Maximizing Sugarcane Yield by Increasing Plant Population Density, Minimizing NO3-N Leaching and Improving Soil Organic Matter in Different Crop Rotations

In a field experiment conducted during 1992–95 at Lucknow, India, sugarcane was planted in rows 60 and 90 cm apart in three crop rotations (rice-sugarcane-ratoon, Sesbania aculeata for green manure-sugarcane-ratoon, and cowpea-sugarcane-ratoon) with 0, 150 and 300 kg N ha⁻¹ as urea either with or without farmyard manure (FYM) at 10 t ha⁻¹. Sugarcane yields were significantly greater in the Sesbania rotation than in the other because of a larger N uptake. N uptake of the crop was significantly affected by soil organic carbon, and available N and K contents. Ratoon yields, however, were largest in the cowpea sequence followed by the rice rotation, probably due to a prolonged residual effect of cowpea and rice root residues. The residual effect of a Sesbania green manure was negligible as demonstrated by the low NO₃-N content of the soil profile after sugarcane harvest compared to the other two crop sequences. The total cane productivity (main sugarcane plus ratoon) was greater (156 t ha⁻¹) in the cowpea rotation than the Sesbania (152 t ha⁻¹) and rice (140 t ha⁻¹) rotations.     

Cover Crops for Saline Soils

A 3-year study was conducted in the Central Valley of California to evaluate 125 prospective winter-growing cover crops for growth and nitrogen productivity in saline soils. Soil saturation paste electrical conductivities (ECes) in the surface 15 cm averaged 7 dS  m⁻¹ at fall planting and 5.3 dS m⁻¹ at spring harvest dates of each experiment. Species evaluated varied substantially in plant height. In general, the tallest plants were the Brassica species, which consistently grew to over 1.4 m. Annual grasses (barley, rye, triticale and wheat) averaged about 1.0–1.3 m in each year. Of the legume species screened, heights were greatest for Hedysarum coronarium , Trifolium alexandrium , Vicia spp., and Medicago polymorpha and truncatula , averaging 59, 47, 39, 38 and 37 cm, respectively, over all experiments. About one third of the species screened produced crop cover in excess of 90 % in each year. Groups of plants with consistently high crop cover percentages included various species/accessions of Brassica , Hedysarum , annual grasses, cool-season annual medics, Medicago polymorpha and Medicago truncatula , and two annual clovers, Trifolium alexandrium cv 'Multicut' and rose clover, Trifolium hirtum cv 'Hykon.' Total above-ground plant dry weights were highest for Brassica spp., which produced twice as much biomass as the annual grass species, and roughly four times as much dry matter as any of the legume species. Hedysarum , Lana and Namoi woolypod vetch, purple vetch, berseem clover, and several of the annual medic species consistently had the highest biomass among the legumes.     

Intercropping Maize with Climbing Beans, Cowpeas and Velvet Beans

When one of the crops is a legume, intercropping has potential to reduce fertilizer nitrogen (N) needs and increase food quality. Total dry matter (DM) and grain yields of different plant populations of intercropped maize ( Zea mays L.) and climbing beans ( Phaseolus vulgaris L.), cowpeas ( Vigna unguiculata [L.] Walp.), or velvet beans ( Mucuna pruriens [L.] DC. var utilis [Wight] Bruck.) were compared in two experiments. Maize populations were 40,400 and 50,500 plants ha⁻¹ in combination with climbing bean populations of 0, 20,200, 40,400 and 80,800 plants ha⁻¹ in Experiment 1. In the second experiment, climbing beans, cowpeas and velvet beans at 215,200 plants ha⁻¹ were intercropped with maize at 64,600 plants ha⁻¹. Climbing beans contributed up to 5% to total DM yields in the first experiment. In the second experiment legume contributions to total DM were 20% for climbing beans, 12% for cowpeas and 8% for velvet beans. Increasing populations of maize and climbing beans increased grain and DM yields. Dry matter yield of maize was lowered by intercropping. However, DM yields of the intercrop were not different to maize sole cropped. Maize/cowpeas produced more total DM than maize/climbing beans. Cowpeas increased the total yield of crude protein by over 15% without lowering total DM yield of the intercrop compared to maize alone and are promising as a legume for intercropping with maize. Climbing beans show little promise as a possible legume for intercropping with maize.     

