lecture ppt on fertilizers-studentcopy23-24

Soil Fertility

The study of supplying plant nutrients from the soil.

CEC (Cation Exchange Capacity)

The single most important concept in understanding soil fertility.

Nutrient analysis

Determines the potential of the soil for supplying nutrients to plants during the growing season.

Organic matter decomposition

One of the ways nutrients become available to plants in the soil.

Fertilizers

Manufactured substances used to supply plant nutrients to the soil.

Fertilizer grade

The proportion of primary nutrients (N-P2O5-K2O) in a fertilizer.

Elemental analysis

The analysis of fertilizer expressed in elemental form.

P2O5 and K2O

The oxide forms of phosphorus and potassium in fertilizers.

Conversion formula

%P2O5 x .44 = %P and %K2O x .83 = %K.

Nitrogen

A major nutrient for plants, taken up in the forms of NH4+ and NO3-.

Nitrogen cycle

The dynamic process of nitrogen in the soil, influenced by soil conditions.

Nitrogen fertilizer

Should be added to the soil when the crop will use it, to avoid environmental harm.

Nitrogen soil testing

A method to determine the availability of nitrate-N in the soil.

N-Credits

Accounting for organic additions with low C:N ratios that add nitrogen to the soil.

Phosphorus

A low solubility nutrient in the soil, readily fixed by Fe, Al, and Ca.

P availability control

Controlling pH, placing fertilizer in bands, and maintaining organic matter levels.

Soil test for P

A method to determine the phosphorus levels in the soil.

Solution phase

The phase in the soil where phosphorus is dissolved and available to plants.

Solid phase

The phase in the soil where phosphorus is bound and less available to plants.

Potassium Fertility (Potash)

Potassium (K+) is a problem on acid soils, soils with low CEC, soils with irrigation or high rainfall where leaching can readily occur. Potassium can be stored in the soil from one year to the next. K is not a pollutant - even if leached from soil, K does not cause environmental problems.

Soil test

0-40 ppm = very low, 40 – 80 ppm = low, 80-120 ppm = medium, 120 – 160 ppm = high, > 160 ppm = very high (> 160 = no K needed)

Potassium

Potassium is found in minerals like feldspars and micas (90% of Soil K). K is fixed inside of clay minerals (9% of soil K). K is on the soil exchange sites (1%). K is in the soil solution (0.1%).

Ca, Mg

Calcium and Mg - when soils are low in Ca, Mg, they have a pH problem and by adding lime or dolomite the pH and Ca, Mg problem is corrected. On some acid, sandy soils Mg deficiency on corn has been noted. 15 lbs as a starter or 75 lbs broadcast corrected the problem.

Sulfur

Most soils in Mn would not respond to additions of Sulfur because of adequate levels and atmospheric deposition. However, on sandy soils in NE Minnesota yields have increased with 25 lbs/Acre to Alfalfa, Corn and Small grains.

Nutrient Analysis

N - P - K = N -P2O5 - K2O. % P = 0.44 x %P205. %K = %K20 x 0.83.

Micronutrients

Iron - Fe, Boron - B, Zinc - Zn, Copper - Cu, Molybdenum - Mo, Chlorine – Cl, Manganese - Mn, Cobalt Co, Nickel.

Role of Micronutrients

Boron is believed to be involved in carbohydrate transport in plants; it also assists in metabolic regulation. Chlorine is necessary for osmosis and ionic balance; it also plays a role in photosynthesis. Zinc participates in chlorophyll formation, and also activates many enzymes. Copper is a component of some enzymes and of vitamin A. Iron is essential for chlorophyll synthesis, which is why an iron deficiency results in chlorosis. Manganese activates some important enzymes involved in chlorophyll formation. Molybdenum is used by plants to reduce nitrates into usable forms. Cobalt is thought to be an important catalyst in nitrogen fixation. Nickel has only recently been shown to be an essential nutrient for plants.

Correcting pH problems for most soils will correct micronutrient deficiencies

Nutrient Management

Need to manage nutrients for plant growth, feeding the world, economic reasons, aesthetic reasons, and environmental reasons (N in drinking water, hypoxia in Gulf of Mexico, eutrophication of fresh waters).

Tools for detecting nutrient deficiency

Tissue testing - involves a complete and detailed laboratory analysis of nutrient elements in the plant leaves. Recommendations are made on the basis of these test results, backed by research and dependent on plant growth stage and plant part.

Soil testing

Collecting a soil sample to determine the current nutrient status of the soil.

Sufficiency Method of Nutrient Needs

Uses soil testing to predict fertilizer needs. Based on greenhouse and field research. Soil test is a predictive tool. Gives soil credit for its nutrient providing ability.

Correlation

Process used to determine if a soil nutrient, as extracted by a soil test, and crop response to added nutrient, are so related that one directly implies the other.

Exploratory fertilization trial

Greenhouse – a controlled environment with soil homogeneity. Trials in field with selected soils not as controlled but needed to verify greenhouse trials.

Low

A soil test category with a 75% chance of a low response to soil testing.