UPMSP Intermediate Agricultural Chemistry flashcards
UPMSP Intermediate Agricultural Chemistry · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Agricultural chemistry
- Branch of chemistry applied to soils, plants, fertilizers, and agro-chemicals, aiming to raise and sustain crop production while conserving soil and environmental quality.
- Law of the minimum
- Liebig's principle stating that crop yield is limited by the essential nutrient present in shortest supply relative to plant need, not by total nutrient abundance.
- Soil fertility
- The inherent capacity of a soil to supply essential plant nutrients in adequate amounts and available forms for healthy crop growth and sustained yields.
- Cation exchange capacity
- Total exchangeable cations a soil can hold, expressed in cmol(+)/kg; it depends mainly on clay type and organic matter content.
- Mobile versus immobile nutrients
- Mobile nutrients such as nitrogen, potassium, and magnesium move to young tissue, so deficiency appears on older leaves; immobile calcium, iron, and boron show symptoms on young leaves.
- Critical level
- Soil-test nutrient value below which a profitable crop response to added fertilizer is likely; above it, added nutrient rarely increases yield.
- Integrated nutrient management
- Combining mineral fertilizers, organic manures, biofertilizers, and crop residues to meet crop nutrient demand while maintaining soil fertility and reducing losses.
- Split nitrogen application
- Applying nitrogen in two or more doses timed to crop uptake peaks, reducing leaching and volatilization losses compared with a single heavy basal application.
- Fertilizer grade
- Percentage of nitrogen, available phosphorus expressed as P2O5, and potassium expressed as K2O in a fertilizer, written in that fixed order.
- Urea
- Concentrated solid nitrogen fertilizer with grade 46-0-0; it hydrolyses in soil to ammonium carbonate and loses ammonia if left on the surface.
- Green manure
- A legume or other crop grown and ploughed into the soil while green to add organic matter and biologically fixed nitrogen for the following crop.
- Biofertilizer
- Live microbial inoculant such as Rhizobium, Azotobacter, or phosphate-solubilizing bacteria that improves nutrient availability to crops through biological activity.
- Fertilizer dose calculation
- Recommended nutrient rate divided by the nutrient fraction of the fertilizer, multiplied by area, gives the weight of fertilizer needed.
- Soil pH
- Negative logarithm of hydrogen ion activity in the soil solution; it governs nutrient availability and the solubility of toxic aluminium and manganese.
- Lime requirement
- Quantity of calcium carbonate or dolomite needed to raise an acid soil to a target pH, determined from soil pH, texture, and buffer capacity.
- Buffering capacity
- A soil's resistance to pH change, greater in soils with high clay and organic matter content because of exchange and dissolution reactions.
- Sodic soil
- Soil with high exchangeable sodium, typically exchangeable sodium percentage above 15, causing dispersion of clay, poor structure, and restricted drainage.
- Organochlorine pesticide
- Persistent, fat-soluble synthetic insecticide such as DDT or BHC that accumulates in animal tissue and biomagnifies through food chains.
- Acetylcholinesterase inhibition
- Mode of action of organophosphate and carbamate insecticides; blocking this enzyme causes nerve overstimulation, salivation, miosis, and muscle twitching.
- Pre-harvest interval
- Minimum number of days between the last pesticide application and harvest, set so residues fall below the maximum residue limit.
- Pesticide half-life
- Time required for 50 percent of an applied pesticide to degrade in soil or on a crop through microbial, chemical, and photochemical processes.
- Composite soil sample
- Mixture of 15-20 cores taken from 0-15 cm in a zig-zag pattern across a field, reduced to about 500 g for laboratory analysis.
- Walkley-Black method
- Wet oxidation of soil organic carbon with potassium dichromate and sulphuric acid, followed by back-titration with ferrous ammonium sulphate to estimate organic matter.
- Olsen phosphorus test
- Extraction of available phosphorus with 0.5 M sodium bicarbonate at pH 8.5, recommended for neutral to alkaline and calcareous soils.
- Electrical conductivity test
- Measurement made on a 1:5 soil-water extract to estimate soluble salt content; values above 4 dS/m at 25 degrees C indicate salinity.
- Cadmium in soil
- Toxic heavy metal entering soil mainly through phosphate fertilizers and sewage sludge, accumulating in crops and posing a chronic kidney risk.
- Nitrate leaching
- Downward movement of nitrate beyond the root zone with drainage water, contaminating groundwater and causing methaemoglobinaemia in infants above 10 mg/L as N.
- Eutrophication
- Enrichment of water bodies with nitrogen and phosphorus runoff, causing algal blooms, oxygen depletion, and death of aquatic organisms.
- Biomagnification
- Progressive increase in concentration of a persistent, fat-soluble pollutant at each higher trophic level, as seen with DDT and methylmercury.
- Organic farming
- Production system excluding synthetic fertilizers and pesticides, relying on organic manures, compost, crop rotation, and biological pest and nutrient management.
- Conservation agriculture
- Farming system based on minimum soil disturbance, permanent soil cover with residues or cover crops, and diversified crop rotation to protect soil resources.
- Integrated pest management
- Pest control strategy combining monitoring, economic thresholds, resistant varieties, and biological control, using chemicals only when justified.
- Soil organic matter
- Decomposed plant and animal material in soil that improves structure, water-holding capacity, cation exchange capacity, nutrient supply, and carbon sequestration.