Influence of soil moisture content on germination and emergence of seeds

Abstract

This study was designed to clarify the relations of germination and emergence of several kinds of seeds to moisture content of soils, with special reference to their moisture constants and moisture supplying capacities.
Seeds were planted in the soils having different moisture contents in the depth of one cm from the surface, and numbers of emerged seeds were counted daily. After the final count, seeds remaining in the soil were exposed and number of germinated seeds were counted. Physical properties of soils used were shown in Table 1.
1. Minimum moisture content allowing germination of radish, rape, and sunflower seeds was close to P. W. P. (permanent wilting percentage) in the fine sandy clay loam (alluvial soil) and the fine sandy loam (volcanic ash soil), but was higher than P. W. P. in the coarse sand (river sand). Minimum moisture content allowing emergence of these seeds was a little higher than that for germination (Fig. 1).
Critical moisture levels for carrot seed were higher than those for other seeds (Fig. 1). This may be due to the lower moisture absorbing power of carrot seed than that of other seeds (Table 3).
2. Average number of days required for emergence of each seed was found to be almost the same in the range down to a certain critical moisture content of the soil, below which number of days increased with the decrease of moisture content. This critical point was close to the minimum capillary moisture content in each soil (Fig. 4, Table 5).
3. Pre-soaking treatment decreased minimum moisture content allowing germination and emergence of pea seed, but had little effect to tomato seed, which was much smaller in size than pea seed (Fig. 5).
4. Basing on the above mentioned results, it may be concluded that minimum moisture content allowing germination or emergence of seeds are determined primarily by the moisture tension of the soil, but, at the same time, it is affected by the moisture absorbing power of seed, amount of moisture which should be absorbed by the seed for its germination or emergence, and moisture holding capacity or moisture supplying power of soil.