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1.
Successful agroforestry systems depend on minimizing tree-cropcompetition. In this study, field experiments and a simulation model were usedto distinguish between tree-crop competition for light and belowgroundcompetition in an alley cropping system. Maize (Zea maysL.) was harvested periodically in three treatments: between vertical barriers ofshade cloth, hedgerows of Flemingia macrophylla (Willd.)Merr., and sole maize. Radiation intercepted by the maize was calculated using asimulation model based on measured values for direct and diffuse light, hedgerowdimensions and leaf area, and solar trajectory. Radiation use efficiency wascalculated as biomass production per unit of intercepted radiation. Maizebiomass and yield in both the alley crop and the shade cloth treatment weregreatest in the center of the alleys. Grain yield between hedgerows was 3.5Mg ha−1 (averaged across the alley), significantlyless than in the shade cloth (7.4 Mg ha−1) or thesole maize (7.7 Mg ha−1) treatments. Lightintercepted by the maize in the alley crop was about half that intercepted bythe maize in the sole crop. The shade cloth intercepted less light than thehedgerows because it did not have an appreciable width. Radiation use efficiencyin the three treatments was 0.75 g mol−1 PAR anddid not differ significantly among treatments. Tree-crop competition wasoverwhelmingly for light. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

2.
Little information is available on soil respiration and microbial biomass in soils under agroforestry systems. We measured soil respiration rate and microbial biomass under two age classes (young and old) of a pecan (Carya illinoinensis) — cotton (Gossypium hirsutum) alley cropping system, two age classes of pecan orchards, and a cotton monoculture on a well-drained, Redbay sandy loam (a fine-loamy, siliceous, thermic Rhodic Paleudult) in southern USA. Soil respiration was quantified monthly during the growing season from May to November 2001 using the soda-lime technique and was corrected based on infrared gas analyzer (IRGA) measurements. The overall soil respiration rates ranged from 177 to 776 mg CO2 m–2 h–1. During the growing season, soil respiration was higher in the old alley cropping system than in the young alley cropping system, the old pecan orchard, the young pecan orchard, and the monoculture. Microbial biomass C was higher in the old alley cropping system (375 mg C kg–1) and in the old pecan orchard (376 mg C kg–1) compared to the young alley cropping system (118 mg C kg–1), young pecan orchard (88 mg C kg–1), and the cotton monoculture (163 mg C kg–1). Soil respiration was correlated positively with soil temperature, microbial biomass, organic matter, and fine root biomass. The effect of alley cropping on soil properties during the brief history of alley cropping was not significant except in the old systems, where there was a trend of increasing soil respiration with short-term alley cropping. Over time, different land use and management practices influenced soil properties such as soil temperature, moisture, microbial biomass, organic matter, and fine root biomass, which in turn affected the magnitude of soil respiration. Our results suggest that trees in agroforestry systems have the potential to enhance soil fertility and sustainability of farmlands by improving soil microbial activity and accreting residual soil carbon.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

3.
The amounts of earthworm surface casts were monitored for 200 days after commencement of casting in three alley cropping experiments of different ages and hedgerow species. Casts were collected twice per week in transects from under the hedgerow to the middle of the interrow space. Average annual cumulative amounts of casts were higher in alley cropping systems with one to five years of cropping than in the no-tree control. After five years of cropping, amounts of casts were similar in all treatments. Within the alley cropping systems, casting activity was highest immediately under the hedgerows and decreased towards the middle of the interrow space. In systems using Leucaena leucocephala as hedgerow species, the hedgerow to interrow space gradient of casting activity became more pronounced with increasing length of cropping. Casting activity in the interrow space was reduced by 12%, 55%, 80% and 86% in the first, fourth, sixth and seventh year of cropping, respectively, compared to the casting activity under the hedgerows. Senna siamea, which produced a more recalcitrant mulch, did not show such a strong decline in casting in the interrow space. In a Dactyladenia barteri system, the difference in casting between interrow space and hedgerows was insignificant. With perpendicular distance from the hedge, largest gradients in casting activity occurred close to the hedgerows with up to −4.00 Mg ha−1 cm−1 in L. leucocephala but only −1.23 and −0.76 Mg ha−1 cm−1 in S. siamea and D. barteri, respectively. The shading effect of trees and a relatively low level of soil disturbance is apparently more beneficial for earthworms in a cropped system than a high supply of readily available food from fast decomposing L. leucocephala prunings. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

