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Home , Intercropping, Land Equivalent Ratio, Miguel Altieri, Phyllotreta cruciferae

Altieri & Nicholls / Agro Sur 46(2): 49-60, 2018 DOI:10.4206/agrosur.2018.v46n2-07

Urban : designing biodiverse, productive and resilient city

Agroecología urbana: diseño de granjas urbanas ricas en biodiversidad, productivas y resilientes

Altieri, M. A.a*, Nicholls, C. I.b

a Department of Environmental Science, Policy and Management, University of California, Berkeley. b Global Studies, University of California, Berkeley.

A R T I C L E I N F O A B S T R A C T

Keywords: Urban (UA) has been bolstered as a major sustainable alternative to enhance food Agroecology security on an urbanized planet. Although it has been estimated that UA can provide 15–20% quality Biological control of global food, it is questionable weather UA can significantly contribute the level of food self- productive,sufficiency ofand cities, resilient due tourban low yieldsfarms. reachedHerein we in mostdescribe existing the principles urban farms. and Agroecology practices used can in help the Original Research Article, redesignenhance theof urban productive agriculture potential featuring: of UA (a)by increasingproviding keysoil principlesquality via forenhancement the design ofof soildiversified, organic Special Issue: Agroecology and Sustainable Agricultural Systems soil nutrients and and (b) enhancement of health through biological control and plant *Corresponding author: productivitymatter content via and optimal biological planning activity of that sequences lead to protection and combinations against pathogens. and efficient use of Miguel A. Altieri E-mail address: [email protected]

RESUMEN

La agricultura urbana (AU) ha surgido como una importante alternativa sostenible para mejorar la seguridad alimentaria en un planeta urbanizado. Si bien se ha estimado que la AU puede proporcionar entre el 15 y el 20% de los alimentos a nivel mundial, se cuestiona si acaso la AU puede contribuir significativamente al nivel de autosuficiencia alimentaria de las ciudades, debido ya losresilientes. bajos rendimientos Aquí describimos alcanzados los principios en la mayoría y las deprácticas las granjas utilizadas urbanas en existentes. el rediseño La de agroecología la agricultura puede urbana ayudar mediante: a mejorar (a) aumentoel potencial de productivola calidad del de suelola AU ala través proporcionar de la mejora principios del contenido claves para de elmateria diseño orgánica de granjas y la urbanas actividad diversificadas, biológica que productivas conduce a la protección contra patógenos y al uso eficiente de los nutrientes y el agua del suelo y (b) mejora de la sanidad vegetal a través Palabrasdel control clave biológico: Agroecología, y la productividad agricultura vegetal urbana, a travéscalidad de del la suelo,planificación control óptimabiológico. de secuencias de cultivos y combinaciones.

INTRODUCTION Given this grim scenario, urban agriculture (UA) has been bolstered as a major sustainable alternative By 2030, 60% of the world’s urban population to enhance food security on an urbanized planet. Pro will live in cities, including 56% of the world’s poor duction of fresh , vegetables, and some and 20% of the undernourished (De Bon et al., 2010). products, within cities can improve local food security- Today, for a city with 10 million people or more, over and nutrition of consumers, especially in underserved 6,000 tons of food has to be imported every day, trave communities (Smit et al., 2001). UA has spread rapidly. ling an average of 1,000 miles (De Zeeuw et al., 2011). - ntries by 3.6% annually and >30% in the past 30 years inFrom the 1950-2005United States UA (Siegner has expanded et al., in2018). developing Although cou it- luresA significant in industrial rise in agriculture, food prices, increased if not food energy shortages costs has been estimated that UA can provide 15–20% of andcan bedemographic expected with pressure, compounding and as factorsmultinational such as cor fai- global food, an important question remains: what le porations increase their control of the food system - tain through UA. A survey with the goal of providing- vel of food self-sufficiency can cities realistically ob- (Holt-Gimenez, 2017). AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS 49 Altieri & Nicholls / Agro Sur 46(2): 49-60, 2018

