WEBVTT 1 00:00:01.125 --> 00:00:03.708 (upbeat music) 2 00:00:07.010 --> 00:00:09.950 line:15% Chris Proctor, I'm a weed extension educator, 3 00:00:09.950 --> 00:00:14.470 line:15% University of Nebraska, we're talking about a topic, 4 00:00:14.470 --> 00:00:17.220 just looking at the influence of soil practices 5 00:00:17.220 --> 00:00:21.870 on how it controls weeds, kind of the effect of herbicides, 6 00:00:21.870 --> 00:00:23.943 and ultimately crop productivity. 7 00:00:26.120 --> 00:00:29.820 It's really the aim or the goal of the study 8 00:00:29.820 --> 00:00:33.160 I'm gonna highlight was to try to understand 9 00:00:33.160 --> 00:00:34.900 what effect is soil management practices? 10 00:00:34.900 --> 00:00:37.840 How does tillage versus no-till versus use of cover crops, 11 00:00:37.840 --> 00:00:40.040 how does that affect weed control? 12 00:00:40.040 --> 00:00:43.270 What influence might that have on residual herbicides 13 00:00:43.270 --> 00:00:45.170 that are applied in those systems? 14 00:00:45.170 --> 00:00:50.170 And how productive are the crops in those systems? 15 00:00:50.280 --> 00:00:54.980 And so thinking about it, you know, we kind of expected 16 00:00:54.980 --> 00:00:57.430 that there would be a difference between soil management 17 00:00:57.430 --> 00:01:01.423 practices on those different areas of crop production. 18 00:01:02.520 --> 00:01:03.700 So the way this study was set up, 19 00:01:03.700 --> 00:01:05.460 so this was a trial that was actually conducted 20 00:01:05.460 --> 00:01:10.460 up in Wisconsin and we had six different soil management 21 00:01:11.930 --> 00:01:14.830 practices and so that was a combination of tillage, 22 00:01:14.830 --> 00:01:19.090 no-till and cover crops with different cover crop 23 00:01:19.090 --> 00:01:21.240 termination timings, and so we had an early 24 00:01:21.240 --> 00:01:26.240 termination timing that was about May 7th timing 25 00:01:27.880 --> 00:01:29.920 that was right around the time of planting 26 00:01:29.920 --> 00:01:33.160 and so in this instance, this was later in May, 27 00:01:33.160 --> 00:01:36.500 around May 23rd and there's two terminations 28 00:01:36.500 --> 00:01:38.160 at the app plant so there was a forage, 29 00:01:38.160 --> 00:01:41.130 where the forage was harvested and collected, 30 00:01:41.130 --> 00:01:43.290 and then it was also chemically terminated 31 00:01:43.290 --> 00:01:46.080 and then a late termination timing around June six 32 00:01:46.080 --> 00:01:47.740 which was chemically terminated. 33 00:01:47.740 --> 00:01:50.480 And that was also, and then the other part of the study 34 00:01:50.480 --> 00:01:53.750 was a comparison of a pre-merger beside versus 35 00:01:53.750 --> 00:01:56.180 a no pre-merger herbicide to see what effect 36 00:01:56.180 --> 00:01:57.013 that might have. 37 00:01:59.170 --> 00:02:04.170 So looking at how these different components were set up 38 00:02:04.290 --> 00:02:08.640 for the termination and burn down part of the study, 39 00:02:08.640 --> 00:02:12.730 glyphosate was applied, for the pre-merge herbicide 40 00:02:12.730 --> 00:02:16.470 you can see in the table there, we had 41 00:02:16.470 --> 00:02:18.180 different pre-merger herbicides that were applied on 42 00:02:18.180 --> 00:02:20.850 the corn and the soybean, and then there was a post-emerge 43 00:02:20.850 --> 00:02:23.750 herbicide that was applied across the entire study, 44 00:02:23.750 --> 00:02:26.700 so all the treatments received the post emergent herbicide. 45 00:02:31.100 --> 00:02:33.970 Cover crops were planted with cereal rye, 46 00:02:33.970 --> 00:02:35.807 and so we just use one cover crop for this study, 47 00:02:35.807 --> 00:02:40.807 and it was about 60 pounds per acre tillage, 48 00:02:40.970 --> 00:02:42.570 it was kind of a two pass tillage system, 49 00:02:42.570 --> 00:02:46.230 so it was a fall chisel followed by a spring field 50 00:02:46.230 --> 00:02:49.500 cultivator, and then the herbicides were applied 51 00:02:49.500 --> 00:02:52.600 for the burn down at the termination of the cover crop 52 00:02:52.600 --> 00:02:54.460 and the pre-merger beside those were applied 53 00:02:54.460 --> 00:02:57.760 with a research backpack sprayer, but the post-merger 54 00:02:57.760 --> 00:03:01.056 was sprayed over the top of everything with a tractor. 