Crop Report – Week of July 24th, 2023

Getting to Know your Manure with a Manure Analysis

The “magical” qualities of manure and organic amendments for providing long-term benefits have been well documented, especially for maintaining and improving soil organic matter. Sourcing off farm manure and organic amendments has become more difficult and expensive with the increased interest in improving soil health, therefore it is more important than ever to know what your “black gold” is providing.

It is recommended to submit a manure or organic amendment sample before you land apply. Once you get your manure analysis report back, what do those numbers mean? Since manure and organic amendments are variable, understanding what nutrients are in the material is important for maximizing economic benefit.

The Analysis Report

Dry Matter/moisture measures how much liquid is in the sample. While self-explanatory, the moisture content does affect economics of application. A material that has 2% dry matter has 98% water. Most reports show nutrients “as-applied,” which means the higher the water content the less nutrients being applied. Moving water will reduce the economic value for materials that require transportation to where application will occur.

Nitrogen, phosphorus, and potassium are the most valuable nutrients; however, organic amendments can also be rich in micronutrients and organic matter. Micronutrients such as sulphur (S), magnesium (Mg) and zinc (Zn) in the manure test can reduce starter fertilizer requirements, especially where manure is applied regularly. Other tests such as pH, total salts, or EC (Electrical Conductivity) and carbon to nitrogen (C:N) ratio can help with nitrogen management. Below are more details to consider about these nutrients:

• Nitrogen is one of the main nutrients in manure and has several different forms, but only organic and ammonium nitrogen provide significant nitrogen contribution to crops
  • Total nitrogen (N) includes all the forms of nitrogen in the material
  • Ammonium N (NH4-N) is the fraction that is immediately plant-available 
  • Organic N is the remaining fraction and is referred to as “slow-release N since it will need to be mineralized by soil microorganism before plant utilization.

The plant available N from manure will depend on management. The NH₄-N fraction can be easily lost depending on timing of application, time to incorporation and weather and soil conditions. Materials applied and quickly incorporated into the soil will have the lowest risk of N losses to the atmosphere or runoff or leaching to water sources. The availability of the organic N fraction will depend on timing of application, and microbial activity based on weather and soil conditions. The organic amendment tool in AgriSuite will provide an estimate of available nutrients and economic value based on analysis and management details.

• Phosphorus (P) content in organic amendments is significant, but variable with different livestock species or types of amendments. Phosphorus is tied to soil particles and when materials are surface applied P is vulnerable to losses through surface runoff or soil erosion. It is reported as percent total P, but on the lab report is converted to phosphate (P₂O₅). About 80% of the P in manure will become available, although not all of it is immediately plant available.

• Potassium (K) content also varies between amendments and can be especially low in sewage biosolids. Potassium is reported as percent K, but on a lab report is usually converted to potash (K₂O). About 90% is assumed to become available for plants.

• Sulphur in organic amendments is available as elemental, or a slow-release form. Spring application of manure may not supply the needs for a crop that has early season sulphur requirements.

• pH measures the acidity or alkalinity of the material.  pH 7 is neutral, but as pH increases to over 7.8, and when combined with temperatures over 20^oC, the amount of N as NH₄-N which attaches to soil particles decreases while the portion as NH₃-N gas increases. Surface applied on hot days could result in complete loss of the NH₃/NH₄ portion within a few hours. Injection or rapid incorporation reduces N loss with high pH materials applied during the growing season (See Figure 1).

Figure 1. Injecting anaerobic digestate after wheat harvest into a growing cover crop to maximize soil health benefits and economic value of nutrients.

• Carbon-to-Nitrogen Ratio (C:N) measures the proportion of carbon to nitrogen in an organic material. C:N ratio indicates how quickly carbon breakdown may occur and whether a material will immobilize or mineralize nitrogen. Mineralization of organic N occurs when there is adequate N to break down carbon. As an organic material’s C:N ratio rises above that of soil (~10:1), soil microorganisms “steal” nitrogen from the soil to breakdown carbon. Solid manure with a high amount of bedding will often have a C:N ratio above 20 to 25:1 and when applied to a corn crop, immobilization of soil N could result in short-term nitrogen deficiency.