300 g day per capita of fresh vegetables, found that African towns and cities produce much food in urban -1 vegetable which may include such recommended nutritional target (Clinton et al., 2018). as and poultry (Zezza and Tasciotti, 2010). For In51 addition,countries UA have would insufficient require urban30% of area the tototal meet urban the area to meet the global demand for vegetables, a spa ce that may not be available due to land tenure issues exampleholds in that60% country of milk aresold involved in Dar es in Salaam,UA. Dakar Tanzania, produ and urban sprawl (Martellozzo et al., 2014; Badami and- comesces 60% from of theUA. nationalSixty-eight vegetable percent consumption of all urban house of Se- negal whilst urban poultry production amounts to 65%- of the national demand. In Hanoi, Viet Nam, 80% of- UARamankutty, is designed 2015). and Othermanaged estimates (i.e. suggest designs, that cropself- fresh vegetables, 50% of pork, poultry and fresh water arrangements,sufficiency could production be achieved, practices but this used, depends size of on plots, how etc.). Several studies estimate that UA may supply from Shanghaifish, as well produce as 40% 60% of eggs, of the originate city’s vegetables, from urban 100% and (Siegner et al., 2018), but the question of how much of ofperi-urban the milk, areas.90% of The the urbaneggs, and and 50% peri-urban of the pork areas and of the30-100% urban produced of city vegetable food is actually demand being in variousconsumed cities by Bon et al., 2010). poultryUA has meat been (van critical Veenhuizen during times and Danso, of crisis. 2007; During De ductionlow-income potential food insecureof urban communitiesagriculture when is beyond designed the World War II, United States households produced andscope managed of this review.using agroecological Our focus is toprinciples. examine the pro- enough to meet 40% of the nation’s fresh vegetable de The majority of urban farmers lack ecological hor mand during the “victory ” movement. In Saraje ticultural skills and do not always optimize crop densi vo, Bosnia and Herzegovina, 2 years after the blockade- ty or diversity, most suffer pest losses and reach poor- - - was estimated to have grown from 10% to over 40% ces are needed to enhance soil quality, crop health and forbegan vegetables in 1992, and self-reliance small livestock in urban (Brown food and production Jameton, productivity.yields, thus modifications Agroecology can of existinghelp realize cultural the produc practi- 2000). During the “special period” right after the collap tive potential of UA by providing key principles for the se of the Soviet bloc, over 26,000 popular gardens co - vered 2,439 ha in Havana, Cuba, producing 25,000 tons- farms. Herein we describe such principles and their - applicationdesign of diversified, to achieve the productive, potential and of UA. resilient urban produce about 50% of the fresh food of the island cove ringof food about each 56,000 year. Today ha. More UA andthan peri-urban 39,000 tons agriculture of meat, THE MAGNITUDE AND SIGNIFICANCE OF URBAN - AGRICULTURE duced in more than 300,000 urban farms and gardens. UA787 generates litters of aboutgoat milk 300,000 and 216jobs, million of which, eggs 66,055 are pro are- The United Nations Development Programme (UNDP) estimated that about 800 million urban dwe and Vázquez, 2016). In Rosario, Argentina, thousands llers are engaged in UA globally, producing 15 to 20% oftaken families by women, were ableand 78,312to feed by themselves young people during (Funes the of the world’s food. In the 1990s this number of people- country’s 2002 economic crisis by growing their own comprised 30% of the global urban population, 200 mi food. More than 800 community gardens proliferated llion of whom produced food for sale (Smit et al., 2001). in the city feeding some 40,000 people. Today Rosario In 1993, just 15% of food consumed in cities world- wide was grown in cities. However, by 2005, that pro of land. is practiced on 24 ha of the total portion increased to 30%. In other words, urban food- areahas five where large more innovative than 600 parks covering grow a total vegetables of 72 ha production doubled in just over 15 years (Martellozzo- for the market and home consumption (FAO, 2015). et al. re continues today. Overall, global estimates of availa PRODUCTIVITY OF URBAN FARMS , 2014). This expanding trend of urban agricultu- 1.4%–11% of the urban area. Projected global produc- Assessments of the productivity potential of urban ble space for UA ranges from 1–7 million hectares or farms have been conducted in many US cities. In 2008, year (Clinton et al., 2018). - Philadelphia’s 226 community and squatter gardens tionData was fromestimated urban at areas100-180 around million the tons world of food indica per grew roughly 900,000 kg of midsummer vegetables and herbs worth $4.9 million US dollars (Kremer and animal intake can be met locally. Studies have repor- DeLiberty, 2011). Running at full bore, Brooklyn’s tedte that that a urbansignificant agriculture portion provides of the local as muchvegetable as 90% and Added Value Farm, which occupies 1,11 ha, funnels of leafy vegetables in Dar es Salaam, Tanzania, as well- income neighborhood of Red Hook. In Camden, New bles in Beijing. It has been well documented that many around 18,000 kg of and vegetables into the low- as 76% of vegetables in Shanghai and 85% of vegeta- Jersey, an extremely poor city of 80,000 people, com- 50 AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS Urban Agroecology as sustainable alternative munity gardeners at 44 sites harvested almost 14,000 AGROECOLOGICAL PRINCIPLES FOR URBAN FARM kg of vegetables, enough food during the growing sea DESIGN son to feed 508 people three servings a day. In Detroit’s vibrant communal and commercial farming com- Agroecology has for decades been applied to im munity, which in 2014 produced nearly 181,000 kg prove small farming agriculture in the developing of food — enough to feed more than 600 people — in- - its more than 1,300 community, market, family and agroecological principles applied in rural areas for school gardens (ENSIA, 2015). world (Altieri, 1995). The same well-established Researchers have calculated that Cleveland, Ohio, with its population of 400,000 habitants, has the po canthe designbe applied and managementto urban farms. of diversifiedAgroecological farms princi whe- tential to meet 100% of urban dwellers need for fresh plesre external (Table 3) inputs are applied are replaced by way by of naturalvarious processespractices vegetables, 50% of poultry and eggs, and 100% of ho- which lead to optimal recycling of nutrients and or- ney (Grewal and Grewal, 2012). Under average growing ganic matter turnover for soil fertility, closed energy - - plot can provide a household’s yearly vegetable needs, regulation all key processes necessary to maintain UA includingconditions much in a 130of the days household’s growing season, nutritional a 10 require x 10 m productivityflows, water (Altieri,and soil 1995).conservation and enhanced pest Agroecological systems are not intensive in the use ner et al., 2018). One of the few studies estimating crop- of capital, labor, or chemical inputs, but rather they yieldsments atfor the vitamins farm level A, C, (Grewal and B complexand Grewal, and 2012) iron (Sieg indi- cates that conventional urban has the lowest yields (1.20–1.35 kg m year ) and thereby the largest- phosphorus,improve the efficiencyand the enhancement of biological of processes biological such activi as land requirements to meet-2 people-1 food needs, while in typhotosynthesis, above and below nitrogen ground. fixation, The “inputs” solubilization of the system of soil tensive urban gardening reached levels of 6.20 kg m - year and thus, smaller land requirements. The latter-2- study-1 showed that the city of Cleveland should be able Table 1. Productivity obtained in a 11.05 m2 urban garden vegetable, fresh fruit, shell eggs, poultry, and honey. featuring 16 crop species in Central Chile (Infante, 1986). to achieveMost of considerablethe above data levels proceed of self-reliance from urban in farmsfresh Cuadro 1. Productividad obtenida en un jardín urbano de not necessarily managed with agroecological methods. 11,50 m2 con 16 especies de cultivo en Chile Central (Infante, When these methods are applied, productivity poten 1986). Crop Production % Contribution to veland study shows that under conventional urban- (kg m-2) total production tial can increase considerably. For example, the Cle- reliance in fresh produce, but more than 50% when Tomato usinggardening intensive the city organic would gardening be able to methods attain 22% (Grewal self- Chard 79.453.9 44.7530.38 and Grewal, 2012). In Cuba, agroecologically based “or Fava beans 12.9

