Corn (Zea mays L.) production under monoculture and conventional-tillage management may cause soil degradation and nitrate (NO$ sb3 sp-)$ pollution. This study was conducted from 1991 to 1993 to evaluate the impact of conventional-tillage (CT) and no-tillage (NT) practices under corn-soybean (Glycine max L. Merill) rotations (C-S-C and S-C-S), continuous corn (C-C-C) and continuous soybean (S-S-S) systems on optimum N fertilization rates, yield and soil residual N levels. Field experiments were carried out on a Ste. Rosalie clay (Humic Gleysol) and an Ormstown silty clay loam (Humic Gleysol). Overall, tillage had little effect on soil and crop N levels or grain yields. Residual soil NO$ sb3$-N in the fall was related to fertilizer N rates in C-C-C, but not with S-S-S or soybean in rotation. Residual NO$ sb3$-N values after soybean were high and at zero added N were equivalent to 90 kg N with C-C-C. Consequently, soybean contributed the equivalent of 90 kg N ha$ sp{-1}$ to subsequent corn. Corn yields following soybean were higher than following corn, and less fertilizer N was required following soybean than following corn.

Maize is the most important cereal crop grown in South Africa. This crop is produced throughout the country under diverse conditions and in diverse environments. The study only focuses on technical efficiency because it is an important subject in developing agriculture where resources are limited, but high population growth is very common. In such a setting, increased output will depend more on efficiency improvements and assessing the scope for such efficiency improvements within the system is a crucial need. The objective of the study was to determine the level of technical efficiency and to identify the socio-economic and institutional characteristics as well as the entrepreneurial spirit that influence the technical efficiency of small-scale maize producers in the Tsolo magisterial district. Purposive and Snowball sampling techniques were used to collect primary data from 120 small-scale farmers. The stochastic frontier model was used to determine the level of technical efficiency. The Multivariate OLS was used to analyze the socio-economic factors and institutional characteristics that have influenced the technical efficiency of maize production. A similar linear regression model was used to estimate the influence of positive psychological capital and entrepreneurial spirit on the technical efficiency of maize production. The stochastic results revealed that small-scale farmers in Tsolo are technically efficient at 98 percent in maize production and experience increasing return to scale (1.37), which means that increase in the use of inputs, will as well increase their productivity and efficiency. The inefficiency model results indicated that age, years in farming, household size and extension contact significant and 3 variables, namely, as years in farming, extension contact and farm size are significant in the OLS model. Lastly the results of the linear regression indicated that, out of the 4 variables estimated in the entrepreneurial spirit, self-efficacy and resilience were significant with respect to its responsiveness to total maize output.

No description available.

No description available.

Three studies, two field and one laboratory, were performed to evaluate Cu or Cu and Zn from either sulfate sources or Cu-enriched pig manure. The studies were designed to investigate the effects of Cu and Zn in soils and corn (Zea mays L.). The first field study consisted of continuing a longterm field experiment which was established in 1967 to evaluate corn response and changes in a Davidson clay loam soil to yearly additions of Cu and Zn sulfates. In 1983, the 17 annual additions of Cu and Zn resulted in cumulative totals of 280 kg Cu and 560 kg Zn ha⁻¹. These Cu and Zn additions, either alone or together, did not cause any grain or stalk yield decreases. The DTPA extractant effectively separated all soil treatment levels for both Cu and Zn. Copper concentrations in the blades and grain were not related to soil additions of Cu or Zn. However, Zn concentrations in blades and grain were directly related to each other, r=0.87**, to soil Zn treatment levels and to DTPA extractable Zn. The second field experiment was designed to evaluate the effects of soil application of Cu-enriched pig manure and CuSO₄ on corn. The five treatments in each of three field locations consisted of a control, low and high Cu-enriched pig manure levels, and Cu, as CuSO₄, equivalent to Cu amounts in the manure. The soils varied in texture from clay loam to fine sandy loam, and ranged in CEC from 5 to 12.3 cmol(+) kg⁻¹. Copper-enriched pig manure, containing 1285 mg Cu kg⁻¹, was produced by pigs fed diets supplemented with 242 mg Cu kg⁻¹. After six years, 198 mg Cu kg⁻¹ had been applied by the high treatments. The DTPA extractable Cu was not related to leaf nor grain Cu levels but was linearly related, r=O.95**, to applied Cu. No nutrient deficiencies or toxicities were observed. The third study was a laboratory incubation of added Cu. The 15 soils ranged from 54 to 489 mg kg⁻¹ in clay and from 5.4 to 7.4 in pH. Extractable Cu had simple correlations with five soil properties, clay, surface area, hydrous Al, hydrous Fe, and hydrous Mn. Three treatments, a control and 22 kg ha⁻¹ Cu as CuSO₄, and as Cu-enriched pig manure (equivalent to 975 mt wet manure ha⁻¹), were applied to the soils at 33 k Pa moisture. Copper was extracted in the following order for the control and CuSO₄, treatments: AlCl₃ in O.5M HC1 > EDTA > DTPA. A different order of Cu extraction occurred for the Cu-enriched pig manure treatment such that EDTA > DTPA > AlCl₃ in 0.5M HC1. Extractable Cu decreased with time regardless of Cu source. / Ph. D. / incomplete_metadata

