Sustainable/Ecological Weed Management

Ecological Weed Management

Description

Crop loss to resource competition with weeds is considerable in sub-Saharan African smallholder systems.  Yet, many weeding recommendations for farmers are based on on-farm experiments that do not account for realistic smallholder agroecological conditions and/or socioeconomic constraints such as labor availability.  Additionally, methods that treat weed emergence, such as herbicides and time-sensitive manual removal, require financial capital and labor during a resource-constrained period in the cropping cycle.  Ecological weed management practices that focus on preventing weed emergence may offer better alternatives.  Examples of ecological weed management practices include employing systems, such as rotations and intercrops, that create an unsuitable environment for weeds.  The efficacy of such practices can be enhanced when they are developed in partnership with farmers in order to address realistic on-farm constraints and opportunities. [read more=”Read more” less=”Read less”]

Fairly little is known about smallholder (<1 hectare) weeding practices and their efficacy across sub-Saharan landscape (Dimes et al., 2004). Without understanding a farmer’s current weeding practices, fertilizer applications, soil conditions, and/or reoccurring weed populations, it is difficult to identify effective and realistic weed management strategies (Collinson, 1998). Disconcertingly, many weeding recommendations are based on fixed or predetermined designs conducted on experimental stations. Unfortunately, management (e.g. weeding date) at these stations do not reflect smallholders’ on-farm variability in pest pressure, rainfall, soil erosion or labor availability. Thus the utility and relevance of fixed weeding recommendations to smallholder farmers is limited and potentially erroneous.

Rural farmers are well aware of the repercussions for not weeding thoroughly, but much of the challenge to weed completely or in a timely manner arise from laborer and financial limitations (Kumwenda, 1997).  One of the most critical times for smallholders to weed their intensified grain cropping systems is three to four weeks after sowing. Unfortunately, this period occurs when a smallholders’ food supply and finances for the year have dwindled.  During this time, available household labor will tend to be allocated for off-farm employment (e.g., contract labor) to supplement finances for food before the harvest season (Giller et al., 2011).

In countries such as Malawi, the agrarian population employ highly variable weeding practices. Much of this variation is attributed to their natural, financial and/or social circumstances (Tafirenyika, 2014). The country’s local language, Chichewa, has no fewer than 36 different words that describe weeding actions such as ‘hoeing’ (Orr et al., 2002). This illustrates the complexity of local weeding practices. Several researchers compiled reports detailing descriptions of these manual techniques (see Figure 1) (Orr et al., 2002; Riches et al., 1993; Sileshi et al., 2008).  Researchers agreed these practices were highly advanced and context specific; although, many lacked punctuality, allowing weeds to flower, reproduce, and reemerge (Orr et al., 2009). Based on these findings it would seem frivolous to advise farmers with limited time, income, and labor to weed more timely and often. Rather, it may be more useful to offer alternative techniques that would require less labor and coincide with a farmer’s current crops, weeds, and agroecological/financial conditions.

In short, there are methods to treat weed colonization, such as manual pulling or herbicide application. These control measures, however, require social and financial capital during times when both are most limited. Yet weeds, like all crops, can be controlled or prevented by increasing competition for light, water and nutrients. Altering the soil environment can also limit their growth. Essentially, weeds can be managed by creating a competitive and unsuitable environment. Thus to prevent weeds through ecological management, farmers can utilize a number of modified indigenous techniques such as: intercropping, perennial integration, crop rotation, push-pull technology, increased crop densities, redundancy, mulching or modified fertilizer application.

For example, there are a number of crop rotations that have been successful in eradicating common weeds from smallholder plots such as Striga. In the sub-Sahara, rotation or the use of intercrops (especially with “trap crops”) that include cowpea, yellow gram, pigeon pea, soybean, groundnut, sweet potatoes, cassava, or cotton have shown promise (Rodenburg and Johnson, 2009). In reviewing these crops, pigeon pea has shown potential in suppressing Striga from its ability to utilize iron-bound phosphorous (P) in alfisols. By increasing total P availability, soil fertility is enhanced; thus reducing parasitic-potential (Ae et al., 1993). Furthermore pigeon pea’s dropped biomass can produce an aboveground blanket. This blanket in turn smothers annual weed growth and has been particularly successful with rice rotation (Roder et al., 1997). Snapp et al., (2002) adds that farmers who utilized double-up legume systems (i.e., bush legumes with an understory legume) profited more from total food production as compared those who intercropped. In South Africa cowpea rotation with maize has been utilized by smallholders and yielded positive results (Stringer et al., 2009).  Other noxious weeds, namely blady grass (Imperata cyndrical) have been controlled in West Africa by rotating grains with velvet bean (Buckles et al., 1998; Chikoye et al., 2000; Place et al., 2003). Despite these benefits, farmers must be willing and able to put land into rotation, which will be limited by landholdings sizes and additional socioeconomic constraints.

