The potential of alley cropping im improvement of cultivation systems in the high rainfall areas of Zambia II. Maize production

Theee trials to evaluat the potential of alley cropping in maize production on the low fertility, acidic soils in Northern Zambia are described. Leucaena leucocephala, Gliricidia sepium, Sesbania sesban, Albizia falcataria, Fleminga congesta, and Cassia spectabilis, were grown in alley crops with hybrid maize and soybean. All trials received recommended rates of P and K fertiliser; N fertiliser was applied at three rates as a subplot treatment. One trial received lime before establishment.Only in the limed trial was there a significant improvement in maize yields through alley cropping; when no N fertiliser was applied, incorporation of Leucaena leucocephala prunings resulted in an increase of up to 95% in yields, with a smaller improvement being produced by Flemingia congesta. There was a significant correlation between the quantity of prunings biomass applied and the proportional increase in maize yields over the control treatment. It is suggested that the lack of effect of most of the tree species on crop yields was due to low biomass production.An economic analysis showed that alley cropping with limed Leucaena was only profitable when fertiliser costs were high in relation to maize prices. However, lime is both expensive and difficult to obtain and transport for most small scale farmers in the region, and is therefore not a practical recommendation. It is suggested that future alley cropping research should focus on screening a wider range of tree species, including other species of Leucaena, for acid tolerance and higher biomass production.     

Effects of no-tillage and alley cropping on soil properties and crop yields in a Typic Kandiudult of southern Cameroon

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.     

Influence of root pruning and cutting interval ofLeucaena hedgerows on performance of alley croppedrabi sorghum

The influence of root pruning and cutting interval ofLeucaena hedgerows on alley croppedrabi sorghum was investigated. Paired (60 cm)Leucaena hedgerows spaced 6.6 m wide were subject to either root pruning, using a country plough during mid-kharif season, or no root pruning. The cutting frequency ofLeucaena hedgerows ranged from one month to six months during therabi cropping period. The effect on soil moisture, crop growth, yield and yield components ofrabi sorghum was examined.Root pruning ofLeucaena hedgerows increased grain and stover yields of the alley croppedrabi sorghum by 33 and 17%, respectively, over root not pruned hedgerows. Similarly, shorter cutting intervals (one and two months) increased crop yields as compared with longer cutting intervals (three and six months). The growth (height and dry matter) of the crop was similarly influenced. Soil moisture studies indicated that the competition between crop and hedgerows was considerably reduced by the root pruning. The results clearly showed that the competition between hedgerows and arable crop can be reduced considerably by root pruning and frequent cutting (at one to two months interval) of the hedgerows.     

Effect of alley cropping with Leucaena leucocephala and fertilizer application on yield of vegetable crops

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     

Alley cropping on an Ultisol in subhumid Benin. Part 1: Long-term effect on maize, cassava and tree productivity

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.     

The potential of alley cropping in improvement of cultivation systems in the high rainfall areas of Zambia I. Chitemene and Fundikila

Three trials investigating the potential of alley cropping to improve the traditional systems of cultivation, chitemene and fundikila, in the Northern Province of Zambia are described. Flemingia congesta, Tephrosia vogelii, and Sesbania sesban, were grown in association with finger millet, groundnut, cowpea, and maize in various traditional cropping sequences. The indigenous species Tephrosia vogelii and Sesbania sesban were not able to withstand repeated pruning and the long following dry season, and were replaced with Calliandra calothyrsus, and Cassia spectabilis.Over a four year period, there was no benefit by alley cropping with any of the tree species on crop yields, and yields in alley crop treatments even dropped significantly below the control treatments in the fourth year, casting doubt on the potential of alley cropping for sustainable production. There was also no consistent effect on soil chemical characteristics in any of the trials. It was suggested that this lack of beneficial response to alley cropping was due to low tree biomass production low quality of prunings, and an inappropriate cropping sequence. There was no evidence that alley cropping contributed to enhanced nutrient recycling, despite substantial localised pools of soil nutrients, particularly in the chitemene, with which recycling could potentially occur.     

Studies withGliricidia sepium for crop/livestock production systems in West Africa

This paper reports for progress of research onGliricidia sepium conducted by the Humid Zone Programme (HZP) of the International Livestock Centre for Africa (ILCA) at Ibadan in Southwest Nigeria in the period 1982–1986. It examines the biological characteristics of the species, with respect to growth, flowering and seed production, and analyses its potential for improving crop production (through soil fertility maintenance) and livestock production (through production of improved fodder). Integration ofGliricidia into cropping systems is necessary for optimum realisation of its crop improvement quality. The alley farming system is presented in the paper as one means of achieving sustainability in crop production through integration of trees, such asGliricidia, into cropping systems. The use ofGliricidia in Intensive Feed Gardens, for production of leguminous fodder is also described as an alternative production system. The paper finally reports on experiences with local farmers in on-farm research and development for the integration ofGliricidia andLeucaena into local farming systems. It ends with a suggestion for more research, targetted specifically at improvement of the species and its utilisation.     

