Short(er) Spring Wheat Crop = Lower Grain Yield?

Jul 07, 2017

By Jochum Wiersma

Some of you have noticed and commented that the spring wheat crop is shorter when compared to the last few years and subsequently questioned its yield potential. A few weeks ago, Dr. Joel Ransom wrote a nice article in the Crop & Pest Report explaining why the spring wheat crop was shorter and whether its yield potential had already been reduced.

The physiology of grain fill has been well researched and we have a good understanding how temperature and droughts tress affect grain fill and grain quality. Table 1 summarizes the results of one of the published studies that illustrates how daytime and nighttime temperatures affect the length of the grain fill period and ultimately yield. The bottom-line is that higher nighttime temperatures are more detrimental than the maximum daytime temperatures.

Just in the last two days has the grain fill suffered some heat-stress, as maximum temperatures had not yet reached above 85F in the two weeks prior while minimum temperatures were mostly in the fifties in the same period (Table 2).

Therefore, I am optimistic about this year’s yield potential, despite the shorter than normal crop as the first weeks of grain fill have been favorable, allowing for a larger proportion of the grain being produced de novo rather than being recycled from the shorter canopy.

The only caveat in this optimism is that the crop didn't suffer any other stresses these past two weeks. Drought stress poses the greatest threat but the cooler temperatures also reduced the crop's daily water consumption considerably.

Table 1 - Effect of daytime and nighttime temperatures on the length of the grain fill period and the average kernel weight (after Altenbach et al, 2003)

T_day (^oF)	T_night (^oF)	Length Grain Fill (days)	Thousand Kernel Weight (grams)
75	63	40	50
99	63	30	40
99	82	18	20

Table 2 – The daily maximum and minimum temperatures at 3 NDAWN locations in NW Minnesota and the number of days the temperatures were outside the optimum range for grain fill for spring wheat.

Date	Humboldt		Ada		Campbell
	T_max	T_min	T_max	T_min	T_max	T_min

6/22	75	51	80	51	80	55
6/23	63	53	68	49	67	50
6/24	55	43	60	44	65	43
6/25	65	39	68	42	70	44
6/26	74	40	76	39	73	40
6/27	79	43	79	49	73	47
6/28	67	57	67	59	76	58
6/29	77	48	76	57	72	57
6/30	70	51	71	54	74	53
7/1	71	48	75	50	79	49
7/2	74	44	74	44	77	52
7/3	79	51	82	51	82	52
7/4	91	62	93	60	93	61
7/5	86	53	89	62	95	67

# Days T_max>85	2	-	2	-	2	-
# Days T_min>60	-	1	-	2	-	2

Source: umn.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.