Climate change will likely compound the battle smallholders face against weeds. As temperatures rise and droughts protract, C4 plants will gain a growing advantage over C3 plants like rice (Rodenburg et al., 2011). With little resources (e.g., biomass, irrigation) to increase soil organic material or moisture, smallholder lands may degrade more rapidly, making them a breeding ground for weeds. Solutions like no-till soil management have been developed for the anticipated events. Yet, when such resolutions require expensive inputs like herbicide, the tradeoff can be too drastic for smallholders (Robertson and Swinton, 2005).

Learning lab member Timothy Silberg is investigating integrated approaches for controlling weeds under intensified grain systems that are adapted to Malawian smallholder weeding practices, crops, and socioeconomic and agroecological conditions.

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Principles:

  • May increase crop yields
  • Employs agroecological resource complementarity
  • May improve soil quality [read more=”Read more” less=”Read less”]
    • Possibility for herbicide reduction
    • Should offer labor complementarity based on cropping cycle
    • May reduce financial and/or labor requirements
    • Often offers secondary benefits of additional crops
    • Should be tailored to farmers’ specific conditions
    • Offers potential for nitrogen fixation
    • Harnesses allelopathy
    • Secondary benefit of pest management (Push-Pull system)
    • May reduce erosion

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Debates:

  • May require additional labor and landholdings
  • May require financial capital (seeds and possibly labor)
  • Potential marginal crop loss of staple crop via loss of space or competition [read more=”Read more” less=”Read less”]
    • May enhance growth of some weeds
    • Possible lack of secondary uses of intercropped species
    • Delayed time to realize benefits
    • Benefits may be specific to soil types or climates
    • Seed availability may be limited
    • Could decrease soil fertility if not managed properly
    • May require specialized knowledge
    • May not be compatible with livestock

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Links:

Weed control by smallholder farmers in Ciskei, Eastern Cape Province, South Africa

The potential benefits of weeds with reference to smallholder agriculture in Africa

The Integrated Weed Management in Zimbabwe’s Smallholder Sector, Where Are We?

Extended Bibliography & Works Cited:

Ae, N., Arihara, J., Okada, K., Yoshihara, T., Otani, T., & Johansen, C. (1993). The role of piscidic acid secreted by pigeonpea roots grown in an Alfisol with low-P fertility. In Genetic aspects of plant mineral nutrition (pp. 279-288). Springer Netherlands.

Akobundu, I. O., & Ahissou, A. (1985). Effect of interrow spacing and weeding frequency on the performance of selected rice cultivars on hydromorphic soils of West Africa. Crop Prot. 4(1), 71–76.

Andersson, J. A., & D’Souza, S. (2014). From adoption claims to understanding farmers and contexts: A literature review of Conservation Agriculture (CA) adoption among smallholder farmers in southern Africa. Agriculture, Ecosystems & Environment, 187, 116-132.  [read more=”Read more” less=”Read less”]

Andersson, J. A., & Giller, K. E. (2012). On heretics and God’s blanket salesmen: contested claims for Conservation Agriculture and the politics of its promotion in African smallholder farming. In Contested Agronomy: Agriculture Research in a Changing World. London: Earthscan.

Baudron, F., Tittonella, P., Corbeelsa, M., Letourmya, P., & Giller, K. E. (2011). Comparative performance of conservation agriculture and current smallholder farming practices in semi-arid Zimbabwe. Field Crops Research, 132(2012), 117–128.

Berner, D. K., Cardwell, K. F., Faturoti, B., Ikie, F. O., & Williams, O. A. (1994). Relative roles of wind, crop seeds, and cattle in dispersal of Striga spp. Plant Disease, 78(4), 402-406.

