amino acid fertilization. Arginine fertilizer (arGrow® Complete) was applied at varying rates (0, 56, 112, 224, and 336 kg N/ha) and compared to an inorganic control treatment (ammonium sulfate 112 kg N/ha). Parameters monitored included tree growth response, foliar nitrogen concentration, and inorganic nitrogen leaching below the rootzone. Results obtained indicate a significant growth and foliar nitrogen response to amino acid treatments, with increasing amino acid application leading to greater growth and foliar nitrogen. However, rates two to three times higher than that of the inorganic control were necessary to provide similar growth and foliar nitrogen responses. These observations were suggested to be due to competition with soil microbes for organic nitrogen, growth inhibition due to the presence of large concentrations of amino acids, or adsorption to cation exchange sites. Amino acid applications did not increase the leaching of inorganic nitrogen due either to the binding of positively charged arginine cations to exchange sites or rapid mineralization followed by plant assimilation. Mineral nitrogen collected in leachate samples increased with the application rate suggesting at least some mineralization in high amino acid application rates. We conclude that growth response and nitrogen use physiology of these species when treated with arginine are largely controlled by soil processes including microbial competition and adsorption. Further studies are being conducted to confirm these hypotheses.  相似文献   

8.

Decline in pH and leakage of base cations have been recorded in beech forest soils in southern Sweden. This study investigated the influence of soil properties on frost sensitivity in beech bark and evaluated the effects on frost sensitivity of soil treatment with lime, wood ash or excessive N fertilization. Beech trees on five experimental sites were studied. The results indicated that beech trees subjected to a comparatively low C/N ratio and low concentration of nutrient elements in the mineral soil layer were predisposed to a higher sensitivity to frost. Seven years after treatment, no effects of N fertilization were detectable in the soil, but positive effects of liming were recorded. There were no obvious effects of bark ash amendments, owing to large differences among blocks at the site.  相似文献   

9.
Long-term patterns in nutrient cycling in regrowing Douglas-fir (Pseudosuga menziesii Mirb. Franco) and red alder (Alnus rubra Bong.) on native soils plus soils previously occupied by other species were simulated using the nutrient cycling model. Simulations of regrowing stands were also compared with observations of nutrient cycling in mature Douglas-fir and red alder. We hypothesized that (1) prolonged presence of red alder will cause a depletion in soil base cations due to increased nitrification and NO3− leaching; (2) lower base cation availability under red alder will ultimately cause biomass production to decline; (3) high N availability in red alder soils will favor regrowth of Douglas-fir; (4) higher base cation and P status of the Douglas-fir soils will favor growth of red alder both in the short- and long-term, since N is not limiting to red alder; and (5) in regrowing red alder, NO3− leaching will increase with time as a result of increased N fixation. All hypotheses were confirmed, but the effect of soil type on biomass production was minimal both for red alder and Douglas-fir. The higher soil organic matter content in the mature red alder stand most likely reflected previous occupation by old-growth Douglas-fir and also a large litter input from the understory vegetation. In general, the nutrient cycling model simulated differences in nutrient cycling patterns at least qualitatively between Douglas-fir and red alder and was helpful in identifying potential gaps in the understanding of biogeochemical cycling as well as uncertainties in the data. The nutrient cycling model did not fully elucidate differences in P cycling between Douglas-fir and red alder and overestimated weathering rates under Douglas-fir. Uncertainties in the data included: (1) temporal patterns in N fixation in the regrowing stands; (2) understory litterfall; and (3) site history and, consequently, presence of pre-existing differences in site conditions.  相似文献   

10.
The fate of applied N in soil and its relative uptake by black pepper vine and erythrina tree on which the vine was trailed, were determined using 15N-labelled urea. Rapid depletion of 15N from 0-50 cm root zone was noticed due to heavy leaching during rains. The isotope content of the soil fell below the detection limit within one month of urea application. Both the vine and support tree absorbed N from the labelled fertilizer applied to the soil basin of the vine. Fertilizer use efficiency in black pepper vine was very low, in the range of 6 to 12%. On the other hand, the contribution of applied urea towards N uptake by erythrina support tree was 24 to 40%. Poor utilization of the applied N by the vine was, besides leaching of the nutrient, due to the severe root competition from the support tree. The overall utilization of the applied N was 51.4% by the vine and tree put together when N was applied at the rate of 25 g plant–1 and 31.0% for the dose of 50 g N plant–1.  相似文献   

