Section 3 - Soil Nutrient Management Flashcards
To identify the most efficient nutrient application rate from soil test results, soil tests must be calibrated against crop responses to applied nutrients in field experiments conducted over a wide range of soils and climate conditions. Yield responses from various rates of applied nutrients can then be related to the number of available nutrients indicated by the soil test. An accurately calibrated soil test.
(1) correctly identifies the degree of nutrient deficiency or sufficiency and
(2) supports the estimated nutrient rate required to optimize crop productivity.
True
Chelate‐micronutrient relationships and stability in soils are utilized in soil testing for micronutrients. Knowledge of chelate availability in soil provides the basis for developing the DTPA soil test for Fe, Zn, Cu, and Mn, which is used in most soil‐testing laboratories.
True
Meeting food security needs for a growing population (estimated to be 9.5 billion in 40 years) will require approximately 50–70% increase in food production on approximately the same or less agricultural land area used today.
True
High crop yields are impossible with low levels of fertility. Soil nutrient supply can be controlled; however, the initial cost of building soil fertility from low to high levels may discourage growers if viewed as an annual investment. Residual nutrient availability from past applications should be included in analyses of nutrient economics.
True
Each nutrient has a specific nutrient absorption rate in a plant leaf which has a specific solution concentration.
True
What are the three soil qualifications that determine their permanence and sensitivity to management?
1) Ephemeral
2) Intermediate
3) Permanent
Soil test calibration studies also provide data to establish fertilizer recommendations. For example, at each field location, P rate required for optimum yield can be determined and displayed.
True
Soil enriching benefits from manure, in addition to those from nutrients, are related to the OM that improves soil structure and moisture relations, increase the mobility of P, K, and micronutrients, and stimulates microbial activity. There is considerable variability in manure, depending on methods of storing and handling; however, with current fertilizer, labor, and equipment costs, it is usually profitable for the grower to use livestock manure.
True
Land managers must adopt economically viable technologies that maintain, enhance, or protect the productive capacity of our soil resources to ensure future food and fiber supplies. While organic nutrient sources are important to meeting the nutritional needs of higher-yielding cropping systems, inorganic fertilizer nutrients will remain the predominant nutrient source.
True
The best extractant should mimic what the roots see in the rhizosphere.
True
Foliar applications do not replace soil applications of macronutrients but work fine for ___.
micronutrients
Late foliar applications can increase nutrient concentrations in the final product (grain, fruit).
True
___: application of nutrients, primarily N, P, K, and S, through an irrigation system. Can be performed in the furrow, center pivot (overhead sprinklers), and micro-irrigation (drip) systems.
Fertigation
The growth stage is important in plant analysis because nutrient status and demand vary during the season. Nutrient concentration in vegetative parts usually decreases with maturity. Misinterpretation of plant analysis results is common if sampling time is not identified correctly.
True
Nutrient analysis on ___ ___ is important in diagnosing the nutrient needs of growing plants.
fresh tissue
Exchangeable plus solution K+ is usually extracted with 1 M NH4OAc. The NH4OAc soil test extracts + in concentrations related to K availability to plants; however, as with P, crops vary in their responsiveness to K.
True
In addition to leaf symptoms, nutrient deficiencies have a marked effect on ___ ___.
root growth
Identify 3 factors why with cooler temperatures nutrient uptake is reduced.
- mass flow of nutrients is reduced by decreased growth rate and transpiration
- diffusion rate decreases with declining temperature and a lower concentration gradient
- Mineralization of organically bound nutrients is reduced.
Crop residue management (tillage) systems have been developed to leave more crop residue on the surface to reduce soil and/or water loss compared with conventional or full tillage systems wherein all residues are incorporated into the soil after harvest and/or before planting.
True
Why is higher soil test P required for a given runoff P concentration in clay soils compared to stand soils?
P is adsorbed more strongly in sandy soils.
P is adsorbed less tightly in sandy soils.
P is held less tightly in the clay compared to the sandy soils.
P leaching occurs more in clay soils through macropore flow.
P is adsorbed less tightly in sandy soils.
Measuring which of the following soil properties would provide a good indication of root penetration, air-filled pore space, and microbial activity in the soil?
Soil OM
sodicity
bulk density
microbial biomass
bulk density
What are the four R’’s
- Rate
- Time
- Source
- Place
Two growers have the same low P soil and plant sorghum. Farmer A broadcasts 45 lb P2O5/a and, Farmer B bands the same rate below the seed at planting. 100 lb N/a were applied to each field. The following results were obtained.