20 kg m year (Funes and Vázquez, 2016). During the- Onions 7.27 ganopónicos”-2 (intensive-1 gardens) reach on average 15- Cabbage 9.73.8 5.472.14 ducted an evaluation of an 11.05 m2 vegetable garden Lettuce (Summer) 2.9 1.63 1984-1985 season in central Chile, Infante (1986) con- or 16 kg Broccoli 2.5 1.41 containingm year (Table 16 1). speciesThe secret displayed of the inhigh complex production-1 rota- Cilantro 2.4 1.35 tions-2 and-1 mixtures produced 177,4 kg year Beets 2.4 1.35 cation of agroecological principles to guide the inten sivepotential cultivation of the ofCuba a diversity and Chile of examplesvegetables, is theroots appli and- Spinach 2.3 1.30 - tubers, and herbs in relatively small spaces. Radish (Winter) 1.4 Following some of the designs and practices used in Cuba and Chile, a 100 m2 Carrot 1.2 0.790.62 tablished in Berkeley, California (Altieri, unpublished Radish (Summer) 1.1 0.62 diversified garden was es- data). The garden contained a total of 492 be Lettuce (Winter) 0.39

- Peas 0.70.4 0.23 oflonging edible to green 10 crop biomass species per grownm2 in a mixed polycul- Brussel sprouts 0.4 0.23 wholetural design. plot) in Total a three production month period reached (Table a yield 2), of close 2.7 kgto Total Production 177.4 kg 100% the desired level of 10 kg m per (a year. total of 270 kg in the -2

AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS 51 Altieri & Nicholls / Agro Sur 46(2): 49-60, 2018

Table 2. Biomass production and nutrient output in a 100 m2 urban garden in Berkeley, California (Altieri, unpublished data). Cuadro 2. Producción de biomasa y salida de nutrientes en un jardín urbano de 100 m2 en Berkeley, California (Altieri, datos no publicados).

Crop # of Edible Edible Edible biomass Calories Vit. A m-2 Vit. C m-2 Protein Protein plants biomass biomass Yield m-2 (g) (g) (g) m-2 (g) ha-1 Crop-1 Plant-1 (g) m-2 (g) (kg ha-1) (kg ha-1) Arugula 83 406 2030 20300 508 15663 305 52 524 Bokchoy 46 966 4828 48283 628

Chard 102 504 2519 25192 6471446222 2173 7245 724453 Green Lettuce 68 425 2125 21250 479319 756196 29 289 Red Lettuce 32 225 1125 11250 180 4720725286 42 15 150 Mizuna 65 1152 864 530

Spinach 15 186 5762 932 57617 214 127995 20939 262 78 784266 Kale 45 353 9317 866 53000 2120 27 565 36 1767 17667 54333 391 5713 130 Pak-choiTOTAL 492 4435 217 1087 10867 217 455360 389 3886 2714 27137 4275 6773

Table 3. Agroecological principles for the design of biodiverse and productive urban farms. Cuadro 3. Principios agroecologicos para el diseño de granjas urbanas biodiversas y productivas.

1. Enhance the recycling of biomass, optimising organic matter decomposition and nutrient cycling.

2. Enhance functional – natural enemies, antagonists, soil biota, etc., by creating appropriate habitats.

3. Provide the most favourable soil conditions for plant growth, by managing organic matter and by enhancing soil biological activity. 4. Minimise losses of energy, water, nutrients and genetic resources via conservation of soil and water resources and agrobiodiversity.

5.

