Months After Transplanting Research Articles

Unraveling the Effects of Pruning Frequency on Biomass Productivity, Nonstructural Carbohydrates and Nitrogen Fixation Rates of Sesbania sesban

Tree pruning is a management tool in agroforestry systems for reducing shade, enhancing nutrient cycling or providing fodder. However, little information is available on the effect of pruning management on plant growth, nonstructural carbohydrate (NSC) levels in the roots and N2 fixation of Sesbania sesban. A glasshouse experiment was conducted to assess the effect of pruning frequency on biomass production, NSC levels and N2 fixation of Sesbania sesban. Pruning treatments consisted of a control (PF0), one pruning at 3 months after transplanting (MAT) (PF1), two successive prunings at 3 and 6 MAT (PF2), and three successive prunings at 3, 6 and 9 MAT (PF3), with each pruning removing shoot biomass above 50% of the initial height. The experiment was laid out in a completely randomized design (CRD) with four replications. Results showed that increasing pruning frequency resulted in decreased nodulation and nonstructural carbohydrate levels in the roots. Above and below ground biomass, root length, percentage N derived from the atmosphere and amount of N2 fixed were decreased in a similar manner whether plants were successively pruned twice or thrice. It can be concluded that two or three successive prunings in nine months significantly reduce nonstructural carbohydrates, DM productivity and N2 fixation of S. sesban, and might result in supply of insufficient biomass required for improving soil N fertility and livestock production.

Growth and Establishment of Cacao Seedlings under Intercrop with Plantain at Different Transplanting Positions

An investigation was carried out in Cocoa Research Institute of Nigeria (CRIN), Uhonmora Station, Edo State to evaluate the effect of transplanting positions of cacao (Theobroma cacao L) seedlings with plantains under field condition. Four treatments were evaluated: Plantain suckers on top of cacao seedlings at transplanting (PTCT), Cacao seedlings on top of plantain suckers at transplanting (CTPT), Cacao seedlings transplanted 30 cm apart from plantain suckers (CT30P) and Cacao seedlings transplanted 150 cm apart from plantain suckers (CT150P) as control. The experiment was arranged in Randomized Complete Block Design (RCBD) with three replications. Plantain suckers were planted at 3 x 3m spacing as shade crop while cacao seedlings (hybrid) were planted on treatment basis. The experiment was monitored for 22 months after transplanting. Data were collected on plant height, number of leaves, stem diameter, number of branches and leaf area at 3, 4, 5, 12, 13, 14 and 15 Months After Transplanting (MAT), and on Survival count (%) at 10 and 22 MAT. The data were analyzed with analysis of variance (ANOVA) as well as descriptive statistics, and significant means separated by Duncan multiple range test (P<0.05). The result showed that cacao seedlings on top of plantain (CTPT) at transplanting had the highest percentage of 91.67 and 75.00 survival count at 10 and 22 MAT, respectively, closely followed by plantain on top of cacao seedlings at transplanting (89.00 % and 72.00%). When compared with CT150P, CTPT increased the plant height, number of leaves, stem diameter, number of branches and leaf area at 4 MAT, at 15 MAT, at 3, 13, 14, 15 MAT, at 3, 15 MAT and at 13, 14,15 MAT, respectively by 1%, 10%, 61%, 2%, 3%, 8%,46%, 11%, 5%, 3% and 13%, respectively. Therefore, cacao seedlings transplanted on top of plantain was the most effective treatment for improving cacao seedling establishment and growth under field condition.