55 00:03:01.056 --> 00:03:03.640 And then we evaluated weed control, so this was right 56 00:03:03.640 --> 00:03:06.430 before the post-merger herbicide was applied, 57 00:03:06.430 --> 00:03:08.650 weed control was evaluated and then yield 58 00:03:08.650 --> 00:03:10.970 was collected at the end. 59 00:03:10.970 --> 00:03:12.780 Another component of the study was to evaluate 60 00:03:12.780 --> 00:03:14.540 herbicide persistence, so how long do those 61 00:03:14.540 --> 00:03:18.090 pre-emerge herbicides remain in the soil? 62 00:03:18.090 --> 00:03:19.580 How long were they there? 63 00:03:19.580 --> 00:03:20.980 How long could we detect their presence? 64 00:03:20.980 --> 00:03:22.210 And what influence did those have? 65 00:03:22.210 --> 00:03:25.470 And so, soil samples were collected about 29 days 66 00:03:25.470 --> 00:03:30.470 after application, and there were applied for the no-till 67 00:03:31.430 --> 00:03:34.750 and that was kind of the control treatment, 68 00:03:34.750 --> 00:03:37.210 and then you had a tillage plus pre-emerge, 69 00:03:37.210 --> 00:03:39.580 no-till plus pre-emerge, and early termination 70 00:03:39.580 --> 00:03:43.070 of the cover crop plus pre -emerge, and then an app plant 71 00:03:43.070 --> 00:03:45.930 termination plus pre-emerge and then late terminatio 72 00:03:45.930 --> 00:03:46.763 plus pre-merge. 73 00:03:46.763 --> 00:03:50.280 So we kinda evaluated kind of the different parts 74 00:03:50.280 --> 00:03:53.740 of the system to see how much of that herbicide 75 00:03:53.740 --> 00:03:58.220 carried over, and then these were analyzed in a laboratory, 76 00:03:58.220 --> 00:04:00.440 they were sent to South Dakota and analyzed there. 77 00:04:00.440 --> 00:04:03.690 And so for corn, while there was a number of herbicides 78 00:04:03.690 --> 00:04:08.140 that applied, the lab was able to detect S-metolachlor 79 00:04:09.430 --> 00:04:13.010 was used and for kind of to evaluate the corn pre-merger 80 00:04:13.010 --> 00:04:17.600 herbicide, and then for soybean, sulfentrazone 81 00:04:17.600 --> 00:04:19.610 was the herbicide that was analyzed. 82 00:04:19.610 --> 00:04:24.410 And so looking at the lab data, really all we saw 83 00:04:24.410 --> 00:04:28.707 was the under tillage, there was higher concentration 84 00:04:29.541 --> 00:04:32.550 of the soybean herbicide Sulfentrazone 85 00:04:32.550 --> 00:04:35.800 compared to no-till and this was pretty similar for corn 86 00:04:35.800 --> 00:04:39.810 but I'm just gonna highlight the soybean data today. 87 00:04:39.810 --> 00:04:43.410 And so some of this is kinda gets into that question 88 00:04:43.410 --> 00:04:45.150 when you start to have residue on the soil, 89 00:04:45.150 --> 00:04:48.120 you have cover crops and residue from the cover crops, 90 00:04:48.120 --> 00:04:51.670 is that begin to tie up some of the herbicide in the soil, 91 00:04:51.670 --> 00:04:54.058 what effect does that have on the persistence 92 00:04:54.058 --> 00:04:57.430 of those herbicides and whether or not 93 00:04:57.430 --> 00:04:59.120 it affects weed control? 94 00:04:59.120 --> 00:05:01.770 And so we did see differences in terms of the amount 95 00:05:01.770 --> 00:05:06.770 that was there, to kind of verify what was being seen, 96 00:05:07.210 --> 00:05:09.800 we use some of those soil samples we need a bioassay, 97 00:05:09.800 --> 00:05:13.671 so we put that soil in pots in a greenhouse, 98 00:05:13.671 --> 00:05:18.671 and then we test it both the use of cucumber 99 00:05:19.950 --> 00:05:23.940 and Palmer amaranth to determine what effect 100 00:05:23.940 --> 00:05:26.673 did the different soil treatments, 101 00:05:28.010 --> 00:05:30.910 soil management treatments have on the persistence 102 00:05:30.910 --> 00:05:32.360 of these herbicides? 103 00:05:32.360 --> 00:05:35.210 And it didn't quite shake out the same as the laboratory 104 00:05:35.210 --> 00:05:39.483 study and so being 29 days out from when we sampled, 105 00:05:40.550 --> 00:05:43.870 I think a lot of the herbicides began to break down 106 00:05:43.870 --> 00:05:47.090 at this point, and so we didn't see as clear 107 00:05:47.090 --> 00:05:50.540 of delineation in terms of no-till having higher injury 108 00:05:50.540 --> 00:05:54.030 on these plants compared to the other treatments. 