Effect of Seeding Date on the Growth of Sod-seeded Lucerne

Lucerne ( Medicago sativa L.) is a valuable forage legume but it is short lived in many regions and periodic reseeding is necessary to maintain adequate lucerne in swards. Sod-seeding is a fast, one pass method of renovation but variable seedling establishment of sod-seeded lucerne has been experienced in the Atlantic Region of Canada. Experiments were conducted in two consecutive years to determine seeding date effects on establishment and growth of sod-seeded lucerne in timothy ( Phleum pratense L.) dominant swards at two sites. In the first experiment lucerne was sod-seeded on four dates in swards, band sprayed with paraquat at 0.5 kg/ha⁻¹, and was compared with sod-seeded red clover ( Trifolium pratense L.). In the second experiment the effects of four sod-seeding dates of lucerne and broadcast or band spraying of paraquat in swards were determined. Sod-seeding lucerne between late April and mid-June resulted in the best establishment and yields. Yields of sod-seeded lucerne were usually greater with broadcast than with band applied paraquat. Red clover established more readily and made a greater contribution to total yields than lucerne.     

Effects of Stocking Rate and Overseeding with Red Clover on Productivity of Native Pasture Continuously Grazed by Yearling Steers

Overseeding with red clover (Trifolium pratense L.) and stocking rate are factors that can affect composition and production of hill land pasture. A grazing experiment utilizing yearling beef steers ( Bos taurus) was conducted using 3, 4, and 5 yearling steers ha⁻¹ (285 kg), on native pasture (predominantly Poa pratensis L.) overseeded with red clover and non overseeded. Paddocks of 1 ha were continuously set stocked from mid May to the end of Sept. Herbage mass, herbage consumed and the percentage of legumes, grasses, dead material, and non-leguminous broadleaf plants were recorded. Animals were weighed at the initiation and end of each grazing season and at 4 week intervals. Overseeding increased legume content 4-fold the seeding year but much of this increase was lost the following year. Herbage mass was greater on overseeded pasture the year following seeding but no effect on animal productivity was found. Stocking rate did not affect percentage legume but the proportions of other broadleaf plants increased at high stocking rates. Average daily gain as well as total gain ha⁻¹ was greatest at 4 steers ha⁻¹.     

Forage Yield and Sucrose Response of Rhodes and Ruzi Grass to Cutting Height and Cutting Frequency Under Irrigation

The development of irrigated pastures in the Sudan is still at its infancy. The present study determined the influence of 2 cutting heights (2.5 and 5.0 cm) and 4 cutting frequencies (4-, 6-, 8-, and 10-week) on forage yield as dry matter and forage sucrose of Rhodes grass ( Chloris gayana Kunth. cv. Massaba ) and Ruzi grass ( Brachiaria ruziziensis Germain et Everard cv. Congo Signal ) under irrigated conditions. Forage yield interactions involving species X cutting height X cutting frequency were significant. These yield interactions were attributed to differences in growth period and growth rhythm of the two species. On average, Rhodes exhibited a short growth period (13 months) compared to Ruzi grass (20 months). Forage yield and forage sucrose were, on average, superior in Ruzi compared to Rhodes grass. Forage yield and forage sucrose averaged 5.2 t ha⁻¹ and 7.2 % fw sucrose in Ruzi compared to 2.8 t ha⁻¹ and 6.9 % fw sucrose in Rhodes grass. Forage yield and forage sucrose of both species were negatively correlated with cutting frequency. The highest forage yield may be obtained at an 8-week cutting frequency in Rhodes (45.6 t ha⁻¹ yr⁻¹) compared to a 10-week cutting frequency in Ruzi grass (88 t ha⁻¹ yr⁻¹). Results suggest that very high forage yields as dry matter and forage sucrose of Rhodes and Ruzi grass may be possible under irrigated conditions in the Sudan at a cutting frequency of between 8 to 10 weeks.     

