Evaluation of some fungal diseases and yield of groundnut in groundnut-based cropping systems

A study on the evaluation of some fungal diseases and yield of groundnut in groundnut-based cropping systems was conducted in 2002 and 2003 planting seasons. Analysis of variance indicated that intercropping was highly significant on leaf spot disease severity 0.76; 0.75, rust 2.75; 2.69, as well as percentage defoliation 78.42%; 78.10% in 2002 and 2003, respectively. Plant population was significant on leaf spot severity 4.52, 4.60 rust 2.76; 366 and defoliation 226.5; 441.1 fungal as well as yield, while interactions were not significant on the fungal diseases and yield. Sole groundnut recorded significantly high severity of the fungal diseases investigated but low yield, when groundnut was intercropped with maize and melon and recorded the lowest yield in 2002 and 2003 respectively. 250,000 plants/ha recorded the lowest severity of the diseases investigated, while 444,444 plants/ha recorded the highest. Sole groundnut also recorded the highest percentage defoliation 79.37%, 79.25% when groundnut was intercropped with maize recorded the lowest 77.06%; 77.60%. 250,000 plants/ha had the lowest defoliation when 444,444 plants/ha had the highest 80.75% 82.13% in 2002 and 2003, respectively. Sole groundnut recorded the lowest in the majority of yields when intercropped with maize and with melon recorded a high yield and yield components in 2002 and 2003, respectively. The microorganisms identified were Cercospora spp., Aspergillus linked and Blastomyces.     

Efficacy of some plant extracts in the management of cercospora leaf spot of groundnut in the Sudan savanna of Nigeria

Field trials were conducted to evaluate the efficacy of neem seed, garlic clove, onion bulb, ginger rhizome and pawpaw leaf extracts applied as foliar spray in controlling cercospora leaf spot of groundnut in the Sudan savanna of Nigeria during the 2002 and 2003 cropping seasons. Ridomil was used as a positive check while the control was left untreated. Three spray regimes (once, twice and thrice) were evaluated. A strip plot design with three replications was used in setting up the experiments. Ex-Dakar, a cercospora leaf spot susceptible Spanish Valencia groundnut variety, was used as planting material. All the plant extracts reduced the incidence and severity of cercospora leaf spot in both seasons compared to the untreated crops. However, neem seed and garlic clove extracts significantly reduced the incidence and severity of the disease compared to the other plant extracts. Ridomil was more effective in controlling the disease than the plant extracts. Three sprays with the plant extracts gave better control of the disease than one or two sprays in the season. The highest seed yield of 3115 kg/ha and 3311 kg/ha in 2002 and 2003, respectively, were obtained with neem seed extract treatment while the lowest seed yield of 2134 kg/ha and 2334 kg/ha in 2002 and 2003, respectively, were recorded from the untreated crops. Also the highest seed yield of 3124 kg/ha and 3418 kg/ha in 2002 and 2003, respectively were obtained following three sprays compared to 2523 kg/ha and 2641 kg/ha for one spray in 2002 and 2003, respectively and 2840 kg/ha and 3085 kg/ha for two sprays in 2002 and 2003, respectively. The highest haulm yield of 4121 kg/ha and 4089 kg/ha in 2002 and 2003, respectively were also obtained following treatment with neem seed extract. The lowest haulm yield of 2951 kg/ha and 3045 kg/ha in 2002 and 2003 respectively, were recorded from the control. Three sprays gave higher haulm yield (4265 kg/ha and 4279 kg/ha in 2002 and 2003, respectively) than one and two sprays in the season. Neem seed extract could therefore be used to control cercospora leaf spot and to improve groundnut production in the Sudan savanna of Nigeria.     

