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In demonstration plots : Harvest yields valuable lessons

Several months ago the LSU AgCenter initiated the core block concept into its Crop Demonstration Program to evaluate recommended soybean, corn and grain sorghum hybrids and varieties over a wide range of locations and other factors, including soil type, region of Louisiana and planting dates.

The core blocks are randomized to maintain statistical validity. This allows us to determine the leading hybrids and varieties.

This year, we initiated 56 demonstrations across the state with county agents in 20 parishes. Five grain sorghum demonstrations were attempted and four were analyzed. Eighteen corn demonstrations were attempted and 17 were analyzed.

Soybeans were broken up into Maturity Groups 4, 5 and 6. We attempted 14 and analyzed 10 in Maturity Group 4. The remaining 19 demonstrations were of Maturity Group 5 and Maturity Group 6. We have analyzed four Maturity Group 5 tests and three Maturity Group 6 tests. Because of weather problems, we are having difficulty harvesting the rest of the demos. In addition, environmental factors such as green bean syndrome and disease have destroyed some tests.

We had eight core block grain sorghum hybrids over four locations with a average yield of 78 bushels per acre. Most parishes that had grain sorghum demonstrations averaged 20 inches or more rainfall, which contributed to the yield drag.

Averaged over all locations, yields for the top five core block hybrids were (1) Terral 9421, 89 bushels per acre, (2) Pioneer 83G66, 85 bushels per acre, (3) DynaGro 751B, 81 bushels per acre, (4) Pioneer 84G62, 78 bushels per acre and (5) Terral 96H81, 77 bushels per acre. With our state average around 60 bushels per acre or less, these yields are exceptional.

We had 11 core block corn hybrids over 17 locations with an average yield of 139 bushels per acre for the core block and 138 bushels per acre when all hybrids were averaged (referred to as the test). The 11 hybrids were ranked as follows with ties listed in alphabetical order: (1) Pioneer 32D99, 148 bushels per acre, (2) Pioneer 31R88, 145 bushels per acre, (3-6) DeKalb DKC 69-70, DynAgro 5515, Pioneer 31B13 YGCB and Terral 26BR10n, 141 bushels per acre, (7-8) Garst 8288 and Terral 2160Bt, 139 bushels per acre, (9-10) DynAgro 58K22 and Terral 2140nRR, 136 bushels per acre, and (11) Golden Acres 8112, 123 bushels per acre.

We broke down corn demonstrations by planting date as well as by south, central and north Louisiana locations for hybrid performance. Regarding planting date, there were slight numeric differences in the March 7-13 and the March 14-20 planting dates. When corn planting was delayed to March 21-27, yields dropped by 25 bushels per acre for the core mean and 22 bushels per acre for the test mean. Some of this dramatic drop can be attributed to excess rainfall.

When the corn demos were analyzed over the south, central and northern parts of the state, there were differences between hybrid yields.

For Maturity Group 4 soybeans, there were six core block varieties over 10 locations with a average yield of 35 bushels per acre for the core block and 34 bushels per acre when all varieties were averaged (the test).

When relative maturity was analyzed in two groups — 4.0 to 4.4 and 4.5 to 4.9 — there were no differences, with the core block and the test averaging 35 and 34 bushels per acre respectively. This point is interesting since we have noticed this anomaly the past couple of years.

Maturity Group 4 beans, regardless of maturity classification, are maturing in about a week of each other when planted on the same day. This has been true in large-scale demonstrations with over 40 varieties over the last couple of years.

For date of planting over 10 locations across the state, the optimal date to plant Maturity Group 4 core varieties, regardless of relative maturity, was the fourth week of April (this is one year's observation). Yields were lower for the other two planting dates, including the third week in April and the second week of May planting. This trend held true for the test when all of the varieties were analyzed for optimal planting date.

When all Maturity Group 4 varieties (the test) were analyzed in the south, central and northern regions of Louisiana, a direct linear trend developed. This trend was that the south yielded the lowest (as was expected with the excess rainfall), the central part of the state did slightly better than the south and the northern part of the state outperformed the central and the southern regions.

When north Louisiana data was analyzed even further over four locations planted in the second, third and fourth weeks of April, the highest yields were reported for the fourth week of April planting.

When the soybean Maturity Group 4 demonstrations were analyzed over the south, central and northern parts of the state there were differences between variety yields, as was expected.

At this point, we do not have data for all of locations in maturity groups 5 and 6. I will provide that data as soon as it is processed.

What does all of this analysis mean? It definitely means that more research needs to be conducted on date of planting in Louisiana. Significant trends from this year are developing, but they are similar to the past couple of years. It does appear that a bell-shaped curve for Maturity Group 4 planting dates could develop. In other words, you could be leaving money on the table if you plant too early or too late.

Analysis related to cost of production per acre needs to be evaluated. For example, a Maturity Group 4 variety planted on April 1 may yield less than the same variety planted on April 20, but it might require fewer pesticide applications. The reduced applications might increase profit for the April 1 planting date. This is difficult to address because we do not have all the answers for genetic potential by planting date.

David Y. Lanclos is the soybean, corn and grain sorghum specialist at LSU AgCenter. e-mail: [email protected]

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