Effect of Azolla on Irrigated Rice in Brazil

A 1-year study was conducted in 1983/84 at 2 experimental sites in Brazil to determine the effect of Azolla green-manure (AO), A. intercrop (OA) and their combination (AA) on rice yield in comparison to mineral fertilization with urea. Nitrogen sources were combined with 4 rice sowing/planting systems.
On terraced terra-roxa soil (Paleudalf) in subtropical northern Paraná State, transplanted rice (T) yielded 8.66 t · ha⁻¹ compared to pregerminated (P), direct-sown (D) and conventionally sown (C) rice with 7.92; 7.73 and 7.48 t · ha⁻¹, respectively. N-source treatments yielded 9.33; 8.54 and 7.34 t · ha⁻¹ for AA, OA and AO compared to 8.46; 7.98 and 6.05 for 100, 50 and 0 kg N · ha⁻¹, respectively. Fertilizer-nitrogen equivalence (FNE) of Azolla treatments compared to urea broadcast in 3 applications ranged between 0 and more than 100 kg N · ha⁻¹.
On hydromorphic latosol (Ustic Dystropept) in tropical Goiás State, rice yields were 4.07; 2.52; 1.46 and. 1.33 t · ha⁻¹ for systems T, P, C and D, respectively. N-source treatments yielded 2.79; 1.98 and 1.78 t · ha⁻¹ for AA, AO and OA compared to 3.43; 2.63 and 1.46 t · ha⁻¹ for 60; 30 and 0 kg N · ha⁻¹ as urea broadcast in 2 applications, respectively. FNE of Azolla was between 0 and 56 kg N · ha⁻¹.     

Yield and Resource Use Optimization in Late Transplanted Mint (Mentha arvensis) under Subtropical Conditions

A field experiment was conducted during 1994 and 1995 at Lucknow (26.5°N, 80.5°E, 120 m above mean sea level) to optimize planting density and fertilizer-N application for high essential oil yield of late transplanted mint ( Mentha arvensis ). The treatments studied were 2.5, 2.0 and 1.66 × 10⁵ mint seedlings ha⁻¹ and 0, 80, 160 and 240 kg N ha⁻¹. Under 3 months delayed planting conditions using 2-month-old seedlings, the high planting density of 2.5 × 10⁵ plants ha⁻¹combined with 160 kg N ha⁻¹ gave significantly higher herb and essential oil yields compared with those of lower planting densities (2 and 1.66 × 10⁵ plants ha⁻¹) and all other rates of N application. It is demonstrated that a transplanted mini crop, yielding essential oil at a level of 164 kg ha⁻¹, is feasible after the harvest of rabi cereal, oil seed or legume crops in the north Indian plains.     

Effect of Integration of Fertilizer and Green Manure Nitrogen on Yield Attributes, Nitrogen Uptake and Yield of Lowland Rice (Oryza sativa L.)

Field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, India, during the wet seasons of 1992 and 1993 to study the effect of full and partial substitution of fertiliser N with green manure N (Sesbania rostrata) on nitrogen uptake, yield attributes and yield of rice. The experiment consisted of eight treatments with two levels of N (100 and 200 kg ha⁻¹) and three sources of N application viz., fertilizer, integrated (1:1 fertilizer and green manure N) and green manure N compared to the recommended practice (150 kg fertilizer plus 6.25 t ha⁻¹ (72 kg N) green manure) and a no N control. Nitrogen application markedly increased the N uptake. Combined use of the two N sources at 200 and 222 kg N ha⁻¹ and of single fertilizer N at 200 kg N ha⁻¹ recorded the maximum N uptake, increased the yield attributes such as number of panicles per unit area, weight per panicle, number of total and filled grains per panicle and test weight. At 200 kg N ha⁻¹ full substitution of N by green manure reduced the grain yield but only partial substitution of N by green manure resulted in almost similar yield as single fertilizer N. Thus 200 kg N ha⁻¹ applied in equal proportions of fertilizer and green manure N can be recommended for medium duration rice cultivars.     