Silent spring on podrot reduction and yield of benniseed in an ultisols

Benniseed (Sesanum indicum L.) is well known oil-seed crop grown mostly in the Savannah areas of Nigeria, and with little cultivation in the forest south. A two-season experiment was conducted in 2005 and 2006 to determine the influence of plant density and nitrogen application on podrot, oil content and pod weight of benniseed in the rain forest belt of Nigeria. Analysis of variance indicated that only the podrot and oil content were affected by plant population. An increase of 17.6% and 18.8% in oil content was recorded when plant density increased from 160,000 to 250,000 plants/ha recorded lowest podrot 2.02; 2.30 in the first and second seasons while 45 kg/ha, recording the lowest podrot of 2.59 and 2.63 in 2004 and 2005, respectively. 0 kg/ha (control) recorded the highest podrot of 3.14 and 3.46 in 2004 and 2005, respectively. An increase of 16.6% and 17.5% oil content was recorded when the plant population increased from 160,000 to 250,000 plants/ha in the first and second seasons, respectively. Further increase from 111,111 to 160,000 resulted in a further increase of 4.8 and 6.2 in the first and second seasons respectively. Nitrogen fertiliser is highly significant on podrot (P < 0.05), more so, interaction of plant density and nitrogen application were highly significant on pod weight with 250,000 plants/ha and 45kg/ha nitrogen recording the highest pod weight in 2004 and 2005, respectively. Mean values of main effect indicated optimal yield at the highest plant population of 250,000 plants/ha in the first and second seasons. However, yield was highest at the combination of 45 kg/ha and 250,000 plants/ha in all the seasons investigated.     

Yield loss of faba bean (Vicia faba) due to chocolate spot (Botrytis fabae) in sole and mixed cropping systems in Ethiopia

Two field experiments were conducted during 2004 and 2005 cropping seasons at Adet Agricultural Research Center, Ethiopia to assess yield losses caused by chocolate spot(Botrytis fabae) of faba bean in sole and mixed cropping systems using two cultivars. Cropping systems were sole faba bean (FB), faba bean mixed with field pea (FB: FP), barley (FB: BA) and maize (FB: MA). Mancozeb was sprayed at the rate of 2.5 kg a.i/ha at 7-, 14- and 21-day interval to generate different levels of chocolate spot disease in all the four cropping systems, and unsprayed control was also included. The treatments were arranged in a randomised complete block design (RCBD) with four replications. FB: MA mixed cropping significantly reduced disease severity and the area under disease progress curve (AUDPC) and increased faba bean grain yield. The highest faba bean grain yield among the three mixed croppings under different spray schedules was obtained from FB: MA mixed cropping in both 2004 and 2005 (2.56 and 3.74 t/ha, respectively) cropping seasons. There were highly significant yield differences (P < 0.05) among the spray intervals of mancozeb in both seasons. The highest grain yield (4.9 t/h) was recorded from the 7-day spray interval in 2005. The unsprayed faba bean had a lower grain yield (1.9 t/ha in 2004 and 2.3 t/ha in 2005) compared to the sprayed plots. The highest relative yield loss (67.5%) was calculated in 2005 from FB: FP mixed cropping in unsprayed plots. The relative yield losses in the unsprayed plots were in the range of 35.8–41.5% in 2004 and 52.6–67.5% in the 2005 cropping season. Severity and AUDPC were inversely correlated with faba bean grain yield. Significant differences were recorded in the 100-seed weight and days to maturity (DM). The unsprayed plots had shorter DM ranging from 126 to 128.5 day (except FB: MA mixed cropping) in 2004 and 122–123.9 days in 2005. In the sprayed plots DM was relatively longer than the unsprayed plots. A higher seed weight was recorded in the sole FB (56 g) and FB: MA (55 g) mixed cropping, and the lowest value of 100-seed weight was recorded from FB: FP (53 g) mixed cropping. The productivity of the mixed cropping evaluated by land equivalent ratio (LER) exceeded that of sole cropping. Faba bean grain yield was highly influenced by the severity of chocolate spot. The disease affects the DM, forcing early maturing of the plants.     