Farmer A Farmer B
Unfertilized grain yield (lb/a) 2400 2400
Unfertilized grain N content (%) 1.2 1.2
Unfertilized grain P content (%) 0.2 0.2
Fertilized yield (lb/a) 3600 4200
Fertilized grain N (%) 1.8 2.4
Fertilized grain P (%) 0.24 0.3
(Hint: nutrient (%) use efficiency=(nutrient uptake–nutrient in unfertilized)*100)/nutrient applied)
a. Calculate the fertilizer P use efficiency (%) for the two growers.
b. Calculate the fertilizer N use efficiency (%) for the two growers.
c. How much fertilizer N remains in the soil profile after harvest for the two growers? .
When solution P decreases with plant uptake, P minerals dissolve or adsorbed P desorbs to resupply soil solution P. Chemical extractants used for P soil tests simulate this process, as they reduce solution Al or Ca. As solution Al or Ca decreases during extraction, native Al‐P or Ca‐P minerals dissolve to resupply solution Al or Ca. Solution P then increases, which provides a measure of the soil’s ability to supply or buffer plant-available P.
True
List 6 reasons why soil testing is important for agricultural development?
- Increasing yield
- Farm profitability
- Crop resilience
- Efficient resource use
- Food & income security
- Environmental quality
The maximum economic yield represents the yield level where the last unit of input pays for itself and is less than the maximum yield.
True
Pre-season approach: (Site-Specific Nutrient management)
- Previous crop yield data obtained from a yield monitor combine
- Soil test data obtained from the grid, cell, or zone sampling
- Digital orthophoto quarter quads (DOQQQ) – aerial photographs
- Aerial or satellite provided NDVI
- Digital elevation
- Soil electricity conductivity (EC) – correlation with soil texture, depth, salinity, etc.
True
Broadcast applied N usually is less efficient than subsurface applied N in high surface residue cropping systems. Use the following data to calculate the % fertilizer N recovery for each system. What caused the difference?
(Hint: N(%) recovery = (method of application N uptake – (N in unfertilized)*100)/N applied)
Broadcast N Subsurface N Unfertilized
N rate 100 lb N/a 100 lb N/a 0 lb N/a
Grain yield 98 bu/a 110 bu/a 75 bu/a
Test Weight 56 lb/bu 56 lb/bu 56 lb/bu
% Grain N 2.1% 2.4% 1.8%
Unfertilized N uptake: (75 bu/a) (56 lb/bu) (1.8% N) = 75.6 lb N uptake
Broadcast N uptake: (98 bu/a) (56 lb/bu) (2.1% N) = 115.3 lb N
% N recovery = [(115.3 lb N - 75.6 lb N) / 100 lb N] x 100 = 39.7%
Subsurface N uptake = (110 bu/a) (56 lb/bu) (2.4% N) = 147.8 lb
% N recovery = [(147.8 lb N - 75.6 lb N) / 100 lb N] x 100 = 72.2%
Immobilization of broadcast fertilizer N by surface residue, volatilization, etc., reduced N availability to crops and reduced fertilizer N recovery.
Water use efficiency (WUE) is the yield of the crop in bushels, pounds, or tons per acre-inch of water from the soil, rainfall, and irrigation. Any practice that promotes plant growth and the more efficient use of sunlight in photosynthesis to increase crop yields will increase WUE.
True
Each visual symptom is related to a nutrient function in the plant. Most nutrients have several functions, making it difficult to identify the reason for a particular deficiency symptom.
True
What are three factors that indicate physical soil loss by water and wind reduces soil productivity?
1) decreasing topsoil thickness and rooting depth
2) decreasing OM and microbial activity, which decreases nutrient supply
3) decreasing depth to higher subsoil clay content, which decreases infiltration and plant available H2O
A nutrient management plan includes:
- Field and soil map
- Soil testing and plant analysis
- Crop and crop rotation
- Yield expectation
- Nutrient sources
- Recommended rates
- Application timing
- Placement method
- Proximity to sensitive areas
True
It is important to recognize that nutrient movement to
surface- and ground-water occurs in natural ecosystems. Water quality standards for drinking water have been established for all elements that adversely affect health when present in high concentrations.
True
If you apply zinc to phosphorus-deficient soil, your yield will at least be better than what it was before you applied it since zinc and phosphorus do not have negative interactions.
