Economic analysis of cut-and-carry,and alley cropping systems of mulch production for plantains in south-eastern Nigeria

Organic mulch is beneficial to plantain because it maintains soil fertility, prevents erosion and suppresses weeds. Mulch availability is however a major constraint. Mulching in a cut-and-carry system withPennisetum purpureum Schum. (elephant grass) was compared with mulching with the prunings ofAlchornea cordifolia (Schum. & Thonn.),Dactyladenia barteri (Hook. f. ex Oliv.)Engel. (Syn.Acioa barteri),Gmelina arborea (Roxb.) andSenna siamea (Lam.) Irwin & Barneby (Syn.Cassia siamea) in alley cropping systems. Plantain inPennisetum mulch treatment gave the highest bunch yield, but similar net revenues per hectare as theDactyladenia treatment, whileGmelina, Alchornea andSenna treatments produced the lowest incomes. But when the land required to producePennisetum mulch was included in the economic analysis, the net revenue per hectare was negative over three years of cropping. The returns to labour were also much lower for thePennisetum compared to the alley cropping systems. Among the in-situ mulch sources,Gmelina had the highest labour requirement because of the high pruning frequency. In addition, weeding inGmelina, Alchornea andSenna treatments resulted in high labour demand due to the rapid decomposition of the mulch materials leaving the soil bare for weeds to invade.Dactyladenia alley cropping was the most profitable of the five plantain production systems studied.IITA Journal Paper No: 94/004/JA.     

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.     

Nitrogen contribution by multipurpose trees to rice and cowpea in an alley cropping system in Sierra Leone

In an alley cropping experiment, a study was carried out on N₂ fixation by Gliricidia sepium, nitrogen (N) accumulation by prunings of Gliricidia, Senna siamea (formerly Cassia siamea) and Gmelina arborea, and the N contribution to associated crops of rice and cowpea.Total N accumulated by the hedgerow trees ranged from 297–524 kg N ha^–1 on average but varied between tree species and depended on the growing season. Gliricidia sepium accumulated 370 kg N ha^–1 on average and more than half of this came from fixation. Senna siamea and Gmelina arborea served as reference trees for estimating N₂ fixation. The estimates of N₂ fixation using Gmelina as a reference gave higher estimates than those using Senna.Although the dry matter and nitrogen yields of prunings from the hedgerow trees were high, their relative nitrogen contribution to the associated crops was generally low ranging from 5 to 29%. Higher crop yields and nitrogen contribution were observed with Gliricidia sepium prunings. The low N contribution from prunings was attributed to the lack of synchronization between the N released from the prunings and the crop's demand for N.     

Root distribution ofDactyladenia (Acioa) barteri andSenna (Cassia) Siamea in alley cropping on Ultisol. II. Impact on water regime and consequences for experimental design

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.     

The vertical distribution of fine roots of five tree species and maize in Morogoro,Tanzania

In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar rooting pattern for nutrients and water.     

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.     

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.     

Root distribution of Senna siamea grown on a series of derived-savanna-zone soils in Togo, West Africa

Although crucial for assessing the functioning of alley cropping systems, quantitative information related to the hedgerow tree root distribution remains scarce. Soil mapping and destructive soil sampling was used to assess the impact of soil profile features on selected root characteristics of Senna siamea hedgerows, growing in alley cropping systems in three sites (Glidji, Amoutchou, and Sarakawa) representative for the derived savanna of Togo, West Africa. While the soil profiles in Glidji and Sarakawa contained a clay accumulation horizon, the Amoutchou profile was sandy up to 1 m. The number of small roots (diameter < 2 mm), quantified on a soil profile wall, decreased with depth in all sites. For most soil depths, the abundance of small roots tended to be higher near the tree base, e.g., ranging from 5.3 dm⁻² in Amoutchou to 21.4 dm⁻² in Glidji for the 0–20 cm layer, than in the middle of the alley, e.g., ranging from 3.1 dm⁻² in Amoutchou to 13.8 dm⁻² in Glidji for the 0–20 cm layer. Root length density (RLD) of the 0–10 cm and 10–20 cm layers was significantly higher in Glidji than in Amoutchou (P < 0.05) and in Sarakawa (P = 0.08). Differences in RLD between sites were not significant for layers below 30 cm. For each layer, root weight densities (RWD) were similar in all sites, e.g., ranging from 0.44 mg cm⁻³ in Amoutchou to 0.64 mg cm⁻³ in Glidji in the 0–10 cm layer, indicating that the roots in the Glidji topsoil had a smaller overall diameter than in Amoutchou. In Amoutchou, the relative RLD was lower than in Glidji or Sarakawa for the top 40 cm of soil, while the inverse was observed for the layers between 50 and 100 cm deep and this was related to the sandy soil profile in Amoutchou. Another consequence of the sandy profile was the larger tap root diameter below 50 cm in Amoutchou compared to Sarakawa. For all sites, significant (P < 0.001) linear regressions were observedbetween RLD's, RWD's, and the abundance of small roots, although the variation explained by the regression equations was highest for the relationship between RLD and RWD. The potential of the hedgerows to recover nutrients leached beyond the reach of food crops or the safety-net efficiency was evaluated for the tree sites. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soil fertility enhancement by planted tree-fallow species in the humid lowlands of Cameroon