Bücherbesprechung (Book Reviews)

Abstract

A field experiment was conducted during 2002 – 2003 and 2003 – 2004 to study the impact of controlling the insect vector, Whitefly, of yellow mosaic virus on the performance of green gram grown under rainfed lowland rice fallow situation. Insecticide, Imidachloprid 12.5 kg a.i./ha, was applied at 15- and 30-days growth to four green gram varieties, direct-sown under residual soil moisture conditions after the harvest of kharif rice. Results showed crops under YMV-management achieved 65.67% more seed yield producing 11.68 q/ha, which was significantly higher than the crops under no YMV management (7.05 q ha^?1). Plants which had been treated with insecticide were found to be less affected (8.50%) by YMV compared to those which had no treatment (20.10%). Varieties PDM 54 and PDM 11 emerged as superior, producing significantly higher seed yields, 12.73 and 11.69 q/ha respectively; while Pusa vishal (8.21 q ha^?1) and Pusa 105 (7.85 q ha^?1) produced moderately compared with the local variety (6.31 q ha^?1). In addition, PDM 54 and PDM 11 showed relatively more resistance against YMV infestation recording 5.23% and 6.01% infected plants.     

Management of peanut budnecrosis disease in groundnut through intercropping with cereal and pulse crops

Intercropping groundnut with sorghum at a 3:1 ration has given lower AUDPC (1018) with a mean pod yield of 1868 kg/ha, and was found significant in reducing the PBND (34.2%) compared to sole groundnut (AUDPC of 1545 mean pod yield of 1407 kg/ha, 52% PBND). In groundnut intercropped with pulses, groundnut + redgram (5:1) was found to be effective in reducing PBND to an extent of 10% and recorded higher equivalent pod yield of 2236 kg/ha with 1014 AUDPC compared to sole groundnut (AUDPC 1078, 63.44% PBND; mean pod yield of 1663 kg/ha). The higher incidence of PBND was recorded in the treatments involving greengram, blackgram and soybean and it was also reflected in realising higher values of AUDPC.     

Application of Heavy Metal Rich Tannery Sludge on Sustainable Growth,Yield and Metal Accumulation by Clarysage (Salvia sclarea L.)

A field experiment was conducted to evaluate the effective utilization of tannery sludge for cultivation of clarysage (Salvia sclarea) at CIMAP research farm, Lucknow, India during the year 2012–2013. Six doses (0, 20, 40, 60, 80, 100 tha^?1) of processed tannery sludge were tested in randomised block design with four replications. Results revealed that maximum shoot, root, dry matter and oil yield were obtained with application of 80 tha^?1of tannery sludge and these were 94, 113 and 61% higher respectively, over control. Accumulation of heavy metals (Cr, Ni, Fe, Pb) were relatively high in shoot portion of the plant than root. Among heavy metals, magnitude of chromium accumulation was higher than nickel, iron and lead in shoot as well as in root. Linalool, linalyl acetate and sclareol content in oil increased by 13,8 and 27% respectively over control, with tannery sludge application at 80 tha^?1. Heavy metals such as chromium, cadmium and lead content reduced in postharvest soil when compared to initial status. Results indicated that clarysage (Salvia sclarea) can be grown in soil amended with 80 tha^?1sludge and this can be a suitable accumulator of heavy metals for phytoremediation of metal polluted soils.     

The incidence of rosette disease in groundnut in relation to plant density and its effect on yield

Trials are described in which the relationships between plant density, rosette disease incidence and the yield and quality of groundnuts were investigated on sprayed and unsprayed groundnut plants. During growth, the number and percentage of sprayed and unsprayed plants showing symptoms of rosette disease was significantly greater at low plant populations than at high. At harvest, in general on unsprayed plots the numbers attacked were also greater at low plant populations, but on the sprayed plots the results were inconsistent. The percentage attack at harvest was much lower on sprayed plots at all plant populations. Menazon used as a seed dressing did not affect the incidence of the disease but used as a spray it significantly reduced the amount of disease found. The spray was applied at a rate of 294 g a.i./ha, four times at 10-day intervals, the first spray being applied 10 days from germination. Spraying controlled secondary spread of the virus within the crop and appeared to reduce the severity of early attack. There was a marked improvement of yields and quality of nuts from sprayed plots. Plant density did not affect quality of the groundnuts obtained, but yields per ha were highest on both sprayed and unsprayed plots at the highest plant densities (seed rate up to 134 kg/ha).     

