SISC's initial suite of metrics addresses some of the most critical areas impacted by the production of fruits, nuts and vegetables. Brief metric summaries, below, include both the rationale for inclusion and a technical overview. To download full metric content, click the link after each summary.

* To download supporting technical guidelines, please scroll down to the Guidelines section.

Metric Summaries

 

Applied Water Use Efficiency 

Water is already in short supply in parts of the world and will become increasingly scarce as populations increase and climate change continues to alter weather patterns. In many places, water is also getting more expensive. Efficient irrigation is a critical component of sustainable crop production.

The Applied Water Use Efficiency metric measures the total amount of applied water used to produce the crop. Note: a second metric, in development but not yet finalized, is Simple Irrigation Efficiency, which measures the amount of water applied to the crop relative to the crop’s water need resulting from transpiration and soil evaporation (ETc). 

Simple Irrigation Efficiency

The Simple Irrigation Efficiency (SIE) metric measures how efficiently irrigation water is used to meet a crop's water demand. A grower can improve the SIE metric score by reducing losses of water to pathways that don’t contribute to crop growth, including soil evaporation, percolation and run-off.  As such, the SIE metric is an indicator of how productively the water resource is being used. 

Habitat and Biodiversity

This metric was developed to measure on farm habitat and biodiversity. Biodiversity is the variety and health of organisms at all levels, from microbes to mammals. Habitats are the environments that support these various organisms. Increased biodiversity and habitat is generally associated with greater ecosystem health, so growers can use this metric as a tool to track continual improvement of ecosystem health on their farm over time.

This metric documents and tracks the extent of on farm habitat and practices associated with positive biodiversity results.

 

Energy Use

Crop production requires a substantial amount of fuel and electricity to power farm machinery and irrigation. In addition, a sizeable amount of energy is required to produce fertilizers, particularly those containing nitrogen. Energy production is resource-intensive regardless of the production method. As energy costs rise, it will be critical to track agriculture's use of energy.

The Energy Use metric includes direct energy from fuel and electricity and indirect energy in the form of energy required to produce fertilizers (“embedded energy”). Because growers of multiple crops often do not know how much fuel and electricity was used any particular crop, we have developed a tool to help allocate data to a particular crop or management area.  This may also be useful to growers of a single crop who would like to estimate energy use by field.

  •  View or download the full Energy Use metric.

  •  For a Webinar excerpt covering only Energy Use, click here.

Nitrogen Use

Nitrogen is a key nutrient for crop production. However, when transported off the farm, it poses an economic loss to the grower and can have detrimental impacts to surface and groundwater quality. Nitrogen lost to the atmosphere as nitrous oxide (N2O) is a potent greenhouse gas, with ~300 times the warming potential of carbon dioxide (CO2). Both nitrogen and phosphorus were chosen for the nutrient metrics as they are widely recognized as pollutants and are a higher priority for environmental improvement than potassium (see also: Phosphorus Use metric).

The Nitrogen Use metric aims to capture the most significant sources of nitrogen being added to the farm system. It includes nitrogen from synthetic and organic fertilizers, nitrates dissolved in irrigation water, and nitrogen fixed from the air by leguminous crops. By accounting for all of these significant sources of nitrogen, a grower should be able to increase the efficiency of nutrient use in crop production.

Phosphorus Use

Phosphorus (P) is a key nutrient for crop production. However, when transported off the farm, it poses an economic loss to the grower and can negatively impact surface and groundwater quality. Both nitrogen and phosphorus were chosen for the nutrient metrics because they are widely recognized as pollutants and are a higher priority for environmental improvement than potassium (see also: Nitrogen Use metric).

The amount of phosphorus that plants can access in soil varies widely. Good stewardship includes taking advantage of existing soil P reserves before adding more P fertilizer.

The approach taken in the Phosphorus Use metric differs from that of the Nitrogen Use metric because the two elements behave differently in the environment. Nitrogen is much more mobile than phosphorus; in contrast, most forms of P are less soluble than nitrate and P has no significant gas phase.

The Phosphorus Use metric takes advantage of the fact that when labs return results of P tests to growers they also offer recommendations for how much P a grower should apply. These recommendations are based on several factors, but a major determinant is the amount of P already available in the soil. The metric, therefore, looks at how much P the grower has applied above that recommended value.

Soil Organic Matter

Soil Organic Matter (SOM) is the organic fraction of soil excluding non-decomposed plant and animal residues. SOM is usually measured by the amount of Total Organic Carbon (TOC) present in the soil. Increasing amounts of SOM, and hence organic carbon, provide significant agronomic and environ-mental benefits including improved nutrient delivery to plants, water retention, drainage, and resistance to disease and erosion. A soil’s ability to store SOM varies greatly depending on climate, soil texture and soil type. To normalize against this variability, SOM is compared with a site-specific estimate of the soil’s potential to hold SOM.

The Soil Organic Matter metric is the measured TOC of the soil divided by that soil’s potential to store organic carbon, as modeled using USDA’s Soil Management Assessment Framework (SMAF).

 

Food Loss

The Food Loss metric is intended for growers to track and report the amount of food grown to the point of maturity but not used; in other words: crops that were “ready for harvest” but did not enter the supply chain for human consumption. Understanding this amount of product ‘loss,’ or product left in the field or culled out at various other stages in the supply chain, will provide growers and associated buyers with useful data on where and why loss is occurring within the boundaries of a single farm operation. The Food Loss metric measures loss at each operational unit under a grower’s operation which may include fields, packinghouse/processing facility, storage, and transport between each link. This metric also tracks destinations for loss, drivers for loss, product loss excluding a change in moisture content, and opportunity cost for returning to the field to harvest what would otherwise become loss. By measuring loss, it is possible for growers to identify adjustment opportunities to improve operational efficiencies.

Guidelines

The supporting guidelines are listed by relevant metric (note, some guidelines support more than one metric).

Guidelines: Nitrogen Use Metric

Protocol for Estimating Nitrogen Fixation of Leguminous Crops

Protocol for Sampling and Testing for Nitrogen Concentration in Irrigation Water

Estimating Nitrogen and Phosphorous Content for Organic Fertilizers

Guidelines: Phosphorous Use Metric

Estimating Nitrogen and Phosphorous Content for Organic Fertilizers

Protocol for Soil Sampling

Guideline: Soil Organic Matter Metric

Protocol for Soil Sampling

Email: info@stewardshipindex.org     SISC is a fiscally sponsered project of Social and Environmental Entrepreneurs 

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