6. Diversify species and genetic resources at the field and landscape level.

Enhance beneficial biological interactions among agrobiodiversity components promoting key ecological processes. are the natural processes themselves; this is why agro THE PILLARS OF AGROECOLOGICAL URBAN FARMS is referred to as an “agriculture of processes” (Gliessman, 1998). - The redesign of urban agriculture arises from the application of agroecological principles (Nicholls et al., 2016) that lead to: (a) increasing soil quality via andThe a soil integrity rich in oforganic a well-designed matter and urbanbiota. Suchfarm farmsrelies enhancement of soil organic matter content and bio on synergies between plant diversity, beneficial logical activity that lead to protection against patho dance of natural enemies and other mechanisms, as - shouldwell as exhibitsoils with lower high pest organic populations matter dueand to active an abun bio- (b) enhancement of plant health and productivity via- logically thus, sponsoring good soil fertility and pre optimalgens and planning efficient of use crop of soilsequences nutrients and and combinations water, and vention of pathogen infection via antagonisms (Altieri- (Figure 1). and Nicholls, 2004). Integration of soil, water, and pest- management practices constitute a robust pathway for optimizing soil quality, plant health, and crop produc tion in urban farms. -

52 AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS Urban Agroecology as sustainable alternative

Enhancing soil quality promoting substances, which promote growth of healthy Addition of organic matter andced nutrientproductive availability, plants (Magdoff and the and production van Es, 2000). of growth- After one or two seasons of applying agroecologi Organic matter and its replenishment is a major cal practices, levels of nitrogen, phosphorus and potas component of soil health and management. Agroecology sium, pH, organic matter and some micronutrients of- ten increase with time (Nicholls et al., 2016). Biomass- and abundance of earthworms also increases which- ping,promotes applications a series ofof soil-health-improving and a variety management of organic amendmentspractices such (Nicholls as complex et al. , crop 2016). rotations, These management - microorganisms thrive, which decompose organic re practices, increase inputs of soil organic matter (SOM), siduesin turn and improves mineralize soil nutrients structure, (Cheeke and other et al beneficial., 2012). decrease losses of carbon, maintain soil cover, and de Mycorrhizal fungi and some antagonists that suppress- biological activities such as antagonisms, litter decompo- to the enhancement of soil chemical and biological sition,crease nutrientsoil disturbance, mobilization, influencing etc. Improved diverse soiland proper crucial many soil-borne diseases also increase with time. Due - have a positive yield response (Abbot et al., 1995). such as more available water, less compaction, enhan- parameters,Table 4 shows most how crops yields grown of tomatoes on compost-amended vary depending ties resulting from such practices have added benefits -

Figure 1.Figure 1.

as. Figura 1. Agroecological principles for the re-design of organically rich soil, diversified and productive urban farms. Principios agroecológicos para el rediseño de granjas urbanas ricas en suelos orgánicos, diversificadas y productiv

Table 4. Yields of tomatoes (var. Principe Borghese) under various organic fertilization regimes (each treatment = N equivalent to 50 kg ha ) in urban farms in Berkeley, California (Altieri, unpublished data). -1 Cuadro 4. Rendimiento de tomates (var. Principe Borghese) bajo varios tratamientos de fertilizacion orgánica (cada tratamiento corresponde a un equivalente de N de 50 kg ha ) en una granja urbana en Berkeley, California (Altieri, datos no publicados). -1 Treatment # Of fruits plant Average fruits weight (kg) Yield plant (kg) -1 -1 No fertilization 10 0.016 0.16 Compost 34 0.021

Fish emulsion 40 0.018 0.73 Mycorrizhae enriched compost 0.019 0.540.70 27 AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS 53