4.
The ability of multipurpose hedgerow tree species to out-compete undesired regrowth during fallow phases was examined. Biomass and spatial distribution of grass and broad leaf volunteers was measured after two years of fallow, in two alley cropping systems planted at six m interrow distance, at the Humid Forest Ecoregional Centre Research Station, Mbalmayo, southern Cameroon. The two experiments had been continuously cropped for five and six years previously. In the experiment cropped for six years, the presence of Senna spectabilis [(DC.) Irwin and Barnaby] hedgerows reduced the biomass of the volunteer regrowth from 9.2 to 4.3 Mg ha−1. Tillage during the previous cropping phase increased the broad leaf biomass from 3.0 to 4.4 Mg ha−1, reduced the biomass of grasses from 3.4 to 2.7 Mg ha−1 but had no effect on the total volunteer biomass. Volunteer biomass was significantly lower within 1.5 m of the S. spectabilis hedgerows than at positions further away. In the experiment cropped for five years, S. spectabilis reduced the volunteer regrowth biomass significantly. Two other hedgerow species, Dactyladenia barteri [(Hook f ex Oliv.) Engl.] and Flemingia macrophylla [(Willd.) Merrill] had no effect on the total amount of volunteer regrowth but did reduce volunteer biomass within 0.5 m of the hedgerows. S. spectabilis caused a stronger reduction of volunteer biomass than D. barteri and F. macrophylla at almost all distances from the hedgerows. The competitiveness of D. barteri and F. macrophylla is insufficient and their growth habit is unsuitable to out-compete undesired species in this alley cropping system. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

5.
Alley cropping is increasingly becoming accepted as an appropriate technology with the potential to provide stable and sustainable food production in the tropics. However, only a few of the potential trees/shrubs have been tested. The performance of Calliandra calothyrsus (Meissn) as an alley cropping species was evaluated on an Oxic Paleustalf. The treatments were: prunings removal, prunings application; and three N levels, 0,45, and 90 kg N ha–1, in a factorial arrangement. The cropping sequence was maize (main season) follwed by cowpea (minor season). Nitrogen fertilizer treatments were applied to the maize crop only. Four annual prunings of Calliandra hedgerows produced a total of 6 t ha–1 of dry matter prunings containing about 200 kg ha–1 of N. Maize yields were increased by the application of prunings but no benefits were obtained by supplementing the prunings with inorganic N. An average maize grain yield of 3.1 t ha–1 per year was maintained without any chemical fertilizer input. However, without any prunings, maize yields were substantially increased by the application of inorganic N. Cowpea yield did not respond to application of prunings but plants grown adjacent to the hedgerows had reduced yield probably due to shading. Our results suggest that six rows (0.57 m inter-row spacing) between Calliandra hedgerows spaced at 4 m are optimum for this cowpea variety. The performance of Calliandra was comparable to that of Leucaena which has been widely shown to be effective in alley cropping systems of the region.  相似文献   

6.
The effect of alley cropping with seven combinations of Acioa and Leucaena hedgerows and a control (no hedgerow) treatment on sequentially cropped maize and cowpea was studied in 1985 and 1986. The trial was carried out on an Alfisol in the humid zone of southwestern Nigeria. Hedgerows were established in 1983, using 4 m inter-hedgerow spacing and pruned to 25 cm height during cropping. Highest dry matter, wood, and nutrient yields of prunings of Acioa and Leucaena hedgerows were obtained with sole cropping. Growing Leucaena and Acioa in the same hedgerow suppressed dry matter production and nutrient yield of Acioa more than of Leucaena owing to the latter's faster growth. Total pruning dry matter yield was reduced as the proportion of Acioa increased in the combination. Leucaena prunings had higher nutrient yield than Acioa. Under 22-month old uncut hedgerows, weed biomass declined in the presence of Leucaena, either alone or in combination with Acioa. Weed weight under sole Leucaena hedgerows was about a third of that in the control plot. There was no significant effect of alley cropping on weed biomass, although alley cropping with Acioa and Leucaena hedgerows resulted in the dominance of broadleaf weeds while the control had a mixture of broadleaves and grasses. Alley cropping with various combinations of Acioa and Leucaena hedgerows increased maize and cowpea yields compared to control. Nitrogen application in both years increased maize grain yield. Mean yield increase due to N application in both years was highest in the control (47.2%) followed by the sole Acioa hedgerow (25.2%) and less in hedgerows with Leucaena. The results of observations over two years do not show any advantage for the tested Leucaena and Acioa combinations on maize and cowpea crops as compared to the sole hedgerows. B.T. Kang (IITA), c/o Miss Maureen Larkin  相似文献   