11.
To help address the physical, chemical, and biological degradation of agricultural soils resulting from indiscriminate use of chemical fertilizers, we developed a slow-release fertilizer from waste paper and urea. This approach has the advantage of a slow-release fertilizer in that it avoids surface runoff or leaching of nutrients, while providing an excellent medium for the recycling of waste paper. The successful impregnation of urea into waste paper was confirmed by scanning electron microscopy. This study also evaluated the release patterns of N from impregnated waste paper using a simulated soil solution and distilled water as leaching solutions. The release patterns of N were examined in both static and continuous-flow conditions for 720 h. Release of N from impregnated waste paper was found to be slow and steady, although the release rate of N was lower in distilled water than soil solution under both conditions. Part of this report was pesented at the Korean Society of Wood Science and Technology in Korea, April 2007, and the 3rd International Conference on Environmental Science and Technology in Houston, USA, August 2007  相似文献   

12.
Fall nutrient loading of deciduous forest nursery seedlings is of special interest because of foliage abscission and varied translocation patterns. For non-deciduous seedlings in the nursery, fall fertilization typically can reverse nutrient dilution and possibly increase nutrient reserves; however, this technique has received little attention with deciduous conifer trees that translocate nutrients before abscising foliage. We evaluated how fall nitrogen (N) fertilization affected N storage and translocation in the deciduous conifer Olga Bay larch (Larix olgensis Henry) seedlings during the hardening period. Seedlings were supplied with 25 mg N seedling?1 for 15 weeks before hardening and fall fertilization treatments began with a three week application period of K15NO3 at 0, 5, 10 and 15 mg N seedling?1. During the hardening period, fall N fertilization had little effect on seedling morphology. The N concentration and content of needles decreased dramatically as needles abscised, while that of stems and roots increased. Six weeks after fall N fertilization ceased, all seedlings translocated similar net N from their needles. For the control seedlings, this accounted for 84 % of the N stored in stems and roots. For fall fertilized seedlings, however, the proportion of N stored in stems and roots translocated from needles accounted for only 41–61 % of the total because of absorption of fall fertilizer that was translocated directly to stems and roots. Six weeks after fall fertilization, the distribution pattern of N concentration and content in seedlings was found in this order: stems > fine roots > coarse roots > needles. Our results suggest that providing deciduous conifer seedlings N during hardening, in this case Olga Bay larch, is a way to promote nutrient loading during nursery production.  相似文献   

13.
The aim of this study was to evaluate the response of soil amendment applications on soil and the foliage nutrient status of a Japanese cypress (Chamaecyparis obtusa Endlicher) plantation established following clear-cutting in a pine-wilt-disease (PWD)-disturbed forest. We established four soil amendment treatments [(compound fertilizer (CF), compound fertilizer + biochar (CFB), compound fertilizer + sawdust (CFS) and a non-treated control treatment] in an 8-year-old Japanese cypress plantation. Soil organic carbon (C) and total nitrogen (N) were not significantly different (P > 0.05) between the soil amendment treatments and the control treatments, whereas extractable phosphorus (P), NH4+, K+, and Mg2+ concentrations were significantly affected by the addition of biochar in CF. The mean soil CO2 efflux rates during the study period were the highest in CFB (0.79 g CO2 m?2 h?1), followed by CFS (0.71 g CO2 m?2 h?1), CF (0.62 g CO2 m?2 h?1), and the control (0.46 g CO2 m?2 h?1) treatments. Foliar N and P concentrations were significantly higher in the CFB than in the control treatments. The results suggest that the addition of biochar in CF can enhance extractable soil nutrients and foliar N and P conditions of Japanese cypress established in a PWD-disturbed forest.  相似文献   

14.
The aim of the present study was to evaluate the effects of the application of wood-bark ash (WBA) on the growth and nutritional status of a 5-year-old hybrid chestnut plantation in two consecutive periods of 3 and 4 years, i.e., from age 5 to 8 years and from age 8 to 12 years, respectively. A field experiment, which included 3 treatments and 4 replicate blocks, was established on an acidic, organic matter-rich mineral soil. The treatments were two different doses of ash (10 and 20 t ha?1) and an unfertilized control. Application of the ash (by spreading on the ground) produced mean increases of 16% in diameter and 11% in height growth of trees during the first 3 years, considering both doses together; the response was also significant for the subsequent period, particularly with the higher dose of ash (increases of 11% in diameter and 15% in height growth). The ash had a marked effect, although clearly short lived, on pH (H2O) levels (an increase of 0.6 units) and on exchangeable soil K, Ca and Mg. The nutritional status of the plantation was improved, mainly in terms of K, Ca and Mg, and the results of a vector analysis indicated that these elements, particularly K, were limiting forest production. Foliar or soil nutrient concentrations in the mineral soil were no longer affected by the ash at age 12 years. We recommend the application of two doses of 10 Mg ha?1 throughout the rotation for fertilizing acid mineral soils that are rich in organic matter.  相似文献   

