[Effects of superphosphate addition on NH3 and greenhouse gas emissions during vegetable waste composting].

To study the effects of superphosphate (SP) on the NH, and greenhouse gas emissions, vegetable waste composting was performed for 27 days using 6 different treatments. In addition to the controls, five vegetable waste mixtures (0.77 m3 each) were treated with different amounts of the SP additive, namely, 5%, 10%, 15%, 20% and 25%. The ammonia volatilization loss and greenhouse gas emissions were measured during composting. Results indicated that the SP additive significantly decreased the ammonia volatilization and greenhouse gas emissions during vegetable waste composting. The additive reduced the total NH3 emission by 4.0% to 16.7%. The total greenhouse gas emissions (CO2-eq) of all treatments with SP additives were decreased by 10.2% to 20.8%, as compared with the controls. The NH3 emission during vegetable waste composting had the highest contribution to the greenhouse effect caused by the four different gases. The amount of NH3 (CO2-eq) from each treatment ranged from 59.90 kg . t-1 to 81.58 kg . t-1; NH3(CO2-eq) accounted for 69% to 77% of the total emissions from the four gases. Therefore, SP is a cost-effective phosphorus-based fertilizer that can be used as an additive during vegetable waste composting to reduce the NH3 and greenhouse gas emissions as well as to improve the value of compost as a fertilizer.

[Nitrogen status diagnosis by using digital photography analysis for organic fertilized maize].

It need a relative long term for the maize nitrogen status diagnosis with a destroyed samples taking. In the present research, a pot experiment with different organic fertilizer and different fertilizer amount input was conducted to study the possibility of using digital photography analysis technology to monitor the N status of organic fertilized maize at 10 leaves unfold stage. The results showed that the greenness intensity (GI) and redness intensity (RI) from maize canopy image had significant inverse linear correlations with the conventional N diagnosis parameters of SPAD readings, upland biomass and upland N uptake. However the blueness intensity (BI) had no significant correlations with those maize N indexes. The correlation coefficient values (r) were from 0.40 to 0.45 for GI, and from 0.45 to 0.53 for RI. To sum totally, the visible digital image color analysis method can be used for the organic fertilized maize N diagnosis at 10 leaves unfold stage. The redness intensity was a relatively better index than others for the organic fertilized maize N status diagnosis in this experimental condition.

[Nitrogen status diagnosis of summer maize by using visible spectral analysis technology].

In the present paper, a field experiment with different N rates was conducted to study the possibility of using the visible spectrum of crop canopy to diagnose N status for the summer maize. Visible spectrum parameters were compared with the leaf SPAD readings, total N concentration and vein nitrate concentration. Field measurement data showed that the greenness intensity, blueness intensity, normalized redness intensity, normalized greenness intensity and normalized blueness intensity of the maize canopy have significant relationships with leaf SPAD readings, total N concentration and vein nitrate concentration (under a low N input condition, with vein nitrate concentration < 2 000 mg x L(-1)) at summer maize 10 leaves unfold stage. The greenness intensity, blueness intensity, normalized greenness intensity and normalized blueness intensity have significant relationship with the vein nitrate concentration under a low N input condition (vein nitrate concentration < 2 000 mg x L(-1)). But when the maize vein nitrate concentration is above 2 000 mg x L(-1), there is no spectral parameter showing significant relationship with the vein nitrate concentration. The visible spectrum parameters reached a plateau with the vein nitrate concentration increasing. To sum up, the normalized greenness intensity (NGI) and normalized blueness intensity (NBI) have higher r values (0.45-0.66) than other parameters.