Four shrub/tree species, Alchornea cordifolia, Pennisetum purpureum, Chromolaena odorata, and Calliandra calothyrsus were evaluated for their potential contribution to soil fertility restoration after two years fallow. Standing biomass, root distribution, nutrient content in the biomass, decomposition and nutrient release patterns, and association with mycorrhizae were the evaluation parameters. Alchornea and Pennisetum produced thehighest above-ground biomass, 66 t and 54 t/ha respectively. Pennisetum had more than 19 t/ha of root, 92% of which was in the 20 cm top soil. Alchornea had 74% of it roots in this soil layer, mostly as coarse roots while Calliandra had a deeper root system. Alchornea fallow accumulated more N and Ca, and Pennisetum fallow, more K than others, and mycorrhizae were mostly associated with Alchornea roots. The ranking of the different species for the decomposition rate was: Chromolaena > Pennisetum > Calliandra = Alchornea. Also release of nutrients during decomposition followed the order K > N > Ca. Alchornea and Pennisetum could be recommended as green manure species especially when high quantities of material are needed for weed or erosion control. Calliandra and Chromolaena, because of the flush of nutrient during early mass, loss can be used as mulch when the crop demand of nutrient is high. Alchornea decomposed slowly and therefore could be used to improve Chromolaena mulch, thus contributing to the build up of soil organic N and providing both short- and long-term nutrient release. This revised version was published online in June 2006 with corrections to the Cover Date.     

Alchornea cordifolia,a promising indigenous browse species adapted to acid soils in southeastern Nigeria for integrated crop-livestock agroforestry production systems

Dry matter (DM) production, crude protein, phosphorus fibre contents and goat preference for eight indigenous browse species,Alchornea cordifolia, Diallum guineense, Ficus capensis, Baphia nitida, Manniophytum fulvum, Homalium aylmeri, Glyphaea brevis andRauwolfia vomitoria, and for two exotics,Leucaena leucocephala andGliricidia sepium, in cultivated plots were compared on acid soil in southeastern Nigeria. Total DM production was higher (P<0.05) forAlchornea cordifolia than for the other browse species.Glyphaea brevis andL. leucocephala were the most preferred species, whileA. cordifolia, G. sepium andR. vomitoria were the least. Mean crude protein content of browse species in this study was higher, whileP and neutral detergent fibre were lower than reported for other browse species in Nigeria. It is argued that the ultimate goal of a crop-livestock agroforestry system such as alley farming, could be better achieved through the complementary use of browse species.     

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.     

Yields of maize/cassava intercrops grown with hedgerows of three multipurpose trees on an acid Ultisol of Cameroon

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.     

Water use assessment in alley cropping systems within subtropical China

Alley cropping systems may influence soil water movement and the water budget because of its complex interactions between crop and tree rooting systems. The objective of this paper was to evaluate water balance and water competition in an alley cropping system, consisting of deciduous tree wild jujube (Choerospondias axillaris) and economic crop peanut (Arachis hypogaea) within subtropical China. Five treatments (20- by 6-m plots) with three replications were included in this study. The treatments were monoculture peanut cropping (P), monoculture younger trees (T1), monoculture older trees (T2), peanut intercropped with younger trees (T1P), and peanut intercropped with older trees (T2P). A multi-layered water balance model, with water movement between soil layers, was implemented by the measurement of soil water potential using sets of tensiometers during the periods from March 1999 to December 2002. The spatial and temporal variations of soil water regime indicated that the trees used soil water below the 60-cm soil depth and alleviated the water stress. The direction of soil water movement indicated that soil water moved to the tree row, which indicated that trees competed with peanuts for water, especially during the seasonal drought period. Water competition was related to the tree spacing and tree age. Compared to the tree monoculture systems, the alley cropping system significantly influenced water budget components and water use patterns, as indicated by the increased evapotranspiration (6–11%), and decreased net drainage (7–45%), water storage (6–29%), and runoff (50–60%). Furthermore, alley cropping systems encouraged the rapid growth of trees, and depressed the biomass and yield of peanuts by 20–50% associated with tree shading effects. The results suggest that competition for water and light must be taken into account when optimizing the alley cropping system.     

