Soil Fertility & Water Use

Base Row Crop Replanting Decision On Calendar, Stand
Around June 10, a corn crop with stands of less than 12,000 plants per acre could be torn up and replanted to a crop like sunflower or soybeans that can be planted at this date and still mature. By June 15, however, the decision may be to keep a stand of 12,000 to
14,000 plants per acre because it would be too late to plant a good alternative.

Uniformity of stand is the key to evaluating a poor stand. If there are no large skips in the field, fairly low plant populations of soybeans (75,000/ac), dry beans (50,000/ac) and sunflower (10,000 to 11,000/ac) can still maintain yields. These plants have the ability to branch or flex and fill in space. This is not as true with corn, and weeds also become a bigger problem.

About the only replant choice in mid-June is flax, buckwheat, early-short season sunflower or proso millet. Other options to consider would be to grow a crop for hay, or plant winter wheat in the fall. Remember to take crop insurance into consideration, and herbicide used in the prior planted crop and whether it may create a problem with injury to a crop change. 

Topdressing N in Wheat
If topdressing for yield, apply N as soon as possible after planting. NDSU data indicates that wheat yield response to topdressing is greatest through tillering. Topdressing N deficient small grains from emergence to the 6-leaf stage may serve to increase yield provided a timely rain incorporates the application prior to jointing. Topdressing after the 3-leaf stage may help head size, spikelet number and kernel number decision, all of which are yield component decisions that the wheat plants make. Topdressing N before the first joint extends will not leave wheel tracks in fields. Traffic across fields later breaks the stem below the joint and will leave tracks visible through harvest.

Topdressing from jointing through the watery ripe stage of grain development will often serve to increase protein content of grain, but will have little if any effect on yield. Applications of N past the watery ripe stage would have no real effect on grain protein content. By the time the wheat crop starts heading out, it has accumulated nearly all of the nitrogen that will eventually show up in either grain yield or protein. (see N use tables, graphics). Consequently, it’s generally recommended that nitrogen applications for enhancing protein be made as soon after tillering as possible and before flowering and pollination.

Approximate Pounds of Nitrogen Per Plant Per Acre for 45 bu/a Hard Red Spring Wheat (Based on Bauers wheat growth studies)

Leaf Stage	4	5	6	7	8	9 Boot	10 Heading	11 Flowering	13 Milky	15 Mealy
GDD	511	657	803	949	1095	1241	1416	1591	2191
	Pounds of Nitrogen
Leaf	15	25	30	35	45	50	50	40	25	5
Stem			10	20	30	35	40	45	40	15
Heads							5	20	55	105
Total	15	25	40	55	75	85	95	105	120	125
The season patterns of accumulation of nitrogen in the different parts of wheat plants are illustrated above. (Source: NDSU Extension Service)

Pounds of Nitrogen in 15% Protein Wheat Grain at Various Yields

Typical Nitrogen Uptake Per Acre for 45 bu/a Hard Red Spring Wheat

An increase in protein as a result of a mid-season application of N is likely to be no more than one whole percent increase; for example, an increase from 13 to 14%. The only exception that is likely to occur is in sites that were very nitrogen-deficient at the time of planting. 

Topdress Dry or Liquid N?
Both dry and liquid N products can be used for topdressing wheat. Dry products may be less expensive, while liquid products may offer the advantage of being used as a herbicide carrier. Urea solutions offer an added advantage of reduced leaf burn. Dry granular products can be applied at any rate. If dry urea is used, it might be wise to also have it coated with Agritain®, which is a tried, tested and proven urease inhibitor, and gives about 10 days of protection from volatility.

The amount of liquid N that can be applied without leaf burn diminishes as temperatures rise and crop growth accelerates. Forty lb N/acre as liquid N is a relatively safe rate when temperatures are cool and small plants provide 40-60% ground cover. With high temperatures and a ground covering crop canopy, safe rates drop to 10-25 lb N/acre with increased margins of safety for urea solutions.

If topdressing applications using liquid N (UAN, 28-0-0), it’s recommended to use streamer bars to minimize and reduce leaf burning and crop injury. Streamer bars concentrate the application into bands, which tend to drive most of the fertilizer to the soil surface rather than coat the leaves, where it could damage the leaf tissue. A concentrated band also slows the rate of urea volatilization from the urea portion (the N in UAN is about 50% urea) of the UAN.

Leaf burn potential when applying liquid N increases as the wind increases. Under windy conditions, the wind breaks the stream apart and converts it into a poor broadcast application, coating leaves and increasing burn. Do not broadcast UAN; the burn will be great and may cause a yield reduction in some cases.

