Maize Dry Matter Production Research Articles

Different sources of nitrogen fertilizer in rainfed maize grown in a semiarid environment

Although nitrogen is the nutrient most required by maize, doses of N lower than those recommended are applied to maize grown in semiarid environments, which limits the achievement of profitable yields. The objective of this study was to evaluate changes in soil fertility, nutritional status and dry matter production of maize plants fertilized with organic and mineral fertilizers in a semiarid region. A factorial experiment was carried out in Sobral, Ceará state, Brazil, in a randomized block design. The factors were two N sources (organic compost and urea), and four N rates: 27.5, 55, 110 and 165 kg ha−1, with three replications. We assessed variables associated with soil fertility, plant nutritional status, chlorophyll content, grain yield and total dry matter production. The highest rates of organic compost resulted in the highest levels of P (17.7 mg dm−3) and K (102.2 mg dm−3) in soil when compared to the control (7.7 and 69.0 mg dm−3, respectively). However, organic compost rates below 110 kg ha−1 of N-equivalent fertilizer were not enough to supply the plants’ demand for P and K. Low N rates promoted a decrease in soil inorganic N in the second year of application. Applying urea to maize plants led to greater dry matter production than organic compost in the second consecutive crop season. The use of organic compost at rates lower than 110 kg ha−1 of N-equivalent fertilizer decreases soil fertility and has no impact on maize dry matter production.

Soil and foliar application of zinc-methionine and zinc sulfate effects on growth and micronutrients enrichment in maize cultivated in lime-rich and poor soils

Less uptake of zinc (Zn) in maize is a serious issue when cultivated in lime soils. The higher concentration of lime significantly affects soil pH. It also minimized the phyto-available pool of micronutrients, i.e., Zn, iron (Fe), copper (Cu), in soil. In these micronutrients, the balance uptake of Zn and its enrichment in maize has prime importance. Application methods and sources of Zn application can overcome this problem. The current study was conducted to assess soil and foliar application's efficacious functioning toward improvement in Zn uptake and dry matter production of maize Two sources of Zn (zinc-methionine and zinc sulfate) were applied at the rate of 5 mg Zn kg−1, 0,2% Zn. Results showed that soil + foliar Zn methionine performed significantly better than all other treatments for increase in dry weight of maize in lime-rich and poor soils. A significant increase in Zn concentration of maize signified soil + foliar Zn methionine's imperative functioning over all the treatments in lime-rich and poor soils. However, results also showed that both sources of Zn application via soil and foliar caused a significant decline in Fe, Cu and Mn concentration in maize in lime-rich and poor soils. On an average, in lime-rich and poor soils, performance was better in lime-poor soils over lime-rich soils. In conclusion, soil + foliar Zn methionine is an effective amendment for improving maize dry matter and Zn enrichment in maize when cultivated in lime-rich and poor soils.

Fortnightly dynamics and relationship of growth, dry matter partition and productivity of maize based sole and intercropping systems at different elevations

Understanding temporal dynamics of growth and dry matter production of sole and intercropped maize under different agro-climatic and cultural conditions is imperative to devise crop models and optimize resources for better crop production. Field experiments comprising seven cropping systems (maize-mungbean, maize-cowpea, maize-soybean, maize sole, mungbean sole, cowpea sole, soybean sole) were performed for three years (2015, 2016 and 2017) at three elevation sites (1500, 1800 and 2200 m from mean above sea level) using factorial randomized complete block design (RCBD) with three replications. Maize growth (plant height, number of leaves, leaf area), dry matter partitioning (leaf, stem, plant) and absolute growth rate (AGR) were observed for five growth intervals (1–15, 16–30, 31–45, 46–60 and 61–75 days after germination, DAG) while yield components (thousand grain weight, grain yield, biological yield) were recorded at harvesting. Furthermore, productivity, land equivalent ratio (LER) and competition index (CR) of cropping systems computed from biomass and grain yields of maize and legumes were also compared in terms of economic and biological yields. The growth parameters, dry matter production and AGR of maize varied significantly (p ≤ 0.05) due to individual and interaction effect of year, elevation, and legume during 31–45, 46–60 and 61–75 DAG but did not vary significantly during the 1–15 and 16–30 DAG. Growth parameters, dry matter production, AGR and harvest yields of maize were the highest during 2015, at 1500 m elevation, and in intercropping with mungbean but at par with maize sole cropping. System productivity and LER were greater for maize-mungbean cropping compared to rest of the cropping systems including sole cropping. Growth parameters and dry matter production of maize were found strongly correlated (r = 0.84−0.98) with its grain and biomass yields. It is concluded that 3rd, 4th and 5th fortnightly intervals are critical periods for intercropped maize where its growth and biomass production are significantly influenced due to competition with legumes. Lower elevations and mungbean as intercrop with maize are recommended for greater economic and biological productivity of maize based intercropping systems.

