SUMMARYThis research was conducted to determine the effects of applying N-fertilizer to standard and semidwarf spring wheat varieties on the components of grain yield, and especially on the ability of tillers to develop and produce ears under semiarid conditions. For two growing seasons at Mandan, North Dakota, tillers were identified and tagged according to the leaf axil from which they originated. The survival and development of these tillers, identified as M, T1, T2, and T3 for main stem and tillers from axils of first, second and third true leaves respectively, were observed and measured from emergence to maturity. N-fertilizer was applied at 0, 50 and 270 kg N/ha annually, representing deficient, adequate and excessive N supply.N-fertilizer application increased grain yield of both varieties, with the increase between 50 and 270 kg N/ha being significant for the standard variety only. Most of this response to N resulted from an increase in the number of ears/ha, arising from reduced mortality of tillers, particularly T2 and T3 tillers during the latter part of the season when water was limited. For a given variety, grain production by M and by T1 tillers was seldom affected by N treatment. Although data were analysed by several means, all results indicate that improved N nutrition enables the later-developing tillers to survive and produce ears more competitively. Final grain yield was closely correlated with N content of a given tiller at the tillering stage, and to dry weight of individual tillers at both tillering and heading. Order of tiller had no appreciable effect on N content of grain. The proportion of final grain yield originating from M decreased from about 60% without N to about 36% for 270 kg N/ha, primarily because of increased survival and production from T2 and T3 tillers following the application of N-fertilizer.

Data on effects of plant and row spacing on yield of soybeans [Glycine max (L.) Merr.] have given conflicting results. Most such experiments were conducted under conditions of little or no water stress. The experiments reported here, conducted under more severe stress conditions, broaden the water‐availability spectrum covered. Each spring, 1976 through 1979, soybeans were seeded on Temvik silt loam (fine‐silty, mixed Typic Haploborolls) at Mandan, N.D., in row widths of 15, 45, and 90 cm, and at within‐row spacings of 11, 15, and 23 cm, which resulted in plant populations of 48,000 to 580,000 plants/ha. Soil water depletion by soybeans was generally confined to the upper 90‐cm soil depth. Average (4‐year) water use was 23.6 cm, and was not significantly affected by plant spacing. In 2 of the 4 years, total water use was greatest and average soybean yields were least Prom the 15‐cm row width. Within‐row spacing affected yields in only 1 of the 4 years. Water‐use efficiency was least for 15‐cm rows in 3 of the 4 years. These data suggest that planting in 15‐cm rows enhances water use prior to flowering. In extreme drought situations, this enhanced earlyseason water use leaves less water available for pod‐fill, and seed yields may be reduced accordingly. Under less severe water stress, however, plant and row spacing has no affect on soybean yield.

Narrow rows or equidistant planting of corn (Zea mays L.) has been beneficial in the Corn Belt. The concepts were evaluated at Mandan, N. D., to determine their influence under dryland conditions and in combinations with early‐maturing varieties which partially evade late season drought. The 68 and 85‐day relative maturity hybrids were grown at plant populations of 20,000; 30,000; 40,000; 60,000 and 74,000 plants/ha in 50 and 100‐cm spaced rows for 3 years. In 1968, a “wet” year, row spacing and maturity class significantly affected dry matter production, but only population influenced grain yield. Plant population and maturity class significantly affected grain yield in 1969 and 1970, but only population influenced dry matter in 1969. Interactions were not significant. Later‐maturing corn averaged 12% greater forage yield, but early‐maturing corn produced 19% more grain. Average grain yields increased from 2,600 to 3,070; 3,090; 2,960; and 2,680 kg/ha with progressive increases in population. Grain yield for 50 and 100‐cm rows averaged 2,890 and 2,870 kg/ha, respectively. Number of barren stalks increased and ear weight decreased with increased population. Optimum plant population for grain and forage ranged from 30,000 to 40,000 plants/ha.

In hydrological studies on Ohio watersheds, Post and Dreibelbis (5) studied types of frost as influenced by various covers. They identified and described three types of frost stmcture, namely: "concrete", "hone1'g966", and "stalactite".' They found that concrets type frost P-revailed under conditions of deep freezing and was impervious to water. The