Current characteristics of cassava mosaic disease in postepidemic areas increase the range of possible management options

As a case study to document the current characteristics of cassava mosaic virus disease (CMD) in postepidemic areas, surveys were carried out, in 2003 and 2004, in Siaya District of western Kenya. This was an area affected by a severe CMD pandemic in the late 1990s. Data recorded on cassava varieties were CMD incidence, severity index and number of adult whiteflies. Farmers (174) were interviewed on their understanding of the disease and their knowledge and practice of management interventions. Cassava cultivation was being re‐established, but local landraces predominated. Resistant varieties were present 13% in 2003, and 4% in 2004, of the surveyed fields. Adhiambolera was the most common variety, occurring in 35% and 40% of fields in 2003 and 2004, respectively, and had an average CMD incidence of 82% in 2003 and 73% in 2004. By contrast, the CMD‐resistant variety Migyera had a low mean incidence (28% in 2003). The overall incidence for both years was 71%, consisting of 61% as a result of infection through planting diseased cuttings and 10% as a result of whitefly infection. In 2003, the total incidence was 72% and the average severity 2.7 (severity index), while in 2004 the incidence was 78% and the severity 2.6. There were significant severity variations in each division of the Siaya District during the 2 years except for Karemo and Ukwala. The abundance of whiteflies on the top five leaves of plants was low in 2003 but high in 2004, with means of 1 and 16, respectively, over the same seven divisions in both years, although this variation was thought to be because of seasonal factors. East African cassava mosaic virus‐Uganda was the predominant geminivirus present in every division. Phytosanitation by farmers was minimal, as evidenced by 29% of farmers using a selection of CMD‐free stems for planting and 15% using hand‐roguing for CMD management. Occurrence of more than 25% CMD‐free plants in 2004, moderate CMD severity and limited spread provide a conducive environment for the use of phytosanitation as a CMD control measure that can be immediately used by farmers growing their own cassava varieties.     

The impact of carbofuran soil application on growth and mycorrhizal colonization by Glomus clarum of groundnut

The influence of soil application of carbofuran on the growth response of groundnut, and both mycorrhizal colonization and sporulation of Glomus clarum was studied in a pot culture experiment. Carbofuran application with or without mycorrhizal inoculation increased the height of the potted plants measured 8 weeks after sowing. Mycorrhizal plants were significantly taller than nonmycorrhizal plants at the final harvest time (14 weeks). Carbofuran, at the recommmended field dose of up to 2 kg/ha, greatly increased shoot dry matter and pod yield in mycorrhizal groundnut. Colonization and sporulation by this VAM fungus were also enhanced significantly at these dose levels. The application of carbofuran at 5 kg/ha inhibited both growth and mycorrhizal status of groundnut.     

Seed yield,head characteristics and oil content in sunflower varieties as influenced by seeds from single and multiple headed plants under humid tropical conditions

Field trials were conducted during 2004 and 2005 to determine the effect of sowing seeds from plants with multiple heads and seeds from single headed plants of sunflower on seed yield, head characteristics and oil content of three widely grown open pollinated varieties (Funtua, Record and Isaanka) in the humid forest—savanna transition zone which is outside the current growing areas with a view to improving stability and sunflower productivity in this region. Seeds from multiple headed plants produced plants that flowered and matured 2–3 days later than plants from single headed plants. Apart from days to flowering in 2004, number of days to maturity and plant height were affected independently by variety and seed source factors. However, the seeds from single headed plants produced plants that recorded significantly (P < 0.01) higher head weight, head diameter, achene weight and number per head than plants from seeds of plants with multiple heads. Seed source had little effect on sunflower seed yield and oil content. However, Funtua produced significantly (P < 0.05) high seed yield (1956.0 kg ha^?1 ± 76.06) when seeds from plants with multiple heads were sown, while Isaanka recorded comparatively high seed yield from seeds of plants from either multiple (1221.0 kg ha^?1 ± 165.90) or single heads (1388.0 kg ha^?1 ± 135.84) and Record (1201.0 kg ha^?1 ± 96.97) when seeds from single headed plants were sown. Therefore, it is recommended that prospective sunflower growers who wish to cultivate Isaanka, can sow seeds from either the multiple or single head and preferably the multiple head for Funtua, and single head for Record.     