Effect of Christmas Island rock phosphate and rice straw compost application on soil phosphorus availability and maize (Zea maysL.) growth in a tropical acid soil of Kelantan, Malaysia

AbstractPhosphorus (P) fixation is very common in Malaysian acid soils due to the fixation of soluble inorganic P by Al and Fe under acidic soil pH conditions. Farmers tend to perform lots of liming and apply excess amount of P fertilizers in order to saturate the Al and Fe in the soil so that the plants are able to absorb the remaining P. Excessive liming and application of P fertilizers are not only not economical but also not environmentally friendly. Compost with a large surface area and pool of negative charges could be used to reduce P fixation in acidic soil. Hence, this study was carried out to assess the effect of amending Christmas Island rock phosphate (CIRP) with rice straw (RS) compost in improving soil P availability, nutrient uptake, and dry matter production of maize cultivated on a Malaysian tropical acid soil. A pot experiment was carried out in this study with the use of maize (FI hybrid sweet corn 801) as a test crop. The chemical properties of soils applied with RS compost were significantly improved (P≤ 0.05) compared to treatments without RS compost. As the soil pH increased, there was significant reduction in exchangeable acidity, Al and Fe in soil due to exchangeable Al and Fe were fixed with negatively charged functional groups of RS compost’s surfaces, thus increased the P availability and exchangeable cations in the soil applied with RS compost. There was also significantly higher N, P, and K uptake in leaf, stem, and root of maize in the treatments applied with RS compost. Application of CIRP with RS compost was found to increase the soil P availability, maize nutrient uptake, and dry matter production at the end of the pot experiment. An application rate of 15–20 t ha−1of RS compost together with 130 kg ha−1urea, 200 kg ha−1CIRP, and 67 kg ha−1muriate of potash is recommended to improve the soil NPK contents and growth ofZea maysin acidic soil.

Amending inorganic fertilizers with rice straw compost to improve soil nutrients availability, nutrients uptake, and dry matter production of maize (<em>Zea mays</em> L.) cultivated on a tropical acid soil

This study was carried out to assess the effect of amending inorganic fertilizers with rice straw (RS) compost in improving the soil nutrients availability, nutrient uptake, and dry matter production of maize cultivated on a tropical acid soil. A pot trial was conducted for 60 days and maize (F1 hybrid sweet corn 801 variety) was used as a test crop. Rice straw compost was applied at rates of 5 t ha-1, 10 t ha-1, 15 t ha-1 and 20 t ha-1, respectively. Treatments of amending inorganic fertilizers with RS compost were found to increase soil total N, available P, and exchangeable K at the end of the pot experiment. This was possible because it increases the nutrients availability in the tropical acid soil by reducing NH3, H2PO-, and K+ loss through volatilisation, leaching and denitrification. The soil pH and the soil EC also significantly increased with the presence of RS compost. Dry weight of maize plants (leaf and stem) and higher N, P, and K uptake in leaf, stem, and root of maize were observed under treatments amended with RS compost. An application rate of 15–20 t ha-1 of RS compost together with 130 kg ha-1 urea, 200 kg ha-1 Christmas Island rock phosphate, and 67 kg ha-1 muriate of potash are recommended to improve the soil NPK contents and growth of Zea mays in acidic soil.

