| Recently, climate change has become a focus of the world for it is becoming the challenge to the world agriculture. And the the main task is to improve soil productivity, reduce greenhouse gases emissions to combat climate change. Currently, researchers are paying more attention on biochar, which is made from straw waste and as a way to increase agricultural productivity, enhance soil carbon sequestration and reduce greenhouse gases emissions. This research was conducted in calcareous entisol from north China with biochar treatment and evaluated the sustainable effect of biochar after once amendment, we hope to provide scientific basis for biochar application in agriculture production.This experiment was based on a field experiment with different biochar levels (0,20 and 40 t hm-2) in Shangqiu city, Henan province, China. In this field site, wheat straw biochar was amendment after wheat harvest in June,2010, no more biochar amended in the following years and other field managements were conducted with conventional practice. The effect of biochar on soil quality, crop yield and nutrient uptake as well as greenhouse gases emissions for the first maize season and the second wheat season have been investigated. And the fourth and fifth crop seasons from October 2011 to September 2012 was investigated in this research. And we discussed the sustainable effect of biochar amendment on soil improvement, crop productivity and GHGs emission combined with the exsiting observation of the first two seasons. The main results were as follows:(1) Improvement of soil properties:Biochar amendment showed no effect on soil pH, available N and available P, but significantly increased soil organic carbon and available K in both crop seasons, being in proportional to the biochar amendment rates. Compared to no biochar treatment, soil organic carbon was increased by 18.44% and 30.95% in wheat season,24.23% and 36.65% in maize season as well as soil available K was increased by 41.67% and 66.67% in wheat season,36.36% and 90.91% in maize season at the rates of 20 and 40 t ha-1, respectively. Soil total nitrogen was only increased in wheat season by 7.69% and 10.00% at the biochar application rates of 20 and 40 t ha-1, but this effect was missing in maize season. Soil bulk density was only significantly decreased in maize season, a maximum decrease of 6.95%. Biochar application increased soil moisture and showed a significant effect at the rate of 40 t ha-1. Biochar had the effect of absorption on soil NH4+-N, but no effect on soil NO3--N.(2) The effect of biochar amendment on crop yield and nutrient uptake:Biochar application had no effect on wheat and maize yields, but significantly increased the nutrient uptake of both wheat and maize. Compared with no biochar treatment, nitrogen content of wheat leaf increased by 27.39% and 34.42% at the rates of 20 and 40 t ha-1, respectively. While it only increased N content of maize leaf by 30.71% at the rate of 20 t ha-1. Howere, biochar amendment had no effect on phosphorus and potassium content of crop leaf, and grain protein content of both wheat and maize. The N accumulation of wheat leaf and plant remarkably increased by 35.14%,48.15% and 8.71%,11.98% at the rates of 20 and 40 t ha-1, respectively. While the cumulative of N for different parts of maize had no changing.(3) The effect of biochar on greenhouse gases emission:For the fifth season, biochar amendment had no effect on soil CO2 and CH4 emissions, while significantly reduced N2O emission, the global warming potential (GWP) and greenhouse gases emissions intensity (GHGI) were significantly reduced by 31.54%,31.62% and 37.69% at the rate of 40 t ha-1.Soil organic carbon and available K content were significantly increased after 2 years of biochar amendment, Soil N2O emission, GWP and GHGI were also reduced. This effect was in proportional to the biochar amendment rates and showed greater stability with the increase in the amount of biochar application. Combined with the observation before, biochar amendment showed a persistent increase in SOC, available K and water content and decrease in soil bulk dednsity, even no effect on crop yield, for 3 years after biochar application. Therefore, biochar amendment could be used as an effective and persistent approach on low carbon agriculture. Meanwhile, the improvement of biochar on soil can be consistent for 3 years, it provide a reference on the reasonable application of biochar. |
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