Growth, yield components and micronutrient nutrition of field-grown maize (Zea mays L.) as affected by nitrogen fertilization and plant density
Growth and yield components in field-grown maize (Zea mays L.) were enhanced by nitrogen fertilization ranging from 50 to 200 kg N ha−1. Ear diameter, kernel depth, grain: stover ratio, number of ears plant−1, plant height and dry matter production increased as N fertilization rate was increased up to 100 or 150 kg N ha−1. Tasselling in maize was hastened by N fertilization. Increasing plant density from 25000 to 75000 plants ha−1 increased plant height, dry matter production and delayed tasseling but reduced ear diameter, kernel depth, grain: stover ratio and number of ears plant−1. Increased N supply and plant density had no influence on the concentrations of Mn, Zn, Cu, and Fe in ear leaf; except that Mn concentration increased as N fertilization rate was increased up to 150 kg N ha−1. Nitrogen × plant density interactions on the concentrations of the micronutrients in maize ear leaf were not significant.
The Relation of Corn Yields to Leaf Nitrogen, Phosphorus, and Potassium Content1
PLANT performance and its relation to internal nutrient concentrations during periods of active growth as revealed by plant and foliar analysis studies is receiving increasing attention. Plant analysis was employed by early workers to establish many of the principles of plant nutrition. It also received considerable early attention as a method of approach to the practical problem of determining the availability of soil nutrients. In contrast to present methods of expressing nutrient concentration in terms of drymatter weight, earlier workers (6) usually expressed concentration in terms of ash weight. Diagnosis based on ash analysis failed largely because it rested on two hypotheses, since disproved, that the plant ash for a particular species was nearly constant and that soil nutrients were of equal availability to all species. The majority of the early studies, moreover, were made either on mature plants, storage organs, or entire plants rather than, as at present, on some functioning plant part which is known to assess nutrient status accurately. Thus, while the idea of plant analysis is not new, the modern approach is different, and when used with the best soil information provides a logical approach to many plant nutrition problems. The literature on the present status of plant analysis is reviewed in recent publications by Scarseth (17), Ulrich (23), Boynton and Compton (i) , and .Thomas (21). The plant-nutrient composition of corn has received the attention of many workers. The early work of Schweitzer (18), Smith (19), and Jones and Huston (10) is noteworthy. This deals primarily with the variation and distribution of plant nutrients in the leaves, stalks, or ears with advancing maturity. More recent work includes that of Lucus, Scarseth, and Sieling (n) on the influence of soil fertility levels on nutrient composition and consumption. Little is known concerning the actual nutrient concentrations present in actively growing corn and their relation to ultimate yield. The Purdue tissue tests (8) are being used extensively in diagnosing nutrient deficiencies in corn. These tests are semi-quantitative in nature and are based on the principle of "critical concentrations". Scarseth (17), Drake (4), and others have used these tests in fertility investigations. The reports of Thomas (20) on foliar diagnosis and of Tyner and Webb (22) on the relation of corn yields to nutrient balance make possible some comparisons of the leaf contents of N, P, and K associated
Treatment of sentence production deficits in aphasia: A linguistic-specific approach to wh-interrogative training and generalization
Abstract The present research examines the effects of a linguistic-specific treatment on acquisition and generalization of wh-interrogative structures in two aphasic subjects presenting with deficit patterns consistent with agrammatism. The underlying linguistic representation of sentence structures selected for treatment and generalization was considered based on aspects of Chomsky's (1981) Government Binding (GB) theory, and a linguistic-based, wh-movement treatment strategy was implemented. Using a single-subject multiple-baseline design across behaviours and subjects, the effects of treatment were explored by examining generalization patterns across wh question forms requiring wh-movement (movement of a direct object NP to COMP). Within question form generalization also was evaluated by examining formulation of untrained sentences of varied complexity—with complexity defined in terms of the number of phrasal nodes in the d-structure representation of sentences. Results indicated that for both subjects...