On September 5,nature food published online the research results of Professor Zhang Weifeng's team from the College of resources and environment of China Agricultural University and the National College of agricultural green development.They called for the precision application of organic fertilizers and technologies in scenarios,revealed the important role of such precision application in synergistically achieving crop yield increase,soil carbon fixation and environmental emission reduction,and formulated a set of precision application strategies of organic fertilizers for global reference.
Organic fertilizer is a"versatile man"
Human beings have a long history of using organic fertilizers,and the types of organic fertilizers are more diverse.Zhang Weifeng,the corresponding author of the paper,introduced that the traditional organic fertilizer mainly adopts the composting method,which piles up wastes(such as soybean meal,pond mud,livestock and poultry manure,etc.)to make them mature and harmless."People don't seem to pay much attention to the difference between the organic fertilizers formed by different raw materials after they are decomposed and where they should be used."Zhang Weifeng said in an interview with China Science Daily.
However,since modern times,the raw material composition and processing technology of organic fertilizers have undergone earth shaking changes.For example,for the organic fertilizer made of pig manure,the composition of pig manure has changed because the pig feed has changed from leftover pig grass to refined processed feed,and the nutritional content of the organic fertilizer made of pig manure has increased.
Zhao shuaixiang,the first author of the paper and a doctoral student of China Agricultural University,told China Science Daily that due to the intensive development of the global aquaculture industry,the use of feed additives and the change of salt intake,the nature of animal manure has changed significantly,and will eventually be presented in the characteristics of organic fertilizer products.
"If we don't fully understand the characteristics of raw materials,we can't apply them scientifically,which may bring a series of soil,crop and environmental impacts."Zhao shuaixiang said.
In addition,the urgent need for green agricultural development also poses more challenges to the application of organic fertilizers.Zhang Weifeng said that in addition to providing nutrients for crops,organic fertilizers also carry the functions of increasing production and efficiency,fertilizing and reducing emissions.
Zhang Weifeng explained that about 30%of organic fertilizer is organic matter,and organic matter is an important material source for soil fertility;The application of organic fertilizer can improve the ability of soil water and fertilizer conservation,thus reducing the input of chemical fertilizer."Among all the measures to improve soil fertility,the correct application of organic fertilizer is the best."Zhang Weifeng said.
At the same time,the return of organic matter to the field is also a carbon fixation process.It not only directly stores carbon in organic matter in the soil,but also provides more opportunities for carbon fixation by promoting crop growth,bringing in more carbon by expanding root systems,or enriching microbial communities.
As the application of organic fertilizer reduces the input of chemical fertilizer,it also realizes environmental emission reduction.
Although organic fertilizer is a multi-functional complex,organic fertilizer in the new era needs to play a variety of functions."However,in the face of the ever-changing and diversified global crop production system,organic fertilizer is often regarded as a universal product in practical application.It is not designed,selected and applied differently according to the specific soil crop growth environment,which restricts the potential of fertilizer efficiency."Zhang Weifeng said that people have not yet established a system of application methods adapted to local conditions.
Apply organic fertilizer according to local conditions
In the face of the needs of the new era,can and how can the ancient organic fertilizers be met?This is a problem worth studying.
"First,there must be data support."Zhao shuaixiang said that it took them three years to build the latest and largest compost product effect database in the world.The team extracted more than 2000 data from 257 papers published worldwide,involving 11 key factors in three aspects:composting characteristics(carbon nitrogen ratio,carbon phosphorus ratio,pH value,soluble salt concentration),nitrogen management(dosage)and crop growth environment(crop type,soil texture,soil organic carbon,pH value,temperature,rainfall).
"By integrating and analyzing these data,we quantitatively evaluated the comprehensive benefits of organic fertilizer application in terms of yield increase,carbon fixation and emission reduction,and quantitatively mined the contribution of relevant influencing factors by using gradient lifting regression model(gbrt)".Zhao shuaixiang explained that the results showed that 11 key factors determined 80%of the organic fertilizer effect.
