Physiological and Agronomic Responses of Four Rice Varieties to Drought in the Rainforest.

The present investigation tested the hypothesis that there would be variation in physiological responses to water deficit among rice varieties from different production ecologies, with contrasting tolerance to water deficit under repeated cycle of soil moisture deficit, at reproductive growth stage. A screen house and a field trial were conducted at International Institute of Tropical Agriculture, Ibadan and Ikenne (Latitude 6° 52' N, Longitude 3° 43' E) respectively. Both experiments had rice varieties ('IR 64', 'WAB 56-104', 'IR 77298-1-2-B-10' and 'NERICA 4') and stress status (stress and control) as treatment factor's, arranged in a randomised complete block design with three replicates. In both trials, the physiological mechanism that underpins varietal differences with repeated cycles of water deficit at the reproductive growth stage was more balanced water status, improved foliar characters, efficient photosynthetic capacity and higher grain yield in comparatively drought tolerant upland rice varieties ('NERICA 4' and 'WAB 56-104'), as opposed with the results for the drought susceptible cultivar 'IR 64'. A converse pattern was observed on water stressed rice, despite fewer cycles of water deficit on the field. The results could have suggested that the initiation of water deficit is the rate limiting step rather than its intensity at the reproductive growth stage

Analysis of grain yield components of selected upland rice grown in valley bottom soil under rates of foliar ortho-silicate acid fertiliser

Attainment of potential yield (PY) of upland rice grown in valley bottom (VB) soil is limited by inadequate supply of beneficial nutrients. Previous study revealed that VB soil increase grain weight plant-1 (GWP) in upland rice by 70%, which is still far below its PY. Application of ortho-silicate acid (OSA) fertiliser, as silicon source at optimum rate, could help to boost the yield of upland rice. Five upland rice cultivars, comprising of three medium maturing (NERICA 1,4,7) and late maturing (MOROBEREKAN and OFADA), were grown in pots filled with VB soil. Four rates of foliarly applied OSA fertiliser (0, 250, 500, and 750 ml ha-1) were imposed across stages of growth of rice cultivars. OSA fertiliser increased GWP significantly (P<0.01) with application of 500 ml ha-1 having the best effect. At 250 ml ha-1, 1000 grain weights was more associated with number of branches panicle-1 and number of grains branch-1 panicle-1; while at 500 ml ha-1, GWP was closely associated with % number of fertile spikelets panicle-1 plant-1 (%NFSPP), total weight of panicle plant-1 (TWPP) and length of panicle plant-1 (LPP). Total number of spikelets plant-1 was more associated with total number of panicle plant-1 at 750 ml ha-1. The highest significant (P<0.01) GWP was observed in MOROBEREKAN (9.27 g plant-1); while the lowest was in Ofada (4.79 g plant-1). Application of 500 ml ha-1 of the fertiliser is recommended for these rice cultivars. Further improvement in yield of upland rice grown on VB soil under foliarly applied silicon should focus on % NFSPP, TWPP, and LPP.L\u2019atteinte d\u2019un rendement potentiel (RP) de riz pluvial cultiv\ue9 dans le sol de fond de vall\ue9e (FV) est limit\ue9e par un apport insuffisant de nutriments b\ue9n\ue9fiques. Une \ue9tude pr\ue9c\ue9dente a r\ue9v\ue9l\ue9 que le sol de fond de vall\ue9e (VB) augmente le poids de grain par plante (PGP) dans le riz pluvial de 70%, ce qui est encore bien en dessous de son rendement potentiel (RP). L\u2019application d\u2019engrais d\u2019acide orthosilicate (AOS), comme source de silicium \ue0 un taux optimal, pourrait aider \ue0 augmenter le rendement du riz pluvial. Cinq cultivars de riz pluvial, comprenant trois \ue0 maturation moyenne (NERICA 1,4,7) et \ue0 maturation tardive (MOROBEREKAN et OFADA), ont \ue9t\ue9 cultiv\ue9s dans des pots remplis de terre FV. Quatre taux d\u2019engrais AOS appliqu\ue9s par voie foliaire (0, 250, 500 et 750 ml ha-1) ont \ue9t\ue9 impos\ue9s \ue0 tous les stades de croissance des cultivars de riz. L\u2019engrais AOS a augment\ue9 PGP de mani\ue8re significative (P <0,01) avec l\u2019application de 500 ml ha-1 ayant le meilleur effet. \uc0 250 ml ha-1, 1000 poids de grain \ue9taient davantage associ\ue9s au nombre de branches par panicule et au nombre de grains par branche et par panicule; alors qu\u2019\ue0 500 ml ha-1, PGP \ue9tait \ue9troitement associ\ue9 au% nombre d\u2019\ue9pillets fertiles par panicule et par plante (% NEFPP), au poids total de la panicule par plante (PTPP) et \ue0 la longueur de la panicule par plante (LPP). PGP significatif le plus \ue9lev\ue9 (P <0,01) a \ue9t\ue9 observ\ue9 \ue0 MOROBEREKAN (9,27 g plante-1); tandis que le plus bas \ue9tait \ue0 Ofada (4,79 g de plante-1). L\u2019application de 500 ml ha-1 d\u2019engrais est recommand\ue9e pour ces cultivars de riz. Une am\ue9lioration suppl\ue9mentaire du rendement du riz pluvial cultiv\ue9 sur le sol FV sous silicium appliqu\ue9 par voie foliaire devrait se concentrer sur le% NEFPP, PTPP et LPP