Significance of Pollination in Seed Setting Efficiency of Berseem (Trifolium alexandrinum L.)

The Egyptian clover ( Trifolium alexandrinum L.) commonly known as berseem in India, is a predominantly self-pollinated autogamous fodder legume. It has a simple valvular type mechanism for pollination wherein tripping agencies like bees are needed for better seed setting. The seed setting efficiency and seed yield of berseem (g. m⁻²) under natural tripping or open tripping condition was extremely high (22.38) as compared to completely caged (0.52) which clearly indicates the significance of pollinators/tripping agencies in seed yield of berseem crop. Further, the influence of pollinators was well marked with diploid strains of berseem as compared to tetraploid because of difference in fertility levels (tetraploids are generally less fertile).     

Effect of High Lucerne (Medicago sativa L.) Sowing Rates on Establishment Year Yield, Stand Persistence and Forage Quality

The effect of very high sowing rates on establishment year dry matter (DM) yield and stand persistence of irrigated lucerne ( Medicago sativa L.) was studied. Two cultivars ('Peace' and 'Apollo II') were sown in 1986 at two row spacings and six sowing rates from 5.6 to 50.4 kg ha⁻¹. Established seedling density (S_d) increased linearly with sowing rate (R):S_d= 24.1R. Establishment year DM yield increased at sowing rates from 5.6 to 16.8 kg ha⁻¹, levelled off as sowing rate increased to 33.6 ka ha⁻¹, and then decreased as sowing rate increased further. Thus, there was a broad optimum sowing rate that gave a maximum sowing year DM yield. Percent plant survival to the third year (1988) decreased with increasing sowing rate so that plant densities became similar for sowing rates greater than 16.8 kg ha⁻¹. Within the range 5.6 to 16.8 kg ha⁻¹, increasing sowing rate increased stand persistence measured as 1988 plant density; however, a corresponding increase in DM yield was not obtained. For all full-production years, DM yield was independent of sowing rate. Sowing rate did not affect three chemical measures of forage quality.     

Effect of spring fertilization on ecosystem services of organic wheat and clover relay intercrops

Nitrogen (N) deficiency and weed infestation are main factors limiting yield and yield stability in organic wheat. Organic fertilizers may be used to improve crop performance but off-farm input costs tend to limit profitability. Instead, forage legumes may be inserted into the crop rotation to improve the N balance and to control weed infestation. In opposition to simultaneous cropping, relay intercropping of legumes in organic winter wheat limits resource competition for the legume cover crop, without decreasing the performance of the associated wheat.The aim of this study is to evaluate the effect of spring organic fertilization on the performance of intercropped legumes and wheat, and on services provided by the legume cover.Two species of forage legumes (Trifolium pratense L. and Trifolium repens L.) were undersown in winter wheat (Triticum aestivum L. cv Lona) in five organic fields during two consecutive crop seasons. Organic fertilizer was composed of feather meal and applied on wheat at legume sowing. The cover crop was maintained after the wheat harvest and destroyed just before sowing maize.Spring organic nitrogen fertilization increased wheat biomass (+35%), nitrogen (+49%), grain yield (+40%) and protein content (+7%) whatever the intercropping treatment. At wheat harvest, red clover biomass was significantly higher than white clover one (1.4 vs. 0.7 t ha⁻¹). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5 t ha⁻¹ whatever the specie. No significant difference in forage legume biomass production was observed at cover killing. Nitrogen accumulation in legume above-ground tissues was significantly higher for white clover than for red clover. Both red and white clover species significantly decreased weed infestation at this date. Nitrogen fertilization significantly increased weed biomass whatever the intercropping treatment and decreased nitrogen accumulation in both clover species (−12%).We demonstrated that nitrogen fertilization increased yield of wheat intercropped with forage legume while the performance of legumes was decreased. Legume growth was modified by spring fertilization whatever the species.     

