Crop Report – Week of August 7th, 2023  

Identifying and Addressing Soil Structure Challenges  

A well-structured soil improves water infiltration, air exchange, rooting, and ultimately crop yield. On the other hand, a cloddy, dense, or compacted soil may result in ponding, nutrient losses, and restricted root systems. Poor soil structure contributes to lower crop yields, especially in seasons that are either too dry or too wet. 

In this article, we will explore how to identify soil structure challenges and how to address them through management. 

What does good soil structure look like? 

The quality of soil structure can be evaluated quickly in-field using a shovel or spade. A soil with good structure should break up easily into relatively small aggregates that are rounded and have plenty of pores and roots within them (Figure 1a). A soil with poor structure will be more difficult to break apart into small pieces and will have sharp angles and very few pores and roots (Figure 1b).

Soil structure changes with depth 

In most cases, soil structure will be best within the top two to three inches, as this is the zone of greatest root concentration and biological activity. Soil typically becomes denser below that zone. In soils with more living roots (e.g., perennial forages) and a history no till or shallow tillage, the soil below the top few inches, while firm, will also often have good porosity and rounded aggregates – both signs of good soil structure.  

Regardless of current tillage practices, soils in most cropped fields break apart along so-called “tillage layers”, which occur at the depths of past primary and secondary tillage. A tillage layer would only be considered a tillage pan if it restricts water movement and root growth.  

Observations from Ontario corn fields in 2023 

Using a method called the Visual Evaluation of Soil Structure (VESS), OMAFRA soil management specialists scored soil across a variety of corn fields this season with varying tillage and cropping practices. Below are a couple of key observations. 

Cropping practices matter: 

The best soil structure was observed in fields with perennial forages in rotation and in those with reduced tillage used alongside winter wheat and cover crops. Even in soils that had tillage layers or dense soil below the top few inches, root channels from prior crops in such fields helped corn roots access deeper soil. Taproot species such as alfalfa, brassicas, and some clovers assist with creating vertical pores, while fibrous-rooted plants such as grasses improve the tilth of the top few inches.  

Compaction is a common issue: 

Although ample rainfall lessened its impact by enabling easier rooting in many corn fields this season, soil compaction was observed at several sites. One striking example showed the impact of trafficking soil before it was fit, with corn less than two-thirds the height of normal where a manure tanker ran in spring ahead of planting (Figure 2). Corn roots growing in compacted soil are typically thicker and have fewer fine lateral roots. Compaction can occur right up to the soil surface – caused by contact pressure – or into the subsoil – often due to a high axle load; either way, it restricts normal root development and lowers yield. 

Evaluating soil structure on your own 

Getting a sense of soil structure doesn’t need to be difficult. To assess the topsoil, simply grab a spade and dig out the top 6-8 inches in a block, leaving one face undisturbed. Look at layers that exist in the topsoil and gently break the soil apart into clumps. Are large pieces of soil easy to break apart with one hand or difficult? Do smaller aggregates look rounded or have sharp, angular corners? And when you look closely, do you see lots of little holes (pores) or does the soil look solid? 

For a more systematic approach, use the Visual Evaluation of Soil Structure, which is described in text and by video on Field Crop Newshttps://fieldcropnews.com/2022/08/visual-evaluation-of-soil-structure/. And to identify subsoil compaction, use a tile probe or even a marking flag under moist field conditions to feel for resistance as you push down slow and steady.  

Improving soil structure  

Practices that contribute to good soil structure include: a crop rotation with small grains (and perennials if possible); reduced tillage, since tillage breaks down soil aggregates; addition of organic amendments; retention of crop residue; and the use of cover crops. Avoiding trafficking fields when conditions are not fit, utilizing newer tire technology, and the installation of automated deflation/inflation systems are all strategies that help prevent soil compaction.  

These best management practices work together to enhance water infiltration, crop rooting, and equipment carrying capacity – all by improving soil structure.  

Weather Data – July 31 – August 6 2023

Location	Year	Highest Temp (°C)	Lowest Temp (°C)	Rain (mm)	Rain (mm) April 1st	GDD 0C April 1st	GDD 5C April 1st	CHU May 1st
Harrow	2023	27.2	13.0	14.2	358	2084	1455	2170
	2022	31.6	18.0	34.0	336	2191	1578	2394
	10 YR Norm (11 – 20)	26.9	16.3	20.8	408	2267	1599	2496
Ridgetown	2023	27.4	11.0	5.8	424	1978	1358	2020
	2022	31.8	15.2	18.7	230	2066	1461	2211
	10 YR Avg. (2011-20)	26.3	13.7	21.3	379	2132	1470	2325
London	2023	27.8	10.5	15.5	425	1969	1349	2016
	2022	30.9	13.2	31.8	263	1998	1403	2134
	10 YR Avg. (2011-20)	26.7	14.2	27.6	382	2112	1454	2308
Brantford	2023	27.0	9.3	3.7	359	1954	1333	1128
	2022	31.8	12.4	18.1	249	2005	1399	2085
Welland	2023	28.0	12.4	14.6	393	1980	1353	2028
	2022	30.2	13.0	10.7	274	2056	1441	2206
	10 YR Avg. (2011-20)	27.1	14.4	17.8	350	2123	1464	2325
Elora	2023	27.3	8.3	26.2	361	1808	1204	1839
	2022	30.2	10.5	24.2	221	1834	1241	1911
	10 YR Avg. (2011-20)	25.2	11.9	26.0	378	1906	1260	2065
Mount Forest	2023	26.3	8.0	11.6	337	1807	1208	1847
	2022	30.3	12.8	39.9	300	1838	1252	1954
	10 YR Avg. (2011-20)	24.9	12.5	21.9	388	1888	1250	2069
Peterborough	2023	27.4	8.7	27.5	372	1836	1220	1825
	2022	31.1	9.4	2.7	265	1850	1242	1948
	10 YR Avg. (2011-20)	27.1	12.0	23.8	344	1937	1291	2073
Kemptville	2023	26.5	7.9	5.1	376	1961	1350	1981
	2022	32.8	9.4	16.8	402	1981	1354	2108
	10 YR Avg. (2011-20)	27.6	13.5	22.7	361	2032	1389	2209
Earlton	2023	26.0	6.5	7.6	274	1667	1103	1730
	2022	30.2	8.3	13.6	290	1659	1100	1803
	10 YR Avg. (2011-20)	24.3	10.2	23.0	322	1642	1080	1834
Sudbury	2023	25.2	6.7	3.9	441	1695	1132	1765
	2022	27.0	12.6	22.1	279	1669	1102	1829
	10 YR Avg. (2011-20)	25.1	12.4	25.3	354	1761	1177	1969
Thunder Bay	2023	30.9	10.0	0.3	212	1518	976	1607
	2022	27.6	10.0	8.4	418	1441	910	1527
	10 YR Avg. (2011-20)	26.1	9.5	17.4	335	1555	982	1688
Fort Frances	2023	30.7	8.0	1.6	255	1684	1135	1809
	2022	26.4	6.4	10.4	533	1515	986	1670
	10 YR Avg. (2011-20)	25.5	8.5	13.2	332	1679	1087	1838