Amending inorganic fertilizers with rice straw compost to improve soil nutrients availability, nutrients uptake, and dry matter production of maize (<i>Zea mays</i> L.) cultivated on a tropical acid soil

Amending inorganic fertilizers with rice straw compost to improve soil nutrients availability, nutrients uptake, and dry matter production of maize (<i>Zea mays</i> L.) cultivated on a tropical acid soil

Integrated weed management in maize-based intercropping systems

Field experiments were conducted to study the effect of intercropping and integrated weed management practices on weeds experiment was conducted at Agricultural College and Research Institute, Madurai (Tamil Nadu) during winter 2013. The experiment was laid out in a split plot design and replicated thrice. The main plots were assigned with three cropping systems, viz. maize, maize + blackgram, maize + cowpea and six weed management practices, Application of pendimethalin at 0.75 kg/ha followed by one rotary hoeing on 35 DAS recorded the highest weed control efficiency (85.9) and reduced weed populations and weed dry matter production at 60 DAS. The maize + cowpea system resulted increased plant height, LAI and dry matter production of maize at 30, 60 and 90 DAS respectively. Application of pendimethalin at 0.75 kg/ha followed by one rotary hoeing on 35 DAS resulted in the highest grain and straw yield of maize 6.05 and 18.15 t/ha, respectively.

Sensitivity of Soil P Availability Tests to Ca-P in Oxisols

ABSTRACTWe assessed the sensitivity of mixed exchange resin (MER) and Mehlich-3 (M3) to calcium-bound phosphate (Ca-P) in Oxisols. These methods were compared with Mehlich-1 (M1) and anion exchange resin (AER), which have high and low sensitivity, respectively, to this soil P form. We used maize (Zea mays L.) as a test plant. Three samples from two Oxisols were treated with five ratios of Triple Superphosphate—TS and Bayóvar Phosphate Rock—BPR (0 + 100; 25 + 75, 50 + 50, 75 + 25 and 100 + 0% TS + BPR). The MER extracted more P than AER and M3 at the highest BPR:TS ratios (high Ca-P) and similar quantities at the higher TS:BPR ratios (low Ca-P) for two soil samples. Unlike M1-extracted P, M3-P, AER-P, and MER-P positively correlated with maize dry matter production and P uptake. Mehlich-3 and MER were suitable to assess P availability in high Ca-P Oxisols.

Maize dry matter production and macronutrient extraction model as a new approach for fertilizer rate estimation.

Decision support for nutrient application remains an enigma if based on soil nutrient analysis. If the crop could be used as an auxiliary indicator, the plant nutrient status during different growth stages could complement the soil test, improving the fertilizer recommendation. Nutrient absorption and partitioning in the plant are here studied and described with mathematical models. The objective of this study considers the temporal variation of the nutrient uptake rate, which should define crop needs as compared to the critical content in soil solution. A uniform maize crop was grown to observe dry matter accumulation and nutrient content in the plant. The dry matter accumulation followed a sigmoidal model and the macronutrient content a power model. The maximum nutrient absorption occurred at the R4 growth stage, for which the sap concentration was successfully calculated. It is hoped that this new approach of evaluating nutrient sap concentration will help to develop more rational ways to estimate crop fertilizer needs. This new approach has great potential for on-the-go crop sensor-based nutrient application methods and its sensitivity to soil tillage and management systems need to be examined in following studies. If mathematical model reflects management impact adequately, resources for experiments can be saved.

Maize Grain Yield and Dry Matter Production Responses to Variations in Weather Conditions