Studies withGliricidia sepium for crop/livestock production systems in West Africa

This paper reports for progress of research onGliricidia sepium conducted by the Humid Zone Programme (HZP) of the International Livestock Centre for Africa (ILCA) at Ibadan in Southwest Nigeria in the period 1982–1986. It examines the biological characteristics of the species, with respect to growth, flowering and seed production, and analyses its potential for improving crop production (through soil fertility maintenance) and livestock production (through production of improved fodder). Integration ofGliricidia into cropping systems is necessary for optimum realisation of its crop improvement quality. The alley farming system is presented in the paper as one means of achieving sustainability in crop production through integration of trees, such asGliricidia, into cropping systems. The use ofGliricidia in Intensive Feed Gardens, for production of leguminous fodder is also described as an alternative production system. The paper finally reports on experiences with local farmers in on-farm research and development for the integration ofGliricidia andLeucaena into local farming systems. It ends with a suggestion for more research, targetted specifically at improvement of the species and its utilisation.     

Effects of alley cropped Calliandra calothyrsus and Cliricidia sipium hedges on weed growth,soil properties,and taro yields in Western Samoa

Field experiments were conducted on a tropical Inceptisol at Apia, Western Samoa to evaluate the effects of alley cropping on soil characteristics, weed populations, and taro yield. Taro yields were compared from Calliandra calothyrsus and Gliricidia sipium alleys, spaced at 4 m, 5 m, and 6 m, and a no tree control. Measurements were made for soil moisture and temperature, weed growth, hedge biomass production, and taro growth and yield. Data was analyzed over 4 consecutive years from 1988 to 1991.Hedge biomass yields ranged from 5.1 to 16.1 t/ha/yr dry weight over the 4 years of the trial, with Calliandra and Gliricidia performing equally well. Biomass yields decreased by about 2 mt/ha with increasing alley width from 4 to 6 m alleys. Weed populations were significantly lower in the 4 m alleys compared to the 5 m, 6 m, and control plots. The 6 m alleys supported the significantly highest weed populations. Soil from alley plots held significantly more water in the 0.3 to 1 bar range than soils from the controls. Four years of mulch application measurably improved soil water holding capacity and bulk density. However, no improvement was seen in nitrogen, phosphorus, potassium, calcium, magnesium and organic carbon content in the alley plots compared to the controls. There was no positive yield effect of alley cropping on taro yield. Yields in the 5 m and 6 m alleys were not significantly different from the control, while the 4 m alleys produce significantly lower yields than the control. Thus, alley cropping did not prove a viable alternative to traditional shifting cultivation after 4 years of continuous cropping, in this trial.     

Productivity of annual cropping and agroforestry systems on a shallow Alfisol in semi-arid India

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.     

Disease incidence and severity on beans in alleys between Leucaena hedgerows in Kenya

The effects of inter-row spacing of Leucaena leucocephala in an alley cropping system on the incidence and severity of diseases on intercropped beans (Phaseolus vulgaris L.) and their yield were examined over two years (1993 and 1994) at Chepkoilel Campus in Kenya. Each experiment consisted of three randomized blocks with treatments of three alley widths (2 m,4 m and 8 m) and a treeless control with two intra-row spacings of Leucaena (0.5 m and 1.0 m). Hedgerows were coppiced at 1.0 m height and pruned subsequently at two-to-three months intervals. No fertilizer was applied but Leucaena loppings were incorporated as green leaf manure. Incidence of angular leaf spot (Phaeoisariopsis griseola) and anthracnose (Colletotrichum lindemuthianum) on beans were assessed at three growth stages in each season, using the Centro International de Agricultura Tropical (CIAT) scales. Microclimate was monitored in treatments, in 1994. Angular leaf spot and anthracnose decreased with increasing alley width and were more severe in bean rows adjacent to hedgerows. Light availability and diurnal temperaturereaching the bean canopy increased with alley width but relative humidity and leaf wetness duration decreased. Proximity to hedgerows also had markedly reduced light levels, lower temperatures and higher relative humidity. Higher incidence and severity of angular leaf spot and anthracnose on beans in alleys than on beans in treeless plots were examined in relation to microclimate, inoculum survival and dispersal. The pattern of the diseases was best explained by microclimate changes induced by Leucaena hedgerows, especially effects of humidity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Incidence and Severity of Bean Rust (Uromyces appendiculatus) in Alleys between Leucaena Hedgerows in Kenya

