Integrated Nutrient Management Section R SWES 316

What is Integrated NM?  Considering more than just yield-limiting factors when managing nutrients.  Simultaneous consideration of: –Factors affecting crop yield –Factors affecting crop quality –Economic factors –Environmental factors –“System” factors

The Goals of Nutrient Management are to…  Optimize plant production –Yield/quality –Profit  Conserve resources  Enhance soil quality and productivity

Why Integrated NM?  One cannot manage nutrients in isolation from other factors. Nutrients must be managed as a part of a cropping system because: –Other factors controlling plant growth will also affect nutrient demand and nutrient fate.

Crop-Related Factors  Growth rate (phenology)  Nutrient uptake rate  Salt tolerance  Heat tolerance  pH tolerance  Is the crop harvested, all or part?  Water consumptive use  Unique nutrient needs  Root system depth and distribution  Tissue test levels throughout growing season  Yield potential  Yield  Soil temp requirement  Insect infestation

Soil-Related Factors  Chemical/Biological: –EC (salt) –SAR (sodium) –CEC –Antecedent plant- available nutrients –pH –OM content –CaCO 3 content –Mineralizable N (SOM) –Disease history  Physical: –Texture –Water-holding capacity –Structure/restrictive layers –Soil Depth  Other –Soil management history –Soil variability

Weather-Related Factors  Annual rainfall/relation to crop C.U.  Annual rainfall distribution  Climate: –Average air/soil temperatures during the year –Heat unit accumulations

Irrigation Factors  Water pH  Water EC w  Water SAR  Water SO 4 2-, Cl -, HCO 3 -, CO 3 2-, H 3 BO 3, Na +, Ca 2+, Mg 2+  Availability/cost of water  Crop leaching requirement  Irrigation system: type of system, capabilities wrt amount of water, frequency, uniformity

Fertilizer Factors  Equipment availability for fertilizer application  Irrigation system capabilities  Inorganic or organic fertilizer?  If organic, need the mineralization rate  Compatibility of fertilizers with soil/water  If CRF, need release rate  Fertilizer costs  Is the fertilizer solid, liquid, gas? Mobile or immobile? Acid or alkaline?

Summary  Based upon these lists, we have counted at least 75 different pieces of information that will be needed to make wise, informed decisions about nutrient management.  Where does the information come from? –Grower Experience –Published scientific information –State Extension services (Land Grant Univ.) –Private sector - commercial enterprises

Crop Factors

Corn Phenology Source: Iowa State University

Corn K Uptake Source: Iowa State University

Broccoli N Uptake

EC and Crop Growth “Non-saline”“Saline”

NO 3 -N in Broccoli Petiole Sap

Malting Barley - Response to N Yield Quality

Good Irrigation Management is Essential Source: Paul Brown, UA

Soil Factors

Soil Test Guidelines for Cantaloupes If preplant soil NO 3 -N is: 0-5 ppm add lb N/acre 6-10 ppm add 50 lb N/acre >10 ppm add 0-50 lb N/acre If preplant soil P (HCO 3 method) is: 15 ppmadd 0 lb P 2 O 5 /acre

Variability of Salinity in Soil In this case, salt management, not nutrients, may be the key to crop productivity.

Irrigation/Water/Weather Factors

Leaching Requirement for Pecans Timing and amount of leaching irrigation should be considered when managing fertilizer.

Ensure fertilizer compatibility with water, and with other injected chemicals in pressurized irrigation systems. Compatibility will depend on water pH, HCO 3 -, Ca 2+, EC, etc.

Fertilizer Factors

Organic Fertilizers

Fertilizer Prices Material$/ton$/#N$/#S Gypsum 40 NA0.11 Sulfuric acid 80(soil) NA0.12 Sulfur 250 NA0.14 Nitro-Sul Thio-Sul N-Phuric UAN NA

Example: Integrated Nutrient Management for Cotton in Arizona Courtesy of J.C. Silvertooth

Key Tools for Managing N in Cotton  Use split applications  Follow crop development/N needs –% Fruit Retention (FR) –Height to Node Ratio (HNR) –Petiole NO 3 -N concentrations (PN)  Remember importance of avoiding excess N because of negative influence on reproductive performance of the plant.

