It has been recognized that a combination of wood-based biochar and mature compost, when thoroughly mixed with soil, would improve soil quality and crop growth. However, for perennial crops, such as coffee, macadamia, or papaya, soil-biochar mixing is not practical. Can surface application of (biochar combined with compost) improve the growth of such crops? If yes, how?
In the researchgate we have discussed many a time that the biochar has long life in soil and it need not be applied every year.Compost or composted manure can be applied every year especially to meet the nutritional needs of crop and at the same time it can improve over time soil quality and water holding power.So biochar can be applied/incorporated in soil in good amount ,for long term benefits in terms of climate change mitigation and soil quality improvement, once in a while or at long time intervals.Compost can be surface applied but it needs incoporation in soil to avoid nutrient and organic matter losses due soil erosion especially in high rainfall areas.
Perennial crops are better placed compared to annual crops in harnessing the impact of biochar alone or biochar plus compost . Addition of biochar plus compost offers the biochar a much better scope to throw out short term crop response compared to biochar alone., regardless of crop. This is the issue , currently being addressed seriously at the global level . IBI is looking this issue very stringently. Please have a look at the enclosed PDF, hope you like the content with regard to on-going discussion...
Biochar + compost has potential to improve soil health irrespective of soil and crops used as it improve soil microbial biomass and respiration, enzyme activity, potentially mineralisable N, microbial biodiversity, fatty acid profiles, and earthwom population. It is a labile source and sink of nutrients. It has positive effect on nutrient cycling.
I have experience in production of roses and avocados. When compost is added to the surface it is possible to see root growth towards the compost after a while. The new roots go to the spots where compost is added, and the density of roots there is higher than spots without application. This improved root growth could improve nutrient uptake, so fertilizers could be used more effieciently by plants. Additionally, it is known that some types of organic amendments can give more resistance to root and soil pathogens. Those are just two ways in which biochar + compost can improve plant growth in perennial species.
I think biochar will last so will the perennial crops, and for that good for the soil in terms of soil structure, aeration. The most important thing is, perennial crops will be there fore sometime but the biochar and organic matter will not. Therefore, how to continue to maintain them is a challenge for everyone. Compost as conventional can be added on the soil surface where it will go many good things to the soil but for the crop will depend on when. Many older crops tend to have specialized roots therefore might have already matured and forgotten what to do with compost on the surface.
Dr.Patrick, this is regarding comparison of life time of perennial crops and biochar.Biochars are expected to remain in soil for long time to provide for the benefits of climate change mitigation and benefits to soil, crop etc.Biochar has found to have a high stability or resistance to decomposition in soil. The mean residence time(MRT) of different biochars has been found to fall mostly in the centennial to millennial scale.Please see the following table
Publication Scale of estimated MRT(years)
Masiello and Druffel Millennial(2400-13,900)
Schmidt et al.,2002 Millennial(1160-5040)
Cheng et al.,2006 Millennial(1000)
For more details the following publication may be consulted.
Biochar carbon stability test method:An assessment of methods to determine biochar carbon stability.International Biochar initiative .September 20,2013.
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