Early Growth Response of Ceiba Pentandra to Organic and Inorganic Fertilizers under Field Conditions in Southeastern Nigeria

This study was carried out at the Department of Crop Science, University of Nigeria, Nsukka to investigate growth response of Ceiba pentandra to organic and inorganic fertilizers under field conditions. The treatments consisted of six fertilizer application rates (No fertilizer, 5 t ha-1 PM + 200 kg ha-1 NPK, 10 t ha-1 PM, 20 t ha-1 PM, 450 kg ha-1 NPK and 20 t ha-1 PM + 100 kg ha-1 NPK). The experiment was laid out in a randomized complete block design (RCBD) with four replications. Data were collected on plant height, number of leaves, stem girth and number of branches at 2, 3, 4, 5, 6 and 7 months after transplanting (MAT). The result of the analysis of variance indicated significant (p<0.05) variation among the fertilizer combinations used with respect to morphological parameters evaluated. Among the fertilizer treatments, sole application of PM at 20 t ha-1 consistently and positively influenced plant height, number of leaves, stem girth and number of branches of Ceiba across the months. Suggesting that the application rate provided adequate nutrients for growth and development of Ceiba. However, sole application of NPK at 450 kg ha-1 and other PM rates in combination with NPK resulted in decrease in some growth attributes probably due to acidification of the rhizosphere. Sole application of PM at 20 t ha-1 improved growth traits of Ceiba pentandra and is recommended for the production of Ceiba in the study area.

Petroleum hydrocarbons degradation in contaminated soil using the plants of the Aster family.

Oil extraction is one of the causes of soil contamination with the total petroleum hydrocarbons. The objective of this study was to clarify the effect of Asteraceae plants on the degradation of petroleum hydrocarbon in contaminated soil. Initial soils with 40 and 90gkg-1 of total petroleum hydrocarbon (TPH) were prepared. There were three treatments: (1) no addition, (2) addition of FeCl3 and nitrilotriacetic acid (NTA) solution, and (3) addition of FeCl3 + NTA and the cultivation of nine Asteraceae plants. The concentration of TPH was measured using infrared spectrophotometer, 2 and 3months after transplanting (MAT). Shoot and root dry weights were measured 3 MAT. The concentration of TPH in soil cultivated with Cosmos caudatus was lower than that of the initial soil (40gkg-1 TPH), 2 MAT. The concentrations of TPH in soils cultivated with Calendula officinalis, Callistephus chinensis, C. caudatus, and Tagetes sp. were also lower than that in the initial soil, 3 MAT. The concentrations of TPH in soils cultivated with Achillea filipendulina, Anthemis tinctoria, Tagetes erecta, Chrysanthemum coronarium, C. officinalis, C. chinensis, and C. caudatus were lower than that in the initial soil (90gkg-1 TPH), 2 MAT. The concentrations of TPH in soils cultivated with T. erecta, A. tinctoria, Zinnia elegans, C. chinensis, C. caudatus, and Tagetes sp. were lower than that in the initial soil, 3 MAT. A. filipendulina and C. coronarium died at both 40 and 90kg-1 TPH soils. These results suggest that the roots of Asteraceae plants degrade petroleum hydrocarbon in contaminated soil and C. chinensis and Z. elegans are more suitable for using TPH remediation. Plant survival and extensive root system are important factors for the remediation of TPH in contaminated soil.

Effects of Organic Amendments on Growth, Establishment and Yield of Cacao (Theobroma cacao L) in Southwestern Nigeria

Low soil fertility is a major problem of growth and establishment of cacao seedlings, as well as the yield on the field. However, cacao (Theobroma cacao L) is characterized by high nutrient demand particularly N, P, K, Ca and Mg, during establishment. In this study, the manurial potentials of some organic wastes and their effects on growth, development and yield of cacao in Ibadan and Owena soils of Southwestern Nigeria were investigated. The experiments in Ibadan and Owena were Randomized Complete Block Design (RCBD) with 3 replicates. Fertilizers were: Goat Dung (GD), Sunshine Organic and Organo-Mineral Fertilizers (OF and OMF) and NPK 15:15:15 at 0, 200, 400 and 600 kg/ha. The fertilizers were applied to treatment plots one month after cacao seedlings were transplanted using ring method (July, 2011). Four hundred and thirty two (432) plantain suckers were planted at 3 x 3 m spacing as shade crop while 432 cacao seedlings (F3 Amazon) were also transplanted at 3 x 3 m respectively at each experimental site. Top soil samples were analysed with standard methodologies. Data were collected monthly on cacao growth parameters such as plant height, stem diameter, number of leaves and number of branches, commencing at 3 months after transplanting (MAT). The experiments were monitored for 36 months (144 weeks after planting of cacao). Survival count was carried out 12 MAT. Data collected were subjected to statistical analysis using Analysis of variance (ANOVA) and significant means were separated by Tukey’s HSD (P < 0.05) test. Cacao seedlings grown under 600 kg/ha OF application had 100 and 95 percent survival count at Ibadan and Owena respectively. All fertilizer types and rates at Ibadan and Owena significantly increased cacao seedlings height, number of leaves, stem diameter and number of branches, relative to the control plots at 3, 4, 5, 15, 16 and 17 MAT. Goat dung applied at 600 kg/ha gave the highest number of flowers, cherelles and pods at 24 and 36 MAT at Owena. However, there were no yield parameters recorded for Ibadan experiment at 24 and 36 MAT.