109 00:05:54.030 --> 00:05:55.800 If you look carefully at some of the polar plants, 110 00:05:55.800 --> 00:05:57.040 you do see a little bit of injury, 111 00:05:57.040 --> 00:06:00.660 but certainly the concentrations weren't high enough 112 00:06:00.660 --> 00:06:02.980 to prevent emergence as we can see emergence all the 113 00:06:02.980 --> 00:06:06.880 way across the board and there weren't strong differences 114 00:06:06.880 --> 00:06:08.003 between the control. 115 00:06:09.390 --> 00:06:11.930 So in this case, kinda given the soils 116 00:06:11.930 --> 00:06:16.930 and the way that the study was conducted, 117 00:06:18.020 --> 00:06:22.720 we didn't see a strong influence of the pre-emerge 118 00:06:22.720 --> 00:06:25.310 herbicide kinda persistent or differences between 119 00:06:25.310 --> 00:06:27.060 the soil treatments in terms of the persistence 120 00:06:27.060 --> 00:06:28.173 of the herbicide. 121 00:06:29.110 --> 00:06:32.310 And so really, I think we might've been too late 122 00:06:32.310 --> 00:06:34.520 when we sampled, I think being a little bit closer 123 00:06:34.520 --> 00:06:36.090 to when those were applied might've given us a little 124 00:06:36.090 --> 00:06:40.150 better picture of what was going on and kinda 125 00:06:40.150 --> 00:06:42.520 looking at that data, I think a combination of lab data 126 00:06:42.520 --> 00:06:45.270 and some of these bioassay screens could give us 127 00:06:45.270 --> 00:06:47.640 a pretty good idea, so this is kind of the first step 128 00:06:47.640 --> 00:06:52.228 at trying to understand what's going on in these situations, 129 00:06:52.228 --> 00:06:55.460 I'll just highlight just a little bit of the field data. 130 00:06:55.460 --> 00:06:57.700 So this is looking at cover crop biomass, 131 00:06:57.700 --> 00:06:59.780 and this is kind of what we would have expected 132 00:06:59.780 --> 00:07:01.730 that the later you terminate, the more biomass 133 00:07:01.730 --> 00:07:05.030 you accumulate, so that kind of followed what was expected. 134 00:07:05.030 --> 00:07:08.080 In terms of weed control, we had one side with pretty low 135 00:07:08.080 --> 00:07:10.180 weed control, the Arlington side on the left, 136 00:07:10.180 --> 00:07:11.660 and so we really didn't see any difference 137 00:07:11.660 --> 00:07:15.840 in percent weed control, compared to the other side 138 00:07:15.840 --> 00:07:20.840 where there was a difference in the using 139 00:07:20.870 --> 00:07:23.610 a pre-merger versus not using a pre-merger beside that side. 140 00:07:23.610 --> 00:07:28.610 So under the tillage condition, including a pre had higher 141 00:07:29.060 --> 00:07:32.350 weed control relative to without the pre-merger herbicide, 142 00:07:32.350 --> 00:07:33.760 but for the other soil treatments 143 00:07:33.760 --> 00:07:34.950 there really wasn't a difference, 144 00:07:34.950 --> 00:07:37.870 which is kind of an interesting outcome. 145 00:07:37.870 --> 00:07:42.470 And then, then looking at yield at the end of the day, 146 00:07:42.470 --> 00:07:45.730 we just didn't see any, yield differences, either the side, 147 00:07:45.730 --> 00:07:48.040 and so, despite I've seen a few differences 148 00:07:48.040 --> 00:07:50.880 in terms of persistence of herbicides 149 00:07:51.970 --> 00:07:55.303 that were detected in the laboratory study, 150 00:07:55.303 --> 00:07:58.620 and some minor differences in weed control early on, 151 00:07:58.620 --> 00:08:01.140 ultimately it didn't translate into any yield differences 152 00:08:01.140 --> 00:08:02.130 in this particular study. 153 00:08:02.130 --> 00:08:07.040 And so, I think kind of the take home is, 154 00:08:07.040 --> 00:08:08.790 we need to pay attention, I think, 155 00:08:08.790 --> 00:08:10.880 to these different systems and how they might affect 156 00:08:10.880 --> 00:08:15.357 our herbicide persistence, because that'll affect 157 00:08:15.357 --> 00:08:18.913 how well we control weeds in these systems, 158 00:08:20.900 --> 00:08:24.300 but ultimately, I think under the soil conditions 159 00:08:24.300 --> 00:08:26.170 tested in the kind of the environmental conditions 160 00:08:26.170 --> 00:08:27.700 that we were looking at, we didn't see strong 161 00:08:27.700 --> 00:08:31.870 differences here, so, that's encouraging in terms of the use 162 00:08:31.870 --> 00:08:35.890 of no-till systems and cover crop systems 163 00:08:37.400 --> 00:08:40.250 'cause of the benefits we can gain there. 164 00:08:40.250 --> 00:08:43.683 So that's what I wanted to highlight related to that study.