Teruo Matsunaka

Two pot experiments were conducted to evaluate biochar derived from dead dairy cattle as a mineral fertilizer, especially phosphorus (P) fertilizer, and to clarify the effect of particle size of biochar on plant growth (Zea mays L.) and P uptake. To produce the biochar, body parts of dead cattle were placed in a charring chamber and allowed to char at 450°C for 4 h. The biochar was of high pH and rich in major plant nutrients, especially P. Application of fine biochar (< 1 mm) increased P uptake by the corn plants grown in soil of low available P status. As a result, plant growth was improved following biochar application and dry matter production was also increased. The effect of the biochar application on the P uptake and plant growth was promoted by the application of mineral nitrogen (N) fertilizer. Soil analysis after harvest indicated that the biochar application increased soil pH, available P and exchangeable calcium (Ca) and magnesium (Mg) compared with the soil before seeding, while soil available N and exchangeable potassium (K) were considerably decreased. The decrease in the soil available N was incomprehensible, because the result of the mass balance given by the difference between input as the applied N from the biochar and fertilizer N and output as the N uptake by the plants was positive. We observed a similar result in the mass balance of K to the case of N. The medium (2–4 mm) and coarse (> 4 mm) grade biochar did not significantly affect plant growth, because P uptake was not, or was only slightly, increased by the application of these biochars. Dissolution of P from the coarser biochars was probably slower than that of the fine biochar. The lower dissolution of P from the medium and coarse biochars was supported by the lower P absorption efficiency of these biochars compared with that of the fine biochar and superphosphate. The effect of fine biochar on plant growth and P uptake was similar to that of superphosphate. We can therefore conclude that fine biochar derived from cattle carcasses is an effective source of P fertilizer and amendment for soil acidity. The N and K contents in the biochar, although relatively high, cannot be relied upon as a mineral fertilizer. Further studies are needed to assess whether the N and K contents of the biochar indicate it can be regarded as a useful fertilizer.

Livestock slurry application to land recycles nutrients for plant uptake, but resulting gaseous nitrogen (N) emissions pose a major challenge to the environment. This study was conducted to investigate environmentally friendly methods for the application of anaerobically digested cattle slurry (ADCS) to soil. Application techniques of control (C), surface application (S), incorporation into the soil (I) and soil amendments with and without a nitrification inhibitor (dicyandiamide, DCD) were compared in a small-scale laboratory experiment. Ammonia (NH3) volatilisation mainly occurred within 5 days after ADCS application. Cumulative NH3 volatilisation loss accounted for 57.0, 59.9, 0.7 and 1.4% of applied NH4+-N from surface applied ADCS without and with DCD, and from incorporated ADCS without and with DCD, respectively. Ammonia volatilisation from surface-applied ADCS was 56 times greater than from incorporated ADCS. The nitrous oxide (N2O) emission flux from soil where ADCS was surface-applied without DCD was significantly (P < 0.01) higher than that from the other treatments. The DCD supplement significantly (P < 0.05) reduced N2O flux from surface-applied and incorporated ADCS. Therefore, the cumulative N2O emission loss from the soil where ADCS was surface-applied was significantly greater than that from the incorporated slurry regardless of the DCD supplement. Total inorganic N (TIN) in the soil for all treatments remained constant, although NH4+-N contents in the soil without DCD decreased continuously and nitrate nitrogen (NO3–-N) contents increased continuously throughout trials. There were significant (P < 0.01) differences in TIN contents among application techniques. NH3 volatilisation from the surface application was a major cause of the differences. Consequently, the incorporation of ADCS with the DCD supplement could be a potential method to successfully reduce emissions of both NH3 and N2O.

"Nitrogen leaching from a timothy sward following application of anaerobically digested cattle slurry in Japan" published on 01 Nov 2005 by Wageningen Academic.