Buckles, D., Triomphe, B., & Sain, G. (1998). Cover crops in hillside agriculture: farmer Innovation with Mucuna. Idrc.

Cassman, K. G., Dobermann, A., & Walters, D. T. (2002). Agroecosystems, nitrogen-use efficiency, and nitrogen management. AMBIO: A Journal of the Human Environment, 31(2), 132-140.

Chikoye, D., Manyong, V. M., & Ekeleme, F. (2000). Characteristics of speargrass (Imperata cylindrica) dominated fields in West Africa: crops, soil properties, farmer perceptions and management strategies. Crop Protection. 19(7), 481-487.

Cook, S. M., Khan, Z. R., & Pickett, J. A. (2006). The use of push-pull strategies in integrated pest management. Annual review of entomology, 52(1), 375.

Cousens, R. (1985). An empirical model relating crop yield to weed and crop density and a statistical comparison with other models. J. Agric. Sci. 105, 513–521.

Cussans, G. W. (1973). A study of the growth of Agropyron repens(L.) Beauv. in a ryegrass ley. Weed Research 13:283-291.

Debra, S.K. (1994). Socio-economic constraints to the adoption of weed control technologies: The case of Striga control in West African Semi Arid Tropics. International Journal of Pest Management 40: 153-158.

Dimes, J., Muza, L., Malunga, G., & Snapp, S. (2004). Trade-offs between investments in nitrogen and weeding: On-farm experimentation and simulation analysis in Malawi and Zimbawbwe. In: Integrated Approaches to Higher Maize Productivity in the New Millennium: Proceedings of the Seventh Eastern and Southern Africa Regional Maize Conference, Nairobi, Kenya, 5-11 February 2002 (p. 452). CIMMYT.

Elzein A., & Kroschel, J. (2003). Progress on management of parasitic weeds. In: Labrada R (ed) Series title: FAO plant production and protection. Weed management for developing countries, Papers 120 Add, Food and Agriculture Organization of the United Nations, Rome, pp 109–143

Erenstein, O. (2003). Smallholder conservation farming in the tropics and sub-tropics: a guide to the development and dissemination of mulching with crop residues and cover crops. Agriculture, Ecosystems & Environment, 100(1), 17-37.

Fagade, S. O., & Ojo, A. A. (1977). Influence of plant density and nitrogen on yield and milling quality of lowland rice in Nigeria. Exp. Agric. 13(1), 17–24.

Franzel, S., Denning, G. L., Lillesø, J. P. B., & Mercado Jr, A. R. (2004). Scaling up the impact of agroforestry: lessons from three sites in Africa and Asia. In New Vistas in Agroforestry (pp. 329-344). Springer Netherlands.

Froud-Williams, R. J., Drennan, R., & Chancellor R. J. (1983). Influence of cultivation regime on weed floras of arable cropping systems. Journal of Applied Ecology 20:187-197.

Fujisaka, S. (1997). Research: Help or hindrance to good farmers in high risk systems? Agricultural Systems, 54(2), 137-152.

Giller, K. E., Witter, E., Corbeels, M., & Tittonell, P. (2009). Conservation agriculture and smallholder farming in Africa: The heretics’ view. Field Crops Research, 114(23-24), 24–31.

Giller, K. E., Corbeels, M., Nyamangara, J., Triomphe, B., Affholder, F., Scopel, E., & Tittonell, P. (2011). A research agenda to explore the role of conservation agriculture in African smallholder farming systems. Field crops research,124(3), 468-472.

Gilbert, R. A., Sakala, W. D., & Benson, T. D. (2013). Gender Analysis of a Nationwide Cropping System Trial Survey in Malawi. African Studies Quarterly. The Online Journal of for African Studies.

Gladwin, C. H., Buhr, K. L., Goldman, A., Hiebsch, C., Hildebrand, P. E., Kidder, G., …& Williams, D. (1997). Gender and soil fertility in Africa. Replenishing soil fertility in Africa: 219-236.

Grabowski, P., & Kerr, J. (2013). Resource Constraints and Partial Adoption of Conservation Agriculture by Hand-Hoe Farmers in Mozambique. International Journal of Agricultural Sustainability , 37–41. http://doi.org/10.1080/14735903.2013.782703

Hadas, A., Kautsky, L., Goek, M., & Kara, E. E. (2004). Rates of decomposition of plant residues and available nitrogen in soil, related to residue composition through simulation of carbon and nitrogen turnover. Soil Biology and Biochemistry, 36(2), 255-266.

