Water soluble P fertilizers have been reported to be best for potato (Mattingly, 1963; Sharma, Grewal & Sud, 1976). However, they are irretrievably fixed in the acid soils because of their high P fixation capacity. Placement of P fertilizers is, therefore, necessary for their efficient use. Furrow placement of P fertilizers reduces their contact with soil and enhances P availability to the plants. Placement of P in spots, rather than in furrows, will further reduce the contact between the soil and the fertilizers and may improve its efficiency over furrow placement. The present investigation was undertaken to study the relative efficiency of these two methods of P application for potato in the spring season.

Organic manures, despite their low nutrient analysis, play a significant role in meeting fertilizer needs of crops. When manures are applied in conjunction with fertilizers, yields are generally higher than with equivalent fertilizers alone. An increase in the yield optima leads to uncertainties in working out fertilizer economy in quantitative terms. In order to overcome this, a concept of fixed yield is described in this paper.

Zinc deficiency has been one of the major micronutrient disorders of flooded rice. Several researchers have reported that Zn deficiency could be corrected by the application of various Zn fertilizers to soil (Mikkelsen & Brandon, 1975), to seedling root (Yoshida et al. 1970; Katyal & Ponnamperuma, 1975) or to plants as foliar spray. Also there has been much speculation about the most suitable form of Zn fertilizer for correcting Zn deficiency of flooded rice. A glasshouse study was conducted to compare the effectiveness of various Zn fertilizers for rice grown under flooded conditions.

Fertilizer work in the savannah soils of northern Nigeria has been largely confined to the two most limiting nutrients N and P. The gradual shift towards continuous intensive cultivation coupled with the introduction of improved crop varieties and better crop management has necessitated the consideration of other elements, such as magnesium. The widespread use of K fertilizer in the absence of Mg fertilization may have an adverse effect on Mg availability in view of the well-known ionic antagonisms between Mg and K in plant nutrition (Jacob, 1958; Welter & Werner, 1963). Plants require greater amounts of Mg than normal to prevent deficiency under conditions of high soil K (Ulrich & Ohki, 1956; Kabu & Toop, 1970). Therefore soils hitherto considered to be adequately supplied with Mg may well be suffering from induced Mg deficiency under the present fertilizer programme which involves only K as the major cation. Tobacco is an important cash crop generally rated as a high Mg demanding crop (Adams & Pearson, 1967). The growth characteristics of the crop (enormous leaf development and rapidity of plant growth) make it an excellent crop to study. The abnormality in growth of tobacco, now known as sand drown, was first observed on tobacco grown on sandy soils, especially during periods of excessive rainfall. The abnormality was later found to be due to Mg deficiency.