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Effects of nutrient concentration in the medium on the growth and mineral uptake in wheat, Agropyron and their hybrids
... It was reported by many respondents in Nakuru and Uasin Gishu districts (80%) that fertilizers used on wheat in the same cu-marginal regions are diammonium phosphate, monoammonium phosphate and urea which are NH 4 + -based. It is established that NH 4 + ions reduce the absorption of Cu 2+ ions (Sigunga et al., 1986;Tills and Alloway, 1981), and enhance the uptake of negatively charged ions like H 2 PO 4 -, HPO 4 = and SO 4 = (Blair et al., 1970;Smith and Jackson, 1987). Tills and Alloway (1981) had observed that high levels of NH 4 + -containing fertilizers used on soils with low copper content could cause copper deficiency in wheat. ...
Land and soil make up the cardinal resource-base in any agricultural production system and, hence, their proper management is vital for sustainable agricultural production. A study was conducted to evaluate the availability and accessibility as well as constraints to utilization of land and soil resources for sustainable agricultural production in Kenya. The study covered 33 districts drawn from 6 out of the 8 administrative provinces in the country. The selected districts were drawn from agriculturally active provinces. The methodology used in data gathering included collection of information from secondary sources, use of questionnaires, field visits and personal interviews. The country has an area of 583,000 km 2 , out of which land and water occupy 571,770 and 11,230 km 2 , respectively. About 33% and 67% of Kenya's land mass are designated as available agricultural land and arid and semiarid land, respectively. Less than 40% of the available agricultural land is utilized. Only 5% of the country's drainage potential is developed. Besides, most of the semiarid land is of high potential for agricultural production provided irrigation is applied. The country's irrigation potential is estimated at 54,000 ha out of which 20% is developed. More land may be reclaimed for agricultural production from the semi-arid land by applying irrigation. Agricultural land availability is, therefore, not limiting to agricultural production. Skewed land ownership that leaves most of the land in the hands of few people is a factor that undermines access to, and development of, the land. Erosion risk and soil shallowness are important constraints. Suitable land/soil conservation measures targeting all forms of soil degradation processes in relation to agricultural systems in given agro-ecological zones need to be developed if the land/soil resources of the country are to be utilized for sustainable agricultural production.
Nitrogen is the most limiting plant nutrient in Vertisols in Kenya. Soilproperties, climatic conditions and management factors as well as fertilizercharacteristics can influence fertilizer nitrogen (N) use efficiency by crops.Vertisols, characterized by low-basic water infiltration rate, are prone towaterlogging under sub-humid and humid conditions. We determined effects ofdrainage, N source and time of application on yields, nutrient uptake andutilization efficiencies by maize grown on Vertisols in sub-humid environments.Treatments comprised two furrows (40 cm and 60 cmdeep) and a check (i.e., no furrow), calcium nitrate to furnishNO3-N, ammonium sulphate to supply NH4-N at 100 kgNha–1, a control (i.e., no fertilizer N), and fertilizerN application at sowing, 40 days after sowing, and split (i.e., half the rateatsowing and half 40 days after sowing). A split-plot design was used in whichdrainage formed the main plots and N source x time of N applicationformedthe sub-plots. Higher grain and total dry matter yields, harvest index, leaf Ncontent, uptake of N, P and K, as well as N agronomic (NAE) and recovery (NRE)efficiencies were obtained from drained compared to undrained plots. The increase ingrain yields as a result of drainage varied from 31 to 45␏or control,35 to 43␏or NO3-N, and 16 to 21␏orNH4-Ntreatments. Drainage resulted in total N uptake increases from 50 to 80kgN ha–1 in control plots, 80 to 130 kg Nha–1 in NO3-N treated plots, and 90 to 130kg N ha–1 in NH4-N treated plots.Ammonium-N source was superior to NO3-N source in terms of higheryields, NAE, and NRE in undrained plots, but the two N sources behavedsimilarlyin drained plots. Delayed or split NO3-N application gave higheryields, NAE and NRE than when all N was applied at sowing in undrained plots.There was no difference between 40 cm and 60 cm deepfurrows in terms of crop yields and nutrient use efficiencies. Thus, drainingexcess water with furrows at least 40 cm deep is essential forsuccessful crop production in these Vertisols under sub-humid conditions.
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