Effect of Irrigation and N-Fertilization (Fertigation) Scheduling on Tomato in the Jordan Valley

Tomato ( Lycopersicon esculentum mill. cv. Petopride ) is the most important vegetable crop in Jordan; its production is characterized by inadequate irrigation and fertilization practices, especially under open field conditions. A field study was carried out to determine the effect of different irrigation intervals and different N-fertilizer doses on water use, tomato yields and residual soil nitrogen.
Results indicated significant differences in water use and tomato yields between irrigation treatments. Highest yield (51.4 ton ha⁻¹) was obtained under three irrigations per week with 504 mm total water supply, whereas under irrigation once a week 35.3 ton ha⁻¹were produced with 353 mm total water supply. There were no significant differences in yield between fertigation with ten equal time intervals and fertigations with intervals as per crop requirements, the yields were 47.1 ton ha⁻¹ and 44.5 ton ha⁻¹, respectively. However, yield was significantly lower with three fertigations at equal intervals and equal doses (35.8 ton ha⁻¹) throughout the season. There were no significant differences between mineral nitrogen forms in terms of yield effects. Significant irrigation effects were observed on total soil nitrogen. Residual soil N was 0.052% in the surface layer (0–30 cm), and 0.030% in the subsurface layer (30–60 cm).     

Effects of Tillage and Fertilization on Biomass, Roots, N-Accumulation and Nodule Bacteria of Vetch (Vicia sativa cv. Alexander)

Field experiments were conducted to determine the effects of tillage (ploughing followed by one rotary hoeing (CT), rotary hoeing (MT) and no-tillage (NT)) and type of fertilization (NP 154/75 kg ha⁻¹, digested farmyard manure 30 t ha⁻¹) on growth (biomass and roots), N-accumulation and nodulation of vetch plants (Vicia sativa cv. Alexander) at different stages. The highest dry matter yields and root weight were determined for the NT and the lowest for the CT systems. The NT system promoted nodulation of vetch plants to a higher degree than the MT and CT systems. At the time just before harvesting, the N-accumulation in the above ground plants, was 54.3 for CT, 76.7 for MT, and 109.0 kg ha⁻¹ for NT, and the corresponding values at roots were 73.3, 112.0 and 173.3 kg ha⁻¹. Growth and nodulation of vetch plants was in general much better on farmyard manure plots than it was with the NP fertilization. The closest correlation coefficients between dry matter of biomass and roots on the one hand, and number of nodules and percentage N in roots on the other, were found with NT. The highest correlation between nodulation and percentage N in roots (r = 0.91***) was observed at the 128-days-old vetch plants. The highest correlation between the number of nodules and percentage N in biomass (r = 0.82**) was found at the beginning of the plants' flowering period. *, **, *** indicate significance at P = 0.05, 0.01 and 0.001 respectively.     