33

Altieri & Nicholls / Agro Sur 46(2): 49-60, 2018 on the applied organic fertilization treatments, where access sources such as wastewater, grey water, or har vested rainwater, and apply such water via irrigation - Berkeley,compost andCalifornia (Altieri, had unpublished the biggest data). production ducers. In areas of water scarcity, productivity should effectsA main in experiments challenge for conducted urban farmers in an is urban to access farm ani in beusually measured in a more per efficientunit of mannerwater (weight than can or rural volume), pro- mal manure as a source of nitrogen, as shortage of avai lable nitrogen may greatly reduce crop yields. Many ci- values > 60% (Barthel and Isendhal, 2013). ties do not allow animal rearing, which further limits- with the goal of irrigation systems reaching efficiency manure availability. As an alternative, many farmers- ture, selection of drought tolerant varieties, alternative grow green manures such as fava beans (Vicia faba L.), tillageIn rain-fedsystems, regionsand mulching improvement are critical of rainwaterto secure good cap- vetch (Vicia atropurpurea Desf.) and peas (Pisum sati- harvests. Addition of organic amendments to the soil is vum vital and many studies are showing that SOM enhances water retention (Altieri et al., 2015). Depending on the strategy L.), orto aincrease mixture nitrogen (at times supply adding for 20% crops. In or addi bar- soil type, it is estimated that for every 1% increase in ley) in fall and winter. This constitutes an inexpensive SOM, the soil increases its storage capacity in 1.5 l m . simultaneously including suppression of weeds, soil- In other words a 1 % increase in soil organic matter-2 bornetion, cover diseases crops and can pests, exhibit protect several the soil multiple from rain effects and of water runoff, improve soil aggregate stability, add active or (Hudson, 1994). Organically rich soils usually-1 contain content can hold an additional 178,000 l ha In California, a vigorous green manure (i.e. fava- ganic matter and scavenge for nutrients (Clark, 2007). vesicular-arbuscular mycorrhizal (VAM) fungi, which incorporation in early spring, typically adds between (Auge,are of particular2001). The significance effect of arbuscular under water mycorrhizal stress condi (AM)- 112beans and or 224vetch) kg growing N ha to for the four soil to for six themonths succeeding before colonizationtions, as VAM by colonization Glomus clarum increases on fruit water yield use and efficiency water crop (Clark, 2012). Yields-1 of most vegetable crops in crease with increasing rates of nitrogen. The C/N ratio der various watering regimes. Mycorrhizal plants had of incorporated materials should be equal to or less- use efficiency (WUE) was evaluated in watermelon un- avoid nitrogen “hunger” (Clark, 2012). Cover crop spe stressedsignificantly or not higher (Kaya biomass et al., 2003). and fruit yield compared ciesthan vary20:1 into nitrogenassure net content short-term and mineralizationmineralization rateand to non-mycorrhizalDuring dry spells plants, (up to awhether period ofplants 10 rainless were waterdays) after incorporation. Leguminous cover crops decom- a key strategy is to use straw or grass as it can pose and release nitrogen more rapidly than grass or - Mulching can retard the loss of moisture from the soil cover crops do not release appreciable nitrogen to a andsignificantly as a result, reduce higher evaporation and uniform from soil the moisture soil surface. regi subsequentcereal covers, crop and beyond even the 6 to most 8 weeks efficient from N-supplying incorpora me can be maintained reducing the irrigation frequen tion. This burst of early nitrogen may not synchronize cy (Ranjan et al - with nitrogen requirements for many vegetable crops,- found higher moisture content in the 0–60 cm soil layer- thus at times urban farmers may have to add additional of the mulched plots., 2017). compared In vegetable to that crops, of the researchers unmulched sources of N (Magdoff and Es, 2000). plots. This moisture difference ranged from 10% one or Many urban soils have been impacted by contami two days after rainfall to more than 22% over a 2 week nation from previous land uses. Surveys in US cities period of break in rainfall, indicating that evaporation have found soil lead concentrations above 400 mg kg - was high in unmulched plots (Daisley et al., 1988). The -1 amendments like animal manure; compost and green tant implications on the utilization of water by crops in many urban gardens. On-farm generated organic andgreater on soil soil reactions profile moisture that control under the mulch availability has impor of nu- due to dilution and stabilization of potential contami nants.manures Increasing have some SOM valueis a critical for low-level amelioration remediation method - in UA as it helps to retain soil nutrients, immobilize- ductiontrients and through biological soil and nitrogen water fixation conservation, (Hanada, enhanced 1991). contaminants, and stabilize pH. Increasing SOM also soilClearly, biological mulching activity provides and improved many benefits chemical to crop and phypro- helps to enhance the abundance of microbial commu sical properties of the soil (Ranjan et al nities which are critical for degrading potential conta - minants (De Kimpe and Morel, 2000). - Crop diversification ., 2017). - Water conservation and use efficiency ecological principle that can be applied to urban farms. By In the event of water shortages or decreasing quali combiningCrop diversification plants in in time and arrangements, space is a key cropsagro- ty of the available water sources, urban producers can and trees in systems, and trees in -

54 AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS Urban Agroecology as sustainable alternative silvopastoral systems, using as cover crops or Synergistic crop combinations include tall and short in rotations, etc., a farming system becomes more com crops, plants that use resources at different times; sha included, leading to more interactions among arthropo- - dsplex and as microorganisms, a larger number components of different ofkinds above of andplants below are tomatoesllow- and and deep-rooted basil or beans; plants lettuce that or exploit mescluns different bet ground food webs (Altieri and Nicholls, 2004). As diver- weensoil horizons. rows of Examplesleek or garlic, include and legumes arugula with under cereals, kale (Brassica oleracea var. sabellica - - lead to increased productivity partly due to the process agroecosystemsity increases, sosustainability do opportunities (Nicholls for et coexistence al., 2016). and ) Good crop mixtures beneficial interference between species that can enhance Temporal diversity: crop rotations byof facilitation,lowering the when population one crop of a modifies pest, or theby releasing environ- nutrientsment in a thatway canthat be benefits taken upa second by the crop,second for crop. example, is the practice of growing a sequen ce of different groups of crop species (legumes, Over yielding crops, fruit crops, and leaf crops) in the same area for- many seasons. By dividing the garden in 4 plots (each A combination of two contrasting species leads to planted to each guild of crops), every successive year