7.
Inadequate supply of fodder is a serious constraint to the potentially-promising small-holder-dairy production system in coastal Kenya. Alley farming could be an approach to addressing this problem. A study of forage production based on Napier grass and leucaena in an alley cropping system was conducted on an infertile sandy soil in lowland coastal Kenya. The effects of leucaena hedgerows,Clitoria ternatea (L.) intercropping, addition of slurry (110 t ha–1 yr–1) and two harvesting managements (severe and lenient) on the yield of Napier grass fodder, were assessed. The study was initiated in 1989 and three years results are reported.Napier grass fodder yields did not decline in the presence of leucaena heggerows in most harvests. Generally, the Napier rows adjacent to the hedgerows gave greater yields than in either the centre or sole Napier rows. Interplanting clitoria between Napier rows had a beneficial effect on Napier yields in the later harvests. Compared with sole Napier, the hedgerow treatment receiving slurry increased yield ha–1 of Napier by 50%, of total forage by 80%, and of nitrogen (measured over two harvests) by 200%.During the first two years of cropping most treatments did not affect the OM and nitrogen content of the soil but by the end of the third cropping year, slurry application increased soil OM by 21% and slurry and clitoria treatments each increased soil nitrogen by 33%.The study demonstrated the increases in the supply and quality of forages for dairy cattle that can be achieved by planting complementary forages, legume and grass species in an intercropping system like alley farming and the benefits to soil composition by the return of slurry.  相似文献   

8.
In southern Benin, West Africa, two alley cropping systems were studied from 1986 to 1992. Yield development was followed in a maize and cassava crop rotation vs. intercropping system, with alleys of Leucaena leucocephala (Lam.) de Wit and Cajanus cajan (L.) Millsp. vs. a no-tree control, with and without NPK fertiliser. Without alleys, NPK fertilisation maintained high yield levels of 2–3 t maize dry grain plus 4–6 t ha–1 cassava root DM in intercropping, 3–4 t ha–1 maize and 6–10 t ha–1 cassava in solercropping. Without NPK, final yields seemed to stabilise at about 1 t maize plus 2 t cassava in intercropping and twice as much in each solecrop. Alley cropping induced significant yield increases by about 50% with both tree species in unfertilised, intercropped maize, and with Cajanus in fertilised, solecropped cassava. In monetary terms, the NPK-fertiliser response of stabilised yields was significant for all treatments except the solecropped Leucaena alleys. It is concluded that on Ultisols with low nutrient status in the upper rooting zone, alley cropping with low-competitive tree species may improve food crop yields but the greatest monetary output is achieved by intercropping with mineral fertiliser independent of the presence or absence of an agroforestry component.  相似文献   

9.
Field experiments were conducted to investigate the effect of alley cropping vegetable crops with Leucaena leucocephala (Lam.) de Wit for two seasons on a sandy loam Oxic paleustalf in southwestern Nigeria. Four vegetable crops (Amaranthus cruentus L.; Celosia argentea L.; Okra, Hibiscus esculentus L.; and tomato, Lycopersicon esculentum Mill.) were grown in control plots and in 4-m wide alleys between established Leucaena hedgerows without and with fertilizer (30 N-13 P-24 K kg ha–1). Leucaena prunings yielded large dry biomass and nutrients during both seasons. Yield of four vegetable crops responded more to fertilizer in control than in alley cropped treatments. Better yield of vegetables in alley cropped plots was in part due to following effect of the Leucaena hedgerows. Fertilizer application increased mean yields of Amaranthus, Celosia, okra and tomato by 325, 164, 47 and 94% in control plots and by 36, 26, 4 and 20% in alley cropped plots, respectively. For both seasons, yields were not significantly different between alley cropped with and without fertilizer and the control with fertilizer treatments. Yield was least in control without fertilizer. Alley cropping with Leucaena can reduce fertilizer requirement for vegetable production. Cost and return analysis using 1988 prices indicated that alley cropping with vegetable crops can be profitable.c/o Miss Maureen Larkin, L. W. Lambourn & Company, 26 Dingwall Road, Croydon CR9 3EE, England  相似文献   

