Shade effects on forage crops with potential in temperate agroforestry practices

Thirty forages, including eight introduced cool-season grasses, four native warm-season grasses, one introduced warm-season grass, eight introduced cool-season legumes, five native warm-season legumes, and four introduced warm-season legumes, were grown in 7.6 L (two gallon) pots in full sun, 50%, and 80% shade created by shade cloth over a greenhouse frame. Experiments were conducted during summer--fall 1994, spring--early summer 1995, and summer--fall 1995. A complete randomized experimental design was used and above ground dry weight was measured in each shade environment. Tukey's studentized range test was used to compare mean dry weights (MDW) within a species. Warm-season grasses displayed significant reductions in MDW under shade regardless of growing season. All cool-season forages grown during spring--early summer showed a decrease in MDW under shade; however, the reductions in dry weights of ‘Benchmark’ and ‘Justus’ orchardgrass, ‘KY 31’ tall fescue, Desmodium canescens and D. paniculatum were not significant under 50% shade. Cool-season grasses showed more shade tolerance when grown during the summer--fall than when grown during the spring--early summer. Seven of the selected cool-season grasses grown during the summer--fall did not display significant reductions in MDW under 50% shade as compared to full sun. Smooth bromegrass grown under 50% shade showed a significantly increased MDW production compared to growth in full sun. With the exception of Justus orchardgrass and smooth bromegrass, growth of cool-season grasses was inhibited at 80% shade. Among the legumes harvested during the fall, the dry weights of both Desmodium species tested and hog peanut (Amphicarpaea bracteata L.) increased significantly under 50% and 80% shade. In addition, ‘Cody’ alfalfa, white clover, slender lespedeza and ‘Kobe’ lespedeza showed no significant reductions in MDW under 50% shade. This revised version was published online in June 2006 with corrections to the Cover Date.     

Allometric tree biomass models of various species grown in short-rotation agroforestry systems

Biomass equations for tree species and the early stages of growth used in short-rotation coppices and agroforestry systems are still lacking. Further, discussion about the structure and parameters of biomass equations are still ongoing. Yield estimations should be precise, while keeping efforts low. To determine the influence of tree species, farming system, and tree position (inner and outer row) on allometric relationships, we derived biomass equations for various tree species from organic and conventional silvoarable agroforestry systems with an alley-cropping configuration. The allometric equations were based on the power relationship between aboveground dry biomass and stem base diameter (SBD) as a single variable or in combination with tree height (H) and were calculated by log-linear mixed-effect regression. Equations span the third and fourth growth year of the first rotation and were validated on the fourth year. Neither farming system nor row position influenced allometric relationship, although biometric variables varied between trees from inner and outer rows. A general model across species explained 95% (\(R_{\text{cond}}^{2}\)) of the variation for tree dry weight or 97% (\(R_{\text{cond}}^{2}\)) with H as covariate. Yet, for the sake of precision, species-specific equations were necessary. The best fitting equation with only SBD as predictor had species-specific allometric factors and a general exponent across species. However, predicted yields were biased by 8–31%. Thus, functions incorporating H are recommended, as compensation for variances in height-diameter relationships due to the ontogenetic stage, site differences, or social status of the tree reduced the bias of biomass estimation (<10%).     

Nutrient cycling in two traditional Central American agroforestry systems

A preliminary nutrient cycling study quantified total and temporal nutrient inputs via litterfall and pruning residues in two agroforestry systems: (1) Coffea arabica (perennial crop)-Erythrina poeppigiana (leguminous shade tree); and (2) C. arabica-E. poeppigiana-Cordia alliodora with emphasis on the effect of the timber tree C. alliodora. The total annual input of litterfall plus pruning residues was similar in both associations. Total annual input from E. poeppigiana was less than half in the association with C. alliodora than without, but the litterfall from this latter species compensated for the loss. Large differences in the total annual nutrient input of K, Ca and Mg was found between associations, but not for N or P. The amount of nutrients recycled by the associated trees reached the recommended level of fertilizer required for coffee production. The inclusion of C. alliodora within the C. arabica-E. poeppigiana association resulted in a more evenly distributed annual nutrient input.     