Many producers in North America are finding it profitable to make the transition from conventional farming to organic agriculture. Organic fertilisers may affect crop production and soil quality differently than inorganic fertilisers. The objectives of this study conducted in Ste.-Anne-de-Bellevue. Quebec were to examine crop yield, grain quality, soil fertility and microbial community parameters in wheat and corn agroecosystems receiving poultry manure or inorganic fertiliser. Wheat grain yield declined and corn grain yield did not increase with higher N rates, suggesting that increased N supply did not encourage grain production. Soil analyses demonstrated high inherent soil fertility at the study site, and fertilisation led to an environmentally undesirable increase in residual soil NO3 concentrations. Microbial biomass and respiration in corn agroecosystems were greater with poultry manure amendments than inorganic fertiliser, but not in wheat agroecosystems due to significant variation among field replicates. Phospholipid fatty acid analysis revealed significant differences between wheat and corn soil microbial community composition, but differences due to fertilisation were less evident. Further work is needed to uncover the relationships among N fertilisation, crop nutrition and soil microbiology in organic agroecosystems.

This study investigated the possibility of using data, acquired from airborne multi-spectral or hyper-spectral sensors, to detect nitrogen status and presence of weeds in crops; with the ultimate aim of contributing towards the development of a decision support system for precision crop management (PCM). / A 24-waveband (spectrum range 475 to 910 nm) multi-spectral sensor was used to detect weeds in corn (Zea mays L.) and soybean ( Glycine max (L.) Merr.) in 1999. Analysis of variance (ANOVA), followed by Scheffe's test, were used to determine which wavebands displayed significant differences in aerial spectral data due to weed treatments. It was found that the radiance values were mainly indicative of the contribution of weeds to the total vegetation cover in various plots, rather than indicative of changes in radiance of the crops themselves, or of differences in radiance between the weed populations and the crop species. / In the year 2000, a 72-waveband (spectrum range 407 to 949 nm) hyperspectral sensor was used to detect weeds in corn gown at three nitrogen levels (60, 120 and 250 kg N/ha). The weed treatments were: no control of weeds, control of grasses, control of broadleaved weeds and control of all weeds. Imagery was acquired at the early growth, tassel, and fully-mature stages of corn. Hyper-spectral measurements were also taken with a 512-waveband field spectroradiometer (spectrum range 270 to 1072 nm). Measurements were also carried out on crop physiological and associated parameters. ANOVA and contrast analyses indicated that there were significant (alpha = 0.05) differences in reflectance at certain wavebands, due to weed control strategies and nitrogen application rates. Weed controls were best distinguished at tassel stage. Nitrogen levels were most closely related to reflectance, at 498 nm and 671 nm, in the aerial data set. Differences in other wavebands, whether related to nitrogen or weeds, appeared to be dependent on the growth stage. Better results were obtained from aerial than ground-based spectral data. / Regression models, representing crop biophysical parameters and yield in terms of reflectance, at one or more wavebands, were developed using the maximum r2 criterion. The coefficients of determination (r 2) were generally greater than 0.7 when models were based on spectral data obtained at the tassel stage. Models based on normalized difference vegetation indices (NDVI) were more reliable at estimating the validation data sets than were the reflectance models. The wavebands at 701 nm and 839 nm were the most prevalent in these models. / Decision trees, artificial neural networks (ANNs), and seven other classifiers were used to classify spectral data into the weed and nitrogen treatment categories. Success rates for validation data were lower than 68% (mediocre) when training was done for all treatment categories, but good to excellent (up to 99% success) for classification into levels of one or the other treatment (i.e. weed or nitrogen) and also classification into pairs of levels within one treatment. Not one classifier was determined best for all situations. / The results of the study suggested that spectral data acquired from airborne platforms can provide vital information on weed presence and nitrogen levels in cornfields, which might then be used effectively in the development of PCM systems.