The effects of inter-row spacing of Leucaena leucocephala (Lam.) de Wit in an alley cropping system on the incidence and severity of rust (Uromyces appendiculatus (Pers.) Unger) on intercropped beans (Phaseolus vulgaris L.) and their yield were examined over 2 years (1993 and 1994) at Chepkoilel Campus in Kenya. Each experiment consisted of three randomized blocks with treatments of three alley widths (2 m, 4 m and 8 m) and a treeless control with two intra-row spacings of Leucaena (0.5 m and 1.0 m). Hedgerows were coppiced at 1.0 m height and pruned subsequently at 2–3 months intervals. No fertilizer was applied but Leucaena loppings were incorporated as green leaf manure. Rust on beans was assessed at three growth stages in each season, using the Centro International de Agricultura Tropical (CIAT) scales. Microclimate was monitored in treatments, in 1994. Bean growth and yield were also measured. Rust increased with increasing alley width and was less severe in bean rows adjacent to hedgerows. Bean yield was highest in the treeless control plots and declined with decreasing alley width. Beans in 2 m alleys had significantly lower (p < 0.05) yields than 8 m alleys and treeless control plots. Bean growth was greatly modified in 2 m alleys and close to hedgerows. Light availability and diurnal temperature increased with alley width but relative humidity and leaf wetness duration decreased. Proximity to hedgerows also had marked effect on microclimate. The changes in yield, rust incidence and severity were examined in relation to microclimate, inoculum survival and dispersal.     

Nitrogen contribution of five leguminous trees and shrubs to alley cropped maize in Ibadan, Nigeria

There are abundant local legume trees and shrubs potentially suitable for alley cropping systems in the sub-Saharan Africa, which are yet to be studied. The nitrogen contribution of two years old Albizia lebbeck and S. corymbosato yield of maize grown in alley cropping was compared to that of Senna siamea, Gliricidia sepium and Leucaena leucocephala in four seasons at Ibadan. Maize shoot biomass and maize grain yield in A. lebbeck alley compared favourably with that in G. sepium and L. leucocephala. Maize biomass and grain yield in S. corymbosa alleys were the lowest. Within A. lebbeck, L. leucocpehala, and G. sepium alleys there were no significant differences in the maize yield in the alleys that received 0, 40 or 80 kg N/ha. Application of more than 40 kg N/ha in S. corymbosa alleys was not necessary as there was no significant increase in maize yield at the higher level of nitrogen. Maize yield and N uptake in A. lebbeck alleys were not significantly different from yield and N uptake in G. sepium, and L. leucocephala at the same fertilizer level. There was a significant correlation between hedgerow tree biomass and maize grain yield. At the end of twelve weeks after pruning application, the organic residues of the pruning applied in the alleys ranged from 5% in G. sepium and 44% in A. lebbeck in the first year compared with the original pruning applied which showed that the slow rate of A. lebbeck decomposition could have a beneficial effect on the soil. The maize N recovery from applied N fertilizer was low (10–22%). Percentage N recovery from the prunings was low in the non-N fixing trees (12–22%), while the recovery was high (49–59%) in A. lebbeck as well as in the other nitrogen fixing tree prunings. Thus A. lebbeck, apart from enhancing maize growth and grain yield like in L. leucocephala and G. sepium, had an added advantage because it remained longer as mulching material on the soil because of its slow rate of decomposition. It was able to survive pruning frequencies with no die-back. This indicates that A. lebbeck is a good potential candidate for alley cropping system in West Africa. S. corymbosa performed poorly compared with the other legume trees. Though it responded to N fertilizer showing a positive interaction between the hedgerow and fertilizer application, it had a high die back rate following pruning periods and termite attack.This revised version was published online in November 2005 with corrections to the Cover Date.     

Stepwise approach to alley cropping technology development and transfer in the forest zone of Cameroon

Two projects on alley cropping research and development have been implemented in the Forest zone of Cameroon (FZC) since 1988. Their goal was to identify the main agricultural constraints in the FZC and to introduce alley cropping in the farming systems to improve soil fertility and crop yields. The first step in the implementation process was the participatory surveys which revealed that (a) the main agricultural constraint in the FZC is low soil fertility; (b) alley cropping is an agroforestry technology which may solve the problem; (c) alley cropping should be first targetted to farmers who own inherited or purchased lands. The second step was the on-station tree screening activity from which Leucaena leucocephala, Gliricidia sepium, Calliandra calothyrsus and Paraserianthes falcataria were identified as promising tree species. The third activity was to test alley cropping with three promising tree species (Leucaena, Gliricidia and Calliandra) on farmers' fields. Results from the first year testing on farmers' fields showed that: (1) the direct seeding method used was ineffective: seedling emergence rate was 45% for Leucaena and 52% for Gliricidia; (2) Cassava suppressed the growth of Leucaena and Gliricidia by 57 and 45%, respectively; (3) three-month-old Calliandra seedlings planted 1 m away from cassava plants had 96% survival rate. Based on these third step findings, all new farms were established with Calliandra seedlings using maize as a test-crop in the year of establishment and the subsequent year. After two years of cropping, maize grain yield in alley plots was 52% higher than maize grown on no-tree plots. In 1993, 52 farmers who had witnessed the alley farm maize growth in 1992 requested to join the project. This sudden interest of farmers to start their own alley farms was considered as a positive sign for adoption and therefore a success in alley cropping (AC) introduction in the zone.     

