Salinity episodes that are common in arid regions, characterized by dryland, are adversely affecting crop production worldwide. This study evaluated the effectiveness of brassinolide (BL) in ameliorating salinity stress imposed on soybean at four levels (control (1.10), 32.40, 60.60 and 86.30 mM/L NaCl) in factorial combination with six BL application frequency (control (BL₀), application at seedling (BL₁), flowering (BL₂), podding (BL₃), seedling + flowering (BL₄) and seedling + flowering + podding (BL₅)) stages. Plant growth attributes, seed yield, and N, P, K, Ca and Mg partitioning to leaves, stems and roots, as well as protein and seed-N concentrations, were significantly (p ≤ 0.05) reduced by salinity stress. These trends were ascribed to considerable impairments in the photosynthetic pigments, photosynthetically active radiation, leaf stomatal conductance and relative water content in the leaves of seedlings under stress. The activity of peroxidase and superoxidase significantly (p ≤ 0.05) increased with salinity. Foliar spray with BL significantly (p ≤ 0.05) improved the photosynthetic attributes, as well as nutrient partitioning, under stress, and alleviated ion toxicity by maintaining a favourable K⁺/Na⁺ ratio and decreasing oxidative damage. Foliar spray with brassinolide could sustain soybean growth and seed yield at salt concentrations up to 60.60 mM/L NaCl.

Crop production under hydroponic environments has many advantages, yet the effects of solution flow rate on plant growth remain unclear. We conducted a hydroponic cultivation study using different flow rates under light-emitting diode lighting to investigate plant growth, nutrient uptake, and root morphology under different flow rates. Swiss chard plants were grown hydroponically under four nutrient solution flow rates (2 L/min, 4 L/min, 6 L/min, and 8 L/min). After 21 days, harvested plants were analyzed for root and shoot fresh weight, root and shoot dry weight, root morphology, and root cellulose and hemicellulose content. We found that suitable flow rates, acting as a eustress, gave the roots appropriate mechanical stimulation to promote root growth, absorb more nutrients, and increase overall plant growth. Conversely, excess flow rates acted as a distress that caused the roots to become compact and inhibited root surface area and root growth. Excess flow rate thereby resulted in a lower root surface area that translated to reduced nutrient ion absorption and poorer plant growth compared with plans cultured under a suitable flow rate. Our results indicate that regulating flow rate can regulate plant thigmomorphogenesis and nutrient uptake, ultimately affecting hydroponic crop quality.

Studies on the availability of plant nutrients in soils treated with manure co-composted feed-stocks are very rare. The present investigation aimed at studying the nutrient release pattern from three soils amended with maple tree leaves co-composted with cow manure. Soils were mixed with the compost at the rate of 20 t/hm2 and incubated at room temperature. Prior to incubation, plants residue samples were analyzed for total elemental concentrations (NO3, NH4, P, K, Ca, Mg, Na, Zn, Mn, Fe, Cu, Ni and Cd). Water extractability of nutrients from soils was affected by the type of soil and ratio of composted manure applied. Extractable NH4, P, K, Ca and Mg concentrations varied in the descending order of sandy clay, sandy loam and silt loam except NO3. The concentrations of P, K, Ca and Mg in the amended soils increased with the ratio of manure co-composted with leaf litter while those of NO3, NH4 and trace elements decreased. The residual nutrients in soil varied directly with their contents in the compost amendments. Co-composting improved the availability of nutrients in soils and this should be an ideal approach to managing the enormous waste generated from the livestock sector for restoring soil fertility. Keywords: macro-elements, micro-elements, varied textured soils, co-composting, cow manure, maple plant residues DOI: 10.25165/j.ijabe.20181105.3494 Citation: Anwar Z, Irshad M, Ping A, Hafeez F, Yang S. Water extractable plant nutrients in soils amended with cow manure co-composted with maple tree residues. Int J Agric & Biol Eng, 2018; 11(5): 167–173.