Transform waste straw into water-holding fertilizer: A targeted modification strategy of functional groups

The goal of this study was to enhance the utilization of millet straw and endow it with the fertilizer function through modifying the carboxymethylcellulose (CMC-NH4), based on wheat straw, by acidification and ammonification to improve water and fertilizer efficiency. Amine group was introduced through the electrophilic substitution to supply nutrients to crops. The order of influential factors on the water absorption property was determined by an orthogonal experiment and showed that the highest water absorbency of 224.7 g/g, which was achieved for the conditions of 3:1 carboxymethylcellulose to nitric acid solution (mass percentage concentration of 50%), 3:1 carboxymethylcellulose to ammonia solution with the mass percentage concentration is 30%. The CMC-NH4 was characterized by scanning electron microscopy, fourier-transform infrared, x-ray diffraction, and X-ray photoelectron spectroscopy techniques, and the results indicated that application of CMC-NH4 promoted the growth indexes of wheat, improved wheat yields. Therefore, the waste straw was modified into the soil conditioner with specific function by the group targeted modification strategy. In addition, the fertilizer efficiency and water-retention behavior of CMC-NH4 encouraged its use as a safe water- and fertilizer-retaining agent in agricultural applications.