Crop Physiology Crop Water Usage

andFertilizer Uptake

Charles Stichler Professor Emeritus

Crop ManagementWithout knowing how a plant grows and develops, it is impossible to make wise decisionsWater, fertilizer uptake and plant growth all effect the response of the other – they work together Crop production is NOT a series of “cook book”steps – “It’s the eye of the feeder that fattens the calf” Each field must be managed separatelyWater is the single most important factor related to productionFertility is second most important factor

Function of WaterWater is the “blood” of a plantCool the plant – transpirationNutrient uptake from soilCell elongation Cell function and enzyme activityPhotosynthesis Nutrient and photosynthate transport

C02 + H2O = C6H12O6

1. Makes Food2. Energy Stored3. Occurs in chloroplasts4. Oxygen is released5. Water is used6. Carbon dioxide is used7. Occurs in light

Leaves are solar collectors

Yield is the result of photosynthetic conversion

The more leaf area – the more carbohydrates are produced The more water use from more leaves The more fertilizer needed to grow the leaves and roots

What is the yield goal of a field????

Planting Harvest

Bloom and seed fill

General Water and NutrientUse Curve for All Crops

0.3

0.1

Inches of water per day

Planting Harvest

Bloom and seed fill 0.3

0.1

Inches of waterper dayRoots pick up ions (nutrients) as they pick up water - themore water the plant picks up - the more nutrients it also picks up.

Soil Microbes – are like cattle in a feedlot

1. They cannot move 2. Heat – 55 F3. Water4. Oxygen 5. Carbohydrates6. N-P-Nitrogen - protein

In the soil – microbes get the nitrogenFIRST – after decomposition – and the microbes die and decompose –the nitrogen is available.

If you plant into a lot of residue – youhave to feed the microbes FIRST –before the crop gets some of the N

Root Hairs do almost all the absorption of nutrients and water

Root hairs are short lived – often onlya few days

98% of Nutrients are absorbed from the soil solution – only about 2% are absorbed directly from soil particles

Black dot represent nitrogen or soluble nutrientsWashington State University

Black dot represent nitrogen or soluble nutrientsWashington State University

Black dot represent nitrogen or soluble nutrientsWashington State University

8 week old corn plant

Corn root development

1. Plant deep enough –1 ½ -2”

2. Side dress fertilizeraway from “crown”roots.

3. Do not cultivate too close to the plant

4. “Dirt” the base of theplant

5. Apply lay-by herbicidesafter “dirting”

V-7 tassel

V-6 plantears begin to develop

About 35 days after emergence, the head begins to form.

Cotton

AT EARLY BLOOM 80-90% OF THE CROP TO BE HARVESTED IS

ALREADY ON THE PLANT.

Water and Fertility Stress

Corn Abortion of ovules on the end of the cobAbortion of ovules from failure to pollinate

Sorghum –@ 40 DAP – stress causes charcoal rot @ 70 – ovule abortion – lack of exertion

Cotton – flower/fruit abortion

Seedling 10 8 2 3 7 6Early Sq. 20 14 5 8 30 25Bloom – Boll 56 42 24 38 46 38Boll-Maturity

48 36 30 51 37 31

Totals 134 61 120

Cotton Nutrient UptakeNitrogen

Pounds %Phos.

Pounds %Potassium

Pounds % 2 Bale Crop

Stage DAP N P KSeedling 0-20 9 2 18RapidGrowth

21-40 61 18 103

E. Bloom 41-60 60 28 85Grain Fill 61-85 27 21 39Maturity 86-95 28 11 13Total Harvest 185 80 285

Nutrient Requirement for 7,500 Sorghum

Stage Days #/N % #/P % #/K %Early 0-25 19 8 4 4 22 9RapidGrowth

25-60 84 35 27 27 104 44

Silk 65-75 75 31 36 36 72 31Grainfill

75- 115 48 20 25 25 36 14

Mature > 115 14 6 8 8 6 2Totals 240 100 240

Nutrient Usage in 180 Bushel Corn

Grain in Corn Growth

0102030405060708090

100

18 22 25 29 32 36 39 43 46 50 57

Average of 3 varieties

Days After Silking

Percent of Total Wt

Early Dent

1/2 Milk Line

Black LayerTop of Cob

Stichler ‘97

Yield is a measure of how much water

a crop uses

Average Yield/Inch of Water

Cotton - 50-60 lbs of lint/inch15 inches X 50 = 750 lbs. of lint

Corn - 7 bushels/inch15 inches X 7 = 105 bushels

Sorghum - 300 lbs/inch15 inches X 300 = 4,500 lbs

Wheat - 3.5 bu/inch15 inches X 3.5 = 52.5 bushels

Corn – High PlainsSeed 0.25Emerg. 0.354 leaf 0.455 leaf 0.706 leaf 0.858 leaf 1.0010 leaf 1.1512 leaf 1.2014 leaf 1.25Tassel 1.25Silk 1.30Blister 1.30Milk 1.30Dough 1.20Dent 1.00½ Milk 0.90Blk Lyr 0.70

Corn – UvaldeSeed 0.20Emerg. 0.254 leaf 0.305 leaf 0.406 leaf 0.488 leaf 0.7810 leaf 0.9512 leaf 1.1514 leaf 1.15Tassel 1.20Silk 1.25Blister 1.35Milk 1.35Dough 1.35Dent 1.35½ Milk 1.30Blk Lyr 1.30

Cotton – HPSeed 0.071st Sq. 0.221st Blm 0.44Peak B. 1.101st OB 1.1025% O 0.8350% O 0.4495% O 0.44

Sorghum – HPSeed 0.40Emerg 0.403 leaf 0.554 leaf 0.605 leaf 0.70Hd. Init 0.80Flg Lf 0.95Boot 1.10Heading 1.10Bloom 1.00Sft Dgh .95Hd Dgh 0.90Blk Lyr 0.85

Crop Coefficient X ET = Water Used

1.35 X 0.289 = .390 Inches/day

Cotton

Calculated water need 18.69 inApplied + rainfall 18.49 in

Yield 101.13 lbs of lint/inch

Average of 50-60 lbs/inch

Total water 14.2 inches

Yield 130 bu = 9.15 bu/in

Average of 7 bu/inch

Available Water

Field Capacity can be thought of as all the water a soil can hold against the pull of gravity

SummaryCrop production is a balance of water, fertility, temperature, sunlight and crop development

The amount of water and nutrients applied is not as important as timing

Understand when the crop needs whatand apply it according to the developmental stage of the crop