Nitrogen Balance of Legume-Wheat Cropping Sequences

In a lysimeter trial the legumes faba bean ( Vicia faba ), red clover ( Trifolium repens ), and alfalfa ( Medicago sativa ) were grown for two years, followed by winter wheat on all plots in the third year. Plots fertilized with mineral nitrogen and a rye/maize – wheat cropping sequence were included for comparisons. These four cropping sequences were replicated twice in 1982–1984 and 1985–1987, respectively. Two soils, a loamy sand and a sandy loam were used.
On average of both soils:
– N fixation during two years was 461 kg N/ha, 803 kg N/ha, and 790 kg N/ha for faba bean, red clover, and alfalfa, respectively.
– Leaching of nitrogen occurred mainly during the periods of winter fallow or, in case of the perennial legumes, after incorporation of residues into the soil and planting of wheat. Average leaching for all 6 years was 49, 28, and 29 kg ha⁻¹ year⁻¹ for faba bean, red clover, and alfalfa, respectively.
– In the period of wheat growth and before planting the new crop (1.5 years) in 1984/85 51–64 kg N/ha and 1986/87 68–94 kg N/ha were leached after growing legumes. Leaching was less for rye/maize fertilized with mineral N, 41 kg N/ha in 1984/85, and 51 kg N/ha in 1986/87, respectively.
– Winter wheat grown after legumes took up 18 kg N/ha < 47 kg N/ha < 65 kg N/ha on average of both soils and 2 years (1984, 1987) after faba bean, red clover, and alfalfa, respectively. This indicates a nitrogen recovery of 24–44% of the legume N potentially available, and consequently a loss by leaching from 56 to 76 %.
On the sandy loam amount of drainage water and N leaching were lower, and faba bean and wheat yields higher than on the loamy sandy soil.     

Intercropping of Corn with Soybean, Lupin and Forages: Silage Yield and Quality

Intercropping of corn with legumes is an alternative to corn monocropping and has a number of advantages, for example, lower levels of inputs, lower cost of production and better silage quality than monocrop systems. An experiment was carried out at two sites in 1993 and 1994 to investigate the effects of seeding soybean or lupin alone or in combination with one of three forages (annual ryegrass, Lolium multiflorum Lam.; perennial ryegrass, Lolium perenne L.; red clover, Trifolium pratense L.) on silage yield and quality. The intercrop plots received 90 kg ha⁻¹ less nitrogen fertilizer than monocrop plots, which received 180 kg ha⁻¹. Corn biomass yield had a variable response to the treatments, but showed no change at most site-years. Soybean and lupin biomass yields were decreased by intercropping (80–98 % for soybean, and 94–100 % for lupin). However, when corn growth was limited due to poor establishment at one site in 1994, soybean was able to grow well and produce yields similar to those of monocropped soybean. The three underseeded forages did not grow well during the period examined (up to silage harvest) and had no effect on the yield of any crop. Total silage yields were similar to corn monocrop biomass yields even during 1994 at the site with low corn population densities because soybean was able to compensate for reduced corn growth.     

Establishment, Development and Yield of Forage Legumes and Grasses as Cover Crops in Grain Corn in Eastern Canada

Interseeded cover crops can minimize soil erosion, increase organic matter and nutrient levels and the yield of subsequent crops. However, their performance is very sensitive to local conditions. Field experiments were conducted at two Quebec locations in 1993 and 1994 in order to evaluate the potential use of forage legumes and grasses as interseeds in corn in eastern Canada. Twelve forage species were evaluated. Fall rye ( Secale cereal L.), hairy vetch ( Vicia villosa Roth), a mixture of red clover ( Trifolium pratense L.) and ryegrass ( Lolium multiflorum Lam), a mixture of white clover ( Trifolium repens L.) and ryegrass, subterranean clover ( Trifolium subterraneum L.), yellow sweet clover ( Melilotus officinalis Lam.), black medic ( Medicago lupulina L.), Persian clover ( Trifolium resupinatum L.), strawberry clover ( Trifolium fragiferum L.), crimson clover ( Trifolium incarnatum L.), annual alfalfa ( Medicago saliva L.) and berseem clover ( Trifolium alexandrinum L.) were seeded at two planting dates (10 and 20 days after corn emergence). The control treatments were: hand weeding, chemical weeding and non-weeded. Early seeded forages established better and had higher biomass accumulation than the late seeded ones. In the presence of larger weed populations, the interseeded forages did not develop well due to competition with the weeds. At Macdonald crimson clover provided good soil cover while Persian clover, fall rye and alfalfa provided relatively little cover. Strawberry clover and hairy vetch did not provide early ground cover due to their late development. Forage mixtures of red or white clover and rye grass established well and achieved high populations at the end of the growing season. Fall rye provided good early ground cover but senesced by the middle of the season. The better establishment and early germination of crimson clover caused a 19% reduction in corn grain yield in 1993. In 1994 none of the cover crops caused a reduction in corn yield.     