15.
The aim of the present study was to evaluate the initial effects of the application of mixed wood-bark ash (MWBA) on growth and nutritional status of a Pinus radiata plantation, and on the dynamics of some of the nutrients. A field experiment, which included four treatments and four replicates in a completely random design, was established on an acidic, mineral soil rich in organic matter. The treatments were two different doses of ash (5 and 10 t ha−1), a soluble NPK fertilizer 8:24:16 (N:P2O5:K2O, 200 g per plant) and an unfertilized control. The MWBA was incorporated into the soil after cutting and chopping the existing shrub vegetation and before planting. Application of the ash produced an increase in soil pH, and in the availability of P, Ca, Mg and K. The effects on soil pH and available Ca and Mg persisted for five growing seasons. The prolonged response in this study may be attributable to the effect of ash incorporation, which may have enhanced the solubility of wood ash compounds, despite the partly combusted material present in the ash. The ash improved the nutritional status, mainly in terms of Ca and Mg, and the vector analysis indicated that these elements were limiting forest production. The soluble NPK fertilizer did not produce any improvement in growth relative to the control. The concentrations of heavy metals in both soil and plant tissue were always low and did not increase significantly after application of the wood-bark ash. The positive effect of ash application on height and diameter growth was significant after 5 years, with similar results for both doses of ash. The improvement was attributed to the increases in Ca and Mg in soil.The differences between the treatments with ash and the control were much greater when the values of biomass per unit area were considered, due to the accumulative effect of a lower mortality and the enhanced growth in basal diameter and height.  相似文献   

16.
The particle size distribution, the nutrient content and the sorption behaviour of six solid wood and ash/charcoal residues collected in three wood-processing companies in Germany and Brazil were investigated in order to elucidate the potential of these residues for the development of new products for soil amelioration. The absorption of N, P, and K by the residues and the leaching of nutrients from impregnated samples were studied in the laboratory at substrate temperatures of 20 and 300°C. The release of elements by the impregnated samples and the sorption behaviour of ash/charcoal incorporated in the soil were also studied in the field on a temperate site (Hamburg, 53°32′N 09°59′E), on a subtropical site (Ivaí, 25°15′S 50°45′W), and on a tropical site (Aripuanã, 10°09′S 59°26′W). Under laboratory conditions the solid wood residues absorbed 2.0–9.1% of the N, 0.1–0.4% of the P, and 1.0–8.5% of the K available in the impregnation solution. At a temperature of 20°C, selected sieve fractions of the ash/charcoal residues absorbed up to twice as much as N and up to 100 times more K than the treated wood residues. The absorption of N, P, and K to the ash/charcoal residues increased significantly at a substrate temperature of 300°C compared to a substrate temperature of 20°C. In absolute numbers, the leaching of N, P, and K from the impregnated ash/charcoal residues was in the range of the release by the impregnated solid wood residues, whilst the relative rate of nutrient leaching was strongly reduced. The field experiments confirmed the results obtained in the laboratory and indicated that ash/charcoal residues are suitable raw materials for the development of new products for soil amelioration, in particular for application under humid climate conditions.  相似文献   

17.
Effects of harvest residues on nutrient leaching and soil chemical properties were studied in a lysimeter experiment. Treatments were: (A) forest floor litter and harvest residues, other than branches, incorporated into the soil, (B) as A, but with branches cut in 20 cm long bits and placed on the soil surface, (C) as B, but with bits incorporated into the soil, (D) as B, but with branches chopped into chips, (E) as C, but with branches chopped into chips, (F) forest floor litter and harvest residues on the soil surface, with branches cut in 20 cm long bits, (G) as F, but with branches chopped into chips, and (H) absence of harvest residues (control). Treatments were applied in zero-tension lysimeters containing 25 kg of soil. Leachates were collected for a 6-year period. At the end of the experiment, lysimeters were dismantled and soil was divided in four layers. Residues, other than branches, increased N leaching, as compared with the control. Branches on the soil surface reduced N leaching when cut in chips. Branches incorporated into the soil reduced leaching independently of their size. Organic residues on the soil surface showed similar effect to those incorporated into the soil. However, harvest residues on the soil surface increased leachate volume, and reduced Ca and P losses. Such a placement of residues led to high contents of Ca and P in the 0–5 cm top soil layer. Contents of organic C, total N and base cations were not affected by the treatments.  相似文献   

