N-deficient Soil Research Articles

Nitrogen-use efficiency of 24 rice genotypes on an N-deficient soil

In many Asian countries the future will demand a higher rate of rice production increase than that obtained in the 1970's. However, low rice prices discourage production and lead to rice shortages. There is a strong interest in identifying rice genotypes which effectively utilize resources on the land, and in developing low-cost production technology for tropical Asia. A method proposed earlier to evaluate N utilization efficiency of 24 rice genotypes, and initially tested on a soil with high N fertility, was tested on a soil with low N fertility in order to evaluate the performance of the genotypes under contrasting conditions. In six consecutive seasons on an infertile Vertic Tropaquept soil in Maligaya, Nueva Ecija, The Philippines, field performance was ranked on the basis of 12 parameters considered in the initial study. Significant differences among genotypes were observed in 68 out of 72 instances during the six seasons. Five parameters were selected for ranking in unfertilized plots and seven for ranking in plots receiving N fertilizer. Principal-component analysis showed that yield was the most significant single parameter in most instances. A two-parameter combination involving yield and ratio of panicle weight to either total N uptake or soil N uptake, however, correlated much better with rankings based on five or seven parameters. In contrast to the IRRI data on a fertile Andaqueptic Haplaquoll soil, significant differences among genotype means for soil N uptake in fertilized plots and total N uptake in unfertilized plots were found in all six seasons at Maligaya. Genotypes 11 and 18 ranked consistently high with all combinations of parameters, whether fertilized or unfertilized. For example, genotype 11 ranked first in all cases at IRRI, and either first or second in all cases at Maligaya. Others such as genotypes 5 and 12 ranked consistently low. The results indicate consistency in rice-genotype performance on soils deficient in N supply as well as those adequately supplied, in both wet and dry seasons, thus extending the applicability of the methodology.

Hydrocyanic Acid Potentials in Leaf Blade Tissue of Eleven Grain Sorghum Hybrids

AbstractHydrocyanic acid potentials (HCN‐p) of grain sorghums [Sorghum bicolor (L.) Moench] need not be considered in grain production but become important when fresh forage is fed to livestock. This study involved determination of seasonal leaf blade HCN‐p levels of 11 field‐grown grain sorghum hybrids, relationships between HCN‐p levels in growth chamber‐grown seedlings and older fieldgrown plants, and effects of N fertilization on seasonal leaf blade HCN‐p levels.Growth chamber plants were grown in vermiculite, subirrigated daily with nutrient solution. Plants were harvested and assayed for HCN‐p 10, 14, and 18 days after planting. In 1972, the 11 hybrids were field‐grown on N fertilized soil. In 1973, ‘DeKalb E‐59’ was grown on N fertilized and on N‐deficient soil. Field‐grown hybrids were assayed for HCN‐p weekly from 27 (1972) or 37 (1973) days after planting until physiological maturity. HCN‐p was determined potentiometrically on homogenized, β‐glucosidase hydrolized leaf blade tissue.Relationships between HCN‐p levels at sampling dates during the season and seasonal average HCN‐p levels indicated that, for purposes of ranking cultivars, approximately equal precision would be attained at any time from growing point differentiation through soft dough. The correlation between HCN‐p levels in 18‐day‐old growth‐chamber plants and seasonal average HCN‐p levels of field plants was significant at the 10% level (r = 0.56) but HCN‐p levels in 10‐ and 14‐day‐old plants were not significantly related to seasonal average HCN‐p levels of field plants. HCN‐p in leaf blade tissue was highly dependent on N availability. At a sustained adequate level of N, HCN‐p levels in sorghum leaf blade tissue declined from the seedling stage to about flag leaf and then remained fairly constant until they declined at the approach of maturity. HCN‐p levels exceeded the “threshold of danger” (200 ppm) until physiological maturity. On N‐deficient soil, leaf blade HCN‐p levels declined to a low level (<100 pm) at soft dough.

Nitrogen and Phosphorus Content of Greenbugs Reared on Fertilized Wheat1

The greenbug, Schizaphis graminum (Rondani), is a major pest of wheat in the Central and Southeastern States. Infestations are common in the High Plains of Texas where fertilizer practices vary from no fertilizer on dryland to high rates under irrigation. However, there is little specific work on the effects of plant nutrients on this aphid. Haseman (1946) indicated that the greenbug has a high nitrogen requirement and will not reproduce as well on small grains grown on N-deficient soil, but Arant and Jones (1951) showed populations to vary inversely with the amount of nitrogen applied to oats. Blickenstaff et al. (1954) also found that in oats and rye the greenbug population decreased as the rate of nitrogen was increased. Daniels and Porter (1956) found that high populations were associated with high nitrogen levels in the soil and with increased plant vigor. Daniels (1957) found that the number of greenbugs per gram of plant varied inversely with the amount of nitrogen applied. He found also that plant growth was improved when phosphorus was used in combination with nitrogen.