• Total Salts (EC) or Electrical Conductivity measures all soluble salts including K, NH4, Mg, Ca, Al and sodium (Na). This measurement can be used to help determine salt additions and potential salinity. In Ontario, adequate rainfall leaches salts out of the root zone however high EC may cause germination/seedling root injury or when planting occurs too soon after application or as leaf burn when applied onto standing crops or if organic materials are surface applied (i.e., no-till) and conditions are very dry. High sodium added to soil can decrease the aggregate structure and porosity of fine / medium-textured soils
  
  
• Other tests – Aluminum (Al), Iron (Fe), Boron (B), or heavy metals (e.g., copper (Cu)) tests can be useful in certain crop circumstances. For example, crop growth could be impacted where biosolids are applied to a sandy field with very low pH due to high levels or aluminum or iron used in the treatment process. Organic amendments applied to forages or pastures used for sheep should be tested for copper since relatively low levels of copper can be toxic to sheep.

Maximize Economic Value by Using Manure Test Results

Manure analysis results are most useful, in combination with soil test results, to calibrate application rates. Applying a rate to meet crop phosphorus needs, where soil fertility levels are already adequate or high, will often require supplementing nitrogen-loving crops with additional commercial N. An organic material should not be applied at a rate where it will meet all the N needs of a crop such as corn or wheat, since cool, wet weather conditions can delay mineralization and/or nitrification of manure N. The release of available N will not always coincide with the timing of peak crop N needs.

Although a manure analysis is just a snapshot of the material being applied, it can provide input in deciding whether a potential organic amendment will economically provide the intended benefits. Using the manure analysis results will help determine which field is the best fit for the nutrient and Organic Matter (OM) composition of the organic amendment and what is the best timing for application. Economic value is maximized when the nutrients and the organic matter in the material are considered and when the composition of the material matches the timing, placement, and location.  

Weather Data – July 17 – 23, 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	28.9	14.0	15.1	289	1779	1220	1788
	2022	30.7	19.0	21.1	301	1866	1323	1988
	10 YR Norm (11 – 20)	28.5	16.0	28.4	377	1961	1363	2114
Ridgetown	2023	27.8	12.0	31.3	380	1687	1136	1662
	2022	32.2	17.5	5.9	210	1751	1216	1823
	10 YR Avg. (2011-20)	28.0	13.8	38.7	335	1843	1251	1969
London	2023	27.5	12.2	11.4	337	1680	1130	1659
	2022	33.5	15.9	25.2	228	1699	1174	1768
	10 YR Avg. (2011-20)	27.7	14.5	15.8	336	1821	1233	1950
Brantford	2023	28.0	11.7	8.6	295	1670	1119	1650
	2022	33.6	16.3	29.3	230	1703	1168	1723
Welland	2023	27.1	13.8	14.8	301	1689	1132	1665
	2022	30.2	17.5	44.3	249	1750	1205	1827
	10 YR Avg. (2011-20)	27.9	15.0	18.3	319	1828	1238	1961
Elora	2023	27.4	10.1	37.7	308	1540	1006	1513
	2022	31.8	13.4	17.2	196	1557	1033	1577
	10 YR Avg. (2011-20)	26.7	12.0	18.2	334	1638	1062	1739
Mount Forest	2023	27.1	11.0	5.1	297	1537	1008	1514
	2022	30.6	14.1	31.8	239	1557	1040	1608
	10 YR Avg. (2011-20)	26.1	12.9	24.1	338	1618	1050	1736
Peterborough	2023	27.8	9.0	35.7	300	1571	1024	1509
	2022	31.1	14.8	34.2	262	1571	1033	1619
	10 YR Avg. (2011-20)	28.4	12.1	19.4	296	1662	1086	1744
Kemptville	2023	29.3	11.2	13.8	315	1685	1144	1645
	2022	30.7	17.0	37.8	384	1682	1124	1747
	10 YR Avg. (2011-20)	28.9	13.3	22.7	326	1744	1169	1856
Earlton	2023	27.5	7.7	11.5	253	1426	932	1445
	2022	31.7	14.0	42.4	251	1409	920	1506
	10 YR Avg. (2011-20)	26.4	10.3	17.3	278	1391	899	1531
Sudbury	2023	26.7	9.1	31.6	401	1442	949	1460
	2022	29.4	15.5	36.8	248	1412	914	1511
	10 YR Avg. (2011-20)	26.7	12.6	24.0	310	1493	978	1638
Thunder Bay	2023	26.7	7.0	14.8	199	1256	784	1297
	2022	32.4	11.7	23.9	388	1184	723	1220
	10 YR Avg. (2011-20)	26.1	11.0	13.0	306	1306	803	1392
Fort Frances	2023	26.6	10.5	36.1	231	1425	946	1510
	2022	28.5	11.6	30.6	505	1267	808	1372
	10 YR Avg. (2011-20)	26.5	10.7	23.1	309	1433	911	1550