Humus is the rich brown or black substance left after organic matter decomposes. It contains essential nutrients like nitrogen, phosphorus, and calcium. High-quality farmland soil contains 3-6% humus
NPK stands for nitrogen, phosphorus, and potassium, essential plant nutrients. Fertilizer labels show nutrient percentages in order (e.g., 5-10-5). Plants need about 16 nutrients, including nitrogen, phosphorus, and potassium
Stem is central axis of shoot system in angiosperms. First stem develops from epicotyl within seed. Stem has multiple uses including food, medicine, and propagation
Humic substances are naturally formed organic compounds from biomass residues. They range in color from yellow to black and are found in soil, peat, coal, and sediments. Humic acid is soluble at neutral and alkaline pH, while fulvic acid is soluble at all pH. Humic substances are a complex mixture of molecules containing carboxyl and phenolic groups
Plant nutrition studies essential elements for growth and reproduction. Liebig's law states plant growth is limited by nutrient deficiency. Plants obtain nutrients from air (C, H, O) and soil (N, P, K, Ca, S, Mg, C, H, O)
CEC refers to soil's capacity to hold and exchange mineral nutrients. Fertilizer salts break down into positively charged cations and negatively charged anions. Soil particles have negative charges that attract positively charged elements