Hakansson, S. (1982). Multiplication, growth. and persistence of perennial weeds. Pages 123-135 in W. Holzner and M. Numata, editors. Biology and ecology of weeds. Dr. W. Junk. The Hague. The Netherlands

Hobbs, P. R. (2007). Conservation agriculture: what is it and why is it important for future sustainable food production? Journal of Agricultural Science, 145, 127–137. http://doi.org/10.1017/S0021859607006892

Hocket, M. (2014). They Say Wealth Is In The Soil: Local Knowledge And Agricultural Experimentation Among Smallholder Farmers In Central Malawi (Masters dissertation). Retrieved from Michigan State University Thesis Database.

Johnson, D. E. (1996). Weed management in small holder rice production in the tropics. IPM Word Textbook, University of Minnesota, St. Paul, MN.

Johnson, K. B., Jacob, A., & Brown, M. E. (2013). Forest cover associated with improved child health and nutrition: evidence from the Malawi Demographic and Health Survey and satellite data. Global Health: Science and Practice, 1(2), 237-248.

Joubert, A. B. D. (2000). Weed control by smallholder farmers in Ciskei, Eastern Cape Province, South Africa. Animal power for weed control. A resource book of the Animal Traction Network for Eastern and Southern Africa (ATNESA). Publication of Technical Centre for Agricultural and Rural Cooperation (CTA), Wageningen, The Netherlands, 214-217.

Kalaba, K. F., Chirwa, P., Syampungani, S., & Ajayi, C. O. (2010). Contribution of agroforestry to biodiversity and livelihoods improvement in rural communities of Southern African regions. In Tropical Rainforests and Agroforests under Global Change (pp. 461–476). Springer Berlin Heidelberg.

Keating, B. A., Carberry, P. S., Hammer, G. L., Probert, M. E., Robertson, M. J., Holzworth, D., … & Smith, C. J. (2003). An overview of APSIM, a model designed for farming systems simulation. European journal of agronomy, 18(3), 267-288.

Khan, Z. R., Midega, C. A., Bruce, T. J., Hooper, A. M., & Pickett, J. A. (2010). Exploiting phytochemicals for developing a ‘push–pull’crop protection strategy for cereal farmers in Africa. Journal of Experimental Botany, 61(15), 4185-4196.

Kristensen, L., Olsen, J., & Weiner, J. (2008). Crop density, sowing pattern, and nitrogen fertilization effects on weed suppression and yield in spring wheat. Weed Science. 56, 97–102.

Kumwenda, J. D., Waddington, S. R., Snapp, S. S., Jones, R. B., & Blackie, M. J. (1997). Soil fertility management in Southern Africa. Africa’s emerging maize revolution, 157-172.

Kwesiga, F., Akinnifesi, F. K., Mafongoya, P. L., McDermott, M. H., & Agumya, A. (2003). Agroforestry research and development in southern Africa during the 1990s: review and challenges ahead. Agroforestry Systems, 59(3), 173–186.

Liebman, M., & Dyck, E. (1993). Crop rotation and intercropping strategies for weed management. Ecological applications, 92-122.

Lillis, A. M. (1999). A framework for the analysis of interview data from multiple field research sites. Accounting and finance, 39(1), 79-105.

Maereka, E. K. (2007). Intercropping and leaf harvest management for improved leaf yields in two traditional vegetables: pumpkin (Cucurbita maxima L.) and mustard rape (Brassica juncea Czern.).  Doctoral dissertation, University of Zimbawbwe.

Mahajan, G., & Chauhan, B.S. (2013). The role of cultivars in managing weeds in dry-seeded rice production systems. Crop Protection. 49:52–57

Mahajan, G. (2014). Recent advances in weed management. B. S. Chauhan (Ed.). Springer.

Mhango, W. G., Snapp, S. S., & Phiri, G. Y. (2013). Opportunities and constraints to legume diversification for sustainable maize production on smallholder farms in Malawi. Renewable Agriculture and Food Systems, 28(3), 234–244.

Mboob, S. S. (1989). A regional programme for Striga control in West and Central Africa. Proceedings of the FAO/OAU All African Government Consultation on Striga Control, Marova. FAO, Rome, 190-194.

