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Soil, Uruguay

INGLEBY Focus on SoilArticles on soil by Ken G. Cassman March 2016 # 1

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Dear Ingleby team,2016 is the Ingleby "Year of Soils". To support this, we have created this news-letter focusing solely on soil. Here, I will write a series of articles on managing our soils to improve production and profitability, while conserving natural re-sources and protecting water quality. The role soils play in supporting human existence and the economic link be-tween soil quality and crop production are the focus of this first article. Following articles will examine:

> The challenge of maintaining soil organic matter > The delicate balancing act of nitrogen management > The role of soil and plant tissue testing to optimise soil supply of essential

nutrients > The importance of favourable soil physical properties

For any questions or discussion, you are welcome to contact me on +1 402 613 9888 or kgc1consulting@gmail.com.

Soil is the thin veneer of the earth’s crust that is responsible for sustaining terrestrial life.

While all of these functions are im-portant, the primary role of agricul-tural soils is to produce food, fibre, for-

age, and biomass to support human well-being.

The good news is that im-proving soil properties that support crops will also con-

tribute positively to the other four ecosystem

services soils provide. And any deterioration in soil properties that support crops will re-duce the capacity of

soils to provide these other services. Hence, Focus on Soil

articles will discuss how to maintain or improve soil quality properties with greatest impact on prof-

itable farming. These include the at-tributes shown in the table on the next page.

The question arises: “Why seek to maintain or improve soil quality if it costs money to do so?” The answer is simple: degrading soil results in higher production costs and lower yields.

Ken G. Cassman

Ingleby Environmental Committee adviser, and a Robert B. Daugherty Professor of

Agronomy, University of Nebraska

Soil is a living, breathing, evolving matrix that supports plants by storing and

providing water and nutri-ents. Plant leaves that are well-supplied with these resources transform the energy from sunlight to produce biomass, seeds, fruit, and tubers.

Modern civilisations emerged 10,000 - 12,000 years ago when humans learned how to manage soils for crop pro-duction. Indeed, history teaches that civilisations rise and fall in relation to the quality of their soils.

Soil provides other ecosystem ser-vices in addition to support for agri-culture. These are: a) habitat for organisms including

bacteria, fungi, protozoa, nema-todes, worms, reptiles and mam-mals;

b) storing water to capture rainfall and reduce runoff and flooding;

c) filtering and detoxifying pollutants to protect groundwater quality;

d) regulating atmospheric composi-tion through releasing, captur-ing, or retaining carbon dioxide, methane, and nitrous oxides - each a powerful greenhouse gas.

INGLEBY Focus on SoilArticles on soil by Ken G. Cassman March 2016 # 1

SOIL PROPERTIES

Type Soil quality attribute Functions influenced Measurement

Physical properties

> Rootable soil depth > Size and continuity of pores

> Compaction > Soil tilth

> Water and nutrient storage capacity

> Aeration > Water infiltration rate > Water holding capacity > Root growth > Energy for tillage

> Depth to bedrock > Soil erosion rate > Bulk density > Water infiltration rate > Water retention curve > Penetrometer resistance

Chemical properties

> Organic matter > Essential nutrient reserves

> pH > Salinity > Toxicities (boron, aluminium, etc.)

> Soil structure > Water holding capacity > Availability and balance of nutrients

> Root growth > Plant nutrient status > Plant toxicity

> Organic matter content > Soil-test nutrient levels > pH meter > Electrical conductivity > Tests for toxic elements

Biological properties

> Microbial populations (general)

> Pathogenic microbe populations

> Insect pest populations > Parasitic nematodes

> Microbial biomass > Disease incidence and severity

> Insect pest damage > Disease suppression > Nematode damage

> Microbial biomass by fumigation method

> Soil respiration rate > Soil-borne disease inoculum levels

> Soil insect and nematode pest population levels

Ken explaining soil structure and properties

to the Ingleby Board

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The figure below shows a relation-ship between crop yield and input re-quirements in soils of different qual-ity. Inputs include fertiliser and other nutrient sources, pesticides, and fossil fuels for tillage and sowing.

While the original soil (A) had good properties that produced high yields with efficient use of inputs, degraded soils give lower yields because of de-teriorated soil quality. While soil deg-radation can take many forms (B, C, or D), in all cases it leads to reduced yields with the same or greater input

requirements to maintain yields. Like-wise, minor stress (e.g. mild drought) can cause relatively large yield de-creases in degraded soils. Eventually, it becomes unprofitable to continue crop production and the land must be returned to less intensive use, such as grazing with lower land value.

Two examples of degraded soil qual-ity found on Ingleby farms because of previous owners include:

> soil compaction and reduced root-ing zone that limits both water and

nutrient uptake. Large amounts of fertiliser and above-average rainfall are then needed to achieve high yields;

> severe soil potassium deficiencies due to cropping systems that heav-ily depleted potassium without replenishing with fertilisers or ma-nure.

In both cases, Ingleby farm managers must now use much greater amounts of fertilisers, pesticides, and energy than would be needed if the soil dete-rioration had been avoided.

Fortunately, soil quality can be re-stored with improved tillage and fer-tiliser management practices, but it requires increased costs over a con-siderable period of time to do so. And most important: The short-term cost-savings from practices that degrade soil quality are much less than the long-term costs of restoring it.

Hence, maintaining or improving soil quality is essential for profitable farming. It helps reduce requirements for fertilisers, pesticides and energy, which in turn decreases negative envi-ronmental impacts from use of these inputs.

The goal of the soil sampling pro-tocols for the Ingleby Sustainability Report, done on each farm every five years, is to measure key properties that provide a benchmark of soil qual-ity, and over time, to ensure our cur-rent management practices maintain or improve these critical soil attributes.

INPUTS

YIE

LD

Decreased soil quality

Original soil

Ya

a

BC

D

YBYC

YD

IX