Farm advice: Know you soil

Farm advice: Know you soil

The foundation of effective irrigation management is understanding our soils, says IrrigationNZ's Stephan McNally

At IrrigationNZ, we recognise the pivotal aspect of soil knowledge in freshwater management, particularly in irrigation system design and management best practices.

Many farmers and growers excel in understanding their land and its nuances, their crops, animals, market forces, and year-on-year climate extremes, yet the focus on things happening well below the soil surface can remain overlooked.

Beyond cursory digs into the topsoil, taking time to observe changes in soil colour, composition, and layers (soil horizons) in a deeper dig can offer valuable insights into structure, texture, and water retention capacities.

Soil characteristics differ widely across New Zealand. The origins and ages of these soils vary greatly even within districts and paddocks, extending deep beyond the surface layer you might know well. Root zones can influence water-holding capacity and productivity to depths of more than 80cm, needing a comprehensive understanding of soil composition and structure. It’s more than just the top 20cm.

The soil’s water-holding capacity and fertility are influenced by a combination of factors, including texture (the ratio of sand, silt, and clay), pore spaces for water and air, organic matter content, and nutrient retention capability.

These factors directly affect irrigation scheduling, with excessive water application leading to drainage and nutrient loss and too rapid application causing runoff and sediment mobilisation.

Good practice irrigation design and management takes into account an understanding of the soils’ ability to infiltrate and hold water to avoid inefficient water use and maximise the benefit from expensive nutrients.

Have you and your irrigation operational staff examined the soil just to understand texture, structure, and layers? It’s essential to pay attention to the less visible but important foundation of our agricultural endeavours.

Understanding soil dynamics, such as water-holding capacity, infiltration rates, and permeability enables customised irrigation plans, maximising plant water and nutrient uptake while reducing environmental harm. Enhanced soil knowledge empowers stakeholders to make sustainable water management decisions.

The foundation of effective irrigation management is understanding our soils.

As we face weather changes and water scarcity, it’s crucial to delve into soil characteristics. By doing so, we can boost agricultural productivity, conserve water, and reduce environmental risks, leading to a more resilient and sustainable agricultural sector. Let’s dig deeper and unlock the potential beneath our feet.

IrrigationNZ is a national membership organisation that looks after the interests of irrigating farmers, growers, and the industry professionals who service them.

We actively engage with our members and other stakeholders in the delivery of irrigation best practices and helping shape freshwater policy.

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