Productivity of alley farming with leucaena (Leucaena leucocephala Lam. de Wit) and Napier grass (Pennisetum purpureum K. Schum) in coastal lowland Kenya

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.     

Intercropping field crops between rows of Leucaena leucocephala under rainfed conditions in northern India

A field study was conducted for six years (1981–1986) on sandy loam soil on intercropping hedgerows of Leucaena leucocephala (Lam) de Wit. with three field crops viz. maize (Zea mays L), black gram (Vigna mungo L) and cluster bean (Cyamopsis tetragonoloba L Taub.). In treatments 1 and 2 Leucaena hedges were planted as pure crops at close (25 cm × 75 cm) and wide (25 cm × 375 cm) spacings. In treatments 3, 4 and 5 the three field crops were intercropped between the hedgerows of Leucaena at the wide spacing, and in treatments 6, 7 and 8 the field crops were raised as pure crops. Leucaena was topped to 75 cm each time it attained a height of 175 cm. The pure crop of Leucaena at close spacing produced an average, over the six years, of 34 t ha⁻¹a⁻¹ of green fodder and 9.4 t ha⁻¹a⁻¹ of air dry fuelwood. The Leucaena at wide spacing produced 18.9 t ha⁻¹a⁻¹ of green fodder and 6.3 t ha⁻¹a⁻¹ of fuelwood. Intercropping with field crops decreased the yield of green fodder and fuelwood. The yield of all the field crops was less when raised as intercrops than as pure crops. Mean maximum net returns were obtained from intercrops of Leucaena and cluster bean (Rs 3540 ha⁻¹a⁻¹) which were significantly higher than the returns from pure crop of Leucaena at wide spacing but similar to the returns from pure crops of cluster bean. Leucaena with maize (Rs 3273 ha⁻¹a⁻¹) and black gram (Rs 3125 ha⁻¹a⁻¹) gave significantly higher net returns over pure crops of Leucaena at wide spacing, maize and black gram. ICRISAT = International Crops Research Institute for the Semi-Arid Tropics- Hyderabad, India. CIAT = Centro International de Agricultura Tropical - Cali - Columbia     

Estimating fuelwood production and yield in regrowth dry miombo woodland in Zambia

A combination of destructive and non-destructive samples was used to develop regression models for estimating fuelwood production and yield in regrowth dry miombo stands aged 6–34 years. Fuelwood yield from understorey species was estimated from girth at stump height (gsh) data while gsh and stem height data were necessary for estimating yield from canopy species. Mean fuelwood production was estimated at 1.93 m³ ha⁻¹ year⁻¹. It was found that canopy species had a greater sustained stem growth than understorey species. Enhancement of regeneration of canopy species is therefore recommended for the management of miombo woodland for fuelwood production.     

Potential of improved fallows to increase household and regional fuelwood supply: evidence from western Kenya

Fuelwood is the main energy source for households in rural Africa, but its supply is rapidly declining especially in the densely populated areas. Short duration planted tree fallows, an agroforestry technology widely promoted in sub-Sahara Africa for soil fertility improvement may offer some remedy. Our objective was to determine the fuelwood production potential of 6, 12 and 18 months (the common fallow rotation periods) old Crotalaria grahamiana, Crotalaria paulina, Tephrosia vogelli and Tephrosia candida fallows under farmer-managed conditions in western Kenya. Based on plot-level yields, we estimated the extent to which these tree fallows would meet household and sub-national fuelwood needs if farmers planted at least 0.25 hectares, the proportion of land that is typically left under natural fallows by farmers in the region. Fuelwood yield was affected significantly (P < 0.05) by the interaction between species and fallow duration. Among the 6-month-old fallows, T. candida produced the highest fuelwood (8.9 t ha⁻¹), compared with the rest that produced between 5.6 and 6.2 t ha⁻¹. Twelve months old T. candida and C. paulina also produced significantly higher fuelwood yield (average, 9.6 t ha⁻¹) than T. vogelli and C. grahamiana of the same age. Between the fallow durations, the 18-month fallows produced the most fuelwood among the species evaluated, averaging 14.7 t ha⁻¹. This was 2–3 times higher than the average yields of 6 and 12-month-old fallows whose yields were not significantly different. The actual fuelwood harvested from the plots that were planted to improved fallows (which ranged from 0.01 to 0.08 ha) would last a typical household between 11.8 and 124.8 days depending on the species and fallow duration. This would increase to 268.5 (0.7 years) and 1173.7 days (0.7–3.2 years) if farmers were to increase area planted to 0.25 ha. Farmers typically planted the fallows at high stand densities (over 100,000 plants ha⁻¹ on average) in order to maximize their benefits of improving soil fertility and providing fuelwood at the same time. This potential could be increased if more land (which fortunately exists) was planted to the fallows within the farms in the region. The research and development needs for this to happen at the desired scale are highlighted in the paper.     