cientlygreater than overall separate productivity . because The the over mixture yielding can each guild moves to the next plot clockwise. Rotating ofuse intercrops resources is (nutrients, measured water,using theand Land ) Equivalent more effi Ra- lies.plant Basic families rules reduces of a good soil-borne rotation include diseases alternating and soil- tio (Francis, 1986). When the value is higher than 1, po dwelling insects that are specific to certain crop fami- lycultures over yield (i.e. a LER of 1.5 it means that a mo- crops of the same family consecutively, and alternating noculture requires 50% more land to obtain the same- cropsbetween with legumes deep and and shallow non-legumes, (Karlen never et al planting., 1994). - As mentioned above, using legumes in the rotation in ley, we have obtained LER values >1.5 in combinations crease available nitrogen in the soil, even after they are ofyield lettuce, of the mizuna, ). kale, arugula In our and experiments others (Table at Berke 5). - harvested, for future crops, thus reducing the need for- et al., 2005). Many researchers and practitioners know that ro external nitrogen inputs (Fageria Table 5. Yields and LER () values - of various vegetable crop combinations in an urban farm in Berkeley, California (Altieri, unpublished data). tating plant families reduces soil-borne diseases and reportedsoil-dwelling that insectsgrowing that beans are after specific wheat to certain resulted crop in Cuadro 5. Rendimientos y UET (índices de uso de la tierra) para varias combinaciones de hortalizas en una granja reducedfamilies. root For example,rot severity Maloy and and increased Burkholder yield. (1959) They urbana en Berkeley, California (Altieri, datos no publicados).

Crop Species Polyculture rootalso concludedrot incidence. that A a numberminimum of ofcover 3-year crops rotation and green with Mizuna 0.599 0.603 manureswheat was used needed in rotation in fields schemes with a can history also ofbe severeeffec tive in suppressing nematode populations and infec Arugula 0.410 0.334 tions (Clark, 2012). Sudan grass (Sorghum sudanenese- LER 1.84 - (Steud.) Millsp. & Chase) has been reported as an effec Kale 1.11 0.522 tive green manure to reduce reproduction of the nema tode Meloidogyne hapla and, therefore, its damage to- Arugula 0.41 0.243 lettuce plants (Abawi and Widmer, 2000). - LER 1.06 Green Lettuce 0.501 0.31 Intercropping Kale 1.11 1.46 LER 1.92 the same plot of land at the same time, resulting in in Mizuna 0.599 0.96 creasedIntercropping , involves which mixtures improves of annualSOM, soil crops cover, in Green Lettuce 0.501 0.85 water retention capacity and microclimatic conditions- favoring production (Francis, 1986). Crop diversity LER 3.2 also enhances resilience to climatic variability and fa Mizuna 0.599 0.85 vors and microorganisms involved in im Arugula 0.401 proved nutrient cycling, soil fertility, and pest regula- LER 2.0 tion (Altieri and Nicholls, 2004). - 0.27 -

AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS 55 Altieri & Nicholls / Agro Sur 46(2): 49-60, 2018

Results from a study involving different combina remain on host plants occurring in monocultures than tions of peanut, watermelon, okra, , and pepper in brassica crops associated with other plant species; planted alone or in various intercropping combina- (b) pests immigrate into polyculture systems at signi nations with peanut, watermelon and okra and peanut,- - watermelon,tions revealed okra positive and LERcowpea values. consistently Within-row over combi yiel- herficantly rates lower than from rates monocultures, than into monoculture (c) if main crops systems; are ded in two consecutive years with LER values ranging intercroppedpests emigrate with from trap crops, these at plantssignificantly can divert hig- - pests from main crops, thus feeding is concen most all instances over their monoculture counterparts trated on the trap crop, instead of on the crop, and (d) (Lithourgidisfrom 1.17 to 1.25. et al .,Intercropping 2011). Furthermore, increased the yields intercrop in al- natural enemies are favored in diverse gardens thus,- the soils and partially returning it via decomposing- and Nicholls, 2004). ping systems more efficiently removed nitrogen from exerting mortality on herbivorous populations (Altieri in the intercropped systems (Ouma and Geruto, 2010). biomass, indicating increased resource use efficiency sociatedStudies with conducted wild mustard, in California Brassica revealed campestris that, than flea production principle based on several years of studies inbeetle monocultures numbers were (Altieri significantly and Gliessman, lower in 1983).collards Flea as- Zhang and Li (2003) proposed a competition-recovery were diverted from collards resulting in dilu growth,on intercropping nutrient uptakeof short-season/long-season and yield of dominant species,species. tedbeetles feeding preferred on the thiscollards plant (Table over 6). collards, The authors thus fleaar butThey decreases suggest growth that interspecific and nutrient interaction uptake of the increases subor gued that wild mustards have higher concentrations of- - dominant species is harvested, the subordinate species- adults) than collards, and therefore the preference of hasdinate a recovery species duringor complementary the co-existence process, stage. so After that the allylisothiocyanate (a powerful attractant to flea degrees of attraction to the foliage levels of this parti red with corresponding sole species. cularflea beetles glucosinolate for wild in mustard the weeds simply and reflectedcollards. Figuredifferent 2, final yields remain unchanged or even increase compa- - Insect pest regulation in diversified urban farms grownillustrates as monoculturesthis preference are in thegreater field thanby showing on collards that intercroppedpopulation densities with wild of mustards flea beetles and on with collard a non plants host ban farms can achieve positive pest management plant such as barley (Hordeum vulgare L.) (Altieri and outcomes,The literature including suggests natural that enemy diversification enhancement, in ur- reduction of pest abundance, and reduction of crop damage (Altieri and Nicholls, 2004). Many studies Schmidt, 1986). Although barley as a non-host might conducted on brassica crops (collards, broccoli, brus have effect a disrupting effect on coloniza- sel sprouts, etc.) have reported four major trends: (a) tion,In the an trapurban cropping setting effect in Albany, of wild California, mustards exertedduring - summera stronger and influence fall of 2004, on beetle insect abundance populations in this and case. yield aphids and flea beetles are more likely to locate and

