Introduction

Just as you wouldn’t begin an operating year without a financial budget, it’s just as important that you establish a nutrient budget. The escalating prices of fertilizers have increased the cost of farming per unit area, coupled with the increasing pressure of environmental regulations. Keeping a record of your nutrient inputs and outputs is paramount. The sustainability of the farm and your license to operate depends on it. At its simplest, a nutrient budget is a tool that estimates the nutrient flows in a farming system, and specifically includes estimates of nitrogen, phosphorus, potassium, Sulphur, magnesium, and calcium loss to water through leaching, plant uptake and/or run-off. Read more about macronutrients and why they are important here.

Nutrient inputs at a particular farm (spatial scale or region) should equal nutrient outputs at the same scale (or be as close to equal as possible). If not managed properly, nutrient inputs (usually from fertilizers or organic amendments) can lead to a nutrient surplus within a farm (given area). When plant nutrient surpluses exist, the potential for non-point nutrient loss is increased. For example, N applied more than plant needs can be transported out of the system in runoff or leachate or can be lost to the atmosphere as ammonia gas (by volatilization). Fertilizers applied more than plant needs can build up in soils and potentially be lost during erosion or runoff events. In cases where the soil has a low nutrient-holding capacity, plant nutrients can also leach into groundwater during heavy precipitation or irrigation events. These have been linked to surface and groundwater pollution. In addition, applying more fertilizers (nutrients) than plants need can place an unnecessary economic burden on farmers. Also, accelerated rates of nutrient loss are evidence of soil depletion and are unsustainable over the long term.

Growers need to implement best management practices (BMPs) and fertilizer management planning to reduce potential nutrient losses from agricultural fields. Demeter Ghana Limited has the expertise in developing protocols that work well for all crops’ nutrient requirements. Considering and integrating soil test results, crop nutrient requirements and other on-farm actions will lead to maximisation of profitability year on year. In turn, Demeter BMPs can help minimize economic and environmental costs.

What is a Nutrient Budget?

A nutrient budget (also called element budgets or mass balances) is a modelled calculation of nutrient losses from your farm. A nutrient budget quantifies the number of nutrients imported to and exported from a system (farm). The budget is considered in balance if inputs and outputs are equal. Like a bank account, the budget tracks inputs (credits) to the system and exports (debits) from the system to evaluate changes in nutrient stocks of the system.

It is based on soil type, topography, rainfall, irrigation type & quantity and farming system inputs and outputs. Inputs include fertiliser, supplements brought on to the farm, effluent spread on the land and use of nitrification inhibitors (e.g., Eco-N).

Nutrient budgets have been compiled around the world, using a variety of scales and methodological approaches (Walker et al., 2021). It is the measure or estimate of inputs and outputs of nutrients (usual macronutrients such as Nitrogen, Phosphorus, Potassium, Sulfur, Magnesium and Calcium) to a field, farm, or system, usually at the farm gate. Nutrient budgeting may operate on a daily, monthly, or annual time frame.

The availability of data, as well as the scale of the unit of interest, will determine which nutrient balance approach is most appropriate. A single year budget for a field might be most useful to a farmer deciding whether to apply supplemental nitrogen, Phosphorus, Potassium, calcium to a plot before planting any crop. Multi-year assessments, for example, are more appropriate for field-scale budgeting in systems that apply fertilizer or compost one in three or four years. Field-scale assessments help managers identify the movement of nutrients within farms while whole farm assessments permit comparisons between farming strategies.

Nutrient budgets may seem like an onerous task, to begin with, but when you stop to think about it it’s extremely beneficial to your business. Keeping accurate maps, blocking your farm accurately and detailing them with soil test information allows growers to hold historical data that they never had before.

With soil test data, fertiliser history and plans and nutrient summaries of what’s required in the nutrient budget, farmers can make smarter business decisions, and plan, because they have both a macro and micro view of what’s happening on their farms. The differing perspectives allow farmers to see and seize production potential and mitigate potential risks.

Why Balance Nutrition?

Cropping without replacing nutrients is like building a house on a poor foundation.  “No matter how much money you put in the top part of the house, it’s subject to premature decay because of that poor foundation,” “Balanced base elements are the foundation for plants to maximize yield.”

There has been recorded evidence of yield plateauing after over-fertilization. However, yields broke above the normal after farmers resorted to nutrient balancing. It has been documented hybrids responded better.

As the world population grows, so does its need for more food, feed, fibre and energy. This means farmers must make greater and more efficient use of mineral and organic nutrient sources.

Nutrient budgets help growers understand the balance between crop inputs and outputs. Inputs include fertilizers, nitrogen (N) fixation by legumes and applied manure, phosphorous (P), potassium (K), Calcium (Ca), Magnesium (Mg), and Sulphur (S). Outputs, or crop nutrient removal, take the form of grains, oilseeds, fruits, vegetables, fibre, hay, and forage that are harvested. Additional outputs include erosion loss, leaching, volatilization, and nitrate reduction.

Nutrient budget can be used:

• As a tool to allow to make optimum use of available nutrients.
• To design and evaluate the viability and sustainability of arable and horticultural crop rotations.
• To assess arable, horticultural rotations or whole-farm systems against organic production standards.
• To indicate likely surpluses of nitrogen and nutrients in farming or horticultural systems and risk of losses from leaching to ground and surface water, especially in Environmentally Sensitive Areas or Nitrate Vulnerable Zones.