Effect of water regime, pruning system and potassium silicate on dry mass production of sweet pepper plants grown in calcareous soil under greenhouse

Two greenhouse experiments were carried out at Army Farm, at El-Amria region, Alexandria, Egypt,during the two seasons of 2016-2017 and 2017-2018, as an attempt to rationalize of irrigation water throughstudying the effect of three water regimes, three pruning systems and four potassium silicate rates on the drymass accumulation in the various plant organs of sweet pepper. Results showed that application of the loweramount of irrigation water (30% depletion ratio) with repeat its addition achieved the highest significant meanvalues of roots, stems, leaves and whole plant dry mass at one, three and nine months after transplanting(MAT), as well as fruits dry mass after three and nine MFT, in the two seasons. Furthermore, the resultsindicated that un-pruned sweet pepper plants achieved significant higher mean values of roots, stems andwhole plant dry mass, at three and nine MAT, in both seasons, as well as fruits dry mass at nine MAT only ,in both seasons. The addition of, foliar application of potassium silicate up to 500 or 1000 mg l-1,significantly, accumulated higher dry weight in roots, branches, leaves, fruits and whole plant of sweet pepperplants after one, three and nine MAT, compared with that unsprayed, in the two seasons. Likewise, sweetpepper plants that un-pruned or pruned up to 3 branches plant-1 and irrigated with the lower amount ofirrigation water (30% depletion ratio) achieved the highest values of the dry mass of branches, leaves, fruitsand whole plant at one, three and nine MAT compared with that pruned on two branches plant-1. However,the highest dry mass value of roots, branches, leaves, fruits and whole plant of pepper were obtained from thetreatment combination included the lower amount of water (30 % water depletion ratio) and spray 1000 mg l-1of potassium silicate, in both seasons, after one, three and nine MAT. Interactions between pruning systemsand potassium silicate concentrations indicated that the highest values of the dry mass of roots, branches andwhole plant of sweet pepper plants were achieved from treatment combinations containing un-pruned plantsand sprayed the plants with 1000 mg l-1 of potassium silicate, in both seasons.

Productivity of sweet orange (Citrus sinensis (L.) Osbeck ‘Agege 1’) intercropped with cassava

Sweet orange (Citrus sinensis (L.) Osbeck ‘Agege 1’) was intercropped with cassava (Manihot esculenta Crantz ‘TMS 30572’) in a transitional forest zone, Ibadan, Nigeria, for three consecutive cassava cropping seasons. The objective was to determine the productivity of sweet orange intercropped with cassava. Results obtained showed that sweet orange trees planted sole were significantly (P<0.05) superior to intercropped trees in terms of plant height, canopy spread and stem girth. Sole sweet orange flowered earlier than intercropped trees. Similarly, the fruit weight of the sole sweet orange trees at 42 months after transplanting (MATP) was significantly (P<0.05) higher than the 0.05 t ha(-1) obtained from intercropped trees. Also tuber yields of cassava planted on ridges 2 and 3 m away from the sweet orange stem were significantly (P<0.05) higher than those on ridges 1 m away from the sweet orange stem. Total soil N increased from 0.2-0.70 g kg(-1) over the three cropping systems, however, P, Ca and K decreased significantly (P<0.05) both in sole planted and intercropped sweet orange plots compared to the pre-planting soil fertility. Revenue from sole planted sweet orange trees at 42 MATP N 48,900 ha(-1) resulting in a deficit of four (N 453,564.00 ha(-1)). Conversely, sweet orange intercropped with cassava had a net benefit of (N 274,370.00).