The vertical distribution of fine roots of five tree species and maize in Morogoro,Tanzania

In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar rooting pattern for nutrients and water.     

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.     

Biomass production and root distribution of Gmelina arborea under an agrisilviculture system in subhumid tropics of Central India

A study of an agrisilviculture system comprising Gmelina arborea and soybean (Glycine max) was conducted in the subhumid region of Central India. Above- and below-ground biomass production and distribution of coarse and fine roots were studied in 4-year-old G. arborea, planted at a spacing of 2 × 2 m, 2 × 3 m, 2 × 4 m and 2 × 5 m. The total biomass varied from 10.89 Mg ha^–1 to 3.65 Mg ha^–1 depending on the tree density. Among the different tree components, stemwood contributed maximum biomass (54.3–79.4%), followed by branches and leaves. Root distribution pattern showed that most of the coarse roots were distributed in the top 40 cm of soil, whereas fine roots were concentrated in the top 20 cm. Coarse root biomass decreased with an increase in spacing. The spread of roots was asymmetrical in trees planted at 2 × 2 m and 2 × 3 m spacings, while it was symmetrical in trees planted at wide spacings. No significant difference was observed in the fine root biomass in different stands. The root:shoot ratio increased with an increase in spacing. Crop (soybean) growth and productivity varied significantly and it increased with a decrease in tree density. Soybean yield varied between 1.5 Mg ha^–1 to 2.1 Mg ha^–1. The role of root architecture of G. arborea trees on productivity of crops under agri-silviculture system is discussed.     

Volunteer biomass production between multipurpose tree hedgerows after two years of fallow in southern Cameroon

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.     

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.     

Microbial community diversity in a 21-year-old temperate alley cropping system

Soil physical and chemical properties in the crop alleys and tree rows in alley cropping systems vary greatly due to differences in litter quality and microclimate under trees compared to the alleys. Variations in soil properties influence microbial diversity and function, and thus, in alley cropping systems, bacterial diversity could be different between soils in tree rows and crop alleys. The objective of this study was to compare and contrast soil bacterial diversity in the crop alleys and tree rows in a 21-year-old alley cropping system in Northeast Missouri, USA. Soil samples were taken in three parallel transects to a depth of 10 cm in the tree row and at the middle of the alley in a silver maple (Acer saccharinum) alley cropping system with a companion maize (Zea mays)—soybean (Glycine max) rotation. Soil bulk density, C and N concentrations were similar between the different transects while minor differences were observed between crop alleys and tree rows. No significant difference in bacterial diversity was observed between the tree rows and alley soil based the denaturing gradient gel electrophoresis profiles, band richness (19.6 and 22.8 for tree row and alley, respectively) and Shannon–Weiner diversity (2.958 and 3.099 for tree row and alley, respectively). Identification of bacterial genera revealed dominance of gram +ve as well as gram ?ve bacteria in both soil types. Ordination plot revealed no clustering effect based on location (transect) or on the cropping system in the different samples. Bacterial diversity in crop alleys most likely was influenced not only by the maize-soybean rotation, but also by the tree rows contributing both above and belowground litter for the past 21 years.     

Comparison of minirhizotron and soil core methods for quantifying root biomass in a temperate alley cropping system

A study was carried out in southern Indiana, USA with the objective of comparing soil core sampling and the minirhizotron technique in quantifying fine root biomass and root distribution patterns in an alley cropping system with black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial variation in tree rooting pattern was investigated prior to planting maize. Tree fine root biomass was quantified at distances of 0, 1.1, 2.3, 3.5, and 4.3 m where 0 m represents the tree row and 4.3 m represents the middle of the alley. Root samples were collected to a depth of 90 cm using a hydraulic auger. Maize rooting pattern was determined 65 days after planting to the same depth. Using plexiglass access tubes installed near the actual soil core locations and a minirhizotron camera root images were recorded on a VHS tape. These images were later analyzed using a raster based GIS software (ERDAS-IMAGINE). Regression analysis revealed significant relationships between root surface area measurements from minirhizotron observations and fine root biomass data from soil coring for all species. Predicted fine root biomass data were also in close agreement with actual fine root biomass for all species examined. Maize root biomass was slightly, but not significantly, underestimated by the minirhizotron technique in the top 30 cm soil layer. No significant underestimation or overestimation of root biomass in surface or deeper soil layers was observed for the tree species. The results indicate that minirhizotron can be used in quantifying fine root biomass if site and species specific predictive models can be developed. This revised version was published online in June 2006 with corrections to the Cover Date.