Mohler, C. L. (1996). Ecological bases for the cultural control of annual weeds. J. Prod. Agric. 9, 468–474.

Neve, P., Vila‐Aiub, M., & Roux, F. (2009). Evolutionary‐thinking in agricultural weed management. New Phytologist, 184(4), 783-793.

Nyankweli, E. M., Mattee, A. Z., & Mwageni, E. A. (200) Assessment of Farmers’ Knowledge and Perception of Striga: The case of Mvumi Makulu and Chipanga’A’villages in Dodoma District, Tanzania.

Nyoka, G. C. (1983). Weed problems and control practices in deepwater and floating rice in Mali. In ‘‘Proceedings of the Second Biannual Conference West African Weed Science Society’’ (M. Deat and P. Marnotte, Eds.), pp. 146–157. West African Weed Science Society, Abidjan, Cote d’Ivoire.

Orr, A., Mwale, B., & Saiti, D. (2002). Modelling agricultural’performance’: smallholder weed management in Southern Malawi. International Journal of Pest Management, 48(4), 265-278.

Orr, A., Mwale, B., & Saiti-Chitsonga, D. (2009). Exploring seasonal poverty traps: the ‘six-week window’in southern Malawi. The Journal of Development Studies, 45(2), 227-255.

Otsuka, K., & Place, F. (2001). Land Tenure and Natural Resource Manageament: A comparative Study of Agrarian Communities in Asia and Africa. Baltimore, MD: Johns Hopkins UP. Print.

Place, F., Barrett, C. B., Freeman, H. A., Ramisch, J. J., & Vanlauwe, B. (2003). Prospects for integrated soil fertility management using organic and inorganic inputs: evidence from smallholder African agricultural systems. Food Policy, 28(4), 365-378.

Pratt, J. H., Henry, E. M. T., Mbeza, H. F., Mlaka, E., & Satali, L. B. (2002). Malawi Agroforestry Extension Project Marketing & Enterprise Program (Main Report No. 47) (p. 139). Malawi: USAID.

Ransom, J.K. (1990). Weed control in maize/legume intercrops. In: Eds S.R. Waddington, A.F.E. Palmer and O.T. Edje, Research methods for cereal/legume intercropping. Proceedings of a workshop on Research methods for cereal and legume intercropping in Eastern and Southern Africa. Jan 23-27, 1989, Lilongwe, Malawi. CIMMYT, Mexico DF, pp. 41-44.

Riches, C. (2003). Integrated management of Striga species on cereal crops in Tanzania. Final Technical Report.

Riches, C. R., Mbwaga, A. M., Mbapila, J., & Ahmed, G. J. U. (2005). Improved weed management delivers increased productivity and farm incomes from rice in Bangladesh and Tanzania. Asp. Appl. Biol. 75, 127–138.

Riches, C. R., Shaxson, L. J., Logan, J. W. M., & Munthali, D. C. (1993). Insect and parasitic weed problems in southern Malawi and the use of farmer knowledge in the design of control measures. Network Paper-Agricultural Administration (Research and Extension) Network, (42), 1-17.

Robertson, G. P., & Swinton, S. M. (2005). Reconciling agricultural productivity and environmental integrity: a grand challenge for agriculture. Frontiers in Ecology and the Environment, 3(1), 38-46.

Rockström, J., Kaumbutho, P., Mwalley, J., Nzabi, A. W., Temesgen, M., Mawenya, L.,… & Damgaard-Larsen, S. (2009). Conservation farming strategies in East and Southern Africa: yields and rain water productivity from on-farm action research. Soil and Tillage Research, 103(1), 23-32.

Rodenburg, J., & Johnson, D. E. (2009). Weed Management in Rice‐Based Cropping Systems in Africa. Advances in Agronomy, 103, 149-218.

Rodenburg, J., Meinke, H., & Johnson, D. E. (2011). Challenges for weed management in African rice systems in a changing climate. The Journal of Agricultural Science, 149(04), 427-435.

Roder, W., Maniphone, S., & Keoboulapha, B. (1997). Pigeon pea for fallow improvement in slash-and-burn systems in the hills of Laos?. Agroforestry Systems, 39(1), 45-57.