Evaluation of maize/pepper intercropping model in the management of pepper veinal mottle virus,genus Potyvirus,family Potyviridae on cultivated pepper (Capsicum annuum L.) in Nigeria

Three pepper cultivars obtained from National Horticultural Research Institute (NIHORT) Idi-Ishin, Ibadan were intercropped with maize for two planting seasons between March and September in each year. These pepper cultivars were NHV1-D96, and NHV1-E96 and NHV1-F96. A 90-day maturing maize variety (DMSR-1) was used as the intercropping companion plant. The pepper seedlings were raised in a greenhouse. A randomised complete block design was used for this experiment. Each variety was intercropped with maize and replicated three times including the sole plot. The results obtained for each year were not significantly different from each other. There was a significant difference in pepper veinal mottle virus (PVMV) disease incidence and severity at a probability of less than 5% in the treatment used. PVMV disease incidence and severity was relatively higher in the sole pepper crop compared with pepper intercropped with maize. In the three varieties of peppers intercropped with maize, less than 17% disease incidence and 15% disease severity were recorded in all the varieties with a minimum yield of 4 tons per hectare compared with the sole pepper cropping of the same variety that recorded as high as 75% disease incidence and 72% disease severity with a maximum yield of 3.3 tons per hectare. There was a significant negative correlation at probability less than 0.05 between disease incidence, severity and the fruit yield of pepper. Variety NHV1-F96 in the maize intercrop recorded the highest yield of 15.99 tons/ha with a land equivalent ratio of 2.4 tons/ha. The success of the PVMV disease management evaluated in this study was judged by the extent of reduction in number of diseased plants and by an increase in vigor of the cultivated pepper crop, with an increase in fruit yield and quality. This signifies that for devising effective viral disease management for any crop it is important that the vectors of the virus present in the particular area are exactly controlled from having contact with the target plant. The reduction of pest incidence with intercropping of non-host plants should be carefully considered.     

Development of pea bacterial blight caused by Pseudomonas syringae pv. pisi in winter and spring cultivars of combining peas (Pisum sativum) with different sowing dates

Pea bacterial blight occurred by natural infection in a field trial on peas in 1995. Disease development in the winter cultivars Rafale, Frilene and Froidure was compared with that in the spring cultivars Baccara, Conquest and Bohatyr, each sown on six dates in October, November, December, mid-March, late March and April. Disease incidence had reached 100% plants affected in all treatments by mid-July. Disease severity was greater in winter-sown (October, November or December) than in spring-sown peas of each cultivar at each assessment. Significant (P < 0.05) differences in disease severity occurred between cultivars in the winter-sown plots in May and June and the spring cultivars were affected more severely than the winter cultivars. Comparison of areas under the disease progress curves for both disease incidence and severity also showed that the winter-sown peas were more affected by disease than spring-sown peas and that spring cultivars were more severely affected than winter cultivars. Yield was strongly correlated with disease severity. A linear regression model suggested that, for peas sown in October, November or December, a yield loss of 0.5 tha^-1 occurred for each 10% increase in canopy area affected by pea bacterial blight.     

Effect of tannery sludge amendments on the activity of soil enzymes and phytoremediation potential of two economically important cultivars of geranium (Pelargonium graveolens)

A field experiment was conducted to observe the effect of TS amendments on soil enzymes and phytoremediation potential of two economically important cultivars of geranium. Different doses of TS were applied in soil to examine threshold limit of HMs where geranium cultivars can be grown successfully in contaminated sites. Treatment variation significantly affected pH, EC, OC, N, P, K and HM content in soil after 50 days of incubation. After harvest, both cultivars were examined to assess the impact of various treatments on their fresh herb, dry matter, essential oil yield and HM accumulation. C/G ratio close to 1 was observed at 50 tha^?1 sludge treatment in both cultivars. Urease and β-glucosidase activities in soil were maximum at 50 tha^?1 whereas dehydrogenase and phosphatase activities were maximum at 100 tha^?1 in both cultivars. β-glucosidase, acid and alkaline phosphatase, urease and dehydrogenase activities were relatively high after 85 days over 45 days in both cultivars. Maximum metal uptake was found in roots of cv. Bourbon followed by leaves. Geranium was observed to be a good candidate for phytoremediation as it mitigates metal toxicity by root absorption and cv. Bourbon is better candidate for the same.     

