The pipette and SediGraph methods of particle size analyses were compared on 55 samples. The best agreement between the two methods was on 12 of the 55 samples treated to remove organic matter and soluble salts. The correlation for all sizes combined from the 55 samples was 0.97 with a standard deviation from regression of 5.54%. The agreement between the two methods was good at all individual sizes except the % < 50 µm where the correlation was 0.12.Neither method is well suited to particle size analysis of suspended sediment samples with low concentrations or limited quantities of sediment. The major differences between the two methods are the time and labor required to perform the actual analysis and to calculate the analytical results.

THREE different commercial particle-size analyzers were compared with the conventional pipet technique to measure the size distributions of IS samples of very fine sediments. These samples were obtained from the deposited sediments in severaloxbow lakes in the alluvial plain in west central Mississippi. Approximately 90% of the material in these samples were less than 10/mi in size. The basic features, principles and underlying assumptions for each instrument are outlined and compared for all analyzers and techniques used. While the results from the four methods showed drastic differences, reconciliation of these data was achieved by use of simple mathematical descriptions of the particle size distributions and of the measurement processes involved with each instrument. INTRODUCTION Knowledge of soil and sediment size distribution is important to several aspects of agricultural soil and water research. Several traditional methods have been used through the years with high success and few problems. For larger particles, sieves have been successfully used. For medium sands, in the range 60 to 1000 pm the visual accumulation (VA) tube is convenient and simple to use. There is a considerable overlap region where both sieves and VA tubes have been used. Below 62 \xm the pipet method ordinarily has been used. This method is time consuming and labor intensive. At a 10-cm withdrawal depth, it requires a full 8-h day to determine the distribution down to 2 pm (the upper limit of what is ordinarily considered the medium and fine clay fraction). This time and labor factor has prompted several soil and sediment analysis laboratories to investigate alternative easier and faster means of analysis in the silt and clay size range. There are several instrument systems available on the market designed to perform this measurement. The systems vary widely in their individual characteristics, advantages, disadvantages, and

Population, N fertilization, and row spacing of grain sorghum were studied on Springer loamy fine sand. In the presence of adequate N, production of grain and residue increased with increasing populations. Optimum populations for both grain and residue production were between 40,000 and 60,000 plants per acre. Maximum yields of grain and residue were obtained with 50 pounds of N, except under above‐average moisture conditions and high plant populations. At populations of 40,000 plants per acre, grain and residue yields in 20‐inch rows equaled or exceeded those in 40‐inch rows. Increased yields with increasing populations and N rates resulted from increased water‐use efficiency rather than from an increase in the amount of water used. Plant populations had little effect on grain residue ratios. Ratios decreased with increasing N rates in one season and increased with increasing N rates in the following season. Nitrogen content of grain and recovery of applied N in grain indicate low efficiency of applied N. The results of this study indicate that grain sorghum, grown continuously, can produce sufficient residue to provide satisfactory wind erosion control on the easily erodible soils of the Southern High Plains. To do this, plant populations must be high (40,000 to 60,000 plants per acre) and sufficient plant nutrients must be supplied to give maximum or near maximum plant growth.

Synopsis A restriction of 0.79 cm. or less for a period of 2 weeks or more on cotton roots reduced lint yield. All plants restricted to 0.32 cm. for 6 weeks or more died. Many plants died when restricted to 0.32 cm. for 4 weeks or' 0.48 cm. for 6 weeks, and the lint yield was very low on the plants that remained. Plant height was reduced by 0.32‐ and 0.48‐cm. restrictions of 4 weeks or more duration. On plants that were not killed, the part of the plant where the clamp was removed grew larger than was normal on check plants.

Grass establishment in semiarid regions is difficult due to insufficient moisture, high temp e r a t u r e s, high evaporation rates, damage to seedlings by windblown soil particles, and slow growth during the seedling stage. Research to find methods to circumvent some of these factors has met with varying success. Army and Hudspeth (1960) were able to improve soil moisture conditions in the seed zone by using a cover of polyethylene plastic. This treatment improved grass seedling emergence and was recommended for small areas or on crops of sufficient value to warrant the high cost of treatment. M c G i n n i e s (1959) found that planting in furrows increased soil moisture content and seedling emergence. These increases were attributed to the accumulation of rainfall in the furrow and to reduced evaporation. He noted, however, that high intensity rains washed soil into the furrows and covered the seed too d e e p. Moldenhauer (1959) found a mulch beneficial in grass establishment, and determ i n e d the probability of mulch needs at two locations in the Southern Great Plains.