Whichever source is used, rain is needed (¼ to ½”) to move the N into the soil so that roots can utilize it. 

Sidedressing Corn, Sunflower
Sidedressing corn (a practice usually reserved for sandy soils prone to leaching) should start when the corn is tall enough that clods do not cover the young plants. Usually 4-8 leaf corn is ideal. Corn can physically be sidedressed until the equipment starts snapping off stalks, but it’s better to apply it earlier than that. If the crop becomes too tall to sidedress by knifing in anhydrous, liquid N can be applied through drop tubes from a high-clearance sprayer, with booms rigged to the same width as the planted rows. Sunflowers can be sidedressed when clod movement danger is past, to when they are too tall to physically get through. Usually 6-18 inches is best.

Applying N in the Fall
Fall anhydrous ammonia application should wait until about October 1 and only when soil temperature at 4 inches in depth, taken between 6-8 a.m., is below 50 degrees F. Application of anhydrous before these conditions usually results in conversion of N to nitrate, which leads to leaching losses in late winter, early spring and denitrification in heavy soils. Application even after these conditions is not totally without risk, but the chances of going into freeze-up with mostly ammonium N are greatly increased.

Application of banded urea should be delayed until about one week following conditions favorable for anhydrous application. Incorporated broadcast urea should be delayed two weeks after conditions are favorable for anhydrous application.

Don’t Short Your ’06 Crop: Soil Sample This Fall
Not knowing how much N is available in the soil for your ’06 crop is like throwing money away, shorting the crop of its yield potential and allowing unused soil N to go to waste.  Soil sampling is also valuable in evaluating other production factors such as soil pH, which can influence the effectiveness of some herbicides.

For more information on soil sampling and soil nutrient management, see the University of Minnesota web site, www.extension.umn.edu. Click on the “farm” link, then “soil nutrient management.” NDSU has soil sampling and fertility information online at www.ext.nodak.edu/extpubs/soilfert.htm.

Stop Losing Crop Income Potential to Poor Drainage
Incorporating subsurface or tile drainage on poorly drained soils typically reduces seasonal yield variation and increases average yields.  There are other advantages: tile drainage will cause soils to warm up and dry out faster in the spring. Fields with intermittent wet spots will dry out more uniformly. And spring field operations on tiled fields will most likely be possible at an earlier date than fields without tile drainage.

Ag engineer Gary Sands and others at the University of Minnesota are involved with research and outreach in recent years concerning tile drainage in northwest Minnesota.

Crop response information from the ongoing project has begun to help quantify the impacts of drainage (or lack thereof) for northwest Minnesota growers. For example, 1990-1998 data for wheat suggests an estimated average loss over the period of 15.25 bu/yr which, at $3.89/bu, is $59.32 per ac per year. If water was the most significant underlying production problem over this period, and if it were responsible for just half the 15.25 bu/yr average loss – and could be corrected through drainage – this would translate to $29.66 per acre per year, or $14,831 per year for a typical 500-acre wheat producer, according to Sands.

There are several links on the MN Wheat web site (www.smallgrains.org) with information about tile drainage. Under Production and Research Info, click on the link “Tile Drainage Info for Minnesota Farmers.” Here, there are FAQs and resources on tile drainage. Click on the link “2004 Wheat Research Review” and then “Determining Wheat Response to Tile Drainage in the Red River Valley” for a report on tile drainage research.  Grygla, MN producer Todd Stanley described his experiences putting in tile drainage in a story for Prairie Grains. To read it online, go to www.smallgrains.org/springwh/Feb05/drain/drain .htm. The U of M Drainage Outlet Web Site is http://d-outlet.coafes.umn.edu.

--------------------------

Water Use of Wheat
A wheat crop of about 50 bushels per acre has a water requirement that is about equivalent to 10 inches. However, because water also evaporates from the soil surface, the actual amount of water needed to produce a crop is higher. Under most conditions in the Northern Plains, small grains will need between 14 and 16 inches of soil moisture per season, depending on climactic conditions and the length of the growing season.

Daily crop water use, also called evapotranspiration or ET, depends on canopy development and will generally peak between heading and early dough stage. Daily ET during this peak period can range from 0.10 to 0.30 inches depending on air temperature and cloud cover. The table below shows estimated daily ET rates figured for spring wheat in central Minnesota at different stages of growth and selected maximum daily air temperature ranges. As weather is variable by location, so too will daily ET estimates vary by location. Real-time estimated daily crop ET may be observed over the Internet during the growing season at: ndawn.ndsu.nodak.edu. 