Growth and yield of coffee plants in agroforestry and monoculture systems in Minas Gerais, Brazil

This research compared coffee plants (Coffea arabica L.) grown in an agroforestry and monoculture systems. Data were collected during two years, on vegetative growth, reproductive development, nutritional status and yield of coffee, besides monitoring air temperature and the tree growth. All trees in agroforestry system increased in growth, resulting in a reduction in the magnitude of the diurnal temperature variation and also maximum temperature. Coffee plants in agroforestry system had less branch growth and leaf production, more persistent and larger leaves, and presented earlier flowering, with a smaller number of productive nodes and flower buds, leading to smaller berry yield than plants in monoculture system. In both systems, the coffee plants showed adequate leaf nutrient levels, except for P and K. The yield of 2443 kg ha^-1 of coffee from the monoculture was greater than 515 kg ha^-1 of coffee from the agroforestry system.     

Carbon stocks and biomass production of three different agroforestry systems in the temperate desert region of northwestern China

Carbon sequestration potential of agroforestry systems has attracted worldwide attention following the recognition of agroforestry as a greenhouse gas mitigation strategy. However, little is known about carbon stocks in poplar–maize intercropping systems in arid regions of China. This study was conducted in the temperate desert region of northwestern China, a region with large area of poplar–maize intercropping systems. The objective of this study was to assess biomass production and carbon stock under three poplar–maize intercropping systems (configuration A, 177 trees ha^?1; configuration B, 231 trees ha^?1; and configuration C, 269 trees ha^?1). We observed a significant difference in the carbon stock of poplar trees between the three configurations, with the highest value of 36.46 t ha^?1 in configuration C. The highest carbon stock of maize was achieved in configuration B, which was significantly higher than configuration A. The grain yield was highest in configuration A, but there was no significant difference from the other two configurations. In the soil system (0–100 cm depth), the total carbon stock was highest in configuration C (77.37 t ha^?1). The results of this study suggest that configuration C is the optimum agroforestry system in terms of both economic benefits and carbon sequestration.     

Medicinal and aromatic plants in agroforestry systems

Agroforestry Systems - A large number of people in developing countries have traditionally depended on products derived from plants, especially from forests, for curing human and livestock...     

Impact of reduced light intensity on wheat yield and quality: Implications for agroforestry systems

Agroforestry Systems - In China, agroforestry is a traditional practice that diversifies agricultural production and enhances natural resource utilization; however, it create competition for light...     

Growth and yield of maize and timber trees in smallholder agroforestry systems in Claveria,northern Mindanao,Philippines

On-farm experiments were conducted in the Philippines to study over a 4-year period the growth of two timber trees, gmelina (Gmelina arborea R. Br.) and bagras (Eucalyptus deglupta Blume), and their impact on the grain yield of intercropped maize. The experiment consisted of maize monocropping plots (control) and maize intercropped between trees planted in block (2 × 2.5 m), and hedgerow arrangement (1 × 10 m). Three maize crops were planted in the block plots before canopy closure, and seven maize crops were planted in the hedgerow and monocropping plots. Maize grain yield in the hedgerow and in the block arrangement with gmelina were respectively 37% (16.58 tons ha⁻¹) and 68% (8.3 tons ha⁻¹) lower than in monocropping (26.21 tons ha⁻¹). In the plots with bagras, maize grain yield in hedgerow and in block arrangement were respectively 19% (24.8 tons ha⁻¹) and 66% (10.4 tons ha⁻¹) lower than in monocropping (30.6 tons ha⁻¹). For both tree species, the diameter at breast height (dbh) was greater in hedgerow than in block arrangement, with the difference being more pronounced with age. It was estimated that gmelina planted in hedgerows would produce 6–8 m³ ha⁻¹ of merchantable volume more than if planted in block. The study verifies the hypothesis that intercropping between widely-spaced trees rows (planted at 10 m or more) is more profitable and feasible to smallholders than either maize monocropping or woodlots, and concludes with recommendations on how to further improve the productivity of tree-intercropping systems.     

Managing native and non-native plants in agroforestry systems

Indigenous knowledge has influenced native species selection in agroforestry systems worldwide. However, scientific advancements in plant sciences, agroforestry technologies and trade have accelerated species movements and establishment beyond their native range. Managing native and non-native species is an important area of research in agroforestry and this thematic issue includes 13 papers that cover a range of topics from the role of non-native species in agroforestry to management interventions to improve yield. As evident from these papers, non-native plants are still an important component of agroforestry in many parts of the world. Whether native or non-native, management interventions can increase the economic, environmental and social values of these species and that of agroforestry. Collectively, these papers attest to the increasing body of foundational knowledge in agroforestry.     

Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield

Tree root pruning is a potential tool for managing belowground competition when trees and crops are grown together in agroforestry systems. We investigated the effects of tree root pruning on shoot growth and root distribution of Alnus acuminata (H.B. & K.), Casuarina equisetifolia L., Grevillea robusta A. Cunn. ex R. Br., Maesopsis eminii Engl. and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was reopened and roots recut at 50 and 62 months after planting. We assessed the effects on tree growth and root distribution over a 3 year period, and crop yield after the third root pruning at 62 months. Overall, root pruning had only a slight effect on aboveground tree growth: height growth was unaffected and diameter growth was reduced by only 4%. A substantial amount of root regrowth was observed by 11 months after pruning. Tree species varied in the number and distribution of roots, and C. equisetifolia and M. lutea had considerably more roots per unit of trunk volume than the other species, especially in the surface soil layers. Casuarina equisetifolia and M. eminii were the tree species most competitive with crops and G. robusta and M. lutea the least competitive. Crop yield data provided strong evidence of the redistribution of root activity following root pruning, with competition increasing on the unpruned side of tree rows. Thus, one-sided root pruning will be useful in only a few circumstances.     

Non-additive effects of litter-mixing on soil carbon dioxide efflux from poplar-based agroforestry systems in the warm temperate region of China

Poplar-based agroforestry systems are one of the most important farming systems on the temperate plains of China, but soil respiration in those systems has seldom been reported. In this study, poplar leaf litter and residues of the two main crops (wheat and peanut) grown in the agroforestry system were amended to form different litter mixing treatments in field experiments at two sites located in Jiangsu Province, China. We measured soil respiration and environmental factors in the different treatments. Soil respiration rates were increased by the addition of plant residues but were strongly influenced by residue quality. During the growing season, soil respiration was negatively related with C/N ratio, while positively related with the initial P concentration of residues (P < 0.05). Poplar leaf litter and crop residues showed non-additive effects on soil respiration when they were mixed. Both air and soil temperature at 10 cm depth explained more than 85 % of the variation of soil respiration at both sites with an exponential model. A significant linear relationship between soil respiration and soil water content at 10 cm depth (W_S) was also observed. The percent of variation in soil respiration explained by a model based on air temperature and soil water content was greater than that explained by a model based on temperature alone. Thus, soil respiration in the studied poplar-based agroforestry systems was driven by both temperature and soil water content. Soil respiration was significantly different between the two sites that had different clay content and C/N ratios. Results from this study are important for us to understand how soil respiration responds to litter mixing or is influenced by biophysical factors in poplar-based agroforestry systems.     

Belowground interactions for water between trees and grasses in a temperate semiarid agroforestry system

A fundamental hypothesis of agroforestry is the complementary use of soil resources. However, productivity of many agroforestry systems has been lower than expected due to net competition for water, highlighting the need for a mechanistic understanding of belowground interactions. The goal of this study was to examine root–root interactions for water in a temperate semiarid agroforestry system, based on ponderosa pines and a Patagonian grass. The hypotheses were: (a) A greater proportion of water uptake by pines is from deeper soil layers when they are growing with grasses than when they are growing alone; (b) Growth of grasses is improved by the use of water hydraulically lifted by pines. We used stable isotopes of O to analyze water sources of plants, and we measured sapflow direction in pine roots and continuous soil water content with a very sensitive system. We also installed barriers to isolate the roots of a set of grasses from pine roots, in which we measured water status, relative growth and water sources, comparing to control plants. The results indicated that pines and grasses show some complementary in the use of soil water, and that pines in agroforestry systems use less shallow water than pines in monoculture. We found evidence of hydraulic lift, but contradicting results were obtained comparing growth and isotope results of the root isolation experiment. Therefore, we could not reject nor accept that grasses use water that is hydraulically lifted by the pines, or that this results in a positive effect on grass growth. This information may contribute to understand the complex and variable belowground interactions in temperate agroforestry.     