10.
Alley cropping would be acceptable to farmers in West Africa, if the amount of tree-crop competition could be reduced and crop yields increased and stabilized. The importance of overall tree-crop competition in alley cropping was therefore quantified at three locations in the Republic of Bénin, by comparing the performance of a maize-cassava intercrop and mixed hedges of Gliricidia sepium and Flemingia macrophylla in an alley cropping system, where the tree-crop interaction was high, and in a cut and carry system with block plantings, where the interface was restricted to one face. The establishment and productivity of trees in both agroforestry systems depended strongly on the natural soil fertility of the site, K and Ca being critical for both species. Alley hedges produced progressively more cut dry matter with higher leaf proportions than tree blocks and hence yielded significantly higher nutrient masses. Overall, the cut dry matter from five cuttings per cropping season ranged among locations from 855 to 1651 kg ha–1 yr–1 for alley hedges and from 777 to 869 kg ha–1 yr–1 for tree blocks. Differences in yields of maize and cassava between both systems were insignificant in all three environments and all cropping years under observation. The results of this study suggest that the overall effect of tree-crop competition was unimportant, but that tree-tree competition was the decisive factor in determining the total system productivity.  相似文献   

11.
Although alley cropping has been shown elsewhere to permit continuous cropping, it has not been widely tested in the highlands of east and central Africa where it has the additional potential of controlling soil erosion. The effect of four rates (0, 30, 60 and 90 kg N ha–1) of inorganic N on the performance of alley cropping using Leucaena diversifolia as the hedgerow species was studied in the central highlands of Burundi. Significant increase in maize yield (average of 26%) due to alley cropping was only first realised in 1992, three years after the commencement of the trial. In 1993, the average yield advantage of the alley cropping plots was 21%. The prunings augmented the response of maize yield to inorganic N in 1992 and 1993. Compared with the control, economic benefits over the five-year period for all the treatments were negative.  相似文献   

12.
The effects of no-tillage and alley cropping withCassia spectabilis hedgerows on soil properties and crop yields in a Typic Kandiudult of the humid forest zone of Central Africa were studied over the period 1990–1992 in southern Cameroon. The experimental treatments were no-tillage and hand tillage, both of which were either alley cropped withC. spectabilis hedgerows at interhedgerow spacings of 6 m or not alley cropped (control). A maize + cassava intercrop was planted in all plots at the commencement of each growing season.No-tillage had no significant effects on soil physical properties except to decrease soil temperature. In comparison to hand tillage, no-tillage increased soil organic C and total N in both years and pH in 1991. Mean organic C and total N with no-tillage were 1.77% and 0.174%, respectively, whereas with hand tillage were 1.35% and 0.145%, respectively. Notillage also resulted in a greater proportion ofC. spectabilis roots occurring in the topsoil. Alley cropping caused significant reductions in dry season soil temperature, surface seal formation and cassava root growth, and increases in exchangeable Ca, effective CEC and water infiltration compared with non-alley cropped controls. Infiltration rate at 2 h after commencing measurements were greater by 75% with alley cropping. Lowest maize cob and cassava tuber yeilds were observed when no-tillage was combined with alley cropping whereas highest yields occurred with no-tillage alone.  相似文献   

13.
An experiment was conducted at ICRISAT Center, Patancheru, India from June 1984 to April 1988 on a shallow Alfisol to determine whether the productivity of annual crop systems can be improved by adding perennial species such as Leucaena leucocephala managed as hedgerows. Except in the first year, crop yields were suppressed by Leucaena due to competition for moisture. The severity of competition was high in years of low rainfall and on long-duration crops such as castor and pigeonpea. Based on total biomass, sole Leucaena was most productive; even on the basis of land productivity requiring both Leucaena fodder and annual crops, alley cropping had little or no advantage over block planting of both components. Application of hedge prunings as green manure or mulch on top of 60 kg N and 30 kg P 2 O 5ha−1 to annual crops did not show any benefit during the experimental period, characterized by below average rainfall. Indications are that (i) alley cropping was beneficial in terms of soil and water conservation with less runoff and soil loss with 3 m alleys than with 5.4 m alleys, and (ii) root pruning or deep ploughing might be effective in reducing moisture competition.  相似文献   