Conservation of Spring Cut Italian Ryegrass as Round Bale Silage: Effect of Stage of Maturity on Ensiling Characteristics and Forage Nutritive Value

Spring cut Italian ryegrass was harvested at two different stages of maturity: lake vegetative (EARLY) and flowering (LATE). The wilted forage was round baled and then ensiled by wrapping in plastic film. EARLY harvest reduced dry matter (DM) yield significantly as compared to LATE (5.6 vs. 10.5 t ha⁻¹; P < 0.01). However, forage quality both before and after ensiling was better for EARLY with higher crude protein (CP) and non-structural carbohydrates content and a lower amount of cell walls (NDF). Higher pH and the fermentation characteristics confirmed the poor quality of LATE silage, having higher content of butyrate, propionate and acid detergent insoluble nitrogen and a lower concentration of lactic acid.
Dry matter intake of EARLY silage by sheep (average 65.0 ± 7.3 kg LW) fed solely forage ad libitum was 37 % higher than LATE (1386 vs. 1011 g DM day⁻¹; P < 0.05) due to its better palatability and digestibility. In vivo DM digestibility of EARLY silage was 76.1 % while it decreased to 58.2 % for LATE silage. Estimated metabolizable energy content of EARLY silage (11.5 MJ kg⁻¹ DM) was 29 % higher than LATE (8.9 MJ kg⁻¹ DM) resulting as similar to the reference value of a high quality perennial ryegrass silage. The forage conservation system of ensiled round bales is effective and recommended when spring cut Italian ryegrass is harvested at an early stage of maturity.     

Effect of Planting Sequence and Time, and Nitrogen on Maize Legume Intercrop Yield

Productivity of maize ( Zea mays L.) legume intercrops is determined by soil, management, and environment. Planting sequence and time and N fertilization are easily controlled management factors but their effects on intercrop yields are not well understood. Maize grown in monoculture or intercropped with polebean ( Phaseolus vulgaris L.) or cowpea ( Vigna unguiculata [L.] Warp.) was studied for two growing seasons at Morgantown, WV. Crops were seeded in the following sequences: maize before legume, both at the same time, and legume before maize. Planting times were early May or mid June. Nitrogen was applied at 0 or 160 kg ha⁻¹. Maize grain and forage, legume grain and forage, and total forage production were determined on a dry matter basis. Intercropping (average of all treatments) reduced maize grain and forage yields compared to maize in monoculture but had no effect on total forage production. However, total forage production was greatest when the seeding sequence was maize intercropped at the same time or before cowpea. Cowpea never produced grain, but forage production was almost double that of polebean. Maize produced most forage when seeded before the legumes, and the legumes produced most forage when seeded before maize. Early planting increased maize production and decreased legume production. Nitrogen increased maize grain, maize forage, and total forage yields but had not effect on legume forage production. It is concluded that maize/legume intercrops show promise for increasing forage production in temperate areas and more research on planting times and densities, weed control, harvesting and management is needed.     

Light Interception, Leaf Area Index and Dry Matter Yield in Fodder Sorghum at Different Plant Populations

Fodder sorghum (M. P. Chari) was grown at varying populations to examine its influence on light interception, leaf area index and biomass production. DMY, CGR and IPAR depending on LAI reached maximum at LAI 5 of 150 000 plants ha⁻¹ stand and thus yielded higher biomass. Therefore, physiological potential of fodder sorghum crop was found to be maximum at a population density of 150 000 plants ha⁻¹. Further increases in population developed mutual shading and adversely affected the crop growth rate and dry matter accumulation. Significant linear relationships of dry matter yield with IPAR, plant population densities, LAI and CGR clearly indicate the interdependence of these characters.