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Yang G.-Z.,Huazhong Agricultural University | Yang G.-Z.,Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River | Chu K.-Y.,Huazhong Agricultural University | Tang H.-Y.,Huazhong Agricultural University | And 2 more authors.
Journal of Integrative Agriculture | Year: 2013

N fertilization of 300 kg N ha-1 is normally applied to cotton crops in three splits: pre-plant application (PPA, 30%), first bloom application (FBA, 40%) and peak bloom application (PBA, 30%) in the Yangtze River Valley China. However, low fertilizer N plant recovery (NPR) (30-35%) causes problems such as cotton yield stagnation even in higher N rate, low profit margin of cotton production and fertilizer release to the environment. Therefore, it is questioned: Are these three splits the same significance to cotton N uptake and distribution? An outdoor pot trial was conducted with five N rates and 15N labeled urea to determine the recovery and distribution of 15N from different splits in cotton (Gossypium hirsutum L. cv. Huazamian H318) plant. The results showed that, cotton plant absorbed fertilizer 15N during the whole growing period, the majority during flowering for 18-20 d regardless of N rates (150-600 kg ha-1). Fertilizer 15N proportion to the total N accumulated in cotton plant increased with N rates, and it was the highest in reproductive organs (88% averaged across N rates) among all the plant parts. FBA had the highest NPR (70%), the lowest fertilizer N lose (FNL, 19%), and the highest contribution to the fertilizer 15N proportion to the total N (46%) in cotton plant, whereas PPA had the reverse effect. It suggests that FBA should be the most important split for N absorption and yield formation comparatively and allocating more fertilizer N for late application from PPA should improve the benefit from fertilizer. © 2013 Chinese Academy of Agricultural Sciences.

Ma Y.H.,Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River | Ma Y.H.,Huazhong Agricultural University | Liu B.,Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River | Liu B.,Huazhong Agricultural University | And 10 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

NH3 volatilization is an important process of N loss from fertilizer nitrogen (N) applied to no-tillage rice fields. It has been demonstrated that no-tillage promotes NH3 volatilization. However, few studies have been conducted to investigate the effects of N management on NH3 volatilization from no-tillage paddy fields. Therefore, a field experiment was conducted on a clay loam soil (Anthrosol, World Reference Base for Soil Resources) to study the effects of N management on NH3 volatilization and N use efficiency from no-tillage rice fields in the city of Wuxue in central China during the 2012 rice- growing season. In this study, five experimental treatments were arranged in a completely randomized design with three replications. Five treatments were applied including five application rates of N fertilizer in the seedling, mid-tillering, flowering and heading stages of rice: 2:2:3:3 (R1), 3:2:2:3 (R2), 4:2:2:2 (R3), 4:3:1:2 (R4) and 0:0:0:0 (CK). The NH3 volatilization fluxes were determined 20 times using a venting method during the 2012 rice growing season. NH+4 concentrations and pH of the soils and field surface water were also measured. The obtained results showed that application of N fertilizer significantly enhanced both NH+4 concentrations of the soils and field surface water and the soil pH. Compared with the other fertilized treatments (R2, R3 and R4), R1 significantly decreased NH+4 concentrations of the soils and field surface water. In the fertilized treatments, during the rice growing season, each application of N fertilizer led to NH3 volatilization fluxes peaking after 1-3 days, and then dropping rapidly to those in the unfertilized treatment levels within 1-2 weeks. The NH3 volatilization fluxes in the CK treatment were relatively low, and remained nearly unchanged. The NH3 volatilization fluxes ranged from 2.0 to 21.94 mg·m-2·d-1 for the CK treatment and from 2.21 to 209.6 mg·m-·2 d-1 for the fertilized treatments. Mean NH3 volatilization fluxes in the R1, R2, R3 and R4 treatments were (13.8±2.0), (15.3± 0.2), (15.8 ±0.1) and (14.2 ±0.1) mg·m-2·d-1, respectively, which were 1.57, 1.81, 1.88 and 1.69 times, respectively, that in the CK treatment. The cumulative amounts of NH3 volatilization were (8.52±0.20) (CK), (19.59± 2.30) (R1), (21.85±0.68) (R2), (21.98±0.45) (R3) and (23.79±1.15) kg N/ hm2(R4). For fertilized treatments, the highest cumulative NH3 volatilization was observed at the mid-tillering stage (accounting for 11.9%-14.7% of the total), followed by the heading stage, with the minimum being found at the seeding and booting stages. Compared with no N fertilizer, application of N fertilizer significantly increased NH3 volatilization by 56.5%-64.2% from the no-tillage paddy fields. In fertilized treatments, N losses through NH3 volatilization accounted for 6.2%-8.5% of the applied N. Among the four fertilized treatments, the cumulative NH3 volatilization was significantly reduced by 9.1%-17.7% under R1 than under the other fertilized treatments. Linear correlation analysis indicated that NH+ 4 concentrations and pH in the soils and field surface water were significantly related to the NH3 volatilization fluxes. Application of N fertilizer significantly affected N uptake of rice, where, compared with the CK treatments, fertilized treatments significantly increased N uptake of rice by 46.5%-89.3%. Compared with the other fertilized treatments, R1 significantly enhanced N use efficiency by 28.4%- 74.9%. Therefore, our results suggest that N application at the late growth stage of rice can decrease NH3 volatilization, thus improving N use efficiency of rice under no-tillage rice fields.

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