Soil respiration and microbial biomass in a pecan — cotton alley cropping system in Southern USA

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.     

Alley cropping with Leucaena leucocephala (Lam.) De Wit and Acioa barteri (Hook.f.) Engl.

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     

Root distribution ofDactyladenia (Acioa) barteri andSenna (Cassia) siamea in alley cropping on Ultisol. I. Implication for field experimentation

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.     

Alley cropping and mulching withErythrina poeppigiana (Walp.) O. F. Cook andGliricidia sepium (Jacq.) Walp.: effects on maize/weed competition

The potential of allye cropping systems to sustain a high productivity with low external inputs and the reduction of maize/weed competition through weed suppression in different alley cropping and sole-cropped mulched systems was studied in Costa Rica at CATIE. Data were recorded eight years after establishment of the experiment. Plant residues ofErythrina poeppigiana trees (10 t/ha dry matter) planted at 6 by 3 m reduced weed biomass by 52%, whileGliricidia sepium trees (12 t/ha dry matter) planted at 6 by 0.5 m reduced weed biomass by 28%, in comparison to controls.Erythrina had a considerable impact on grass weeds, whileGliricidia reduced the incidence of some dicot weeds. Weed competition significantly reduced maize yield in all systems. Nevertheless weed suppression contributed to the higher maize grain yield underErythrina andGliricidia alley cropping of 3.8 t per hectare as opposed to the unmulched control yield of 2.0 t per hectare.     

Sewage sludge fertilisation of a silvopastoral system with pines in northwestern Spain

The use of municipal sewage sludge as a fertiliser could be a more adequate means of disposal of this residue than its transport to the dump. The objective of this experiment was to evaluate the effects of different doses of sludge and sowing a mixture of cocksfoot (Dactylis glomerata) and clover (Trifolium repens) on pasture production, botanical composition of the pasture, forage quality, and changes in soil chemical properties. Treatments applied were: (1) no fertilisation (L0), (2) fertilisation with 26 Mg ha^–1 of sewage sludge with no sowing (L40), (3) fertilisation with 26 Mg ha^–1 of sewage sludge and sowing with 25 kg of Dactylis glomerata L. cv Artabro (Dg) and 3 kg Trifolium repens cv Huia per hectare and (4) 52 Mg ha^–1 of sewage sludge with no herbage sowing (L80). Plots were established in a silvopastoral system with Pinus radiata D. Don at a density of 1666 trees ha^–1 (3 × 2 m). The improvement of soil fertility due to organic fertiliser application and the use of Dactylis glomerata increased the production and quality of pasture as well as reduced the risk of fire and erosion, as grasses dominated shrubs. Fertilisation with sewage sludge in soils of acid origin increased the concentration of copper in the pasture and, if cocksfoot was not sown, the levels of this element exceeded the maximum tolerable dietary levels for sheep. On the other hand, fertilisation also increased the levels of zinc in pasture, but values were not above toxic limits for sheep, horses and cattle.This revised version was published online in November 2005 with corrections to the Cover Date.     

Vesicular-arbuscular mycorrhiza effects on Gliricidia sepium and Senna siamea in a fallowed alley cropping system

Nitrogen fixing and non-N₂ fixing legumes such as Gliricidia speium and Senna siamea have been used in alley cropping systems for soil improvement and source of N for food crops. However their establishments could be limited by P and moisture deficiencies in degraded soils. Vesicular-arbuscular mycorrhizal fungi can help to overcome these deficiencies. We examined the effects of a vesicular-arbuscular mycorrhizal (VAM) fungus, Glomus deserticola, on the performance of sole hedgerow trees of Gliricidia sepium and Senna siamea and their mixtures (interplanted) in a fallowed alley cropping experiment on a degraded Alfisol in southwestern Nigeria. Percentage root infection by VAM fungi was higher in inoculated plants than in uninoculated ones irrespective of whether they were interplanted or non-interplanted. Inoculation with G. deserticola increased dry matter accumulation and nutrient uptake (N. P, Mg and K) but there was no significant interaction between mycorrhizal inoculation and interplanting for growth and nutrient uptake except for the uptake of P, Mg and K in G. sepium. Inoculation with G. deserticola reduced leaf shedding of G. sepium by 50% but did not have the same effect for S. siamea. For both tree species inoculated plants extracted more water from 0–30 cm depth than the uninoculated ones.