This study was conducted to evaluate the effects of reseeding sub clover as a cover crop on silage corn growth, nitrogen accumulation, and the changes in soil nitrogen under different chemical nitrogen application levels. The cropping systems of sub clover reseeding based management and fallow treatment were compared to DM and N accumulation of silage corn at 0, 50, and 100kg N ha^-1 application levels. The experiment was conducted at two sites, one where no-till corn was sown in June, and the other where conventional corn was sown in July. DM accumulation of corn in the fields of sub clover reseeding system was significantly higher than in the fields of fallow system at both sites. Based on this co-relationship, the amounts of nitrogen supplied by sub clover reseeding to no-till and conventional tilled corn estimated to be 108 and 88kg N ha^-1, respectively. However, the evaluation of sub clover N supply in this experiment was obviously influenced by sub clover N that was also produced other years were obvious. So these results also suggested that there is some possibility to increase the soil total nitrogen in the field of sub clover reseeding system. However, the amount of sub clover N supply per year is still not clear, so additional research is needed.

View full abstract

Cover crops may be effective tools for managing the sustainable agriculture, however, tillage systems should be discussed how to introduce cover crops to the farmer's field. In this research, we investigated the performance of rotary tillage in the cover crop fields compared with fallow. Main results are follows.
1) Before rotary tillage, the soil dry densities in the 15-20cm soil depth layer in the cover crop fields were lower than that in the fallow field. After rotary tillage, soil dry densities in the fields of sub clover, crimson clover, and heary betch were almost same as that in the fallow, but that in the rye field was the lowest.
2) After rotary tillage with 3 levels of tilling pitch ranging from 1.0 to 7.0cm, the mean diameters of soil clods in the fields of cover crops were larger than that in the fallow field. One of the reasons was that there were some soil clods with diameter over 32mm in cover crop fields.
3) The problem that the cover crops were wound around the shaft of rotary tiller during tilling was obviously decreased by mowing the cover crop before rotary tillage.
4) After rotary tillage with 1.0cm tilling pitch, 60-70% of the plant bodies of cover crops was buried under the 5cm depth layer of soil in the fields of sub-clover, crimson-clover and heary betch, but that in the rye field was buried only 50%.
5) After rotary tillage with 1.0cm tilling pitch, the emergence ratios of silage corn as a subsequent crop in the fields of sub-clover, crimson-clover and heary betch were over 75%, these values were almost same as that in the fallow field. However, that in the rye field was the lowest.
6) Rotary tillage with 1.0cm tilling pitch after mowing made an appropriate seedbed in the fields of legume cover crops, because legume cover crops did not have so much dry matter and stem strength. Meanwhile, rotary tillage in rye field did not make a good seedbed with any tilling pitch and regardless of mowing treatment. These results suggested that another tillage system should be appropriate in the field of rye cover crop.

View full abstract

Efficiencies of a hand-held vibrator for harvesting fruit from ‘Tifblue’ (Rabbiteye blueberry) [Vaccinium ashei (Reade)] were investigated in relation to the properties of fruit and force required to dislodge fruit.
It was found that the heavier fruit dislodged quicker than the lighter fruit, it is thought that this is due to increased inertia movement associated with the heavier fruit.
The degree of force required to dislodge the fruit from the pedicel was much the same as one required to dislodge the pedicel from the peduncle in green fruit. In ripe fruit (all blue color), on the other hand, the former was far less than the latter. This indicated that the pedicel, an unwanted item in the market, was separated from ripe fruit more readily compared with green fruit.
Ripe fruit dislodged more readily at a low vibrant frequency than less ripe fruit. Ripe fruit dislodged most efficiently at a 30mm stroke and 7.5Hz frequency, although with this vibration mode almost all the green fruit did not dislodge.
On the other hand, when applying the vibration to the shoot (30mm stroke and 7.5Hz frequency), among the fruit which were dislodged there were a few fruit with pedicels attached which needed to be graded out before shipping to the market. However, there were few ripe fruit among the fruit left on the shoot, and the fruit dislodged were mostly ripe fruit.

View full abstract