Variations in weather conditions could alter maize (Zea mays L.) growth and development. This study was conducted to determine the eco‐physiological determinants of variations in maize yield with weather conditions, and the relationship between grain yield, dry matter production, and climatic factors. Eight sowing dates were set at 15‐ to 20‐d intervals from mid‐March to mid‐July during 2012 and 2013 in the Huang‐Huai‐Hai region of China. When the sowing date was delayed, the yield increased initially and later declined, and the greatest yield was obtained at 12 June (SD6) sowing date for both years. The increased yield for SD6 was mainly attributed to the 1000‐kernel weight and post‐silking dry matter production, which were mainly influenced by the post‐silking plant growth rate. Variations in temperature and radiation were the primary factors that influenced the post‐silking dry matter production of maize, and eventually influenced grain yield. High temperatures (daily maximum temperature [Tmax] > 28.1°C) during post‐silking under early sowing conditions and low temperatures (daily minimum temperature [Tmin] < 17.7°C) under late sowing conditions combined with low radiation (accumulated radiation [Ra] < 1 005.4 MJ m2) decreased the post‐silking plant growth rate, thereby decreasing the dry matter production and grain yield. Therefore, when the sowing was done from 25 May to 27 June, the relatively higher maize yield would be obtained. We conclude that variations in weather conditions (temperature and radiation) from silking to maturity significantly affect the plant growth rate of maize, influence post‐silking dry matter production, and grain yield.

Influence of zinc deficiency on the mineral composition of maize plants in contrasting soils

In Brazil, Zn deficiency is common in soils used for maize cultivation. However, the changes in the mineral composition in plants with Zn deficiency have been little studied. Thus, this study aimed to evaluate the relationship between Zn deficiency and the mineral composition in the parts of maize plants grown under contrasting soils. Maize was grown in greenhouse conditions with increasing of Zn rate (0, 0.125, 0.25, 0.5 and 1.0 mg kg -1 ) in two soils (Ferralsol and Cambisol). After 60 days of emergence, the plant were separated into roots, stalk nodes, stalk internodes, leaves and leaf sheath, and subsequently determined the dry matter and mineral composition (P, Ca, Mg, K, Zn, Fe, Mn, Cu and Al). Besides the symptoms commonly described for Zn deficiency, darkening of the stalk nodes was found (related to the preferential accumulation of Fe), and also occurred maize P deficiency in the Ferralsol. The Zn deficiency favored increasing concentrations of Fe, Mn and Al in all parts of maize plants in Cambisol, whereas in Ferralsol this did not happen for any of the elements analyzed. Relations between the elements and Zn were more correlated with maize dry matter production than Zn concentrations in leaves, leaf sheaths and stalk nodes. In conclusion, the accumulation of minerals in maize was favored by Zn deficiency, especially for maize in Cambisol.

Impact of cadmium on field grown maize in three consecutive growing seasons

The effect of cadmium (Cd) of atmospheric origin was investigated on certain terms in the heat balance and on the dry matter production of maize grown in the field at two water supply levels (rainfed and irrigated) in Hungary between 2010 and 2012. In contrast to previous experiments, the plants were exposed to pollution every week throughout the vegetation period. Among the plant parameters, a record was made of plant height, leaf area index and the length of the growing period. Water utilisation was estimated on the basis of water use efficiency, and efficiency from global radiation. Polluted maize used more water for the incorporation of unit dry matter, and was unable to absorb as much solar radiation as the unpolluted control plants. Irrigation moderated the negative effect of Cd on these parameters, suggesting that it could be of primary importance in overcoming the effects of Cd pollution of atmospheric origin.

Influence of component crop densities and planting patterns on maize production in dry land maize/cowpea intercropping systems.

An experiment was conducted to test the effect of four plant densities (10, 20, 30 and 40,000 plants ha-1) and four planting patterns (1rowM:1rowC, 1rowM:2rowsC, 2rowsM:2rowsC and 2rowsM:4rowsC) on the growth and dry matter production of a dryland maize/cowpea intercrop at three sites in Limpopo and North West province. The experiment was a split plot incorporated in randomized complete block design with four replications, where maize plant density was the main plot factor and subplot factor was the planting pattern. Sole maize flowered and reached physiological maturity later than intercropped maize, while sole cowpea flowered and matured earlier than under intercropping. Higher plant densities of 30 000 and 40 000 maize plants ha-1 delayed flowering and maturity of both component crops in sole and intercropped arrangements. Significant differences in maize and cowpea dry matter yields were observed at all trial sites. The 1rowM:2rowsC pattern and plant density of 30 000 plants ha-1 with 92 000 plants ha-1 of cowpeas was superior in maize dry matter production at all trial sites, whereas sole cowpea at 40 000 plants ha-1 gave the highest dry matter yield than the intercrop arrangements. The results of this study show that high plant density causes stress to plants and reduces plant growth, whereas intercropping has a negative influence on cowpea plant growth. Key words: Planting density, planting patterns, plant growth, maize/cowpea intercrop.

