Response of Field Beans (Phaseolus vulgaris L.) to Unacidulated Phosphorus Source in an Andosols in Kenya

The agronomic effectiveness of minjingu rock phosphate (MRP) was compared with that of highly soluble phosphate triple superphosphate (TSP), in pot studies with field bean (P. vulgaris L. ) in a greenhouse at the field station of Faculty of Agriculture, University of Nairobi, Kenya. MRP finely ground with 30 Grade % P and TSP with 99.6 Grade % P fertilizer at rates 0, 30, 45 and 60mg P pot-1 were applied on 2kg soil pot-1. The soil used in the study was an acid humic andosol from fields with moribund tea bushes, tea bushes planted in 1958 and 1979 and newly cleared forest in Kagaa, Kenya. Shoot and root dry matter yields, dry seed yield responses and their response estimates were determined and showed positive significance in most cases when TSP fertilizer was applied on the soils except that from moribund tea field. The relative agronomic effectiveness (efficiency) of MRP on biomass and also seed yield of beans was found to be significantly inferior to TSP in most of the soils except that from moribund tea field where both sources were found to be ineffective. This study confirms that inspite of its high reactivity, MRP is still agronomically ineffective as nutrient source of Phosphorous for growing P. vulgaris in acid soils. Journal of Agriculture, Science and Technology Vol. 2 (1) 1999: 32-4

Peanut response to lime and molybdenum application in low pH soils

Liming acid soils is considered to assure the availability of Mo in crops. Additionally, in peanuts (Arachis hypogaea L.) the positive response to liming is associated to a better supply of Ca+2, Mo for the nitrogenase-complex activity, and other non-nitrogen fixing activities of the crop. This study was thus undertaken to assess the effect of lime, Mo, and the lime-Mo interaction on peanut crop, on an acid Ultisol at the Mococa Experimental Station, Instituto Agronômico, São Paulo State, Brazil, from 1987 to 1990. A randomized complete block design with four replications, in a 4 x 4 factorial arrangement, was used in the study. The factors included four lime rates (0, 2, 4, and 6 t ha-1) broadcast and incorporated into the soil, and Mo (0, 100, 200, and 300 g ha-1) as (NH4)2MoO4 applied as seed dressing. Lime was applied once at the beginning of the study while Mo was applied at every planting. Peanut seed cv 'tatu' was used. Significant increase in peanut kernel yield with liming was only evident in the absence of Mo, whereas the peanut response to Mo was observed in two out of the three harvests. A higher yield response (28 % increase) was found when Mo was applied without liming. Soil molybdenum availability, as indicated by plant leaf analysis, increased significantly when lime was applied. Molybdenum fertilization led to higher leaf N content, which in turn increased peanut yield in treatments with smaller lime doses

Silicon in vascular plants: uptake, transport and its influence on mineral stress under acidic conditions

So far, considerable advances have been achieved in understanding the mechanisms of Si uptake and transport in vascular plants. This review presents a comprehensive update about this issue, but also provides the new insights into the role of Si against mineral stresses that occur in acid soils. Such information could be helpful to understand both the differential Si uptake ability as well as the benefits of this mineral element on plants grown under acidic conditions. Silicon (Si) has been widely recognized as a beneficial element for many plant species, especially under stress conditions. In the last few years, great efforts have been made to elucidate the mechanisms involved in uptake and transport of Si by vascular plants and recently, different Si transporters have been identified. Several researches indicate that Si can alleviate various mineral stresses in plants growing under acidic conditions, including aluminium (Al) and manganese (Mn) toxicities as well as phosphorus (P) deficiency all of which are highly detrimental to crop production. This review presents recent findings concerning the influence of uptake and transport of Si on mineral stress under acidic conditions because a knowledge of this interaction provides the basis for understanding the role of Si in mitigating mineral stress in acid soils. Currently, only four Si transporters have been identified and there is little information concerning the response of Si transporters under stress conditions. More investigations are therefore needed to establish whether there is a relationship between Si transporters and the benefits of Si to plants subjected to mineral stress. Evidence presented suggests that Si supply and its subsequent accumulation in plant tissues could be exploited as a strategy to improve crop productivity on acid soils