Water consumption of spring wheat, potatoes, sugar beet, and onions grown in a lysimeter placed inside of a green house was measured using the change of soil water content profiles. The results obtained were summarized as follows :
1) Water consumption per day of each crop gradually increased with crop growth up to August. The increases of water consumption pattern and their volume, however, were different among these crops. Spring wheat showed the largest water consumption,and it reached 12mm«d_1 on July. An irrigation after water stress increased water consumption of potatoes.
2) Total water consumption from initial stage to August showed following order : spring wheat > sugar beetpotatoes > onions. Water consumption of potatoes grown in Volcanic ash soil was about 10%more than that grown in Brown forest soil. There were no differences in water consumption between the wet and dry soil water treatments.
3 ) Soil chemical properties influenced dry matter production of crop and top—root ratio. And it is considered that increase of top—root ratio increased evapotranspiration. That may be one of important facters to explain the difference in total water consumption through the grown period and Apparent Water Requirement (defined as amount of water consumed to produce unit dry weight) between soils.
4 ) Apparent Water Requirement was higher in the dry treatment than the wet one. Therefore this suggests that the crops wasted water in the dry treatment.
This paper is intended as an investigation of water resistance on Kanto loam with rainfall. A great deal of effort has been made on the study of erosion since old times. What seems to be lacking, however, are studies about the dispersion of soil aggregation and the permeability for ground water. The purpose of this paper is to show how to decide the value of man — made slope design against erosion control. Permeability test,pF test,pinhole test were made to carry out the purpose. The tested samples were the undisturbed and the compacted samples of Kanto loam which were obtained from experimental fields of ROLLING LAND LABORATORY, Tokyo University of Agriculture and Technology. The pF test was carried out using the pressure plate apparatus to obtain to soil moisture characteristics curves .Pinhole test was made to the pinhole test apparatus that was improved the J.L.Sherard’s model. The conclusion are as follows ；
(1）Kanto loam is easily eroded with rainfall because it has the pores in 15〜17% of the soil volume,which is called “mesovoid” by Brewer s pore size classification system.
(2) Kanto loam compacted greater than 0.6g/cm3 in dry density has high water resistance of soil.
(3) The Water resistance of the undistubed Kanto loam is evidently different from that of the compacted soil.
In order to investigate the simultaneous movement of salt and water in unsaturated soil, or in order to determine the dispersion coefficient associated with soil solution, we need the sensor that can monitor quickly the salinity of the soil solution and its changes with time. In this paper, we developed a method to determine the changes in NaCl concentrations (C) and water contents (θ)in a laboratory soil column, in which bulk soil electrical conductivities (ECa) were measured by the fou卜electrodes and matric suction by tensiometers simultaneously. We get a calibration equation for a sandy soil without clay particles that gives the bulk soil electrical conductivity (ECa) from volumetric water content (θ)and soil water electrical conductivity (ECw): ECa= a • ECw •θ2+ b•θ
where a and b are experimental coefficients. Examples of applying this method for monitoring simultaneous movement of water and salt in the unsaturated sand during infiltration and evaporation process were shown.
This report summarizes the soil survey results of peaty paddy—upland rotation fields spread along the basin of the lower stream of the River Ishikari.
1) The thickness of surface soil layer,composed of peat and clayish dressed soil,is about 30cm in average.
2) Soil physical properties of surface layer are better than those of the fields of clayish lowland and upland soils. But some fields have too—thick clayish surface layer caused bad soil tilth and poor surface permeability.
3) Ground water level of upland crop fields is above 60cm in the farming season, and trafficability for tractor is not inferior to that of the fields of clayish soils.
4) In this area , soil dressing by government enterprise started around 1955—1960 , and it was carried out 3—5 times in total so far at each field.
This report summarizes the cultivation experiment results of subsoil improvement by peat layer mix plowing for the peaty paddy—upland rotation fie Id (upland crop use) which have too—thick clayish surface layer.
1) Soil tilth,soil porosity and surface permeability were improved by layer mix plowing.
2) Trafficability for tractor is not inferior to that of the fields of normal plowing.
3) The whole field ground did not subsided after layer mix plowing,but the degree of configuration is worse than that of the field of normal plowing.
The effects of soil dressing on the silicic acid supplying capacity of paddy field soil were invesitigated, and the results of invesitigation were summarized as follows.
1. Available silicic acid content of soil for dressing was very high compared to that of paddy field soil.
2. Elution patterns following the change of pH of extraction buffer and extraction capacity are different for soil for dressing and paddy field soil. This result suggest the difference in the forms of supplying source.
3. From the quantitative ratio of silicic acid and alumina which is eluted simultaneously, the form of supply source was assumed to be aluminosilicate, and results of calculation were as follows. SiO2 (Al2 03)i.52 for paddy field soil and SiO2 (Al203)o.» for soil for dressing.
4 . Effect of supplying silicic acid by soil dressing was large in test cultivation of paddy rice and amount of absorption of silicic acid was so large as 2—5 times compared to the plot without soil dressing.
5 . Easy solble silicic acid which is contained in soil for dressing is estimated to be migrated and accumlated in soil layer in soil excavation site.
6 . Based on the results of invesitigation of paddy field site, effect of silicic acid by soil dressing showed decrease following the passage of year, and its years of lasting was supposed to be about 10 years.
The operation of the soil dressing using Pumice Flow Deposit (Pfld) has been spreading in recent years to improve productivities of upland crops. However, quantitative date to evaluate this type of soil dressing were still lacking. In this study, field experiment were conducted at three site of different soil origins in Abashiri district. The amount of applied Pfld were 50 and 100mm for Fine Brown Lowland soil, and 36,70 and 100mm for Fine Brown Forest soil and for Kuroboku soil. As Pfld, which is a kind of volcanic ash, is composed of high rate of pumice sand, its fertilities are very poor except for phosphorus. Pfld has pH of about 7. Some physical properties of these soils were ameliorated by application of Pfld. These were an increase of sand fraction, a convergence of solid ratio to 0.4m3m-3 and of bulk density to 1.0Mg m~3, an increase of easily available moisture when its value of original soil was under 0.lm3m~3, an increase of saturated hydraulic conductivity of the order of 10_6m s—1,and an improvement of soil tilth for fine soils with the decrease of soil stickiness. However, soil pH was unchanged, and CEC, exchangeable cation and available nitrogen were decreased slightly by the soil dressing. Pot experiments showed that mixing 0.6m3m-3 of Pfld with fine lowland soil suppressed crust formation and the rate of emergence increased up to 80%. Crop yields except of potatoes and sugar beet in Fine Brown Forest soil decreased with the increase of the Pfld applied. The cause of lower yields were considered by the decrease of soil chemical fertilities. However the facts that lower inner quality of crops and higher T/R ratio with higher yield at the 70 or 100mm dressing plot, indicate the higher release of soil nitrogen in a latter growth stage. While in the Kuroboku soil, outer color of potatoes became to light due to decrease of the adhhesion of soil particles. Above results indicate that application of Pfld as the soil dressing does not always increase crop yields but improves some physical properties of the soils which enhances efficiency of field operations. Therefore we have to estimate not only crop yields but various factors such as workabilitiy or crop quality when we judge the effect of soil dressing.