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.     

On-farm evaluation of two fast growing trees for biomass production for industrial use in Andhra Pradesh,Southern India

On-farm experiments were conducted in Khammam district of Andhra Pradesh from 2001 to 2006 to evaluate the biomass productivity, intercrop yields and profitability of Eucalyptus tereticornis clonal and Leucaena leucocephala variety K-636 based systems. Trees were planted at a spacing of 3 × 2 m and evaluated at three locations. Height growth was significantly higher in leucaena during the 4 year where as difference in diameter growth was not significant. Biomass partitioning to the bole was high in case of leucaena, ranged from 83% in 2.5–5 cm diameter at breast height (DBH) trees to 89% in 12.5–15 cm DBH trees and in eucalyptus clones the corresponding values were 71% in 2.5–5 cm DBH trees and 83% in 12.5–15 cm DBH trees. Marketable biomass productivity was higher with leucaena (95 Mg ha⁻¹) in comparison to eucalyptus (87 Mg ha⁻¹). Competition effects of trees on intercrops were observed from the 2 year (2002 post-rainy season). Intercrop yields were 45% of the sole crop in eucalyptus system and 36% in leucaena system during the 2 year. Sole eucalyptus and leucaena plantations and intercropping systems recorded higher gross and net returns over arable cropping. Therefore, it can be concluded that leucaena variety K636 and eucalyptus clonal based agroforestry systems are profitable alternatives to arable cropping under rainfed conditions.     

The effects of alley cropping withLeucaena leucocephala and of different management practices on the productivity of maize and soil chemical properties in lowland coastal Kenya

The effects of leucaena hedgerows, mulching with leucaena foliage (0,50 and 100% of harvested foliage), cowpea intercropping and adition of dairy cattle slurry (55 t ha^–1 per maize crop) on the yield of maize from a sandy soil were assessed. The four-year results from five maize crops are reported.Except in the first year, yields of maize grain and stover were significantly reduced by 30% in the presence of leucaena hedgerows. Use of leucaena mulch eliminated this effect; application of all the harvested leucaena mulch (100%) increased the total maize grain yield of the five crops by 44% over sole maize. Hedgerow and mulching management required an additional 36 mandays labour ha^–1 which was more than compensated by the increased maize yields. Furthermore leucaena hedgerows substantially depressed the growth of weeds between cropping seasons.Intercropping with cowpea significantly depressed yields of maize grain and stover when both crops were sown together, but not in later seasons when cowpea was sown four weeks after the maize. Application of slurry increased the total yields of maize grain and stover by 35 and 37%, respectively. The grain yield of maize in leucaena hedgerow treatments fertilized with slurry did not respond to application of more than 50% of leucaena foliage, which suggested that half of the foliage could be spared for feeding to livestock. The cumulative yield of maize grain from the highest yielding organic system was 85% of the yield from the fertilizer treatment.The study, which is continuing, demonstrates that large increases in agricultural productivity are possible through the intercropping of maize with woody forage and grain legumes and the integration of dairy cattle production into the system. It thus shows the importance of exploiting crop/livestock interactions.     

Tree/crop complementarity in an arid zone runoff agroforestry system in northern Kenya