Generalized Flower Curve Heat Units Accumulated After Planting Number of Fresh Blooms Pinhead Square Peak Bloom Cut-out

Manage Arizona Cotton for High Fruit Retention and Earliness  NOTE: Earliness is important in desert cotton production for several reasons: –Avoidance of insect problems (whiteflies) –The first fruiting cycle is the most productive, where most yield is to be found –Late flowering (i.e. during the monsoon) can lead to low levels of fruit retention, lower yields

Possible N Management Approaches  Scheduled fertilization based upon either –stage of growth or calendar dates  Feedback approach (recommended) –crop condition (HNR, FR, PN) –Interpretation of feedback depends on stage of growth (HUAP) –reference to established baselines

Feedback Management Requirements  Useable / accessible measurement  Established baselines / guidelines –reference base  Common variety types (species)  Regionally specific baselines  Validation of recommendations

Optimal N Management  Provides for optimal N efficiencies –agronomically (crop response) –economically –environmentally  Improved fertilizer N efficiency –better fertilizer N recoveries  Reduced leaching losses

Steps for Optimal N Management 1. Establish a realistic yield goal 2. Account for soil and irrigation water available N 3. Split N applications 4. Follow crop conditions throughout the growing season and adjust N application accordingly

Optimal N Management (Step 1)  Use realistic yield goal –60 lbs N/bale Unruh, B.L. and J.C. Silvertooth –Upland and Pima, Arizona Mullins, G.L. and C.H. Burmester –Upland, Alabama –sets upper limit for crop N needs assumes high N fertilizer efficiency

Optimal N Management (Step 2)  Account for residual soil NH 4 -N and NO 3 -N –Each 1 ppm NH 4 -N or NO 3 -N in the top 12 inches of soil equals about 4 lb N/ac of available N  Account for irrigation water NO N 2.7 X ppm NO 3 - -N = lbs N/acre ft water  Subtract these values from total N needs

Optimal N Management (Step 3)  Split N fertilizer applications –follow crop condition (HNR, FR, petiole concentration) –window = PHS - PB ( HUAP)  Avoid preseason N applications if possible

N Application Window Heat Units Accumulated After Planting Number of Fresh Blooms Pinhead SquarePeak Bloom Cut-out Split N Applications

Optimal N Management (Step 4)  Monitor Crop Condition: –Fruit Retention (FR) Yield potential is generally related to fruit retention. Lower fruit retention, especially late in the season means lower yield potential. –Height to Node Ratio (HNR) HNR is related to vegetative/reproductive balance. Higher-than-normal values mean excessively vegetative plants, so N application should be delayed. –Petiole NO 3 -N A direct measure of plant N status

Optimal N Management Example  3 bale yield goal X 60 lbs N/bale = 180 lbs N/acre (estimate of upper N fertilizer rate)  Subtract residual soil and irrigation water N –Ex. 15 ppm NO 3 - -N residual/top 12 in = 60 lbs N  Subtract water NO 3 -N –Ex. 5 ppm NO 3 -N x 4 ac ft/ac = 54 lbs N  180 – 60 – 54 = 66 lbs N minimum  Add 20% to allow for inefficiency = 80 lbs N  Split in 3-4 applications (PHS-PB)

N Management Irrigated Cotton  First application at PHS –approximately 50 lbs N/acre  Irrigate/cultivate  Second application near FB –evaluate crop condition (FR, HNR, petioles)  Irrigate/cultivate  Third application before PB –evaluate crop condition (FR, HNR, petioles)

HNR Baselines

FR Baselines

Petiole NO 3 - -N Concentration Baselines

Crop Monitoring - N Management

Crop Monitoring  Case 1 –High fruit load (high fruit retention) HNR within thresholds N input needed If decline in petiole NO 3 - -N is observed –provide application of N fertilizer

Crop Monitoring  Case 2 –Low fruit load (low fruit retention) HNR is high (relative to guidelines) –hold back or reduce N fertilizer inputs –consider Pix application

Crop Monitoring  Case 3 –HNR is low (relative to guidelines) maintain N fertilizer inputs Pix is not needed –Crop is experiencing some form of stress water, N, salinity, etc. –limiting growth –Identify and correct