Thesis (M. Sc. (Agricultural Management)) -- University of LImpopo, 2002 / Refer to document / NRF (National Research Foundation) and WRC (Water Research Commission)

Phosphorous fertilizer has an efficiency of about 10 percent, and this efficiency must be improved, in order to avoid excessive loss of a non-renewable resource. Ammonium lignosulphonate (ALS), a by-product of the pulp and paper industry, is expected to improve efficiency of fertilizer phosphate (P) for corn (Zea mays L.) production. Field experiments were conducted to investigate effects of added ALS and P on soil organic matter and P fractions, as well as corn yields and nutrient uptake in a Ste. Rosalie clay soil and an Ormstown silty clay loam soil in 1990 and 1991. Incubation studies showed that added ALS increased organic matter but added P as diammonium phosphate (DAP) decreased organic matter in the fertilizer band location in both soils. Applied ALS with P increased Mehlich-III (M$ sb3$P) extractable P and bicarbonate extractable P in the fertilizer band location in both soils during early incubation periods. Soil Ca-P was decreased with increased ALS. However, soil Al-P and Fe-P compounds were increased with increased ALS. Applied P increased corn shoot P concentration at the six leaf stage, and increased grain yields, total dry matter (TDM) and N and P uptake in both soils. Applied ALS at up to 608 kg ha$ sp{-1}$ with P increased corn shoot P concentration at the six leaf stage in the Ste. Rosalie soil in 1991. Applied ALS at up to 304 kg ha$ sp{-1}$ with P increased grain yield, N and P uptake. However, applied ALS without P decreased stover N concentration. Thus, ALS may improve efficiency of fertilizer P for corn production depending on soil and application methods.

Biological soil inoculants are products that contain beneficial microorganisms with the ability to increase plant-available nutrients. Soil inoculants are claimed to serve as a supplement for fertilizer N, improve germination and tilth, improve root systems, and increase crop quality and yield. The inoculant evaluated in this study was Effective Microorganisms (EM) produced by Nature Farm Foundation of Lompoc, California. A field trial with corn (Zea mays, L.) was conducted at Oakwood Organic Farm in East Central Indiana in 1992. Two soil types were used in the study, a Genesee silt loam (Fluventic Eutorchrept) and a Sloan silt loam (Fluventic Haplaquoll). Soil nitrate level measured through the growing season was not significantly affected by the addition of EM. Neither foliar nutrient content nor grain dry matter yield were significantly greater with use of EM compared to the control. / Department of Natural Resources

Fertilizer applications of urea and triple superphosphate (TSP) suffer from low efficiency for corn production. Band or broadcast application of urea with acidic-P fertilizers may increase fertilizer efficiency. Urea and acidic-P fertilizer interactions in soil-fertilizer microsites were investigated using two Quebec soils. Adding acidic phosphates such as TSP and monoammonium phosphate (MAP) to urea reduced pH in microsites, urea hydrolysis, NH$ sb3$ volatilization, and increased soil NH$ sb4$- and NO$ sb3$-N contents. Ammonia loss decreased as P$ rm sb2O sb5$: urea-N ratios increased. Adding urea to P fertilizer increased soil pH and P sorption when using CaCl$ sb2$ as the electrolyte. Urea application increased 0.5 M NaHCO$ sb3$ extractable P. Banding urea with TSP caused dissolution of organic matter in soils, and increased P diffusion and P concentration in soil solution sampled with filter paper or in 1 M KCl extraction. Two years of field experiments demonstrated that banding urea with TSP or MAP increased soil extractable P (Mehlich-3), N and P nutrient uptake, plant growth and development of corn. Greater P fertilizer efficiencies and higher yields were achieved by banding urea-acidic P fertilizers.

An experiment was conducted to investigate the effects of N formulation, application rate, and application time on corn yield and quality under Eastern Canadian conditions, to evaluate the hypothesis that application of N will increase corn grain yield and protein concentration without decreasing the total energy content. Three N formulations, each with the rates of 90, or 180 kg ha$ sp{-1}$ were applied at different times. The results indicated that the grain yield increased with increasing N fertilizer rate and with increasing numbers of N application times. N application significantly increased grain protein concentration, on both a per kernel and a dry matter basis, and protein yield. Such as, N application increased the averaged protein concentration, on a dry matter basis, of corn grain by about 8.40% as compared to the control. The protein concentration was not affected by the number of N application times before the plants were 90 cm high. Neither lipid nor non-structural carbohydrate concentration, on both a per kernel and a dry matter basis, were significantly affected by N application in most of the location-years. In addition Near infrared reflectance (NIR) was used to determine the lipid concentration in the aerial corn tissue at different growth stages. The correlation coefficients between the standard analytical method and the NIR method of lipid concentration were all above 0.95, and were significant at 0.01 level.

The objectives of the study were to determine whether intercropped alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) or rye grass (Lolium multiflorum Lmk.) could simultaneously contribute to the nitrogen regime of grain-corn (ie: increased yield), improve edaphic quality, and decrease the level of inorganic nitrogen present in the soil after corn harvest. To achieve these objectives the seeding of the intercrops was delayed, the corn population was increased, and the red clover was spring-ploughed. / Fall-ploughed red clover maintained the mean weight diameter (MWD) of aggregates on the Ste-Rosalie clay. Spring-ploughed red clover on the other hand caused a decrease in bulk density in the top 10 cm of the Chicot loam. / The nitrogen-response of corn indicated that the intercrops did not contribute to the nitrogen regime of grain-corn. There were also indications that intercrops competed with corn for available inorganic nitrogen and water. The intercrops, however, did reduce the levels of soil inorganic nitrogen in the fall allowing for a possible decrease in the nitrogen load of soil percolates. / Despite the beneficial effect of nitrogen fertilisation on the organic nitrogen content of the soil, the presence of leguminous intercrops did not prevent the increase of the soil CN ratio.

Corn dry matter and grain yields were evaluated for 40 unique limited irrigation treatments and compared to a standard nonlimited treatment. The various treatments were imposed by an interaction of time (i.e., growth stage) and water level . Irrigation was so scheduled that each treatment received water at evaporative demand rates during either the vegetative or the pollination stage . The total irrigation water applied for the growing season ranged from 11 em to 43 em. Dry matter and grain yields were essentially the same for all treatments. Limited irrigation in the vegetative stage did not reduce growth if there were no further limitations in the pollination stage Limited irrigation in the pollination stage did not result in yield reductions if there were no limitations in the vegetative stage. Limited irrigation in the maturity stage did not effect yields if there were no limitations in the vegetative stage and/or the pollination stage. Chronic, season long irrigation deficiencies resulted in yield reductions. In each case, the soil water profile was full at the outset of the growing season. The silt loam soil of the experimental site was able to supply sufficient water to the plants during periods of nonirrigation or limited irrigation . The corn plants responded to available water, whether it was supplied by irrigation or the soil . Limited irrigation was effective in saving irrigation resources without reducing yields. Some of the variables which appeared to have a significant effect on yield response to limited irrigation included : beginning soil water status, soil water storage capacity, timing of irrigation, and corn hybrid and climatic interactions. Management decisions relating to limited irrigation on corn should not be made independent of these factors.

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