We tested the hypothesis that shallow-rooted crops and deep-rooted trees will share the available water in a complementary manner, when grown together, in a field trail in the Turkana district of northern Kenya during 1994 to 1996. Such studies have been few in dryland agroforestry. The effects of two different Acacia saligna (Labill.) H. Wendl. tree planting densities (2500 and 833 trees per ha), tree pruning (no pruning vs. pruning) and annual intercrops (no intercrop vs. intercrop) on total biomass production and their interactions were tested. In 1996 Sorghum bicolor (L.) Moench was used during the first vegetation period and Vigna unguiculata (L.) Walp. during the second. We used naturally generated runoff water for irrigation to supplement low rainfall amounts typical for the area. High biomass production (> 13 t ha^–1 over a two year period) was observed irrespective of intercropping of pruned trees or sole tree stands. Although the pruning treatment reduced total tree biomass yields by a quarter, the introduction of annual intercrops after the pruning of trees outweighed this loss. The yields of the intercrops in the pruned tree treatments were similar to their yields when grown as monocrops. The calculation of land equivalent ratios showed overyielding for intercropped, pruned systems. The high values for LER (1.36 at low and 1.47 at high density of trees) indicate that there is complementarity in resource use between the different species.This revised version was published online in November 2005 with corrections to the Cover Date.     

Cacao-coconut intercropping in Ghana: agronomic and economic perspectives

In Ghana, shade for cacao (Theobroma cacao L.) is becoming a critical issue because of extensive deforestation. Unlike in some other cacao-growing countries, cacao is not grown under the shade of coconut (Cocos nucifera) in Ghana. An experiment to compare the merits of four cacao-coconut intercropping systems with the traditional cultivation of cacao under Gliricidia sepium shade was undertaken at the Cocoa Research Institute of Ghana. Cacao seedling girth was not affected when intercropped with coconut but was significantly (P = 0.01) reduced when intercropped with G. sepium. High density cacao facilitated better early canopy formation. Yield of cacao spaced at 2.5 m triangular (1739 plants ha^–1) with coconut at 9.8 m triangular (105 plants ha^–1) was significantly higher (P = 0.05) than from the other treatments during 1993/94 to 1995/96. There were no major disease problems associated with intercropping cacao with coconuts. Widely spaced coconuts intercropped with cacao spaced at 3 m × 3 m showed better flowering and gave higher coconut yields, but cacao spaced at 2.5 m triangular under coconuts spaced at 9.8 m triangular was more profitable than the other treatments. Moisture stress was the greatest in cacao system with G. sepium shade and this could be responsible for the low yield of cacao in that treatment. It is suggested that properly arranged high density cacao under widely spaced coconuts can be a profitable intercrop system for adoption by cacao farmers in Ghana.This revised version was published online in November 2005 with corrections to the Cover Date.     

The agronomic and economic performance of banana,bean and tree intercropping in the highlands of Burundi: an interim assessment

To meet their wood, fodder and fruit needs, resource-poor farmers with only small land holdings are forced to mix trees in their food crop plots. An experiment was conducted to study the effect of nine tree species planted at 312.5 trees ha^–1 (4×8 m) on the yield of bananas planted at 625 stools ha^–1 (4×4 m) and beans (80000 plants ha^–1) as well as the wood production of the trees when intercropped. In addition, an economic analysis was done to compare the different tree/banana/bean associations.After three and one-half years, wood volume (in m³ ha^–1) ofGrevillea robusta (18.1), was highest and that ofErythrina poeppigiana (2.7),Cedrela odorata (2.4) orMarkhamia lutea (0.8) was the lowest. Volume ofCedrela serrata (13.7) was not significantly different from that ofAlbizia chinensis (12.8) but was significantly higher than that ofLeucaena diversifolia (6.8),Acrocarpus fraxinifolius (6.7) orCalliandra calothyrsus (6.0).None of the tree species had a significant influence on the yields of the bananas and none affected the yield of the bean crops until the seventh cropping season, three years after the trees were planted. In that year, Grevillea reduced bean yield by 29%, Albizia by 34% and Leucaena by 36%. From the economic analyses, all the treatments except Leucaena and Markhamia had positive net benefits relative to the control (banana/bean) but the results were highly variable.C. serrata was found to be the best tree to be intercropped in a banana/bean system.     

Early growth of Eucalyptus camaldulensis under agroforestry conditions at Mafiga,Morogoro, Tanzania

The growth of Eucalyptus camaldulensis clean weeded, spot weeded and intercropped with maize and beans was studied. At 4 m × 4 m and 5 m × 5 m spacings trees were significantly shorter after 15 months under a conventional spot weeding regime than with clean weeding or intercropping with beans. A satisfactory maize yield (683 kg ha^?1) was recorded from plots with trees spaced at 5 m × 5 m. Plots where trees were spaced at 4 m × 4 m and 3 m × 3 m gave significantly lower yields (444 kg ha^?1 and 283 kg ha^?1, respectively).     