18.
Forest harvesting and subsequent regeneration treatments may cause changes in soil and solution chemistry that adversely affect forest productivity and environmental quality. The objective of this study was to assess soil carbon (C), nitrogen (N), and base cation pools and fluxes, and to construct a hydrogen ion (H+) mass balance to identify major processes controlling acidity production and consumption 14 years following whole-tree harvesting and regeneration in a northern forested wetland with underlying mineral soils derived from calcareous glacial drift. Results for soil elemental and nutrient pools in the harvested/regenerated stand were compared to an adjacent non-harvested stand and a riparian zone. The riparian zone had the highest soil total C, total N, and exchangeable calcium (Ca) and magnesium (Mg) pools; however, no difference in exchangeable potassium (K) was evident among stand types. Moreover, no differences between the harvested/regenerated and uncut stands were evident in any of the soil chemical pools.Net export of base cations was minimal and the H+ mass balance indicated that net cation exchange was not a significant process in H+ production or consumption in either the uncut or harvested/regenerated stands. The most striking differences in the H+ mass balance were (1) eight times the H+ consumption from sulfate (SO42−) reduction in the harvested/regenerated stand compared to that in the uncut condition and (2) nearly twice the H+ production due to N immobilization in the harvested/regenerated stand. However, both stand types were net H+ sinks and increases in H+ export due to whole-tree harvesting were not evident.The riparian zone was a net exporter of base cations. This finding was attributed to a combination of base cation exchange and carbonate mineral weathering; data suggested the importance of the latter. More research, however, is required to isolate the contributions of cation exchange and carbonate weathering on base cation export from the riparian zone. Stream chemistry was consistent with that of the riparian zone, indicating a strong linkage between the riparian zone stream chemistry, and whole-tree harvesting had no intermediate term (i.e., 14 years) effects on stream acidification in this managed northern wetland ecosystem.  相似文献   

19.
甘肃中部引黄灌区枸杞施肥管理与土壤养分状况调查分析   总被引：1，自引：0，他引：1  
通过对景泰县草窝滩镇枸杞幼龄园(1～4年生)和盛果期成龄园(5～8年生)施肥管理现状调查,并结合其20～40 cm土壤养分测试,分析目前该区构杞养分管理中存在的问题及不同龄期枸杞园土壤养分特征.结果表明,该区枸杞养分管理中注重有机肥投入,但施用量不足;化肥施用中重氮素、磷素,轻钾素现象较为普遍.全量养分中有机质和全氮含...  相似文献   

20.
A hedgerow intercropping study was conducted for 7 years in West Sumatra, Indonesia on an acid and highly A1-saturated (72%) soil to determine growth and yield responses of tree hedgerows and upland rice and cowpea intercrops. Three tree species,Paraserianthes falcataria, Calliandra calothyrsus, andGliricidia sepium, and a no tree control were planted at three lime rates of zero, 375 kg ha–1, and liming to 25% Al+H saturation. Annual fertilizer inputs of 20 kg P and 50 kg K ha–1 were kept low to approximate low input farming systems. The trees were pruned 4 to 6 times per year and prunings applied to the intercrops.Paraserianthes andCalliandra grew vigorously, whileGiricidia grew poorly and was replaced after four years withFlemingia macrophylla. Hedgerow growth and yields were reported in a previous paper [Evensen et al., 1994].Rice and cowpea yields initially increased with lime andParaserianthes pruning application, but yields and soil cations (Ca, Mg, and K) declined until fertilizer inputs were increased after four years. Thereafter, crop yields increased and soil cations returned to original levels. Soil C and N were maintained over the 7 years on plots with trees. These results indicate little build-up of nutrient cations due to recycling by the trees and suggest that successful alley farming on such highly weathered soils requires maintenance of soil fertility with external inputs.  相似文献   

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