On this basis,the team established the selection mechanism of organic fertilizer according to local conditions.For example,organic fertilizer can play a better role in acidic soil,sandy texture,dry climate,high temperature and other conditions;The soil with low carbon level is suitable for matching the organic fertilizer with low carbon nitrogen ratio and carbon phosphorus ratio,while the soil with high carbon level is suitable for matching the organic fertilizer with high carbon nitrogen ratio and carbon phosphorus ratio.
based on these latest understandings,this study proposed a precision compound strategy(PCS)to match composting products and technologies with crop growth environment,and outlined the key steps of this strategy:diagnosis of local biological environmental conditions and obstacles;Design and produce special products that meet the needs of local crop soil climate conditions;The best integrated management technology combined with carbon and multiple nutrient elements(n,P and other necessary and beneficial nutrients).
"The poor effect of improving soil organic matter caused by the inaccurate application of organic fertilizers has been ignored all over the world.There has been almost no large-scale increase in global soil organic matter in the past years,even if organic fertilizers are widely applied in Europe and the United States all the year round."Zhang Weifeng said that they used the random forest machine learning algorithm(RF)to predict and characterize for the first time the global pattern and potential of the precise application strategy of organic fertilizer on the increase of major grain production and carbon fixation in the farmland.
The results show that if the precise application strategy of organic fertilizer is adopted,the output of the world's major grain crops(rice,corn,wheat and barley)can be increased by 4%(96.3 million tons);At the same time,it can increase soil carbon fixation by about 26%(19.5 billion tons of carbon equivalent)."If the global organic fertilizer can be applied more accurately in the next 20-30 years,it is completely possible to achieve it."Zhao shuaixiang emphasized.
The paper reviewer pointed out that in general,this is a very excellent work and a very good summary of the existing technology.In addition,this study has proved that the close coordination between the application effect of organic fertilizer and the application scenario,products and technologies is very important.
Another reviewer believed that in terms of theme,this work was closely related to sustainable agricultural development,because it provided a systematic assessment of current knowledge of organic fertilizer use and how to optimize organic fertilizer use globally to achieve sustainable multi-objective synergy.
How the social system promotes the precise application of organic fertilizer
Zhang Weifeng told China Science Daily that in order to verify this strategy,the team has carried out practice in many places in China.
On Chongming Island in Shanghai,local farmers grow a kind of orange"red beauty"with high economic value.However,because Chongming Island is located at the mouth of the Yangtze River,the salt content in the water is high,and the quality of citrus is affected by irrigation and planting with river water or groundwater."We suggest that they apply earthworm manure organic fertilizer with low salt content and collect rainwater for irrigation,so as to replace river water and groundwater."After organic fertilizer and salt reduction,the quality of citrus was greatly improved.
In Jinsui banana garden of Nanning,Guangxi,soil acidification is unfavorable to banana growth,and alkaline organic fertilizer is the best way to improve the soil;In the saline alkali land of Hexi Corridor,in order to reduce the soil pH value,the application of acid organic fertilizer has achieved very good results.
The above practice has achieved obvious effects.However,"in the past,some places applied organic fertilizer but did not increase soil carbon fixation,which is because organic fertilizer was not selected correctly."Zhang Weifeng said that with this precise application strategy,the application of organic fertilizer can be adapted to local conditions.
However,in Zhang Weifeng's view,it is both a scientific issue and a social system driven issue to promote this strategy on a large scale and achieve the comprehensive goal of increasing production,carbon fixation and emission reduction by using organic fertilizers.
When Zhang Weifeng showed some enterprises their designs of organic fertilizer products,the entrepreneur's reply made him feel the importance of formulating and implementing relevant policies:"I have never produced this kind of organic fertilizer according to your requirements."
"We in China especially need this set of precision use strategy,because we are vigorously promoting the return of organic fertilizer to the field,and we need to move in a more precise direction from the type of raw materials to the process and product design."Zhang Weifeng said that if it is not accurate,it will cost a lot to turn waste into organic fertilizer and then apply it to farmland,but it does not play its due role.
Zhang Weifeng suggested that the one size fits all management of organic fertilizers should be changed,and classified management should be implemented according to the nature and effects of different organic fertilizers,so as to guide enterprises to create organic fertilizers with different functions.This is an important measure to ensure that organic fertilizers support green agricultural production.