Development and Evaluation of Methods to Identify Sea Oats Breeding Lines for Beaches with Shallow Dunes

Sea oats (Uniola paniculata) is an aesthetically pleasing native plant used for beach restoration along the northern Gulf of Mexico coast. Many beaches in this region have shallow, saturated dune profiles, which reduces sea oats survival. The objective of this study was to develop methods to identify saturation-tolerant sea oats breeding lines. Sea oats seedlings were evaluated for saturation tolerance in greenhouse, beach, and field environments from 2010 to 2012. In 2010, sea oats grown under eight treatments (seven greenhouse treatments and a natural beach site) were examined. In 2010, sea oats seedling survival 2 and 3 months after transplanting (MAT) was greatest for four greenhouse treatments (nonflooded control, 6 cm cyclic flood, 6 cm static flood, and 10 cm cyclic flood) and least at the beach environment (Holly Beach, LA). In 2011 and 2012, sea oats grown under six treatments (four greenhouse treatments, a natural beach site, and a saturated field site) were examined. In 2011, sea oats seedling survival 3 MAT ranged from 0.3% to 98%. The nonflooded greenhouse control had the greatest survival, whereas plants grown on dry bench regularly watered with 35 parts per thousand (ppt) saline solution had the least survival. Sea oats constantly flooded with 14 cm of saline water in the greenhouse had the least survival 2 and 3 MAT, 70% and 41%, respectively. Sea oats survival when flooded with 14 cm of fresh water 3 MAT correlated with a saturated beach environment, Holly Beach, LA, 6 MAT (r = 0.970, P = 0.030) and a saturated field environment, Baton Rouge, 6 MAT (r = 0.994, P = 0.006). These findings suggest that survival of sea oats grown in a greenhouse in 14 cm fresh water for 3 months correlates to sea oats survival at saturated beaches after 6 months, in the absence of significant storm events. Identifying protocols for selection of saturation-tolerant sea oats lines is essential to increase the efficiency and effectiveness of northern Gulf of Mexico sea oats breeding programs.

Influence of Irrigation Regime on Water Stress and Growth of Ligustrum japonicum and Myrica cerifera During Establishment

Native plants are often promoted for water conservation in urban landscapes. However, direct comparisons between native and introduced species utilizing physiological measures of plant water stress are unavailable to support or refute such recommendations. Ligustrum japonicum and Myrica cerifera, representing evergreen introduced and native species, respectively, were selected based on similar landscape function, non-stressed photosynthetic rates, and water use efficiencies. Both species were transplanted into a fine sand soil to evaluate establishment rates and growth characteristics under two irrigation regimes, irrigated either daily or every 3 d at 1.3 cm (0.5 in) of irrigation per event for the first 8 months after transplanting (MAT). Water potentials were recorded on two consecutive days each month, with cumulative stress intervals calculated. Water potential was significantly influenced by day of water stress level. On days without irrigation, water stress was generally greater and affected growth. Of the two species, Myrica irrigated daily had the greatest shoot growth, yet plants receiving irrigation every 3 d had the lowest root mass and biomass 8 MAT. In contrast, Ligustrum exhibited no differences in most parameters measured between irrigation regimes except for growth index. These contrasting differences stem from different strategies for coping with water stress.