14.
Tree pruning is a common management practice in agroforestry for mulching and reducing competition between the annual and perennial crop. The below-ground effects of pruning, however, are poorly understood. Therefore, nutrient dynamics and root distribution were assessed in hedgerow plantings of Acacia saligna (Labill.) H.L. Wendl. after tree pruning. Pruning to a height of 1.5 m was carried out in March and September 1996. In July and October 1996, the fine root distribution (< 2 mm) and their carbohydrate contents were determined at three distances to the tree row by soil coring. At the same time, foliar nutrient contents were assessed, whereas nutrient leaching was measured continuously. The highest root length density (RLD) was always found in the topsoil (0–0.15 m) directly under the hedgerow (0–0.25 m distance to trees). Pruning diminished the RLD in the acacia plots at all depths and positions. The relative vertical distribution of total roots did not differ between trees with or without pruning, but live root abundance in the subsoil was comparatively lower when trees were pruned than without pruning. In the dry season, the proportion of dead roots of pruned acacias was higher than of unpruned ones, while the fine roots of unpruned trees contained more glucose than those of pruned trees. Pruning effectively reduced root development and may decrease potential below-ground competition with intercropped plants, but the reduction in subsoil roots also increased the danger of nutrient losses by leaching. Leaching losses of such mobile nutrients as NO3– were likely to occur especially in the alley between pruned hedgerows and tended to be higher after pruning. The reduced size of the root system of pruned acacias negatively affected their P and Mn nutrition. Pruning also reduced the function of the trees as a safety net against the leaching of nutrients for both NO3– and Mn, though not for other studied elements. If nutrient capture is an important aim of an agroforestry system, the concept of alley cropping with pruning should be revised for a more efficient nutrient recycling in the system described here.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

15.
Root observations were carried out on a typic Paleudult in the humid forest zone of south eastern Nigeria in an alley cropping trial usingDactyladenia (Acioa) barteri andSenna (Cassia) siamea as hedgerow trees and the interrow space planted to maize/cassava intercrop. Rooting depth ofD. barteri andS. siamea exceeded 1.6 m. Lateral root propagation ofS. siamea was 15 m, and ofD. barteri was 5 m from the hedgerows. The whole no-tree control plot was within the range of roots of the adjacent hedgerows. Rooting density and depth ofS. siamea in the no-tree control plot was generally higher than of cassava.S. siamea and cassava root density were inversely correlated. Assuming radial symmetry of root propagation, water and nutrients were available from an area 6.1 and 2.3 times larger than the allocated plot size ofS. siamea andD. barteri, respectively. Data obtained in alley cropping trials, not considering lateral root propagation, can be invalidated through exploitation of the no-tree control treatment and nutrient acquisition by hedgerow species from a larger area than allocated, thus underestimating and overestimating the performances of the respective treatments. Possible alternative measures for avoiding root interference are discussed but no good solution can be given.  相似文献   

16.
Fine root dynamics of shaded cacao plantations in Costa Rica   总被引：1，自引：0，他引：1  
Root turnover may contribute a significant proportion of recycled nutrients in agroforestry systems and competition between trees and crops for nutrients and water may depend on temporal fine root regrowth patterns. Fine root biomass ( 2 mm) and fine root productivity were measured during one year in plantations of cacao (Theobroma cacao) shaded by Erythrina poeppigiana or Cordia alliodora planted on a deep alluvial soil in Turrialba, Costa Rica. Fine root biomass of approximately 1.0 Mg ha–1 varied little during the year with maximum values at the beginning of the rainy season of 1.85 Mg ha–1 in the cacao-C. alliodora system compared to 1.20 Mg ha–1 for cacao-E. poeppigiana. Fine root productivity of C. alliodora and E. poeppigiana (maximum of 205 and 120 kg ha–1 4 week–1, respectively) was greatest at the end of the rainy season, while for cacao it was greatest at the beginning of the rainy season (34–68 kg ha–1 4 week–1), which suggests that if nutrient competition occurs between the shade trees and the cacao, it could be minimized by early fertilization during the beginning of the rains immediately after pruning the shade trees. Annual fine root turnover was close to 1.0 in both systems. Assuming that fine root biomass in these mature plantations was constant on an annual basis, nutrient inputs from fine root turnover were estimated as 23–24 (N), 2 (P), 14–16 (K), 7–11 (Ca) and 3–10 (Mg) kg ha–1 year–1, representing 6–13% and 3–6% of total nutrient input in organic matter in the C. alliodora and E. poeppigiana systems, respectively.  相似文献   