No description available.

No description available.

MSCAGR (Soil Sciece) / Department of Soil Science / In most parts of Limpopo Province of South Africa, crop yields are low and continue to decrease due to decline in soil fertility, which has been identified as a major constraint to crop production. Therefore, there is a pressing need for soil amendments such as the application of biochar, which has the potential to improve soil fertility due to its physical and chemical properties. Biochar is the product of incomplete combustion of biomass in the absence of oxygen. The overall objective of the study was to determine the effects of biochar and NPK fertilizer on maize performance and selected soil nutrient levels. A 3x2 factorial experiment was conducted at the School of Agriculture Experimental Farm for two consecutive seasons (2015/16 and 2016/17 seasons). Treatments consisted of biochar applied at three levels, viz. 0, 10 and 20 t/ha and NPK inorganic fertilizer applied at two rates viz. NPK0 (zero NPK fertilizer) and NPK1 {N (150 kg/ha) P (50 kg/ha) K (20 kg/ha)}. The treatments were laid out in a randomized complete block design (RCBD) and replicated three times. Maize cultivar (DKC 2147) was used as the test crop. Maize growth and yield measurements assessed included: plant height (cm), stem diameter (cm), number of leaves, leaf area, dry biomass (kg/ha), nutrient uptake, cob yield, grain yield and harvest index. Soil samples were collected from 0-10 cm and 10-20 cm soil depths at the end of each season to determine total N, P, K nutrient levels in the soil. Data collected was subjected to two-way analysis of variance using the general linear model (GLM) procedure of Genstat software version 17. Comparison of means was done using the Standard Error of Deviation (SED) method at 5% level of significance (p<0.05). Biochar and NPK fertilizer had no effect on total N and exchangeable K at all soil depths in 2015/16 and 2016/17 seasons. Biochar had no effect on phosphorus at all soil depths in 2015/16 and at 0-10 cm soil depth in 2016/17 season. The effect of biochar and NPK fertilizer was highly significant (p<0,001) on available P at 10-20 cm soil depth in 2016/17 season. Significant interactive effect of biochar and NPK fertilizer on soil total N at 10-20 cm (in 2015/16 season), available P and exchangeable K at 10-20 cm soil depth in 2016/17 season was also observed. Plant growth parameters increased with biochar addition at 20 t/ha and NPK1 (150 kg N/ha, 50 kg P/ha, 20 kg K/ha) fertilizer. The results of this study showed that biochar application at the rate of 10 and 20 t/ha has the potential to influence selected soil nutrient levels, maize growth, yield and yield components with and without NPK fertilizer application. Since this study was conducted over two seasons and biochar properties changes over a long-term period, more research is needed to evaluate the effect of biochar on soil nutrient levels and maize growth, nutrient uptake and yield over a long period of time. / NRF