Management of Atriplex Nummularia Lindl. in a Salt Affected Soil in a Semi Arid Region of Brazil

This study aims to investigate the behavior of Atriplex nummularia under field conditions, including its growth, periodic cuttings, salt extraction, and soil chemical properties monitored for 16 months. Three treatments were evaluated: soil cultivated with Atriplex pruned at 6 and 12 months after transplanting (MAT); soil cultivated with plants that were harvested only at the end of the experiment (16 MAT); and a control (uncultivated soil) with four replications. Soil samplings were taken at 0, 6, 12, and 16 MAT. The samples were taken at depths of 0–20, 20–40, 40–60, and 60–80 cm. Biometric variables for growth were monitored monthly. The shoot was divided into leaves, thin stems (≤3 mm diameter), and thick stems (>3 mm diameter) to determine its content of Ca, Mg, Na, K, and Cl. We concluded that pruning regime for Atriplex was efficient mainly because it stimulated regrowth of less lignified material (leaves and stems ≤3 mm). We found that elements extracted by plant tissue can be quantified accurately, making them valuable indicators of the efficiency of the recovery process. The use of the Atriplex is recommended because the the possibility of revegetating areas inhospitable to most species used in conventional farming.

Effects of shade regimes and planting geometry on growth, yield and quality of the natural sweetener plant stevia (Stevia rebaudiana Bertoni) in north-western Himalaya

During 2008 and 2009, field experiments were conducted at the research farm of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India to assess the effect of shade levels (no shade, 25% shade, 50% shade, 75% shade) and plant geometry levels [30 × 15 cm (north–south, N–S), 45 × 10 cm (N–S), 30 × 15 cm (east–west, E–W) and 45 × 10 cm (E–W)] on the growth, yield and quality of stevia. Plant development was fastest in controls and slowest in stevia plants growing at minimum light (75% shade). These plants showed delayed bud formation and flowering. Significantly, higher dry leaf yield was recorded when the crop was grown under 25% shading than under 50 and 75% shade. Total steviol glycosides content decreased with increasing shade levels. All shade levels resulted in the same leaf-to-stem ratio, which was significantly higher than that obtained under ambient light. Plant geometry significantly affected the number of leaves and leaf dry weight plant–1. During both years, dry leaf weight was highest in the wider row spacing (45 × 10 cm) than in the narrow row spacing (30 × 15 cm). Stevia spaced at 30 × 15 cm in an E–W direction recorded significantly higher total steviol glycosides at 2 months after transplanting (MAT).

Optimizing the width of strip weeding in arabica coffee in relation to crop age

The aim of this study was to determine the weed strip control (WSC) required for adequate coffee growth after transplanting. A non-irrigated, field-planted (spaced 3.80 x 0.70 m) crop was used. The experimental design was a randomized block, with four replicates. The treatments were arranged in a 9 x 18 split-plot design to test the WSC of 0, 15, 30, 45, 60, 90, 120, 150, and 190 cm, which involved continuously hand-weeding at each side of the coffee row, and 18 coffee growth measurements. Multiple regression analyses were carried out relating to growth-variables as a function of both WSC and growth-evaluation times. Brachiaria decumbens was the main weed accomplishing 88.5% of the total weed dry mass. The minimum width of the WSC increases as the crop ages after transplanting. Assuming reductions of 2% and 5% in the maximum coffee growth, the recommended WSC was 75 and 52 cm at 4 months after transplanting (MAT), 104 and 85 cm at 6 MAT, 123 and 105 cm at 9 MAT, 134 and 116 cm at 12 MAT, 142 and 124 cm at 15 MAT, and 148 and 131 cm at 18 MAT, respectively. It was concluded that integrated weed management in young coffee crops must focus on the weed control only in a minimum range along coffee rows, which increases with coffee plant age, keeping natural vegetation in the inter-rows.

Developmental Change of Vegetative Plant Architecture of Annual-Form-Wild Rice (&amp;lt;i&amp;gt;Oryza rufipogon&amp;lt;/i&amp;gt; Griff.) Elevates Competitive Ability during the Late Development under a Dense Condition