17.
Tensiometer measurements were carried out on a typic Paleudult in the humid forest zone of south eastern Nigeria in an alley cropping trial using fertilized and unfertilizedDactyladenia (Acioa) barteri andSenna (Cassia) siamea as hedgerow trees and a no-tree control. The interrow space of alley cropped and no-tree control plots were planted to maize/cassava intercrop. Water withdrawal during short dry spells and the dry season occurred fastest in the no-tree control plot and resembled the pattern in the adjacentS. siamea alley cropping. Previous root investigations showed that the whole no-tree control plot was within the range of root propagation of the adjacent hedgerow trees. Installation of a 70 cm deep root barrier led to a retarded water withdrawal in unfertilized no-tree control plots to a depth of 150 cm. In fertilized no-tree control this retardation occurred to a depth of 110 cm, while at 130 and 150 cm water withdrawal with root barriers was faster than without barriers. Results indicate thatS. siamea depleted water resources in the no-tree control plot and shortened the growing season of cassava. Restricting roots to the assigned plot size can reduce competition for water in adjacent plots even in layers below the depth of the barrier but can also induce compensative water withdrawal from layers which were not necessarily affected by the barrier. It appears that currently no standard methodology is available to conduct agroforestry trials without the risk of invalidation through root interference. Methods to determine minimum plot size in order to reduce the risk of invalidation and misinterpretation of results are suggested.  相似文献   

18.
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   

19.
Above and below ground interactions in alley-cropping in semi-arid India   总被引：7，自引：0，他引：7  
The influence of micro-environment on the growth and yield of cowpea, castor and sorghum was investigated in a 10 m wide alley cropping system. The alleys were formed by Leucaena hedgerows pruned for both fodder and pole production. Below-ground interaction was examined by installing a polythene root barrier between the root systems of crops and Leucaena and by measurements of both soil moisture and root growth. Microclimate measurements included light, wind speed, humidity and temperature.Growth and yield of crops declined from 150 to 30% of sole crop as the distance from the hedgerows decreased from 5 to 0.3 m. The presence of the root barrier had a marked effect on crop growth and completely eliminated any reduction in crop yield, although shading by the hedgerows reached 30 to 85% of full sunlight. There was some modification of the microclimate in the alleys but the changes were not great enough to significantly influence crop yield. The substantial increase in crop yield in the middle of the alleys was explained by the residual effect of a previous hedgerow, removed 12 months previously, on probably the infiltration rate and nutrient status of the soil. These results clearly showed that alley cropping in the semi-arid tropics induces competition for moisture between the trees and crops which may severely reduce crop yield.  相似文献   

20.
Maize/cassava were intercropped between hedgerows of Senna spectabilis [(DC.) Irwin and Barneby], Flemingia macrophylla [(Willd.) Merrill] and Dactyladenia barteri [(Hook f ex Oliv.) Engl.] for five consecutive years on an Ultisol in southern Cameroon. Crop yields and hedgerow biomass production in the third to fifth year of cropping are reported. S. spectabilis produced more biomass than F. macrophylla and D. barteri in all years. Cumulative maize grain and cassava tuber yields were highest in F. macrophylla alley cropping, outyielding the no-tree control consistently by 42 to 67% (average 56%). Between hedgerows of D. barteri and S. spectabilis, crops yielded 17% and 16% more than the no-tree control, respectively. However, between S. spectabilis hedgerows, yields were highly variable between years (–15% to +35% compared to the no-tree control) and thus the system is at risk of failure. F. macrophylla is recommended for continuous alley cropping of maize/cassava intercrop. The use of D. barteri may require fallow phases for biomass accumulation followed by cropping phases with rigorous pruning. Although this may lead to lower cumulative yields, the products of the fallow phase, such as stakes and firewood, may provide some compensation.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

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