Studies on biological decomposition of wheat straw

Summary The incorporation of undecomposed wheat straw in the soil along-with the micro-organisms favourably increased the yield of groundnut crop. An increase of 37 per cent in yield was recorded when wheat straw was inoculated withPenicillium digitatum and the C:P ratio was adjusted to 65. Inoculated treatments of narrower C:P ratio gave a higher yield than wider C:P ratio treatments inoculated with the same cultures. An increase in nitrogen uptake by groundnut plants was recorded due to incorporation of straw alongwith the micro-organisms in soil. The organic carbon and nitrogen content of the soil increased with all the treatments except control. The highest increase in organic carbon and nitrogen of the soil was observed with a treatment of wheat straw of 65 C:P ratio inoculated withS. coccosporum. The yield of wheat crop after groundnut was significantly more with several treatments than control plots. The highest increase of 79 per cent in grain yield of wheat was observed in the plots previouslq received with wheat straw of 200 C:P ratio.This paper is based on the data presented at IV Southern Regional Conference on Microbial Inoculants, held at Parbhani during 3–4 July 1978.     

Eco-friendly approaches for the management of fenugreek root rot

To evolve eco-friendly management of fenugreek root rot caused by Rhizoctonia solani, a field trial was conducted during Kharif 2002 and Rabi seasons of 2002–2003 and 2003–2004. Experiments were conducted with eight treatments and three replications in RBD using the variety CO-2. The pooled analysis of the three season data showed that seed treatment with Trichoderma viride at 4g/kg of seed + soil application of Trichoderma viride at 5 kg/ha + soil application of neem cake at 150 kg/ha (T₃) recorded a percent disease index (PDI) of 23.1 versus 65.5 PDI in the control which accounted for a disease reduction of 64.7%. It was on par with seed treatment with Trichoderma viride at 4g/kg of seed + soil application of T. viride at 5 kg/ha (T₂) which reduced the disease incidence by 62.3% (24.7 PDI). The chemical treatment used for comparison, i.e. seed treatment with carbendazim + soil drenching at 0.1% + soil application of neem cake at 150 kg/ha recorded the lowest PDI of 16.8 with 74.4% disease reduction. Among the various treatments T₃ gave a seed yield of 572.7 kg/ha followed by T₂ (555.7 kg/ha). Treatment T₇ recorded the highest yield of 578.7 kg/ha. In the control plot the recorded yield was only 359.3 kg/ha. Though T₃ was more effective at reducing the disease incidence than T₂, the C:B ratio was higher (1:9.1) in respect of T₂ than T₃, which gave a C:B ratio of only 1:3.9. Hence, seed treatment with T. viride at 4g/kg + soil application of T. viride at 5kg/ha is a cost effective, eco-friendly management strategy for fenugreek root rot.     

Monovalent cation transporters; establishing a link between bioinformatics and physiology

Toxic aluminum (Al) ion is a major constraint to plant growth in acid soils. Aluminum tolerance in wheat (Triticum aestivum L.) is strongly related to the Al-triggered efflux of malate from root apices. A role of the secreted malate has been postulated to be in chelating Al and thus excluding it from root apices (malate hypothesis), but the actual process has yet to be fully elucidated. We measured Al content and root growth during and after Al exposure using seedlings of near-isogenic lines [ET8 (Al tolerant) and ES8 (Al sensitive)] differing in the capacity to induce Al-triggered malate efflux. Aluminum doses that caused 50% root growth inhibition during 24-h exposure to Al in calcium (Ca) solution (0.5 mM CaCl₂, pH 4.5) were 50 μM in ET8 and 5 μM in ES8. Under such conditions, the amount of Al accumulated in root apices was approximately 2-fold higher in ET8 than ES8. Al-treated seedlings were then transferred to the Al-free Ca solution for 24 h. Compared to control roots (no Al pretreatment), root regrowth of Al-treated roots was about 100% in ET8 and about 25% in ES8. The impaired regrowth in ES8 was observed even after 24-h exposure to 2.5 μM Al which had caused only 20% root growth inhibition. The addition of malate (100 μM) during exposure to 50 μM Al in ES8 enhanced root growth 1.6 times and regrowth in Al-free solution 7 times, resulting in similar root growth and regrowth as in ET8. Short-term Al treatments of ES8 for up to 5 h indicated that the Al-caused inhibition of root regrowth started after 1-h exposure to Al. The stimulating effect of malate on root regrowth was observed when malate was present during Al exposure, but not when roots previously exposed to Al were rinsed with malate, although Al accumulation in root apices was similar under these malate treatments. We conclude that the malate secreted from root apices under Al exposure is essential for the apices to commence regrowth in Al-free medium, the trait that is not related to the exclusion of Al from the apices.     