Average Water use for Wheat in Inches/Day in Central Minnesota

Temp.(°F)	Week After Emergence
	1	2	3	4	5	6	7	8	9	10	11	12	13	14
50-59	.02	.03	.05	.06	.08	.09	.10	.10	.09	.09	.07	.05	.03	.02
60-69	.03	.05	.07	.09	.12	.13	.15	.14	.13	.13	.10	.07	.05	.03
70-79	.04	.07	.10	.12	.17	.17	.19	.19	.18	.17	.13	.10	.07	.04
80-89	.05	.08	.12	.16	.20	.22	.24	.24	.22	.21	.16	.12	.08	.04
90-99	.06	.10	.15	.18	.24	.26	.29	.28	.26	.25	.19	.15	.10	.05
		^	^			^		^			^	^
Growth Stage		Tiller ing	Jointing			Heading		Early Milk			Soft Dough	Hard Dough

Troubleshooting Nutrient Deficiencies
Back-to-Basics, an informative crop fertility web site sponsored by Mosaic (IMC Global/Cargill Crop Nutrition), has one of the most comprehensive photo illustration guides to troubleshooting crop nutrient deficiencies on the Internet. Go to www.back-to-basics .net and click on the link “Nutrient Deficiency Symptoms.” There, visual nutrient deficiency symptoms can be found for various field crops, including corn, canola, soybeans, and wheat.

A flow chart for identifying nutrient deficiencies in corn, compiled by the University of Minnesota Extension Service, can be found online at www.extension.umn.edu/cropenews/2002/nutrientdeficiencyflowchart.pdf.

Nutrient deficiency symptoms for a number of crops can also be found online at www.nrs.mcgill.ca/whalen/nutrient/Symptom.html, web site of Joann Whalen, Soil Fertility Program, MacDonald College of McGill University, Canada.  The images (prepared by the Potash & Phosphate Institute) take time to download, but are unique in that deficiency symptoms of secondary and micronutrients are illustrated, along with N-P-K.

Potassium Deficiency in Wheat

Nitrogen Deficiency in Wheat

Phosphorus Deficiency in Wheat

------------------------------

Determining Yield Probability Based On Soil Moisture
Studies at NDSU have indicated that 5 inches of water is needed by wheat to reach the heading growth stage. After this requirement is met, each additional inch of water will produce 4-7 bushels of wheat. The water can be provided by soil or rainfall.

Sandy soils hold about 1 inch of plant available water, clay soils about 2 inches and loam soils 2.25 inches per foot of soil at field capacity. Average May, June, July rainfall in North Dakota is about 8 inches. Rainfall, depending on crop growth stage, is more efficiently used in June than in other months, which may provide increased yields above predicted yields.

Total -Water Available Wheat Yield Bu/A Barley Yield Bu/A 8 12-21 21-30 9 16-28 28-40 10 20-35 35-50 11 24-42 42-60 12 28-49 49-70 13 34-56 56-80 14 38-63 63-90 15 42-70   16 46-77

Critical growth stages for major crops1 Crop Critical period Symptoms of water stress Other considerations Alfalfa Early spring and immediately after cuttings Darkening color, then wilting Adequate water is needed between cuttings Corn Tasseling, silk stage until grain is fully formed Curling of leaves by mid-morning, darkening color Needs adequate water from germination to dent stage for maximum production Sugar beets Post-thinning Leaves wilting during heat of the day; abnormal dark green color Most sensitive to moisture shortages in early growing stages but peak moisture use comes later in the season when they have complete ground cover Soybeans Bloom and fruit set Leaf wilting Any stress from R4-R6 (late pod development/early seed fill) causes more yield reduction than at any other time Small grain Boot and bloom stages Dull green/bluish color, rolled up leaves; firing of lower leaves Small grain crop injury from drought stress can appear similar to herbicide injury symptoms Potatoes Tuber formation to harvest Wilting during heat of the day Water stress during critical period may cause cracking of tubers Sunflower Preplant, bud and bloom Leaf wilting Most sensitive to moisture stress during flowering; least sensitive during vegetative period (emergence to early bud) 1 NRCS Colorado Irrigation Guide, NDSU, Colorado State University See the NDSU web site www.ag.ndsu.nodak.edu/drought/drought.htm for more information on coping with drought and dry conditions, covering various crop and livestock issues, with good links to other drought-related web sites as well.