Effects of Terralyt - Plus on soil pH, nutrient uptake and dry matter yield of maize

Acid soils are common in the tropics and managing them for sustainable cropping usually demands soil amendments. A greenhouse experiment was conducted at the Institute of Agricultural Research and Training, Ibadan, Nigeria to evaluate the effects of a soil amendment substance - organic biostimulator - Terralyt-Plus® on the growth, soil pH, nutrient uptake and dry matter production of maize. The soils used for the study (Entisol, Alfisol) were collected from the coastal and forest zones of Nigeria. The Terralyt-Plus® was applied (0, 20, 40 and 60 ml m-2) with the conventional urea, single super phosphate and muriate of potash fertilizers. These were compared with a no-fertilizer control. The experiment was laid out with completely randomised design (CRD) replicated three times. Maize was grown for six weeks when the shoot and roots were harvested for dry matter yield assessment and determination of selected chemical constitutuents. Complementing inorganic fertilizer application with Terralyt-Plus® significantly improved maize performance on the soils. Shoot dry matter yield increased from 15 - 32% compared with sole inorganic fertilizer treatment. It was 64 -77% over the control. Phosphorus uptake was highest at 40 ml m-2 on the soil at Ilora while for soils at Ikenne and Badagry; it was at 20 ml m-2. Application of 20 - 40 ml m-2 (200 - 400 l ha-1) gave optimum height and dry matter yield of maize, and improved nutrient uptake of maize pla

Effect of K-N-Humates on Dry Matter Production and Nutrient Use Efficiency of Maize in Sarawak, Malaysia

Agricultural waste, such as sago waste (SW), is one of the sources of pollution to streams and rivers in Sarawak, particularly those situated near sago processing plants. In addition, unbalanced and excessive use of chemical fertilizers can cause soil and water pollution. Humic substances can be used as organic fertilizers, which reduce pollution. The objectives of this study were to produce K- and ammonium-based organic fertilizer from composted SW and to determine the efficiency of the organic-based fertilizer produced. Humic substances were isolated using standard procedures. Liquid fertilizers were formulated except for T2 (NPK fertilizer), which was in solid form. There were six treatments with three replications. Organic fertilizers were applied to soil in pots on the 10th day after sowing (DAS), but on the 28th DAS, only plants of T2 were fertilized. The plant samples were harvested on the 57th DAS during the tassel stage. The dry matter of plant parts (leaves, stems, and roots) were determined and analyzed for N, P, and K using standard procedures. Soil of every treatment was also analyzed for exchangeable K, Ca, Mg, and Na, organic matter, organic carbon, available P, pH, total N, P, nitrate and ammonium contents using standard procedures. Treatments with humin (T5 and T6) showed remarkable results on dry matter production; N, P, and K contents; their uptake; as well as their use efficiency by maize. The inclusion of humin might have loosened the soil and increased the soil porosity, hence the better growth of the plants. Humin plus inorganic fertilizer provided additional nutrients for the plants. The addition of inorganic fertilizer into compost is a combination of quick and slow release sources, which supplies N throughout the crop growth period. Common fertilization by surface application of T2 without any additives (acidic and high CEC materials) causes N and K to be easily lost. High Ca in the soil may have reacted with phosphate from fertilizer to form Ca phosphate, an insoluble compound of phosphate that is generally not available to plants, especially roots. Mixing soil with humin produced from composted SW before application of fertilizers (T5 and T6) significantly increased maize dry matter production and nutrient use efficiency. Additionally, this practice does not only improve N, P, and K use efficiency, but it also helps to reduce the use of N-, P-, and K-based fertilizers by 50%.