Performance of maize (Zea mays) cultivars as influenced by grade and application rate of Organo-mineral fertiliser in a transitory rain forest

Field trials were conducted in a transitory humid rain forest, Abeokuta, Nigeria  (Latitudes 7◦ 15ꞌN, 3◦ 25ꞌE, altitude 144 above sea level) in early wet cropping  seasons of 2014 (site A) and 2015 (site B). The trials were aimed at investigating  the effects of application rates of grades of organo-mineral fertiliser on maize (Zea  mays)cultivars. The trials were in split-split plot arrangement fitted into randomised  complete block design and replicated three times. In the main plot was variety {Oba super 2 (hybrid) and Suwan 1[open pollinated variety (OPV)]}, sub-plot consisted of grade of organo-mineral fertiliser (A, B, C), while the sub-sub plot was made of  application rate (0, 2.5 and 5.0 t ha-1). Oba super 2 had significantly (P< 0.05)  more assimilatory surface, with more 100 grain (7.13 g) and ear weight (0.08 kg),  harvest index (37.60 %) than OPV maize cultivar (Suwan 1) in 2015. Maize  cultivars sown with grade B organo-mineral fertiliser had delayed tasselling (57.50  days) and silking (66.33 days) compared to when sown with other organo-mineral  grades. Increasing application rates of organo-mineral fertiliser resulted in  increased assimilatory surface and a higher grain yield and its attributes in both  years.Keywords: Hybrid, Open Pollinated Maize, Transitory Rain Forest, Silking, Tassellin

Growth, assimilate partitioning and grain yield response of soybean (Glycine max L. Merrrill) varieties to carbon dioxide enrichment and arbuscular mycorrhizal fungi in the humid rainforest

This investigation tested variation in the growth components, assimilate partitioning and grain yield of soybean (Glycine max L. Merrrill) varieties established in CO2 enriched atmosphere when inoculated with mixtures of Arbuscular mycorrhizal fungi (AMF) species in the humid rainforest of Nigeria. A pot and a field experiment were established in Abeokuta (7°15’N, 3°28’E; 75 m asl), Nigeria in 2015. The pot experiment had CO2 concentration, AMF inoculation and soybean varieties as treatments, in completely randomised design, repeated three times. On the field the treatments were in a split split-plot arrangement fitted into randomised complete block design. The main plot had CO2 concentration [ambient (≈385 ppm) and elevated (≈550 ppm)], AMF inoculation in the sub plot (+ AMF and – AMF), while the sub sub-plot were soybean varieties (TGx 1448-2E, TGx 1440-1E and TGx 1740-2F), replicated three times. In both experiments assimilatory surface increased in CO2 enriched atmosphere, with increased relative growth rate. The increased relative growth rate on the field was with increased leaf relative growth rate, reduced leaf area ratio and increased net assimilatory rate. Both trials had higher grain yield at elevated CO2 than the ambient. Growth response to AMF inoculation was with reduced specific leaf area and increased leaf weight ratio. Soybean variety TGx 1448 -2E was more adaptive to variation in AMF inoculation and CO2 enrichment. Soybean TGx 1740-2F was more responsive to combined effect of AMF inoculation and CO2 enrichment, but less suitable in the absence of both in this ecology.Keywords: Assimilatory surface, carbon dioxide enrichment, inoculation, soybea

Variation in the performance of contrasting maturity class of cowpea cultivars (Vigna unguiculata L. Walp) in the derived Savanna

Three field trials (2009, 2010 and 2011) were established at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta (7°38′N, 3°88′E; 450 m asl). The trials aimed to evaluate the performance of cowpea cultivars of contrasting maturity class in the derived savanna. Four short and seven medium duration (local check inclusive) cowpea cultivars were sown in a randomised complete block design, replicated three times. Across the years cowpea cv. IT98K-573-2-1 (short duration) had the significantly (p < 0.05) highest seed yield (2486 kg ha-1), an observation that could be attributed to its pod yield (3651 kg ha-1), stand count (73.1) and earliness (49.22 days). Cowpea cv. IFE-98-12 (medium duration) produced significantly low pod weight (1826 kg ha-1), with the least shelling weight (613 kg ha-1) and stand count (44.87) across the years. Three clusters of cowpea cultivars were identified in Principal Component Analysis biplot. They were identified based on their superior performance on seed yield, duration of development and dry fodder weight for short duration, medium duration and local check, respectively. It is concluded that these attributes could form the basis of their use and crop improvement programme in the derived savanna.Keywords: Earliness, medium duration, shelling weight, short duratio