Annual-form-wild (AFW) rice developmentally changes the vegetative plant architecture from flat to elect shape. The main objective of the present study is to suggest that the change might be related to competitive ability (CA). Recombinant inbred lines (RILs) derived from a cross between an AFW rice and a cultivar were grown under high-density (H) and low-density (L) conditions in a weedy paddy field. At two and three months after transplanting (MATs), we evaluated the two traits associated with utilization of light resource, tiller angle (TA) and actual plant height (APH), and amount of the growing weeds using an index, weed-denseness score (WDS). Then, DC-TA, DC-APH and SC-WDS was defined as the amount of change in TA, APH, and WDS from two to three MATs, respectively. Multiple regression analysis revealed that only DC-TA significantly affected SC-WDS specific under H condition that is relatively similar to habitats of AFW rice. Quantitative trait locus (QTL) analyses identified that one of the two QTLs associated with DC-TA shared a linked molecular marker with a QTL associated with SC-WDS only under H condition. Further, RILs with AFW-rice-derived allele on the QTL associated with DC-TA tended to show drastic changes of TA toward narrow angle as well as large decreases of weed amount. All the QTLs associated with DC-APH were not linked to the QTL associated with SC-WDS under H condition. Therefore, it is suggested that under the crowded conditions during the late plant development, AFW-rice plants might not survive through canopy domination but elevate CA through increases of efficiency of capturing light due to changes from wide to narrow tiller angle. Since flat-plant shape of AFW rice during the early development would have been evolved by trampling pressures, the present finding suggest that different selective pressures in life time might have cooperatively evolved the developmental change.

Manure placement effects on root and shoot growth and nutrient uptake of 'PITA 14' Plantain hybrid (Musa sp. AAAB)

Low soil organic matter and associated poor soil fertility cause yield decline in Musaspecies, necessitating external nutrient input to maintain yield. Best fertilization practices include applying the correct fertilizer at the correct rate, time and place. In this regard, manure placement effects on growth, root system development and nutrient uptake of a plantain hybrid were evaluated in a screen-house. Three manure placement methods, whereby the full dose of manure was applied as top-dressing (T1), bottom-dressing (T2), or a split combination thereof (T3), were assessed together with a no manure control (T4). There was significant (P < 0.05) treatment effects on most of the parameters studied. T1 gave the best growth indices 3 months after transplanting (MAT) but not at 5 MAT. The highest root NPK and leaf N at 3 MAT was associated with T3. T3 also induced the best plant growth at 5 MAT, followed by T2. Expectedly, the control treatment produced plants with the poorest growth. Whole-plant biomass yield and distribution were influenced by manure placement as was specific leaf area. Significantly large correlations between leaf-3 parameters and whole-plant growth indices were observed. Thus, dry weight of leaf-3 predicted whole-plant biomass yield with high reliability (r2 = 94.1%), supporting leaf-3 analysis as a non-destructive alternative for assessment of plant performance in response to manure. It was apparent from the study that plant performance indices at 3 and 5 MAT showed that split dressing at the top and the bottom of the pots (T3) was a more sustainable method for manure application to Musa. Key words: Plantain hybrid, manure placement, root and shoot growth, nutrient uptake, biomass yield.

Performance of Sesbania sesban infested by the defoliating beetle Mesoplatys ochroptera in Zambia

Developing integrated pest management practices against the defoliating beetle Mesoplatys ochroptera is an important aspect of the adoption of Sesbania sesban as an improved fallow species in southern Africa. The effect of defoliation by M.ochroptera on the growth of S. sesban(provenance Kakamega) was studied during 1998–2000 at Msekera Research Station in eastern Zambia. To determine the relationship between M. ochroptera densities and degree of defoliation, potted seedlings were infested manually with different densities of larvae and adults. Infestation of two to three month old seedlings with 5–30 larvae or adults resulted in less than 20% defoliation. Infestation of seedlings with 90–150 larvae(>3 masses of eggs) led to 80–100% and 50–80% defoliation in two and three months old seedlings, respectively. The time of infestation and degree of defoliation that lead to reduction in growth and biomass were determined using simulated (manual) defoliation of one to three months old S. sesban seedlings. Manual removal of 50–100% of the foliage atone and two months after transplanting (MAP) appeared to reduce plant height, basal diameter, primary branches, leaf and wood biomass compared to that done atthree MAP. Removal of 25–50% of the sesbania foliage three months after transplanting apparently leads to overcompensation. In sesbania, compensatory growth occurred when 25–50% of the leaves were defoliated three months after transplanting. Therefore, farmers need to protect sesbania seedlings from defoliation against insects such as M. ochroptera only during the first two months after transplanting.

