corn production

Estimated % corn grain yield loss due to defoliation at various growth stages¹.

	% Leaf Defoliation
Growth Stage²	10	15	20	25	30	35	40	45	50	55	60	65	70	75	80	85	90	95	100
	- - - - - - - - - - - - - - - % Yield loss - - - - - - - - - - - - - - -
7 leaf	0	0	0	0	0	0	1	1	2	3	4	4	5	5	6	7	8	9	9
8 leaf	0	0	0	0	0	1	1	2	3	4	5	5	6	6	7	8	9	10	11
9 leaf	0	0	0	1	1	2	2	3	4	5	6	6	7	7	9	10	11	12	13
10 leaf	0	0	0	1	2	3	4	5	6	7	8	8	9	9	11	13	14	15	16
11 leaf	0	0	1	1	2	3	5	6	7	8	9	10	11	12	14	16	18	20	22
12 leaf	0	0	1	2	3	4	5	7	9	10	11	13	15	16	18	20	23	26	28
13 leaf	0	1	1	2	3	4	6	8	10	11	13	15	17	19	22	25	28	31	34
14 leaf	0	1	2	3	4	6	8	10	13	15	17	20	22	25	28	32	36	40	44
15 leaf	1	1	2	3	5	7	9	12	15	17	20	23	26	30	34	38	42	46	51
16 leaf	1	2	3	4	6	8	11	14	18	20	23	27	31	36	40	44	49	55	61
17 leaf	2	3	4	5	7	9	13	17	21	24	28	32	37	43	48	53	59	65	72
18 leaf	2	3	5	7	9	11	15	19	24	28	33	38	44	50	56	62	69	76	84
19-21 leaf	3	4	6	8	11	14	18	22	27	32	38	43	51	57	64	71	79	87	96
Tassel	3	5	7	9	13	17	21	26	31	36	42	48	55	62	68	75	83	91	100
Silked	3	5	7	9	12	16	20	24	29	34	39	45	51	58	65	72	80	88	97
Silks brown	2	4	6	8	11	15	18	22	27	31	36	41	47	54	60	66	74	81	90
Pre-blister	2	3	5	7	10	13	16	20	24	28	32	37	43	49	54	60	66	73	81
Blister	2	3	5	7	10	13	16	19	22	26	30	34	39	45	50	55	60	66	73
Early milk	2	3	4	6	8	11	14	17	20	24	28	32	36	41	45	50	55	60	66
Milk	1	2	3	5	7	9	12	15	18	21	24	28	32	37	41	45	49	54	59
Late milk	1	2	3	4	6	8	10	12	15	18	21	24	28	32	35	38	42	46	50
Soft dough	1	1	2	2	4	6	8	10	12	14	17	20	23	26	29	32	35	38	41
Early dent	0	0	1	1	2	3	5	7	9	11	13	15	18	21	23	25	27	29	32
Dent	0	0	0	1	2	3	4	6	7	8	10	12	14	15	17	19	20	21	23
Late dent	0	0	0	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Nearly mature	0	0	0	0	0	0	0	0	1	2	3	4	5	5	6	6	7	7	8
Mature	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

¹Adapted from the National Crop Insurance Association's "Corn Loss Instruction" (Rev. 1984). ²As determined by counting fully expanded leaves (i.e., those with 40-50% of leaf exposed from whorl and whose tip points below the horizontal.)

Corn Planting

Planting a crop is probably the most important part of the corn production cycle. Typically, the crop must be planted early into a warm, moist and firm seedbed. To maximize yield, the seed needs to be placed at a uniform depth and be evenly spaced in the row. Commercially available row crop planters are capable of doing a good job, but traveling too fast in the field can reduce planting accuracy.

Studies at NDSU found that planters are at their peak performance at low speeds under 5 mph. At speeds above 5 mph, planting accuracy starts dropping off. At 7 mph, seed spacing accuracy dropped off 10 to 15% compared to speeds of 5 mph. Seeding accuracy is a trade-off between speed, plant spacing and number of seeds planted. As your planting speed goes up, potential yield loss goes up.

Seed size does not affect most newer planters ability to meter seeds as long as the correct plates or discs are used along with the correct air flow or vacuum depending on planter design.

Corn Production Guide (continued)

Corn Planting