Table 6. Flea beetles (Phyllotreta cruciferae (Altieri and Gliessman, 1983). Goeze, 1771) in various collard cropping systems in Santa Cruz, California Cuadro 6. Poblaciones del crisomelido (Phyllotreta cruciferae Santa Cruz, California (Altieri and Gliessman, 1983). Goeze, 1771) en varios sistemas de produccion de coles en No. of flea beetles Cropping system Per 10 collards* Per 5 weeds‪ Damaged Leaves per collard Collard monoculture % 34.0a ____ 54.4a Weedy all season 6.6b 25.0 29.9b Weed-free all season

2.3c ____ 34.1b Collard- bean polyculture Weedy all season 0.6c 15.0 32.1b Weed-free all season

‪Brassica spp. weeds. *MeansPercent of leavesfollowed in eachby the collard same letterplant inwith each insect column damage are not significantly different (P = 0.05). (all means are averages of three sampling dates).

56 AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS Urban Agroecology as sustainable alternative

Figure 2. PopulationFigure trends 2. of Phyllotreta cruciferae plant (wild mustard) and a nonhost plant (barley) (Altieri and Schmidt, 1986). in collard monocultures and in collard polycultures mixed with a host Figura 2. Tendencias poblacionales de Phyllotreta cruciferae en mono y policultivos de coles mezcladas con una planta hospedera (mostaza silvestre) y una no hospedera (cebada) (Altieri and Schmidt, 1986).

parameters were monitored in broccoli monoculture coli. The seasonal effectiveness of natural enemies and polyculture systems with or without competition of B. brassicae was increased by composting despite from Brassica spp. (mustard), or Fagopyrum esculen- tum (Ponti et al. organic (compost) or synthetic . Intercrop lowerA survey aphid ofabundance 25 community in compost-fertilized gardens in the California broccoli Moench, 1974 (buckwheat), and with addition of central coast, 2007). conducted by Egerer et al. (2018) in June summer and mustard was found to be better than- and August, found that in June, aphid density increa buckwheatping significantly at controlling reduced pestaphids, pressure probably only due in theto sed with host plant volume but decreased with greater mustard being able to serve as a trap crop (Figure 3). - A positive effect of intercropping on natural enemies aphid density. In August, host plant volume similarly positivelyfloral density, affected while aphid parasitism density was and only host influenced plant densi by ty had a strong negative effect on parasitism. Authors rasitizationwas evident rates in the on summerbroccoli. experiment,Synthetically whenfertilized the suggested that urban gardeners might be able to re- broccoliproximity produced of flowers more significantly biomass, enhanced but also aphidrecruited pa- higher pest numbers. It is known that compost relea ce density and strategically spatially distributing host- ses mineral nitrogen in the soil at a slower rate than plantsduce aphid throughout pest densities garden by beds. increasing A common floral resourrecom- synthetic fertilizer and this has been related to lower- mended strategy to enhance biological foliar nitrogen content leading to reduced pest inci - dence. Despite lower aphid densities, however, broc kwheat, sweet alyssum, coriander, wild carrot, phace coli fertilized with compost consistently had higher- liais toand plant fennel. borders If these or speciesstrips of are34 flowers planted such early as in buc the- parasitization rates than synthetically fertilized plants- -

lady bugs and many parasitic wasps could increase decreased pest abundance in broccoli regardless of season in urban farms, the abundance of syrphid flies, (Table 7). In summary, intercropping and composting (Altieri and Nicholls, 2005). A higher diversity and In addition, depending on the intercropped plant and abundanceas the flowers of natural provide enemies them with early pollen in the and season nectar is theinterspecific growing season competition (summer from vs. intercropped fall), intercropping plants. enhanced natural enemies of cabbage aphid in broc (Mata et al., usually useful in preventing pest population build-up - 2017). AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS

57 Altieri & Nicholls / Agro Sur 46(2): 49-60, 2018

Figure 3. Figure 3. M, mustard Cumulative polyculture counts without of aphids competition; on five broccoliMC, mustard plants polyculture per plot at withthe different competition) sampling and datesby fertilizer as influenced levels (S, by syntheticcropping system levels (“-” monoculture; B, buckwheat polyculture without competition; BC, buckwheat polyculture etwith al. competition; Figura 3. Densidades acumuladas de pulgones en cinco plantas por parcela en diferentes épocas de muestreo según la fertilizer; O, organic fertilizer-compost) in two (summer and fall) experiments at Albany, CA in 2004 (Ponti , 2007). con competencia; M, policultivo de mostaza sin competencia; MC, policultivo de mostaza con competencia) y por niveles de influencia de sistemas de cultivo (“-” monocultivo; B, policultivos de alforfón sin competencia; BC, policultivo de alforfón California en 2014 (Ponti et al. fertilización (S, fertilizante sintético; O, fertilizante orgánico-compost) en dos experimentos (verano y otoño) en Albany, , 2007).