Arbuscular mycorrhizal inoculation and superphosphate application influence plant development and yield of coffee in Brazil

This paper reports a 6-year field study of the effects of mycorrhizal pre-colonization of coffee seedlings on initial crop development and coffee bean yield in a low-fertility Oxisol amended with superphosphate (P) at planting. The experiment included five P rates (0, 20, 40, 80 and 160 g plant–1 P2O5) combined with seven fungal treatments [non-mycorrhizal control, pre-colonization with a mix of Glomus clarum and Gigaspora margarita (CM) and with five isolates of Glomus etunicatum]. Inoculated and non-inoculated outplants were raised under glasshouse conditions, transplanted into the field in January 1989 and monitored until July 1995. Plant height and stem diameter were greatly enhanced by P application and were higher in mycorrhizal seedlings than in controls up to 19 months after transplanting (MAT) but were not different at 26 MAT. Inoculation effects on tree canopy diameter were significant up to 26 MAT, at which time mycorrhizal colonization was high (43–55%), but did not differ amongst plants, regardless of whether or not the plants had been pre-colonized at the nursery stage. Root colonization and spore number in the soil were reduced by high P rates at 26 MAT. The first bean yield (1991) was highly enhanced by P and all pre-colonization treatments (38% increment over control) and these factors showed a significant interaction. Three isolates of G. etunicatum showed yield enhancements above 50%. The P rate for maximal yield was 207 g plant–1 P2O5 for non-pre-colonized and approximately 100 g plant–1 for pre-colonized plants. For this harvest, the mycorrhizal biofertilizer effect was equal to 254 kg ha–1 P2O5. In subsequent years, pre-colonization effects were reduced and inconsistent. In 1992, 1993 and 1995, yield was affected by P but not by mycorrhizal inoculation. In 1994 there was a P versus mycorrhiza interaction and CM and G. etunicatum-Var gave higher yields than non-precolonized plants. Considering accumulated yield for this 5-year period, P application resulted in high yield increment in all treatments, whereas pre-colonization effects were extremely diminished. However, despite inconsistency amongst mycorrhizal treatments, pre-colonization effects were detected at the fifth harvest in some fungal treatments. Based on the total yield of five harvests, maximal productivity was achieved with CM at 20 g plant–1 P2O5 and with CM and G. etunicatum-Var at the highest P rate. Diminishing mycorrhizal effects over time are related to colonization of non-precolonized seedlings by the indigenous fungi and to the reduced external P requirement of the mature crop. If adequate phosphorus is applied at planting, pre-colonization of outplants with selected arbuscular mycorrhizal fungi enhances early crop development and productivity of coffee in low-fertility soils of Brazil.

Active N2 fixation in several Faidherbia albida provenances

For tree legumes, Faidherbia albida is among those with low symbiotic capability, and for which significant improvement is needed. An experiment was conducted in the greenhouse, using the 15N isotope dilution technique to measure differences in the proportion (%Ndfa) and total N fixed in seven F. albida provenances grown in an Arenosol soil in Senegal. Total dry matter and N yield values were not significantly different among the seven provenances. In contrast, significant variability was measured in N2 fixation, with %Ndfa ranging from 0% in two provenances to 38% in the Kabrousse provenance. Also, total N fixed was highest in Kabrousse, 0.44 g N plant‐1, compared with the 0 to 0.26 g plant‐1 fixed in the other provenances. Based on these results, Kabrouse was selected for further examination in the field, where still higher %Ndfa values were obtained, 54, 58, and 54% at 3, 6, and 15 months after transplanting (MAT), respectively. These are higher than the commonly reported values of %Ndfa for F. albida, and indicate the potential of screening as a tool for obtaining higher N2 fixation in NFTs. Total N fixed, unlike %Ndfa, which remained fairly constant during the three harvest periods, increased from 0.54 at 3 MAT to 1.41 g N plant‐1 at 15 MAT.