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 dm2 in Amoutchou to 21.4 dm2 in Glidji for the 0–20 cm layer, than in the middle of the alley, e.g., ranging from 3.1 dm2 in Amoutchou to 13.8 dm2 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 cm3 in Amoutchou to 0.64 mg cm3 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.
Tag: alley cropping
AFRENA project Burundi: progress report for the period November 1988 to February 1990
At the end of 1986, ICRAF launched an agroforestry research network. for the highlands of East and Central Africa with USAID funds. The network is part of ICRAF’s AFRENA programme, which encompasses three other ecological zones in subsaharan Africa. The 2 main objectives of the AFRENA programme are: 1. To develop appropriate agroforestry technologies for land use systems within an ecological zone, and 2. To develop national/regional capacity to plan, formulate and implement agroforestry research
Agroforestry systems: Meta-analysis of soil carbon stocks, sequestration processes, and future potentials
Agroforestry (AF) has the potential to provide a broader range of ecosystem services such as carbon (C) sequestration and biodiversity. Advantages and processes for global C sequestration in AF are unknown. We used a meta-analysis of 427 soil C stock data pairs grouped into four main AF systems—alley cropping, windbreaks, silvopastures, and homegardens—and evaluated changes in AF and adjacent control cropland or pasture. Mean soil C stocks in AF (1-m depth) were 126 Mg C.ha-1, which is 19% more than that in cropland or pasture. The highest C stocks in soil were in subtropical homegardens, AF with younger trees, and topsoil (0–20 cm). Increased soil C stocks in AF were lower than aboveground C stocks in most AF systems, except alley cropping. Homegardens stored the highest C in both aboveground and belowground, especially in the subsoil (20–100 cm). Advantages of AF ecosystem services focusing on mechanisms of belowground C sequestration were analyzed. AF could store 5.3 × 109 Mg additional C in soil on 944 Mha globally, with most in the tropics and subtropics. AF systems could greatly contribute to global soil C sequestration if used in larger areas. Future investigations of AF should include (a) mechanistic – and process-based studies (instead of common monitoring and inventories), (b) models linking forest and crop growth with soil water and C and nutrient cycling, and (c) accurate assessments of the AF area worldwide based on the remote sensing approaches .
Agroforestry in acid soils of the humid tropics
The majority of the soils in the humid tropics are acidic and infertile. Agroforestry systems are the most appropriate forms of sustainable, productive management of soils in the humid tropics because perennial woody vegetation can recycle nutrients, maintain soil organic matter, and protect the soil from surface erosion and runoff. This chapter evaluates three agroforestry systems that are helpful to overcome these constraints to production—namely, alley cropping systems; managed leguminous fallows to accelerate the restoration of soil fertility and reduce the duration of the fallow period; and fruit tree-annual crop sequential cropping systems. These technologies represent a range of agroforestry options, the suitability of which will vary with the relative availabilities of land, labor, and capital. Alley cropping may contribute to the maintenance of soil fertility under annual cropping by improved nutrient cycling, but the system’s total labor and possibly capital requirements are likely to be greater than those with shifting cultivation. Hence, the system seems appropriate for situations of limited land availability. In contrast, managed fallows might reduce the duration of the fallow period and improve productivity per unit time by accelerating weed suppression and nutrient accumulation in the fallow biomass. This system requires relatively small quantities of labor and capital, but like most fallow-based systems, it requires moderate to high land availability. Finally, cultivation of fruit trees can help alleviate labor and capital constraints by spreading labor over periods of low demand and by providing additional income through the sale of fruits and other products.
Models as part of agroforestry research design
Agroforestry deals with land use systems which are more complex that the usual agronomic experimental designs can cope with. A combination is needed of process-based models, simple summarizing parameters of component interactions, experiments to highlight the interactions and surveys of the real world variation in farmer developed agroforestry systems and possible components. A framework is presented for such a step-by-step approach, in which model development and experimental work go hand in hand.