Supporting and regulating ecosystem services in cacao agroforestry systems

Cacao agroforestry systems (CAFS) can provide supporting services such as optimum light conditions for cacao growth, water and nutrient cycling and regulating services such as pest and disease control and climate regulation. This review considers recent literature on the manifestation of these services in CAFS around the world to provide an overview of scientific knowledge. Crown structures of associated trees can facilitate optimum light conditions for cacao growth, and provide water through vertical root segregation. Leaf litter fall and roots from associated species contribute to nutrient cycling. Both nitrogen-fixing and non-nitrogen-fixing species can provide nutrients to the cacao plant, though competition from certain species may limit phosphorus and potassium uptake. Pest and disease regulating services can arise through careful shade management to create a microclimate which reduces susceptibility of cacao to fungal diseases and sun-loving pests. All CAFS store carbon to varying degrees; those resembling original forest much more than simple two-species systems from which shade trees are removed after maturity of the cacao stand. CAFS also promotes biodiversity conservation depending on structure, management, and landscape arrangement, though not to the extent of natural forests. Research opportunities to increase provision of these services include optimal spatial arrangement for nutrient cycling and functional diversity as well as landscape connectivity for biodiversity conservation. Trade-offs between carbon storage, biodiversity, cacao yield and socio-economic resilience are presented, indicating that optimization of ecosystem services in CAFS requires consideration of interactions between all services, including socio-cultural and economic ones.     

Tree phenology and water availability in semi-arid agroforestry systems

Four common agroforestry trees, including both exotic and native species, were used to provide a range of leafing phenologies to test the hypothesis that temporal complementarity between trees and crops reduces competition for water in agroforestry systems during the cropping period and improves utilisation of annual rainfall. Species examined included Melia volkensii, which sheds its leaves twice a year, Senna spectabilis and Gliricidia sepium, which shed their leaves once during the long dry season, and the evergreen Croton megalocarpus. Phenological patterns were examined in relation to climatic conditions in the bimodal rainfall regions of Kenya to identify factors which dictate the intensity of competition between trees and crops.

The main differences in leaf cover patterns were between indigenous and exotic tree species. The Central American species, S. spectabilis and G. sepium, shed their foliage during the dry season before the short rains, whereas the native species, M. volkensii and C. megalocarpus, exhibited reduced leaf cover during both dry seasons. C. megalocarpus was the only species to maintain leaf cover throughout the 2-year experimental period. M. volkensii and S. spectabilis exhibited similar leafing phenology, losing almost all leaf cover during the long dry season (July–October) and flushing before the onset of the ensuing rains. S. spectabilis lost few leaves during the short dry season, whereas M. volkensii shed a greater proportion of its foliage before flushing prior to the long rains (March–July). M. volkensii lost much of its leaf cover during the 1997/1998 short rains (October–February), when soil water content was unusually high. Although essentially evergreen, leaf cover in C. megalocarpus decreased during the dry season and increased rapidly during periods of high rainfall. G. sepium exhibited a period of low leaf cover during the long dry season and did not regain full leaf cover until mid-way through the short rains. The mechanisms responsible for these phenological changes and the implications of tree phenology for resource utilisation and competition with crops are discussed.     

Livestock activities in agroforestry systems in Guadeloupe: systems of production and functions

The value enhancement of Guadeloupe's private forests (48% of the total) is a major challenge for the territory in terms of agroecological transition combined with diverse ecosystem services (ES). In many Latin American regions, agroforestry systems (AFS) include a significant proportion of livestock, but very few are described in Guadeloupe. In this study, AFS including livestock activities were classified through semi-open interviews (n?=?50) based on two dimensions: the agricultural region and the farmer’s main production strategy. Results showed that, on average, AFS are family farming systems (more than 30%) and the percentage of farmers with multiple activities is high (77%). Mixed tree-crop-livestock systems are very frequent, with 1/3rd of the sub-units devoted to animal husbandry. Farmers preferably raise small ruminants, backyard animals, and large herbivores (20 to 25% of answers each), and to a lesser extent raise pigs and keep bees (12% each). Mixed animal units exist (50%) with between two and six species. More than 80% of farmers use their farm resources (pastures, natural fodder trees or crop by-products) to feed their animals. Even though self-consumption remains widespread (50% of responses), 80% of the farmers want to give a more economic orientation to their activities. The other responses (16%) concerned socio-cultural functions. Several ES are described and are discussed here at different levels (farm, territory, society). In conclusion, in the forested area of Guadeloupe, there is a potential for the development of efficient livestock farming using an agroecological approach. Complete mixed systems (tree-crop-livestock) should be promoted for the provision of multiple ES.

