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Maphumulo S.G.,University of KwaZulu - Natal | Derera J.,University of KwaZulu - Natal | Qwabe F.,University of KwaZulu - Natal | Fato P.,University of KwaZulu - Natal | And 4 more authors.
Euphytica | Year: 2015

Breeders face serious challenges in breeding early-maturing maize hybrids which are required by farmers in marginal environments. The objectives of the study were to determine the genetic gain for breeding for high yield, and investigate levels of genetic variation, heritability and associations between grain yield and secondary traits in early-maturing hybrids. Fifty maize hybrids were evaluated at three sites in KwaZulu-Natal, South Africa in a 5 × 10 α-lattice design with two replications. Genetic gain for grain yield of 18 % was reflected by the top five experimental hybrids over the population mean, indicating a significant improvement. One of the top five hybrids 14XH293 was early-maturing and non-significantly different from other three top yielding intermediate to late hybrids but was as early as the early commercial checks. Significant genetic variation for grain yield, plant and ear height, grain moisture, days to anthesis and silking, ear position, ear prolificacy, number of ears and anthesis-silking interval was observed, indicating opportunities for further improvement of the hybrids. Grain yield was highly heritable (75 %) but heritability ranged from low (3 %) to high (79 %) for secondary traits. Both correlation (P ≤ 0.001) and regression (P ≤ 0.001) indicated that ear prolificacy is the highest contributor to grain yield improvement. Furthermore, ear prolificacy displayed the major direct effects on yield that was greater than its correlation with yield, indicating that selection for this trait would indirectly improve grain yield of early-maturing maize hybrids. © 2015, Springer Science+Business Media Dordrecht. Source

Nyagumbo I.,International Maize and Wheat Improvement Center | Mkuhlani S.,International Maize and Wheat Improvement Center | Pisa C.,University of Zimbabwe | Kamalongo D.,Chitedze Research Station | And 2 more authors.
Nutrient Cycling in Agroecosystems | Year: 2015

Sustainable intensification cropping systems involving improved maize and legume seeds and conservation agriculture (CA) are potential avenues towards improved productivity. This study evaluated CA based cropping systems effects on maize yields with respect to herbicide use, crop establishment techniques and legume rotations in four contrasting agro-ecologies of Malawi and Mozambique from 2010/11 to 2013/14. No significant (p > 0.05) yield differences, at 4100 versus 3900 kg ha−1 were observed in Malawi when CA was implemented with and without herbicides respectively, suggesting herbicides were not a precondition for CA’s success. CA basins depressed maize yields by 3 % in north-western Mozambique and also offered no advantages in Malawi’s lowland districts (Ntcheu and Salima). In contrast, significant yield gains (p < 0.05) emerged from dry Balaka (<600 mm year−1) with mean yields of 2400 from the CA basins compared to 1800 kg ha−1 from farmer practices, an effect also confirmed by the yield stability analysis showing CA basins superiority in unfavourable rainfall environments. Thus CA basins performance was site dependent with no benefits on waterlogged soils or high rainfall conditions where direct seeded dibble stick or jab planting provided a better crop establishment option. Across all agro-ecologies, soyabeans, cowpea and groundnuts rotation systems, significantly increased maize yield, amounting to 20, 38 and 54 % respectively, except for the maize–common bean rotations in north-western Mozambique, which failed to offer any yield advantages. Probabilities of achieving higher CA yield ranged from 58 to 71 %. The study suggests CA based cropping systems offer an opportunity for intensifying maize production in the region. © 2015 Springer Science+Business Media Dordrecht Source

Manhica A.A.,Institute Investigacao Agraria Of Mocambique Iiam | da Rocha M.P.,Federal University of Parana | Timofeiczyk Junior R.,Federal University of Parana
Floresta e Ambiente | Year: 2013

This research aimed to analyze the production cost of lumber using randomized and programmed cutting systems for different diameter classes. We selected 80 logs of Pinus spp with diameters ranging from 24 to 33 cm, divided in four diameter classes, with 20 logs per class. In each class, the logs were separated in two lots of 10 units - the first batch was subjected to randomized cutting and the second batch was submitted to programmed cutting. The cost analysis showed that there was reduction in values when the programmed cutting system was used. Source

Manhica A.A.,Institute Investigacao Agraria Of Mocambique Iiam | da Rocha M.P.,Federal University of Parana | Timofeiczyk Junior R.,Federal University of Parana
Cerne | Year: 2013

This research evaluated a methodology of cutting logs that involves both their classification and the establishment of cutting models for different diametrical classes. The software MaxiTora was employed aiming the optimization of cutting logs. A total of 80 logs of Pinus sp had been selected with diameter that varied from 24 cm to 33 cm, gathering four diametrical classes with 20 logs each. In each diametrical class, the logs had been separate in two lots with 10 units, where the first lot was submitted to conventional cutting and the second lot was submitted to the programmed cutting. For each log the effective time of cut was recorded until the last lumber piece was edged. For the conventional cutting system, the efficiency reached from the same cutting system varied from 9.71 to 11.22 m3/operator.day and the general average corresponded to 10.18 m3/operator/day. In the programmed cutting system, the efficiency reached through the same cutting system varied from 7.78 to 8.99 m3/operator.day, while the general average corresponded the 8.07 m3/operator.day. The general average efficiency achieved in the programmed sawing process was smaller in relation to general average efficiency obtained with conventional sawing process. The sawing efficiency achieved in the programmed sawing process was reduced due to the lack of experience of machine operators. Source

Fonseca A.R.,Minas Gerais State University | Carvalho C.F.,Federal University of Lavras | Cruz I.,EMBRAPA - Empresa Brasileira de Pesquisa Agropecuaria | Souza B.,Federal University of Lavras | Ecole C.C.,Institute Investigacao Agraria Of Mocambique Iiam
Revista Colombiana de Entomologia | Year: 2015

Chrysoperla externa (Neuroptera: Chrysopidae) is one of the natural enemies of the corn leaf aphid Rhopalosiphum maidis (Hemiptera: Aphididae) and has potential application in the biological control of that pest. The effect of’ temperature on the development and the predatory capacity of this chrysopid fed with R. maidis nymphs was investigated. Fresh eggs of C. externa were maintained at 15, 20, 25 or 30 °C under 70% relative humidity and 12 h photophase, and the duration of the embryonic stage, as well as the duration and viability of the larval (first, second and third instars), prepupal, pupal and adult forms of the predator were evaluated. The duration of each of these stages decreased with increasing temperature, whilst the viabilities of all forms attained 100% at 20 and 25 °C. The threshold temperature and the value of the thermal constant K obtained for the complete life cycle (egg to adult) were, respectively, 10.7 °C and 377.8 degree-days. Independent of temperature, the consumption of R. maidis nymphs by C. externa increased as the larvae reached maturity. At 20 and 25 °C the average number of aphids consumed during the complete larval stage was maximal at approximately 350 specimens. It is concluded, therefore, that the development of the immature forms of C. externa fed on R. maidis as well as its viability and predatory capacity, were favored at temperatures between 20 and 25 °C. © 2015, Sociedad Colombiana de Entomologia. All rights reserved. Source

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