True
False
False
Many factors can interfere with the foliar application, so:
- Foliar nutrients should be applied before plant demand is high
- Plants with severe nutrient deficiency respond quickly to foliar application
- Plants with hidden hunger may show yield response
- Excessive foliar nutrient application can cause leaf burning
- Application when leaves are wet increases absorption and response
- Heat or moisture stress reduces the nutrient absorption rate
- Leaf cuticle thickness with plant age: applications are more effective early in the season
- Nutrient application can be reduced by physical droplet runoff: use surfactant
True
What does MAR stand for?
Maximum accumulation rate
Soybean:
- Uptake Order: N>K>Ca>P>Mg>S
- N and P redistribution from leaves into grains, while K redistribution from the stem into grains
- K maximum accumulation rate takes place earlier (R2-R3
True
Earlier planting dates extend the growing season for spring-planted crops, which generally increase yield potential. For example, soybean yield response to increasing soil test K level was greater with earlier planting.
True
___ ___ ___: With mobile nutrients, soil test buildup and/or maintenance programs are not viable, because these nutrients are readily mobile in the root zone in many soils.
Mobile Nutrient Recommendations
Greenhouse Strip Tests Simple greenhouse tests involve growing plants in small amounts of soil collected from a field suspected of being nutrient deficient to assess nutrient availability.
True
___ ___ ___ can be related to factors other than nutrient stress.
Visual deficiency symptoms
___ ___: nutrients applied directly to leaves to remedy obvious (visual) nutrient deficiencies or prevent hidden hunger (not visual) that impacts crop yield or quality
Foliar application
When buying land, the producer may choose high- or low-priced property. The higher-priced land is generally more productive, is fertile, and has better improvements. The lower-priced land may be a good buy, provided the land is not severely eroded or has no other physical limitations to productivity. Low-priced land is usually infertile and may need considerable lime and/or nutrients. Adequate liming and fertilization, as indicated by soil tests and combined with other good practices, can rapidly increase productivity.
True
At optimum N rates, about 10–20% may be residual for next year’s crop if it is not leached below the root zone. The residual value of P and K can vary from 25 to 60%, depending on the rate applied, crop removal, and soil properties influencing P and K availability.
True
What does NSI stand for?
Nitrogen Sufficiency Index
Under normal conditions, if a plant nutrient is mobile in the plant, its deficiency symptom will first show up in older leaves.
True
False
True
The Late 1940s, soil testing became an important practice for determining the need for lime and fertilizer in the United States
True
What can I do to improve soil quality on my farm or garden?
- Plant cover crops!!!!!!!!
- Keep something growing year-round! Never expose the soil to raindrops!
- Leave lots of plant residue on the soil surface. Mulch garden!
- Avoid tillage if at all possible!
- Soil test and follow the recommendations.
- Plant crops adapted to your area and time of planting.
The plant sap test is used for:
semi-quantitively determine the concentration of
essential nutrient in plant tissue
determine soil nutrient concentration
accessing soil air quality
determine plant growth
semi-quantitively determine the concentration of
an essential nutrient in plant tissue
As plant nutrients cycle through the soil-plant-atmosphere continuum, some will be recovered through plant uptake, incorporated into OM, adsorbed to mineral and OM surfaces, and precipitated as solid minerals. The remaining nutrients can be transported from the field through runoff and subsurface lateral flow toward streams and rivers, and by leaching to groundwater.
True
Most of the errors that take place in the soil testing processes are caused by not taking the correct soil sample.
True
False
True
What does CNR stand for?
Critical Nutrient Range
What are the three objectives of soil testing?
- provide an index of nutrient availability in soil.
- predict the probability of obtaining a profitable response to fertilizer or lime.
- provide a basis for the development of fertilizer and lime recommendations.
What is Chlorosis?
Uniform or interveinal yellowing or light green coloring of leaves
The amount of nutrients required depends on the plant (crop, yield level, variety/hybrid, planting rate), environmental conditions (moisture and temp), soil (properties, fertility, landscape), and soil/crop management
True
Plant response to fertilization can be greatly increased if nutrients are applied properly. Under reduced and no-tillage systems, surface accumulation of residue and nutrients combined with cooler temperatures and higher moisture in the spring can influence nutrient use. In many cropping systems, especially with low soil test P and/or K, nutrients applied below the soil surface often enhance plant growth and yield.
True