Maize growth and soil nitrogen availability after fertilization with cattle manure and/or gliricidia in semi-arid NE Brazil

Cattle manure is used as fertilizer by farmers in northeastern Brazil. However, the manure is insufficient to fertilize all cropping areas and is usually of low quality and may immobilize N. The use of Gliricidia sepium as green manure could increase the amount and quality of organic fertilizers. However, the high-quality biomass of this legume is valued as forage and may also decompose too quickly and cause nitrogen (N) leaching. This study aimed to identify efficient management practices for cattle manure and Gliricidia to improve N uptake and crop productivity in semi-arid NE Brazil. For this, we conducted three experiments. In the greenhouse, we evaluated maize growth and N uptake after application of Gliricidia and/or cattle manure under different soil moisture conditions. A litterbag field experiment evaluated the decomposition dynamics of Gliricidia or manure. Finally, a field experiment tested the effects of mixing and/or splitting Gliricidia and manure on maize productivity and N uptake. In the greenhouse, maize dry matter production and N uptake and apparent N recovery from fertilizers were significantly greater in treatments with higher proportions of Gliricidia, but mainly under high soil moisture conditions. The litterbag experiment showed that Gliricidia indeed decomposed twice as fast as cattle manure, that decomposition was up to 2.5 times faster when the materials were incorporated rather than surface applied, and also that N release was more synchronized to maize demand when fertilizers were split in two applications. In the field experiment, we observed that both mixing cattle manure and Gliricidia and splitting the application in two increased in maize productivity up to 350%.

Comparative environmental impacts of intensive all-grass and maize silage-supplemented dairy farm systems: a review

Abstract New Zealand dairy farmers are lifting stocking rates and increasing available feed through nitrogen (N) fertiliser applications to pasture, growing maize for silage and other supplementary crops for silage or grazing on-farm, and/or procuring feed supplements off-farm. This has raised concerns about the possibility of increased risk of nutrient losses to waterways and the atmosphere. This paper reviews NZ and overseas data on the integration of maize silage into dairy systems. Maize silage is a low protein forage which helps optimise animal protein intake and reduces N loss. Maize silage-supplemented dairy farms leached more nitrogen per hectare but less per kg milksolids (MS) than intensive all-grass systems. Feeding maize silage on a feedpad and spreading the resulting effluent uniformly over the farm further reduces N leaching. In the Resource Efficient Dairying (RED) trial, total emissions of nitrous oxide (N2O, a potent greenhouse gas) for the maize-supplemented farmlet was 14% lower on a per hectare basis and 22% lower on a kg MS basis than the all-grass system when both received 170 kg N/ha as urea. The increases in maize dry matter production in response to incremental additions of N and water, where production is constrained by these inputs, can be 2-3 times greater than that for pasture. Using a feed and stand-off pad and managing maize growing through minimising tillage effects, determining soil N status at planting and timing N applications appropriately further reduce the environmental impact of maize silage-based dairy systems. Keywords: all-grass, environment, greenhouse gases, intensive dairy systems, maize silage, nitrates

Soil Productivity after Decomposition of Waste Materials under Different Soil Moisture and Temperature

Productivity of the soil with waste material (WM), i.e., bagasse, coir dust, rice chaff and rice straw decomposed for two months at various temperatures and soil moisture were investigated by analyzing the chemical properties and growth of maize cultured on the soil for 45 days. The soil with decomposed WM (WM soil), tended to show lower pH values than the soil without WM soil (control) as a whole. The values of electric conductance were higher in WM soil, especially in the soil with decomposed rice chaff and rice straw referred to as rice-chaff and rice-straw soils, respectively. The total N content tended to be higher in the WM soil except for coir dust soil. The total C content tended to be higher in all WM soils. The difference in the content of total N and total C between WM and control soils was remarkable in bagasse soil. The change of the chemical properties of the soil did not apparently correlate with the rate of CO2 generation during incubation of WM soils, but pH, electric conductance, content of total N and total C contents were higher in the soils generating CO2 at a rate of 40 to 80 ppm min−1, in bagasse or rice straw soils. The dry matter production of maize on WM soils was positively correlated with the rate of CO2 generation. It was suggested that the WM soils generating little CO2, such as the soil with bagasse or rice straw decomposed in a dry condition, tended to inhibit maize growth owing to low pH and shortage of available nitrogen by rapid decomposition just after the start of maize growth. The wet WM soils generating CO2 format a rate of 40 to 80 ppm min−1, e.g., bagasse and rice straw soils might be favorable for dry matter production of maize.