Table 7. Seasonal cabbage aphid parasitism (±SE) by Dia- CONCLUSIONS retiella rapae (M’Intosh, 1855) during summer and autumn et al., fertilization experiments at Albany, California (Ponti Cuadro 7. Parasitismo estacional del pulgon de la col (±DE) Examples from urban farms around the world su- 2007). potentially be achieved at the level of a community or por la avispa Diaretiella rapae (M’Intosh, 1855) ggest that self-sufficiency in terms of vegetables could perimentos de fertilización en verano y otoño en Albany, Cali fornia (Ponti et al. durante ex- city if such UA farms were re-designed and managed - farms can be up to 15 times more productive in terms of totalusing output agroecological than rural principles. holdings. In Well-designed Cuba, an area ofurban just , 2007). % Parasitism one square meter can provide 20 35kg of food a year (200 Summera Autumnb tomatoes (30 kg) per year, 36 heads of lettuce every 60 days, 10 cabbages every 90 days and 100 onions every Synthetic 4.2 ± 0.4 0.5 ± 0.1 120 days). Considering the average requirements for , a Organic 8.3 ± 1.3 2.5 ± 1.4 10 m2 bed in an intensive garden can yield up to 200-1 onekg of person vegetables of vegetable per year, crops potentially is about providing 72 kg year about a P = 0.004 synthetic vs. organic fertilizer (F1,20 b P = 0.03 synthetic vs. organic fertilizer (F 1,20 = 5.14) (Infante, 1986). = 9.97) 55 % of the yearly vegetable needs of a family of five

58 AGROECOLOGY AND SUSTAINABLE AGRICULTURAL SYSTEMS Urban Agroecology as sustainable alternative

A productive UA also requires that citizens have Agriculture. CRC Press. Boca Raton. access to sources of green biomass and/or manure as Altieri, M.A., Nicholls, C.I., 2004. Biodiversity and pest ma nutrient sources. Some cities provide weekly residen nagement in . The Harworth Press, - tial collection for plant debris and food scraps. In 2010, Binghamton, New York. the city of Berkeley, California collected 13,650 tons of- Altieri, M.A., Nicholls, C.I., 2005. Manage Insects on Your Farm: A Guide to Ecological Strategies. Sustainable Agri residential food and green waste and 6,500 tons of food scraps from commercial customers. This material is llege Park, MD. - processed by a private composting company, which at Altieri,culture M.A., ResearchNicholls, C.I.,and Henao,Education A., Lana,Handbook M.A., Series2015. 7.Agro Co- the end of each month from February to October makes 3 of compost to residents. ming systems. for Sustainable Development- ecology and the design of change-resilient far- freelydiversity, available complemented 61-92 m by organic soil management. TogetherAgroecological these comprise designs an feature effective well-planned agroecological crop 35(3) 869-890. https://doi.org/10.1007/s13593-015- strategy to improve nutrient cycling and soil fertility. arbuscular0285-2g mycorrhizal symbiosis. Mycorrhiza 11(1), Auge, R.M., 2001. Water relations, drought and vesicular- They also limit nutrient and water losses, reduce im pacts of pests, diseases and weeds and enhance overall Badami, M.G., Ramankutty, N., 2015. Urban agriculture and food3-42. security: A critique based on an assessment of productivity and resilience of the cropping system (Ni- cholls et al., 2016). But diversifying urban farms per se https://doi.org/10.1016/j.gfs.2014.10.003 - does not necessarily mean that they are being managed Barthel,urban S., Isendahl, land constraints. C., 2013. Urban Global gardens, Food Security Agriculture, 4, 8-15. and agroecologically, unless the collection of crops chosen interacts biologically. Many urban farms are diversi 234.water https://doi.org/10.1016/j.ecolecon.2012.06.018 management: Sources of resilience for long-term Such farms do not reach full potential, as the crops do- Brown,food K.H., security Jameton, in cities.A.L., 2000. Ecological Public EconomicsHealth Implications 86, 224- notfied interactin response with to each food other security synergistically, or market demands.often ne of Urban Agriculture. Journal of Public Health Policy or . The key is for researchers and- cessitating external conventional or organic inputs of Agriculture21(1), 20-39. Network https://doi.org/10.2307/3343472 Handbook series 9. Beltsville, MD. Clark, A., 2007. Managing cover crops profitably. Sustainablerd Edition that complement each other to achieve over yielding. practitioners to find the right combinations of crops Enhancing productivity of urban farms can contribute Clark,Clinton, A., N., 2012. Stuhlmacher, Managing M.,Cover Miles, Crops A., ProfitablyUludere Aragon,3 N., substantially to improving local food security. In addi Wagner,USDA-SARE, M., Georgescu,Beltsville. M., Herwig, C., Gong, P., 2018. A tion, biodiverse UA offers potential to ameliorate a host Global Geospatial Ecosystem Services Estimate of Ur of urban environmental problems by increasing vege- tation cover, which provides a host of ecological servi - ces such as conservation of plant and insect biodiversi- Cheeke,ban. T.E., Agriculture. Coleman, D.C.,Earth’s Wall, Future D.C., 6(1),2012. 40-60. Microbial https://doi. Ecology - inorg/10.1002/2017EF000536 Sustainable Agroecosystems CRC Press, Boca Raton. ty, uptake of CO2 and resiliency to weather variability (Faeth et al., 2011). - Daisley, L.E.A., Chong, S.K., Olsen, F.J., Singh, L., George, C.,

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