Crop Report – Week of September 4th, 2023

For forage producers, the production year starts in the fall. What farmers do from mid-August to the end of the growing season impacts this winter’s feed inventory and next year’s forage yield potential.

Feed the crop that feeds the livestock!

Forage crops have the highest crop nutrient removal values of any field crop grown in Ontario. Harvesting the whole crop while it is still green removes far more nutrients from the soil than harvesting grain and straw. Grain crops are fully mature, and as they dry down before harvest, water-soluble nutrients like potassium leach back out into the soil through the roots.

Potassium(K) is important for regulating the water content of plants and is essential in perennial forages as they prepare to overwinter. To get the most value for money, K should be applied about a month before alfalfa starts to harden off for winter. Using the average fall rest period start dates as a guide (Figure 1), this means that potash should be applied mid-July in the north, late July in eastern, central, and western Ontario, and early August in the south.

Since a fertilizer application is being made anyway, this is a good opportunity to also apply any phosphorus (P) and sulphur (S) the crop may need. Remember to factor in nutrients from manure applications when planning top-ups from purchased fertilizer.

Take a break for yield potential’s sake!

Perennial forage crops store energy in their lower stems and roots to fuel early growth the following spring. Alfalfa is especially sensitive to cold stress and issues at green-up if it is not able to create adequate energy reserves in the fall. It takes 450 Growing Degree Days (Base 5˚C) for alfalfa to properly prepare for winter, which is typically about 6 weeks in the fall. This “no cut” time is known as the fall rest period (Figure 1). Once the first killing frost hits – (is minus 4 ˚Celcius (40˚ Fahrenheit) for at least four hours) – alfalfa goes dormant. By not harvesting alfalfa during the fall rest period, growers give it a better chance of overwintering well.

Figure 1. Average start date of the six-week fall rest period for alfalfa.

If winter feed inventory is a concern, growers could take a cut of alfalfa after the killing frost without doing too much damage to the forage crop. Since the alfalfa is dormant, it won’t try to grow back until the spring, which is when it needs the energy stored in its roots. Another option for a fall forage cut are hay fields that are predominantly grass or clover. These crops may smother over winter if they are more than 20 cm (8 inch) tall. They are less sensitive to cold stress than alfalfa and generally do not winterkill because of a fall cutting.

Another way to boost forage inventories is by harvesting annual forages as baleage or silage. These species are often seeded as cover crops, but a good annual forage stand typically requires higher seed rates and some added nutrients. Cereals, peas, and clovers all store well, but growers should avoid harvesting brassicas, turnips, radishes, sunflowers, and other broad-leaved forbs. They are too wet to ferment well and are more prone to spoiling in storage. These complex mixtures are better suited to grazing.

Assess risk and start planning for spring!

Yield potential is an important consideration in a forage production system. The equipment and labour costs per acre barely change between harvesting a low-yielding crop and a high-yielding one. This means that the best way to reduce the cost per tonne of forage is to keep yield potential high.

A fall plant count can provide a baseline to compare to next spring. This is an effective way to assess how much winterkill has occurred. Alfalfa stands thin naturally over time, so only doing spring plant counts doesn’t differentiate between winterkill and thinning during the growing season. See Table 1 for thresholds.

Table 1. Target alfalfa stand plant count.

Age of stand	Healthy plants
New seeding	53+ plants/0.25m2 (20+ plants/ft2)
Year 1	32-53 plants/0.25m2 (12-20 plants/ft2)
Year 2	21-32 plants/0.25m2 (8-12 plants/ft2)
Year 3 or older	13 plants/0.25m2 (5 plants/ft2)

Guidelines for alfalfa now say to terminate the crop after a lifetime total of 9 to 12 cuts. Cutting is a stressor and taking more than 12 cuts impacts alfalfa’s ability to fend off insect pests and diseases. Planned termination keeps the crop healthy, yield potential high, and cost per tonne low.

Cutting timing and frequency are not the only stressors that affect overwintering success and yield potential in alfalfa. The disease resistance status of the variety, soil fertility levels, and soil drainage also affect winterkill risk. See the score chart on page 121 of OMAFRA Publication 30: Guide to Forage Production to assess your own fields.

Weather Data – August 28 – September 3, 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	29.0	7.8	0.0	570	2612	1848	2823
	2022	30.0	14.9	9.8	387	2778	2026	3127
	10 YR Norm (11 – 20)	27.2	13.3	24.7	492	2850	2042	3228
Ridgetown	2023	29.5	5.5	4.3	500	2484	1729	2635
	2022	30.0	11.0	8.6	277	2632	1887	2893
	10 YR Avg. (2011-20)	26.9	11.6	20.4	444	2685	1882	3007
London	2023	28.1	7.3	3.7	543	2463	1708	2620
	2022	29.7	10.4	10.6	318	2562	1827	2823
	10 YR Avg. (2011-20)	26.4	11.4	23.2	462	2659	1861	2984
Brantford	2023	28.3	6.3	3.9	441	2444	1688	2592
	2022	30.7	9.2	10.9	287	2577	1831	2769
Welland	2023	26.5	8.3	2.7	489	2493	1731	2666
	2022	29.3	10.4	22.2	316	2630	1874	2909
	10 YR Avg. (2011-20)	26.4	12.1	19.8	409	2679	1879	3013
Elora	2023	27.5	5.6	7.4	436	2263	1524	2382
	2022	29.7	8.7	10.3	254	2363	1630	2543
	10 YR Avg. (2011-20)	25.3	9.3	25.2	459	2405	1620	2671
Mount Forest	2023	26.8	5.2	9.0	392	2261	1527	2391
	2022	28.2	7.1	38.0	374	2353	1626	2578
	10 YR Avg. (2011-20)	24.5	9.5	32.3	478	2392	1615	2689
Peterborough	2023	28.9	4.5	0.4	410	2317	1566	2402
	2022	29.9	8.7	7.0	323	2370	1623	2554
	10 YR Avg. (2011-20)	25.4	7.0	19.8	409	2438	1652	2670
Kemptville	2023	28.7	7.2	25.4	506	2463	1717	2595
	2022	31.6	8.2	25.6	454	2525	1758	2762
	10 YR Avg. (2011-20)	24.9	9.4	17.1	453	2563	1778	2854
Earlton	2023	29.1	4.2	26.7	338	2109	1409	2241
	2022	28.8	4.6	24.5	351	2133	1434	2353
	10 YR Avg. (2011-20)	21.9	6.4	20.0	406	2089	1388	2361
Sudbury	2023	26.3	5.3	33.3	511	2140	1442	2291
	2022	27.6	3.9	14.5	318	2169	1462	2433
	10 YR Avg. (2011-20)	23.5	7.3	16.2	439	2238	1514	2547
Thunder Bay	2023	32.8	1.9	5.1	271	1972	1294	2128
	2022	29.4	1.9	3.6	457	1936	1266	2114
	10 YR Avg. (2011-20)	22.9	4.8	18.1	402	2006	1292	2215
Fort Frances	2023	32.1	4.5	0.5	308	2142	1458	2338
	2022	30.2	2.3	3.6	575	2016	1347	2263
	10 YR Avg. (2011-20)	23.0	5.4	16.0	405	2131	1399	2364