Agroforestry systems for soil and water conservation and sustainable production from foothill areas of north India

Some conservation based agroforestry systems (AFS) were developed for possible adoption in place of high risk rainfed farming on land capability classes Ito IV of a typical topo-sequence of foothill north India. The agri-silvi-horticulture system integrating leucaena, lemon, papaya and turmeric on class I irrigated land provided sustainable mean net returns of Rs. 17066 against Rs. 7852 ha.^–1 yr.^–1 from double cropped agricultural system. The intercropping of cluster beans with leucaena gave the highest net returns of Rs. 3540 ha.^–1 yr.^–1 in the agri-silvicultural system adopted on class II land. Eucalyptus terettcornis (Smith) in top and Bhabbar grass (Eulaliopsis binata Retz) in the understorey on a sandy loam class III land gave four years (1985–1988) mean air dry grass yield of 4.2 (used for paper pulp) from October and 1.19 t. ha^–1 yr.^–1 (used for fodder) from June cut. The net returns from grass alone were Rs. 4672 against Rs. 1679 ha.^–1 yr.^–1 from rainfed field crops raised on an adjoining plot. The returns from trees would be additional. Bhabbar grass raised under Acacia species on a 25 to 30% sloping gravelly class IV land provided yield varying from 2.18 to 4.31 from October cut and 0.50 to 1.1 t. ha.^–1 yr.^–1 from June cut with 6 years mean of 3.9 t. ha.^–1 yr.^–1 which at 1988 prices provided net returns of Rs. 2402 ha^–1. These AFS proved superior to traditional farming on each land capability class.     

Performance of maize, beans and ginger as intercrops in Paulownia plantations in China

Yield, morphology and specific leaf weight of summer crops maize, beans and ginger were studied in relation to tree proximity and PAR transmissivity in a 7-year old plantation of Paulownia elongata grown at a spacing of 15 m x 5 m in Eastern China. The yield of beans and maize was significantly reduced, compared to controls, at all positions relative to the trees. This yield depression was particularly marked at positions closest to the trees. Beans grown at 2 m from the trees had reduced height and specific leaf weight. These crops would yield more at wider tree row spacings. Ginger gave high yields when intercropped and is an ideal shade crop for these systems. Further research is required on optimisation using a bioeconomic approach. Further agronomic, physiological and biochemical work is required on ginger and other economic members of its family as these appear to have compatibility with dense agroforestry plantings. This revised version was published online in August 2006 with corrections to the Cover Date.     

Consumption Patterns of Fuelwood in Rural Households of Dolakha District,Nepal: Reflections from Community Forest User Groups

Biomass plays a vital role in the energy supply of many developing countries. It is the major energy source for the rural population of Nepal, where 70 % of the total energy is derived from woody plant biomass in the form of fuelwood. The main aim of this study is to describe the fuelwood consumption pattern and the role of community forests and trees on private farmland in biomass supply to rural households in Nepal. The study investigates whether demography and socioeconomic attributes of households affect fuelwood consumption. A household survey was conducted, along with measurements of fuelwood mass for six community forest user groups in Dolakha district of Nepal. Average daily household fuelwood consumption was estimated to be 8.4 kg, giving a mean annual consumption of 3060 kg per household. Per capita fuelwood consumption per day was found to be 1.7 kg. Total fuelwood consumption of households is significantly correlated with household size, ownership of cultivated irrigated terraces and number of livestock per household, and negatively significantly correlated with ownership of cultivated rain-fed terraces. Fuelwood consumption varies significantly between seasons. Among various sources of biomass energy, fuelwood from community forests contributes 23 % and trees on private farmland contribute 12 %. The rest is provided from other biomass sources, including the remains of fodder collected from private farmland vegetation, wood previously used for fences and trellises in private farmland, crop residues, and purchased fuelwood.     