Romney, D. L., Thorne, P., Lukuyu, B., & Thornton, P. K. (2003). Maize as food and feed in intensive smallholder systems: management options for improved integration in mixed farming systems of east and southern Africa. Field crops research, 84(1), 159-168.

Sileshi, G. W., Kuntashula, E., Matakala, P., & Nkunika, P. O. (2008). Farmers’ perceptions of tree mortality, pests and pest management practices in agroforestry in Malawi, Mozambique and Zambia. Agroforestry systems, 72(2), 87-101.

Sirrine, D., Shennan, C., & Sirrine, J. R. (2010). Comparing agroforestry systems’ ex ante adoption potential and ex post adoption: on-farm participatory research from southern Malawi. Agroforestry Systems, 79(2), 253–266.

Snapp, S. S., Jones, R. B., Minja, E. M., Rusike, J., & Silim, S. N. (2003). Pigeon Pea for Africa: a versatile vegetable—and more. HortScience, 38(6), 1073–1079.

Snapp, S. S., Rohrbach, D. D., Simtowe, F., & Freeman, H. A. (2002). Sustainable soil management options for Malawi: can smallholder farmers grow more legumes? Agriculture, ecosystems & environment, 91(1), 159-174.

South, T. S., & Queensland, E. (1989). PRODUCTIVITY AND POPULATION DYNAMICS OF SILVERLEAF DESMODIUM (DESMODIUM UNCINATUM), GREENLEAF DESMODIUM. Tropical Grasslands, 23(1), 43.

Stringer, L. C., Dyer, J. C., Reed, M. S., Dougill, A. J., Twyman, C., & Mkwambisi, D. (2009). Adaptations to climate change, drought and desertification: local insights to enhance policy in southern Africa. Environmental Science & Policy, 12(7), 748-765.

Tafirenyika, M. (2014, January). What went wrong? Lessons from Malawi’s food crisis. United National Africa Renewal (Online), p. 9. Malawi. Retrieved from http://www.un.org/africarenewal/magazine/january-2013/what-went-wrong-lessons-malawi%E2%80%99s-food-crisis

Tefera, T., & Tana, T. (2002). Agronomic performance of sorghum and groundnut cultivars in sole and intercrop cultivation under semiarid conditions. Journal of Agronomy and Crop Science, 188(3), 212-218.

Tembakazi, Silwana, T., & Lucas, E. O. (2002). The effect of planting combinations and weeding on the growth and yield of component crops of maize/bean and maize/pumpkin intercrops. The Journal of Agricultural Science,138(02), 193-200.

Thangata, P. H., Hildebrand, P. E., & Gladwin, C. H. (2002). Modeling agroforestry adoption and household decision making in Malawi. African Studies Q, 6, 1–2.

Tittonell, P., Vanlauwe, B., De Ridder, N., & Giller, K. E. (2007). Heterogeneity of crop productivity and resource use efficiency within smallholder Kenyan farms: Soil fertility gradients or management intensity gradients? Agricultural systems, 94(2), 376-390.

Tittonell, P., Vanlauwe, B., Leffelaar, P. A., Shepherd, K. D., & Giller, K. E. (2005). Exploring diversity in soil fertility management of smallholder farms in western Kenya: II. Within-farm variability in resource allocation, nutrient flows and soil fertility status. Agriculture, ecosystems & environment, 110(3), 166-184.

“United Nations.” Malawi Country Profile. United Nations, 2014. Web. 11 Dec. 2014.

USDA (2014) “Forestry.” Sustaining Agroforestry Systems for Farms and Ranches. United States Department of Agriculture (USDA), 2014. Web. 2 Dec. 2014. <http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/landuse/forestry/sustain/>.

Vogel, H. (1995). The need for integrated weed management systems in smallholder conservation farming in Zimbabwe. Der Tropenlandwirt-Journal of Agriculture in the Tropics and Subtropics, 96(1), 35-56.

Witt, W. W. (1984). Response of weeds and herbicides under no-tillage conditions. Pages 152-169 in R. E. Phillips and S. H. Phillips. editors. No-tillage agriculture: principles and practices. Van Nostrand Reinhold. New York. New York, USA.

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Tags: Agricultural Economics, Agrobiodiversity, Agronomy, Climate Change, Extension, Sociology, Soil Science, Sustainability Science