     

Growth,yield and stem form of young African mahoganies (Khaya spp.) in mixed-species plantations and successional agroforestry systems

New Forests - African mahoganies can be an alternative for wood production in agroforestry systems and/or mixed-species plantations. In this study, we aimed to evaluate the growth, yield and stem...     

Pests and diseases in agroforestry systems of the humid tropics

Few studies have included detailed investigations of the interactions of agroforestry techniques with pests and diseases, although the relevance of such interactions has long been recognized. The objectives of this review are to provide basic information on pests and diseases in tropical agroforestry systems and to develop concepts which can assist in the future in the systematic data collection and analysis in this field. The emphasis is on simultaneous agroforestry systems with annual and perennial crops, although rotational systems are also discussed. Crop rotation is an important pest and disease control strategy in annual cropping systems, and the principle of altering host with non-host plants can also be applied in improved fallow systems, provided that hosts of crop pests and diseases are avoided when selecting the fallow species. When annual cropping systems are transformed into simultaneous agroforestry, the control strategy of frequent disturbance of pest and disease populations is to some extent substituted for the strategy of increased stability and internal control mechanisms. However, reduced pest and disease risk is not automatically achieved by introducing perennial plants and increasing the plant diversity in a system. If plant species are introduced that harbor pests or diseases of other species in the system, the risk of pest and disease outbreaks may actually increase. For evaluating such risks, it is important to consider host-ranges of diseases on the pathovar instead of the species level. Beside the selection of compatible plant species, their spatial arrangement may be important for reducing the spread of pest and disease organisms through the system, although little information is available on such effects, and they may be largely irrelevant for organisms with efficient dispersal mechanisms such as wind-dispersed fungi. In addition to the species-specific, biological effects of plants on pests and diseases, their unspecific, physical effects can be of major relevance for pest and disease development as well as the susceptibility of the affected plant species. Increased pest and disease incidence has often been observed directly at the tree-crop interface, caused by the humid microclimate, physical protection of mammal and bird pests by the trees and eventually reduced pest and disease tolerance of competition-stressed crops. Linear tree plantings and hedgerows affect the wind transport of small insects and disease propagules, the active immigration and emigration of pest organisms as well as the populations of natural enemies. Similarly, overhead shade has a major effect on the micro-climatic conditions under which pest and disease organisms, their natural enemies and the crops themselves develop, and its optimization is a highly efficient control strategy for many pests and diseases. On infertile soils, the susceptibility of crops to pests and diseases is strongly affected by the availability of plant nutrients, which may be influenced by agroforestry techniques in various ways. Soil management measures such as mulching and planting cover crops may affect crop health by improving soil fertility and by directly acting on pest and disease populations. The importance of a more systematic collection of pest and disease related information for agroforestry, e.g., in a central database, and of the development of strategies for reducing pest and disease risks in agroforestry in cooperation with farmers is stressed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Seedling survival and growth of Aquilaria malaccensis in different microclimatic conditions of northeast India

We studied seedling survival and growth of Aquilaria malaccensis in three different environmental conditions(homegardens,green house and in different canopy conditions) of northeast India.Results show that mean seasonal survival was highest in green house(95.53%±2.33),followed by homegardens(89.3%±1.89) and different canopy conditions(77.62%±6.73);the highest values were found during February to April for both the homegardens(96%±1.68) and green house(98% ± 0.88) and lowest during November to January(78%±2.99) in homegardens and May to July(90%±4.53) in green house.In case of transplanted seedlings in different canopy conditions,mean seasonal survival was highest during May to July(98%±1.92) and lowest during August to October(66%±12.81).However,mean seasonal growth of collar diameter was highest in different canopy conditions(23.99%±1.76) compared to green house(21.52%±2.70) and homegardens(12.44%±1.33) and it was highest during rainy season(May to July) and lowest during dry winter(November to January) in all the three experimental sites.These variations may be due to the different microclimatic conditions as well as nutrient status of the soil in all the three experimental sites.Although,seedling quality plays a great role in their survival and growth,based on the result of green house experiment,it can be concluded that maintenance of seedlings in green house conditions during their early growth period may improve both the survival and growth for large scale plantation of the species.Thus,the species can be reintroduced in its natural forest range to compensate the loss of natural population of this precious species in northeast India.