Decomposition of Pruned Tea Plant Material by Different Methods

Objective Different means of utilizing the pruned plant material for tea plantation fertilization were evaluated according to the organic matter decomposition.

Method Discards from tree pruning were returned to the field by ways of surface mulching (T1), deep burying the plant waste in ground (T2), adjusting carbon/nitrogen ratio of the waste prior to turning into soil (T3), or returning the waste with addition of a decomposing aid (T4). Effects of the varied treatments were compared by continuously monitoring for years on the annual decomposition rate, nutrient releases, and carbon/nitrogen ratio of the plant material in soil.

Result It took T2 the shortest 0.9 year to reach 50% decomposition and 3.5 years to achieve 95% decay on the pruned material. All treatments with the waste embedded in soil rendered significantly higher rates of decomposition than T1, with T2 being the highest at the time of every sampling. For instance, after 360 d of treatment, T2 had a rate 1.8% to 27.5% higher than the others. On carbon release, T1 was significantly lower by 8.4%~19.6% than the others, while T2 gave the fastest nitrogen release in all test periods. On the 30^th, 180^th, and 360^th day, T2 also delivered the greatest release of phosphorus at 49.0%, 70.3%, and 85.1%, respectively. Meanwhile, the potassium release was nearly complete, i.e., 92.1% under T1, 93.7% under T2, 93.3% under T3, and 93.6% under T4. The carbon/nitrogen ratios ranked T2>T3>T1>T4 with increases by 104.1%~215.3% over that on the 30^th day. And the lignin and cellulose contents were lower under T4 than the other treatments on the 90^th, 180^th, and 360^th day.

Conclusion Deep burying, carbon/nitrogen ratio adjustment, and decomposing agent addition could all accelerate the decomposition process of pruned tea plant discards in the field. By plowing the waste material into ground significantly promoted the decaying. It significantly hastened the release of potassium, which was followed by nitrogen, phosphorus, and the slowest, carbon. All these treatments could promote the release of carbon.