Tree row spacing affected agronomic and economic performance of Eucalyptus-based agroforestry in Andhra Pradesh, Southern India

The 3 × 2 m spacing currently used for eucalyptus plantations in the state of Andhra Pradesh, southern India does not permit intercropping from the second year. This discourages small landholders who need regular income from taking up eucalyptus plantations and benefiting from the expanding market for pulpwood. Therefore, on-farm experiments were conducted near Bhadrachalam, Khammam district (Andhra Pradesh) for over 4 years from August 2001 to November 2005 to examine whether wide-row planting and grouping of certain tree rows will facilitate extended intercropping without sacrificing wood yield. Eucalyptus planted in five-spatial arrangements in agroforestry [3 × 2 m (farmers’ practice), 6 × 1 m, 7 × 1.5 m paired rows (7 × 1.5 PR), 11 × 1 m paired rows (11 × 1 PR) and 10 × 1.5 m triple rows (10 × 1.5 TR)] was compared with sole tree stands at a constant density of 1,666 trees ha^?1. Cowpea (Vigna unguiculata) was intercropped during the post-rainy seasons from 2001 to 2004, and fodder grasses (Panicum maximum and Brachiaria ruziziensis) were intercropped during both the seasons of 2005. At 51 months after planting, different spatial arrangements did not significantly affect height and diameter at breast height (dbh). Total dry biomass of eucalyptus in different spatial arrangements ranged between 59.5 and 52.9 Mg ha^?1, the highest being with 6 × 1 m and the lowest with 10 × 1.5 TR, but treatment differences were not significant. The widely spaced paired row (11 × 1 PR) and triple row (10 × 1.5 TR) arrangements produced 62–73% of sole cowpea yield in 2003, 59–66% of sole cowpea yield in 2004, and 79–94% of sole fodder in 2005. In contrast, the 3 × 2 m spacing allowed only 17–45% of sole crop yields in these years. The better performance of intercrops in widely spaced eucalyptus was likely because of limited competition from trees for light and water. Intercropping of eucalyptus in these wider rows gave 14% greater net returns compared with intercropping in eucalyptus spaced at 3 × 2 m, 19% greater returns compared with that from sole tree woodlot and 263% greater returns compared with that from sole crops. Therefore, in regions where annual rainfall is around 1,000 mm and soils are fairly good, eucalyptus at a density of 1,666 plants per ha can be planted in uniformly spaced wide-rows (6 m) or paired rows at an inter-pair spacing of 7–11 m for improving intercrop performance without sacrificing wood production.     

Influence of Acacia senegal agroforestry system on growth and yield of sorghum, sesame, roselle and gum in north Kordofan State, Sudan

We examined the effects of intercropping with Acacia senegal (L.) Willd on growth and yield of sorghum (Sorghum bicolor L.), sesame (Sesamum indicum L.) and roselle (Hibiscus sabdariffa). Field experiments were conducted in El-Obeid Research farm (13°10’ N; 30°12’ E), North Kordofan State, Sudan, during 2002 2003 in an 11-year-old A. senegal plantation. The experimental design was randomized complete block design (RCBD) with four replications. Data were recorded for plant height (cm), fresh weight (kg ha -1 ), dry weight (kg ha -1 ), crop yield (kg ha -1 ), and gum yield (kg ha -1 ). We used Land Equivalent Ratios (LER) and simple financial analyses of gross surpluses to evaluate the productivity and profitability of the different treatments. The results indicated that A. senegal trees had a beneficial effect on crop performance and yield as well as gum yield. Significant differences (p<0.05) were obtained for plant height, fresh weight, dry weight and crop yield. Therefore, yield of sorghum, sesame and roselle under intercropping system were 13.7%, 23.8% and 20.9% higher than that obtained in the sole cropping system respectively. The highest yield increase was observed with sesame (23.8%). Gum yield (g/tree/picking) was signifi- cantly (p<0.05) increased for sorghum, sesame and roslle under inter-cropping system. The highest yield of (298g/tree/picking) was obtained when roselle was intercropped with A. senegal, while the least gum yield of (239 g tree-1 ) was recorded in pure A. senegal plot. All the treatments gave land equivalent ratio (LER) of more than one-indicating the superiority of growing the field crops in intercropping over the sole cropping systems. The highest LER of 3.8 was obtained for sesame intercropped with A. senegal (Hashab), followed by 3.7, when sorghum was intercropped with A. senegal and 3.3 when roselle intercropped with A. senegal. All the treatments gave positive net revenues, the highest being for intercropped sorghum (558 SDG ha -1 ) (SDG=Sudanese gienh). The intercropping of roselle gave the second net revenue (518 SDG ha -1 ),while the sole sorghum gave the lowest net revenue (501 SDG ha -1 ).     

Decreasing rice and cowpea yields in alley cropping on a highly weathered Oxisol in West Sumatra,Indonesia

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.     

