Sustainable Agriculture has become a popular theme in development circles. In fact, it appears everything needs to be “sustainable” these days. However, the focus on EMI projects is the inclusion of Sustainable Agriculture where appropriate for client ministries. This is so the project – whether it be a school, hospital, or orphanage – can be maintained (or supported to the desired degree or target) by production of a reliable supply of food.

There are many definitions of “sustainability”, depending on the context and the type of project. Generally, sustainability in EMI projects includes economic, environmental and social aspects. The “sweet spot” of the Venn diagram (below) is where sustainability can be achieved (Choi, 2015).^{Note 1} In addition, the consequences of including two aspects but not the third is apparent.

Consider, for example, the effects of open cast mining. This may provide economic benefits for the mining company and resources for industry, as well as social benefits in the form of employment and income for the community. However, it can be deficient in the environmental aspects of scarred landscapes left behind. This may be an “Equitable” situation but not a “Sustainable” one since it involves the exploitation of a non-renewable resource.

Current thought on sustainability has covered the three topics above: Environmental, Social and Economic - sometimes with varying degrees of emphasis on each topic. When considering agriculture, the situation is somewhat different. Agriculture is an ongoing activity and is anticipated to be under continuous review. Implicit in the ongoing discussions of Sustainable Agriculture is the (usually unstated) assumption that if something is sustainable, it will last forever!

However, there is a saying:

“In the short term, everything is sustainable.
In the long term, nothing is sustainable!” (Anon)

Accordingly, there is a fourth aspect that has received little attention: This is the Time Period for which something is considered to be sustainable. An alternative way of looking at Sustainable Agriculture is to address sustainability as a process – an ongoing evaluation to ensure agricultural productivity is maintained. One of the primary measures of agricultural productivity is yield. Monitoring of yield on a continuing basis will provide an indication of changing conditions and prompt the necessity for further evaluation.

In certain contexts, sustainability has an implicit timeframe. Buildings, for example, are generally designed for an anticipated lifespan of 50 years. Dams and bridges are usually considered for longer periods due to their community importance and since their failure would have a wider impact.

Following research at Colorado State University, an investigation of agricultural practices in the western US indicated that a 50-year (or two generation) time period was appropriate for consideration of technology in current use (Sands and Podmore, 1999).^{Note 2} The factors influencing this choice were the anticipated time-periods for technological and sociological changes to take place. After this time, the surveyed practices were considered to have changed and were no longer valid for the analysis.

When applying this research concept in the majority world, where technological changes were anticipated to be slower and social changes slower still, a time-period of 100 years (or four generations) was estimated. This is only an estimate based on experience, however. Developments such as the adoption of mobile phone technology in majority world countries shows that the impact of technology changes needs periodic evaluation.

Adoption of changing technologies in some areas of the majority world can be more rapid and these emerging advances may invalidate the 100-year time-period. However, in some parts of the world, settled agriculture has been going on for some 9,000 years. Farmers are generally “risk averse” and so little may have changed over this period since changes in practices might adversely affect yields. This is the case when agriculture is the livelihood and the survival of the farmer and his family from one crop season to the next is at stake.

Accordingly, the 100-year time-period is proposed as a starting point when considering agricultural technologies and practices for EMI projects. When proposing a cultivation practice or cropping system, attention must be paid to the economic, environmental, and social impacts. The impact of agricultural practices are considered within the selected timeframe. (Please note that for animal-based agriculture, the considerations are different since the useful lifespan of the animals must be included.)

However, there is little current research to suggest firm guidelines. In addition, “best practices” based on local experience need to be defined before they can be adopted. As an example, the evaluation of cropped agriculture for sustainability can be considered:

For a given farming practice, an appropriate time-period for sustainability must be established – say 50 years. While monitoring of the agricultural system may be ongoing, a thorough re-evaluation should be performed at the 25-year halfway point to ensure conditions are stable. Obviously, only those aspects that change need investigation. At one time, climate would have been considered as constant but that is no longer the case. Soil structure can change, but only slowly, while soil fertility varies more quickly. This evaluation process gives a basis for applying the criteria to the farming system on a timely basis. The object is to identify modifications to the farming system so that its productivity can be maintained.

Factors considered in an evaluation are given below. It should be noted that some of these categories may be predefined by the nature of the location, altitude, and climate under consideration. These conditions should be documented to recognize the opportunities for and limitations on agriculture at a given site:

1. Climate – inferred from location of the site under consideration.
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   1. Growing season(s) – the location and climate will indicate the growing season(s) present, usually delineated by temperature and rainfall.
   2. Seasonal potential evapotranspiration – the amount of water used by crops during the growing season, developed from climatic parameters and the crop characteristics.
   3. Seasonal rainfall – quantity, intensity and dependability.
2. Topography – determined from the nature of the site, usually developed from site inspection and a topographic survey.
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   1. Areal extent of land under consideration –from the site boundaries.
   2. Distribution of land – either as a single tract or multiple pieces, whether separate or contiguous.
   3. Shape of land area – from the site survey.
   4. Surface slope – as it varies over the site. A contour map is generally developed from the site survey.
   5. Surface roughness (micro-topography) – from site inspection, as it affects water flow over the land surface. Also may affect ease of site access.
3. Soils – information obtained from the site, assisted by soils maps. (Soils maps typically available are on a large scale and only provide a general indication of the soils in the area.)
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   1. Soil texture – expressed as the percentage composition of sand, silt, and clay according to the USDA classification.
   2. Water holding capacity (usually given as Total Available Water) – an expression of the amount of water which can be held in the soil and a proportion of which is available for plant use.
   3. Depth of soil profile – obtained from a soil profile, giving the depth of the topsoil suitable for root growth.
   4. Infiltration rate – the ability of water to enter the soil surface and be stored in the soil profile.
   5. Drainage – the ease with which water moves through the soil profile, indicated by the soil’s hydraulic conductivity.
   6. Fertility and soil chemistry – the chemical status of the soil, which is indicative of the fertility level of the soil for plant growth. Determined from soil samples in a soil analysis laboratory although an approximate indication can be given by field tests.
   7. Salinity level – the soil salinity can be a limiting factor in crop growth and is usually determined from the electrical conductivity of a saturated soil extract.
   8. Erodibility – the ease of erosion of soils will indicate the need for erosion control measures on the site.
   9. Potential for surface crusting – some soils form significant soil crusts under the action of rainfall impact, restricting the ability of plant seedlings to emerge from the soil.
4. Water Supply – where water is required for crop growth and development in excess of natural rainfall in the form of irrigation.
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   1. Source(s) and location(s) – since the water available is not generally local to the required point of application.
   2. Amount of water – the volume and flow rate available from the source(s) during the growing season.
   3. Timing – since the water available can be variable during and between growing seasons.
   4. Availability – (see D.2).
   5. Dependability – the variability of the water sources compared to the crop growing season requirements.
   6. Quality – Water quality is affected by salinity, sediment load, and chemical pollutants – all of which can affect plant growth and development.
   7. Equitability – where water use from a given source is shared by several users, the equality of water distribution needs to be determined.
   8. Cost –while some societies regard water as a “free good,” there are costs associated with its supply and distribution, e.g. pumping energy costs and canal or pipeline maintenance.
5. Cropping System – the crops grown will be determined by local needs and the crop types and varieties available.
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   1. Crops – the traditional crops grown may be necessary for cultural reasons. Alternative crops may be substituted due to higher yields and/or greater profitability.
   2. Crop consumptive use – the seasonal water use of crops varies by crop type and variety (see A.2).
   3. Seasonal, annual, or perennial crops – crops vary by length of growing season and the need for annual planting.
   4. Rooting depths – crops vary by rooting depth, which can also be affected by the depth of the soil profile (see C.3).
   5. Drought tolerance – in times when water availability is limited, the ability of crops to withstand water shortage.
   6. Physiological critical water stress periods – some crops are particularly sensitive to water shortage during certain periods of the growing season.
   7. Tolerance to wetting/surface ponding – some crops are sensitive to excess water and have specific root aeration requirements.
   8. Planting method – the planting method will depend on the level of mechanization used, whether row planted, drilled, or broadcast.
6. System Management – assessing the level of management present on the system.
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   1. Education level – the level of education and appropriateness of those in charge of managing the system and that of the labor employed.
   2. Technology level – the familiarity of the management and labor with the technology used and the repair infrastructure required. Also the necessary provisions for marketing of the crops produced, including storage requirements.
7. Tillage and Harvesting Equipment – mechanization is a significant agent in the improvement of productivity.
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   1. Level of mechanization –how much mechanization is appropriate will be dependent on the items in Section F – System Management.
   2. Equipment employed – the size and maneuverability of the machinery used must be suited to the land areas.
8. Drainage Requirement – the removal of excess water from the site to ensure good growing conditions for the crops.
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   1. Groundwater level and fluctuation – monitoring during the growing season to ensure that water is not present in the crop root zone for extended periods.
   2. Groundwater quality – salinity in groundwater is frequently harmful to optimal crop growth.
   3. Outlets for drainage water – disposing of excess water in growing season in outlets that do not cause harm downstream.
9. Socio-Economic Considerations – agriculture is a social as well as a technical undertaking.
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   1. Land tenure – the system of land tenure in the location is frequently a limitation to improvements in the condition of the cropped area.
   2. Land holding sizes – related to norms of land tenure, land holdings can become uneconomic when subdivided.
   3. Labor availability – the crops grown have labor requirements and, in order to be successful, that labor must be available when needed.
   4. Labor education – given the increasing complexity of efficient crop production, the educational level and appropriate experience of the management staff and labor force employed.
   5. Relative costs of labor and technology - compared to the value of production, these will establish the profitability of the system.
   6. Social organizations – such as co-operatives that enable economic advantages such as bulk purchasing and timely acquisition of inputs. Marketing of crops can also benefit from group activities.

While this list may appear daunting, many of the considerations can be determined by location, literature review, and/or previous experience. The identification of knowledge gaps can be valuable in determining the data to collect on a site visit or in interviews with local personnel. Site investigation becomes an important activity and adequate time must be devoted to determining the site conditions and local practices. The sources of local knowledge, such as Agricultural Extension Services and research stations also need to be identified.

More than a buzzword, sustainability related to agriculture has a particular context and depends on many variable aspects covering a wide range of technical and social considerations. Ongoing review of these factors within a selected time-period will indicate adjustments to the production system that will enable productivity to be maintained.