Crop rotation and soil N amendment effects on maize production in eastern Canada

Relying less on fertilizer N and more on crop residual and biological N2 fixation by legume crops has been suggested as an effective way to meet the challenge of maximizing economic return while minimizing environmental pollution. A field study was conducted on a Brandon loam soil (Orthic Humic Gleysol) to determine the effects of crop rotation and N amendments on grain yield, crop growth, N uptake and use efficiency (NUE) of maize ( Zea mays L.) and fertilizer replacement values of legume. The rotations included maize in annual rotation with soybean [Glycine max (L.) Merrill], alfalfa ( Medicago sativa L.) or continuous maize. The soil N amendments included no amendment, NH4NO3 at 100 kg N ha-1, stockpiled or rotted dairy manure at 50 Mg ha-1 (wet weight). Averaged across 4 yr, increases in maize grain yield, total plant N uptake, and NUE ranged from 13 to 35% in the maize-soybean and maize-alfalfa rotations compared to continuous maize monoculture. During the study, total dry matter production was 15 to 35% higher and crop growth rate was 13 to 23% higher for maize following alfalfa than for continuous maize monoculture. The effect of legumes on the subsequent growth of maize (i.e., total dry matter production a n d crop growth rate) was most apparent during the grain filling period. Total maize dry matter production was similar up to silking stage for all three rotation systems; however, the difference in total dry matter between maize monoculture and maize in rotation with legume continued to increase after this stage so that the greatest differences were observed at physiological maturity. Grain yield was 19% higher in the 100 kg N ha-1 treatment and 23% higher in the repeated manure amendment than in the unfertilized treatment. Fertilizer N replacement values were on average, 68 kg ha-1 for soybean and 133 kg ha-1 for alfalfa. Our results indicate that maize in annual rotation with legume crops could increase the maize yields by as much as 20% and reduce the amount of chemical fertilizer N by as much as 180 kg N ha-1. The effect of legume preceding crop on maize dry matter production and N uptake is expressed mostly in the later stages of crop growth in this mid- to short-growing- season region. Key words: Rotation, Zea mays, dry matter accumulation, crop growth rate, manure, nitrogen use efficiency

Soil fertility and crop yields under improved-fallow systems in southern Mali

Improved fallows involving short-rotation woody and/or other perennial species are increasingly being tried as a means of sustaining crop production in impoverished farming systems of sub-Saharan Africa. The soil-improving potential of two tree species [Gliricidia sepium (gliricidia) and Pteocarpus erinaceus (pterocarpus)] and a shrubby legume Stylosanthes hamata (stylosanthes) was investigated in a four-year study on farmer's field and in a research station in the Koutiala region in southern Mali (12.25° N, 5.42° W; 650 to 850 mm annual, unimodal rainfall; on a Typic Plinthustalf). Two strategies for soil improvement were tested: improved fallow sensu stricto and biomass transfer, the former ‘on-farm’ and the latter ‘on-station.’ In the on-farm experiment, maize (Zea mays) yielded best when it followed a two-year fallow of gliricidia alone or in association with stylosanthes. On the research station, maize dry matter production and grain yields during two seasons following the application of ex-situ grown biomass were similar and highest in the stylosanthes- and manure-applied treatments. The biomass decomposition rates of the three species were in the order: gliricidia > stylosanthes > pterocarpus. The treatments did not have any significant effects on the soil fertility parameters that were monitored, possibly because of the short-term nature of the study. The treatments effects on crop yields were, however, significant. Gliricidia + stylosanthes in combination appeared to be particularly promising as short-rotation-fallow species in the region.