A theoretical study for North Vietnam of alternative agroforestry systems to pure cassava

Cassava is recognized in the region as the second most important crop after paddy rice. In Vinh Phu province of Vietnam, it is usually grown on highly erodible slopes of the small hills surrounding paddy fields. Cassava crop land is generally in annual use until the yield is less than 3–4 t fresh tubers/ha. This constant cropping system rapidly depletes the soil as fertilizers are infrequently used and crop residues are usually removed from the fields. Erosion is a major problem as the soil is exposed through hand cultivation and regular weeding during a cropping season which coincides with the wet season. Sustainable and productive cropping systems are needed.In order to take a first step towards sustainability, this paper presents several possible agroforestry systems in which cassava could be intercropped with a number of nitrogen fixing trees and shrubs. Several theoretical combinations have been examined assuming a critical lower production limit of 3–4 t fresh tubers/ha. Those with sustained high potential yields are recommended for future field experimentation.     

Soil fertility changes and response of maize and beans to green manures of leucaena,sesbania and pigeonpea

Three multipurpose tree species (MPTS)-leucaena (Leucaena leucocephala), sesbania (Sesbania sesban var. nubica) and pigeonpea (Cajanus cajan) were pruned at a height of 60 cm above the ground every two months, and resulting plant biomass was incorporated into the soil as green manure. For comparison, maize (Zea mays) stover was also incorporated into some plots, while some other plots were left fallow. Varying quantities of plant biomass which were incorporated into the soil over a period of 12 months caused large changes in major soil plant nutrients, and it substantially improved soil fertility. To test for improved soil fertility, test crops of maize and beans (Phaseolus vulgaris) were grown on the plots after six biomass incorporations of 4806, 13603, 16659 and 7793 kg. ha^–1yr^–1 for pigeonpea, sesbania leucaena and maize, respectively. Responses of the test crops indicated that sesbania and leucaena green manures improved maize stover, cobs and grain yields; and bean haulms and grain yields by 77.6% when compared to fallow plots. Residual effects of green manures still resulted in significant (P < 0.05) yield differences in the test cropin the third testing season. Economic significance of green manures in increasing food crop yields to small scale farmers is discussed.     

Forage yield and quality of Leucaena leucocephala and Guazuma ulmifolia in mixed and pure fodder banks systems in Yucatan,Mexico

In tropical areas of Mexico, Leucaena leucocephala is widely used in silvopastoral systems. However, little information exists on other native woody species of high forage potential, such as Guazuma ulmifolia. The aim of this study was to evaluate the components of biomass, forage yield and quality, and availability of N in fodder banks of L. leucocephala, G. ulmifolia, and a mixture of both species during dry and rainy seasons, under sub-humid tropical conditions. The experimental unit was a 5 × 10 m plot, containing three rows with 2 m between rows; each row had 20 plant positions with 0.50 m between plants. Within each plant position there was either a single plant, in the case of pure-crop, or two plants, in the case of mixed of both species. A complete randomized block design with three repetitions was used. In both seasons, there were a significantly greater proportion of leaves in the G. ulmifolia fodder banks (71 %) and in mixed fodder banks (69 %) than in L. leucocephala fodder banks (64 %). Consequently, these systems had leaf-to-stem ratios of 2.4, 2.2 and 1.9, respectively. The forage yield of fodder banks was not influenced by season. The mixed fodder bank had greater forage yield (5.1 t DM ha^?1) than the L. leucocephala fodder bank (3.4 t DM ha^?1) in each season. Additionally, the mixed fodder bank accumulated more forage yield during the experimental period (10.2 t DM ha^?1 year^?1) than G. ulmifolia (9.0 t DM ha^?1 year^?1) or L. leucocephala (6.9 t DM ha^?1 year^?1). The concentrations of CP, C and C:N were not influenced by season. Forage NDF and ADF concentrations were greater in the rainy season (476 g kg^?1 DM) compared with the dry season (325 g kg^?1 DM). Mixed fodder banks had the greatest N yield (185.9 kg ha^?1) and consequently the greatest availability of N (371.8 kg N ha^?1 year^?1). We conclude that mixed fodder banks of L. leucocephala and G. ulmifolia are a better option for improving productivity and forage quality in comparison with pure fodder banks in Yucatan, Mexico.