Mineral Nutrition (chapter 4) Mineral Nutrition How plants acquire and use mineral nutrients Why is mineral nutrition important? What are the essential mineral nutrients? • classification systems Mineral nutrients in the soil • nutrient availability • adsorption to soil particles • effects of pH Roots and mineral nutrient acquisition • root structure • depletion zones Mycorrhizae Nitrogen - the most limiting soil nutrient Why is mineral nutrition important? Fertilization increases crop production Crop Yield, tons/hectare Fertilizer used, kg/hectare Add more fertilizer nitrogen, get more crop production Crop Yield, tons/hectare Nitrogen added, kg/hectare Trends in global use of fertilizer N, P, & K Why is mineral nutrition important? In most natural soils, the availability of mineral nutrients limits plant growth and primary productivity Nutrient limitation is an important selective pressure and plants exhibit many special traits related to the need to acquire and use mineral nutrients efficiently 2 What are the essential mineral nutrients? Macronutrients - present in relatively high concentrations in plant tissues N, K, P, Ca, Mg,S, Si Nitrogen is most commonly limiting to productivity of natural and managed soils Phosphorus is next most limiting, and is most limiting in some tropical soils Micronutrients - present in very low concentrations in plant tissues All mineral nutrients together make up less than 4% of plant mass, yet plant growth is very sensitive to nutrient deficiency Not considered mineral nutrients Micronutrients are present in very low concentrations ppm Very low concentrations, but still essential because of specialized roles in metabolism How to classify all of these macro and micro nutrients? By biochemical function Mineral nutrients in the soil Larson Soils particles are generally negatively charged and so bind positively charged nutrient ions (cations) Cation Exchange Capacity refers to a soil’s ability to bind cations NH4+, NO3-, Cl-, PO4-2, SO4-2 Soil pH influences availability of soil nutrients 4 Roots and mineral nutrient acquisition Fine roots and root hairs “mine” the soil for nutrients Mycorrhizal hyphae this even better Fig 5.7 Fig 5.8 More on Nitrogen •Why is N so important for plant growth? •What percentage of the mass of plant tissues is N? •What kinds of compounds is N found in? •Why is there a strong relationship between the N concentration of leaves and photosynthesis? [...]... 3 Mineral nutrients in the soil Larson Soils particles are generally negatively charged and so bind positively charged nutrient ions (cations) Cation Exchange Capacity refers to a soil’s ability to bind cations NH4+, NO3-, Cl-, PO4-2, SO4-2 Soil pH influences availability of soil nutrients 4 Roots and mineral nutrient acquisition Fine roots and root hairs