Kosei Tsunoda

Assessment of No-tillage Farming. VI. Renovation of No-tillage Field Passed 11Years.

In this study, we practiced a renovation trial by plowing to the continuous no-tillage field passed 11 years. The field seemed to be deteriorated for cultivation judging from the changes of soil condition and crop yield. The renovation trial based on the two-factors experiment with three levels of tillage and three levels of materials for soil improvement was started at April in 1991.1) Water content of soil in NC (renovation of notillage plot) was equal to that in CC (continuous plowing plot), but soil hardness (penetration resistance) in NC was higher than that in CC.2) Field efficiency of plowing in NC was higher than that in CC. Depth of tillage in NC was equal to that in CC, but the average value of width of tillage estimated from total width of plowed area and number of furrow in NC was wider than that in CC.3) Fuel consumption per unit area in NC was 5% higher, and the consumption per unit time in NC was 14% higher than those in CC.4) Specific resistance of soil estimated from the measured values, such as fuel consumption and traveling speed, in NC was higher by 8% than that in CC.5) From the result of analysis of variance for dry matter yield of corn, there was the significant difference with 1% level for tillage factor only. When we adopted the value of 100 to crop yield in CC as a standard, the crop yield in NC was 97, that was 67 in NN (continuous no-tillage plot), respectively.6) From the result of analysis of variance for the quantity of weed, there was the significant difference with 5% level for the tillage factor only. The quantity of weed in NN was much than any other plots.7) In NN, notable pH drop was observed at the soil layer of 5-10cm in depth. The pH profile in NN at the layer of 0-20cm approached to that in CC which showed an uniform distribution of pH.8) In spite of the deteriorated field by continuous no-tillage farming for 11 years, the crop yield almost recovered to the yield level in CC by only once tillage as a renovation.

Effect of Irregular Disposition of Planted Hills under Broadcasting Condition on the Growth and Yield in Rice Plants

Responses of the growth, yield and its components in rice plants to the irregular disposition of planted hills under broadcasting condition were examincd by setting up ten kinds of treatment-plots differing in the coefficient of variation (CV) of the number of planted hills among four small sections in a plot. 1. The larger the CV of the number of planted hills among small sections was, the larger the degree of decrease in yield becamc, and the high correlation could be recognized between these two factors. The result was directly due to the shortage of yield compensating of plants in the dense planting sections for the decrease of yield in the sparse planting sections. 2. The bad effects of irregular disposition on the yield was considered to consist or three factors, namely, (1) the percentage of missing plant area to the total one, (2) the difference in the number of hills among the planted sections and (3) the arranged condition of planted sections in a small area. These three factors affected severely in the order of (1) > (2) > (3) on the yield. 3. The grain yield was influenced mainly by the number of panicles and the bad effect of irregular disposition upon the number of tillers and panicles was clearly seen after maximum tillering stage.