Effect of irrigation frequency and nitrogen on groundnut yield and nutrient uptake

Summary Field experiments were conducted during 1979 and 1980 summer seasons on sandy loam soils of low moisture retentive capacity to study the effect of high frequency irrigation at different levels of N on groundnut yield and nutrient uptake (NPK). Four irrigation frequencies (irrigation at 2, 4, 6 and 8 cm cumulative can evaporation, corresponding to irrigation once in 3, 5, 7 and 10 days respectively) and four levels of nitrogen (0, 20, 40 and 60 kg N/ha) were tested in a factorial randomized block design with three replications. Pod yield of groundnut was maximum (3,293 kg/ha) when irrigations were scheduled at 4 cm cumulative can evaporation (once in 5 days). Addition of N did not increase the pod yield. N and P uptake by the crop was maximum (180 kg N and 18 kg P/ha) with high frequency irrigation of scheduling irrigation at 4 cm cumulative can evaporation. Highest uptake of N (183 kg/ha) and P (19 kg/ha) was with a combination of 20 kg N/ha and high frequency irrigation (4 cm CCE). K uptake was low with low irrigation frequency, while it was highest (67 kg K/ha) at 20 kg N/ha.     

Dry season groundnut stover management practices determine nitrogen cycling efficiency and subsequent maize yields

It is generally thought that grain legume residues make a substantial net N contribution to soil fertility in crop rotation systems. However, most studies focus on effects of residues on crops immediately sown after the legume crop while in fact in many tropical countries with a prolonged dry season there is a large gap before planting the next crop with potential for nutrient losses. Thus the objectives of this study were* to improve the efficiency of groundnut (Arachis hypogaea L.) stover-N (100 kg N ha ^–1) recycling by evaluating the effect of dry season stover management, i.e. surface application and immediate incorporation after the legume crop or storage of residues until next cropping in the rainy season. N dynamics (litterbags, mineral N, microbial biomass N, N ₂O emissions) were monitored and ¹⁵N labelled residues were applied to assess the fate of residue N in the plant–soil (0–100 cm) system during two subsequent maize crops. Recycling groundnut stover improved yield of the subsequent maize (Zea mays L.) crop compared to treatment without stover. A higher N recycling efficiency was observed when residues were incorporated (i.e. 55% total ¹⁵N recovery after second maize crop) than when surface applied (43% recovery) at the beginning of the dry season. This was despite the faster nitrogen release of incorporated residues, which led to more mineral N movement to lower soil layers. It appears that a proportion of groundnut stover N released during the dry season was effectively captured by the natural weed population (54–70 kg N ha ^–1) and subsequently recycled particularly in the incorporation treatment. Despite the presence of weeds major leaching losses occurred during the onset of the rainy season while N ₂O emissions were relatively small. There was a good correlation between soil microbial biomass N and first crop maize yield. Incorporation of groundnut residues led to small increases in economic yield, i.e., 3120 versus 3528 kg ha ^–1 over two cropping cycles in the surface versus incorporation treatments respectively, with corresponding residue ¹⁵N uptakes of 4 and 8%, while ¹⁵N recovery in water stable aggregates (9–15%) was not significantly different. In contrast, when stover was removed and applied before the first crop, yield benefits were highest with cumulative maize yields of 4350 kg ha ^–1 and residue utilization of 12%. However, N recycling efficiency was not higher than in the early incorporation treatment due to an asynchrony of N release and maize N demand during the first crop.