The level of sulfate substitution of polysaccharide regulates thermal-induced egg white protein gel properties: The characterization of gel structure and intermolecular forces.

Sulfated polysaccharides exhibit great potential for regulating protein-protein interactions. In the present study, three sulfated microcrystalline cellulose (MCS) with different degrees of sulfate substitution (DSS: 0.33, 0.51, 0.61) were synthesized and the effects of DSS on the regulation of egg white protein (EWP) aggregation and gelation properties were investigated. The results found that the improvement of protein mechanical properties by MCS is closely related to the level of sulfate substitution. The higher the DSS, the more ordered protein aggregates and compact gel network formed during heating as compared to that of pure EWP. Lower DSS (0.33) shows little effect on the mechanical properties of EWP. Furthermore, all the MCSs could significantly destroy the tertiary structure of protein molecules during heating, while for the secondary structure, MCS with higher DSS (0.51 and 0.61) could effectively control the decreasing tendency of α-helix and increasing tendency of ß-sheet. Hydrophobic interactions were recognized as the major intermolecular force in the compact mixed gels (EWP/MCS2 and EWP/MCS3 gels, DSS was 0.51 and 0.61, respectively). These findings provide a vital understanding of the gelling mechanism of the protein-polysaccharide system and the application of sulfated polysaccharides in protein-based food products.

Effect of topdressing time on spring maize yield and nitrogen utilization in black soil of northeast China.

Topdressing time is crucial to achieving a high yield. To determine the optimum topdressing time for spring maize in the black soil of northeast China in the "one base and one topdressing" mode, the effects of topdressing time of nitrogen (N) fertilizer on maize yield, N utilization, and inorganic N residue and distribution were investigated by using 15N labeling technique. Four treatments were designed: no N fertilizer (N0), N fertilizer topdressing at jointing stage (N1), N fertilizer topdressing at belling stage (N2), and N fertilizer topdressing at tasseling stage (N3). The results showed that compared with N1 and N3, the maize yield, N uptake and N use efficiency (NUE) in N2 treatment significantly increased by 12.1% and 24.7%, 10.0% and 16.0%, and 26.4% and 38.9%, respectively (P < 0.05). The later the topdressing time, the more inorganic N remained in the soil profile (0-60 cm). The rate of potential N loss was higher when the topdressing time was too early or too late. Compared with N1, the residual amount of 15N in the soil profile (0-60 cm) of N2 and N3 treatments increased by 17.2% and 44.8%, respectively. The soil inorganic N (SIN) accumulation in the deep soil profile (40-60 cm) of N2 treatment decreased by 7.6% and 42.7%, respectively, as compared with N1 and N3. Therefore, the application of N fertilizer at the belling stage was beneficial to the high yield and efficient production of maize in the black soil region of Northeast China.

How long-term excessive manure application affects soil phosphorous species and risk of phosphorous loss in fluvo-aquic soil.

The excessive application of manure has caused a high load of phosphorus (P) in the North China Plain. Having an understanding of how manure application affects soil P changes and its transport between different soil layers is crucial to reasonably apply manure P and reduce the associated loss. Based on our 28-year field experiments, the compositions and changes of P species and the risk of P loss under excessive manure treatments were investigated, i.e., no fertilizer (CK), mineral fertilizer NPK (NPK), NPK plus 22.5 t ha-1 yr-1 swine manure (LMNPK), and NPK plus 33.75 t ha-1 yr-1 swine manure (HMNPK). Manure application increased the content of orthophosphate and myo-inositol hexaphosphate (myo-IHP), especially the orthophosphate content exceeded 95%. The amount of orthophosphate in manure and the conversion of organic P to inorganic P in soil were the main reasons for the increased soil orthophosphate. Compared with NPK treatment, soil microbial biomass phosphorus and alkaline phosphatase activity in LMNPK and HMNPK treatments significantly increased. Compared with NPK treatment, a high manure application rate under HMNPK treatment could increase the abundance of organic P-mineralization gene phoD by 60.0% and decrease the abundance of inorganic P-solubilization gene pqqC by 45.9%. Due to the continuous additional manure application, soil P stocks significantly increased under LMNPK and HMNPK treatments. Furthermore, part of the P has been leached to the 60-80 cm soil layer. Segmented regression analysis indicated that CaCl2-P increased sharply when Olsen-P was higher than 25.1 mg kg-1, however the content of Olsen-P did not exceed this value until 10 years after consecutive excessive manure application. In order to improve soil P availability and decrease the risk of P loss, the manure application rate should vary over time based on soil physicochemical conditions, plants requirements, and P stocks from previous years.

Effects of Mixed Controlled Release Nitrogen Fertilizer with Rice Straw Biochar on Rice Yield and Nitrogen Balance in Northeast China.

A 3-year fixed site experiment was carried out on a Planosol in Northeast China to study the effects of biochar and controlled-release nitrogen fertilizer on rice yield, nitrogen-use efficiency, residual nitrogen, and nitrogen balance in soil-crop system. Five treatments were established: control (CK), bare urea (BU), controlled-release urea (CRU), 50% BU + 50% CRU (MBC), and 50% BU + 50% CRU + biochar (MBCB) treatments. The results showed that, compared with the BU treatment, the yield, N-use efficiency (NUE) and N agronomic efficiency (NAE) of the CRU treatment increased by 12.2%, 33.9% and 4.3 kg kg-1, respectively; while the soil residual N and N surplus at harvest decreased by 11.6% and 10.7%, respectively. Compared with the MBC treatment, the yield, NUE and NAE of the MBCB treatment increased by 10.2%, 16.5% and 4.0 kg kg-1, respectively; while the soil residual N and N surplus at harvest decreased by 10.8% and 12.3%, respectively. Therefore, mixed application of bare urea, controlled-release urea and biochar was effective for obtaining high rice yield, and high fertilization efficiency as well as for sustainable agricultural development in Northeast China.