Productivity and profitability of maize-legume cropping systems under conservation agriculture among smallholder farmers in Malawi

ABSTRACT

A study was conducted from 2014 to 2017 in Malawi to elucidate the short-term effects of maize-legume intercropping and rotation systems under conservation agriculture (CA) and conventional tillage (CT) on crop productivity and profitability. Twelve farmers hosted on-farm trials per district, in three districts, with each farmer having six plots. The design of the study was randomised complete block design arranged in a split plot fashion with tillage as main plot and cropping systems as sub-plots, with each farmer acting as a replicate. CA had 1400 and 3200 kg ha^?1 more maize grain yield in the second and third seasons, respectively compared with CT. In the first two seasons, CT had 310, 180 and 270 kg ha^?1 more cowpea, soybean and pigeon pea grain yields in Salima, Mzimba and Mangochi districts, respectively, compared with CA. Similarly, CA had 1100 and 950 kg ha^?1 more groundnut grain yields than CT in Salima and Mzimba districts in the second and third seasons, respectively. Over the three-year study period, partial land equivalent ratio for maize ranged from 0.78 to 1.24. Largest net returns were achieved by intercropping maize with pigeon pea in Mangochi and rotating maize and groundnut in Mzimba and Salima districts.     

Workshop summary statement: Terrestrial bioshperic carbon fluxesquantification of sinks and sources of CO2

Understanding the role of terrestrial ecosystems in the global carbon (C) cycle has become increasingly important as policymakers consider options to address the issues associated with global change, particularly climate change. Sound scientific theories are critical in predicting how these systems may respond in the future, both to climate change and human actions. In March 1993, 60 scientists from 13 nations gathered in Bad Harzburg, Germany, to develop a state-of-the-science assessment of the present and likely future C fluxes associated with the major components of the earth's terrestrial biosphere. In the process, particular emphasis was placed on the potential for improving C sinks and managing long-term C sequestration. The majority of the week's work was conducted in eight working groups which independently considered a particular biome or subject area. The working groups considered: the Global Carbon Cycle; Boreal Forests and Tundra; Temperate Forests; Tropical Forests; Grasslands, Savannas and Deserts; Land and Water Interface Zones; Agroecosystems; and Biomass Management. This paper presents a brief overview of their major conclusions and findings. In addition, Table 1 brings together the best estimates from each group as to the current magnitude and estimated future direction of changes in the terrestrial C fluxes.     

Constructing a nitrogen fertilizer recommendation system using a dynamic model: what do farmers want?

Abstract. An effective fertilizer recommendation system requires information on seasonal, soil-related and cultural variations in soil mineral nitrogen (N) and nutrient requirements of the crop. This can be provided by dynamic N turnover models, such as listed by Plentinger & Penning De Vries (1996). In this paper, we describe a survey of farmer opinion designed to ascertain what farmers want from such a decision support system. Over 100 farmers were surveyed. Surveyed farmers requested that default values be available for all model inputs. Inputs should be entered both by windows-based menu (for clarity) and tabular format (for speed), have user-selected units, and be fully supported by context-sensitive help. The system should have a hierarchical structure allowing access to fixed parameters, and be compatible with commonly used farm recording packages. Recommendations should be provided both for the field (single and optional application rates), and in tabular format across the whole farm. Simulations should be easily rerun using more recent crop and weather data. Turnover processes underlying recommendations should be illustrated by flow diagrams of flux between pools, pie charts of fertilizer fate, bar charts of movement down the soil profile and graphical plots of changes in N status against time.     

Edge Effects in a Cocoa Shade and Manurial Experiment

The separate recording of “edges” and “cores” of the plots of a cocoa shade and manurial experiment has shown that the gross plot yield exceeds the guarded plot yield by about 17%. Previously published yields of this experiment have been based on unguarded plots and are presumably correspondingly in error, at least in recent years. (The edge effects may not have been so great in earlier years.)

At interfaces between manured and unmanured plots there was a substantial manurial edge effect, the edge rows of the unmanured plots apparently deriving almost as much benefit from the fertilizer as did the manured plots themselves.     

Molecular, ultrastructural, and biological characterization of Pennsylvania isolates of Plum pox virus

Plum pox virus (PPV) was identified in Pennsylvania in 1999. The outbreak was limited to a four-county region in southern Pennsylvania. Initial serological and molecular characterization indicated that the isolates in Pennsylvania belong to the D strain of PPV. The Pennsylvania isolates were characterized by sequence analysis, electron microscopy, host range, and vector transmission to determine how these isolates related to their previously studied European counterparts. Genetically, Pennsylvania (PPV-Penn) isolates were more closely related to each other than to any other PPV-D strains, and isolates from the United States, Canada, and Chile were more closely related to each other than to European isolates. The PPV-Penn isolates exist as two clades, suggesting the possibility of multiple introductions. Electron microscopy analysis of PPV-Penn isolates, including cytopathological studies, indicated that the virions were similar to other Potyvirus spp. PPV-Penn isolates had a herbaceous host range similar to that of European D isolates. There were distinct differences in the transmission efficiencies of the two PPV-Penn isolates using Myzus persicae and Aphis spiraecola as vectors; however, both PPV-Penn isolates were transmitted by M. persicae more efficiently than a European D isolate but less efficiently than a European M isolate.     

Hormone induced spawning of red snapper, Lutjanus campechanus

Red snapper, Lutjanus campechanus, were induced to ovulate following injections of Human Chorionic Gonadotropin (HCG). Females were injected initially with 1.1 IU/g body weight. When subsequent injections were necessary, 0.55 IU/g of body weight was used. Ovulation occurred between 42 and 56 h following injection. Eggs were wet stripped and fertilized simultaneously with sperm from two males. Initial mitosis was detected 30 min post fertilization. Hatching occurred in 20 h at 27°C.     

Wireworm damage to wheat seedlings: effect of temperature and wireworm state

We describe the results of four laboratory studies designed to measure the effect of temperature and wireworm appetence, weight, and degree of Metarhizium infection on their ability to damage wheat seedlings. Wireworm activity, measured from wireworm speed, increased linearly from 6 to 18 °C and leveled off thereafter. Plant emergence and growth increased exponentially from 6 to 22 °C for wheat cultivars AC Barrie and AC Unity VB. Plant root:shoot ratio at Zadoks 13 was highest at 14 °C and lowest at 22 °C for AC Barrie. Wireworm weight and degree of infection with Metarhizium did not affect their ability to kill wheat seedlings, but wireworms in a feeding state caused significantly more damage than those in a non-feeding state when wheat was grown at 10, 14, 18, and 22 °C. Wireworms (ww) in a feeding state destroyed 1.8 seedlings/ww in 14 days at 22 °C if there were 1 or 2 wireworms in a pot, and 1.5 seedlings/ww if there were 4 wireworms in a pot. If 5 wireworms were placed in a pot, wireworms in a feeding state destroyed 0.3, 1.0, 0.9, 1.3, and 1.4 seedlings/ww in 46, 32, 25, 25, and 25 days at 6, 10, 14, 18, and 22 °C, respectively. Wireworm mortality from Metarhizium during 60 days of containment in pots in the study was higher in non-feeding than in feeding wireworms, and higher if wireworms were selected from a Metarhizium-infected colony than those selected from a non-infected colony. Some of the implications of these results for wireworm management and laboratory trials are discussed.