Cocoyam (Xanthosoma spp.) is the most important export crop of all the root and tuber crops grown in Nicaragua. Despite its importance, the total planted area and yield have significantly decreased during the past few years, a decrease that is mainly due to diseases that are disseminated through the planting material. In this study virus-free (NI) and virus-infected (I) in vitro plants from three genotypes were established in a non-traditional production area. The aim was to evaluate their agronomic performance, and to study the re-infection of dasheen mosaic virus (DsMV) and its effect on yield. Repeated measurements of morphological traits were made during the experimental period. The height of the plants, the diameter of the pseudo-stem and the leaf area increased continuously up to 217 days after planting after which the growth curves declined. The genotypes differed in all yield components, except in yield per plant. Regardless of genotype, the NI plants produced a larger number of cormels that were heavier and longer than the cormels produced by I plants. This resulted in a higher yield from NI plants (18.2 t ha−1) compared with I plants (13.6 t ha−1). Seven months after planting between 60 and 90 % of the NI plants, depending on genotype, were infected with DsMV. Aphis gossypii was the only aphid observed in the field trial and is therefore most probably the vector responsible for the transmission of the virus.

Growth and photosynthetic performance of banana (Musa sp.) grown in three levels of natural shade (33, 55 and 77% reduction in incoming radiation) were compared to an unshaded control treatment. Net CO2 assimilation rates generally decreased with increasing shade. Chlorophyll fluorescence revealed short-term dynamic photoinhibition under high light conditions but no evidence of sustained photoinhibitory damage to photosystem II. Dynamic photoinhibition decreased with increasing shade, with the greatest depression in the variable to maximal fluorescence ratio (Fv/Fm) occurring in unshaded plants during the middle of the day. Specific leaf area and leaf area ratio increased proportionately with increasing shade, whilst the chlorophyll a/b ratio decreased, reflecting a greater efficiency of light utilization under shady conditions. The optimum shade level for photosynthetic productivity would be one at which the level of photosynthetic photon flux density (PPFD) is high enough to saturate CO2 assimilation but low enough to induce shade acclimation and to reduce photoinhibition. Under the conditions studied here, the saturation level of PPFD was around 1000 μmol m−2 s−1, a light level typical of the tree-based intercropping systems in which banana is commonly grown in the tropics.

Effects of rainfall on yield of cocoa from a large-scale experiment has been investigated at 10 and 12 sites, over seven years, in the Eastern and Ashanti regions of Ghana. There was a positive association between yield and rainfall at certain times of year, but a negative association at other times. Variation due to the regression of yield on monthly rainfall varied up to 23 per cent, while a maximum variation of 31 per cent accounted for the regression of yield on the total rainfall of February to April in the Eastern region.

Poor access to improved seeds in West and Central Africa has compromised crop yields and productivity as most farmers source the bulk of their seeds from informal channels. The use of farmer produced seeds has mostly resulted in high seedling mortality thereby presenting challenges to cocoa rehabilitation programmes across the sub region. With the aid of a mobile data collection system (MDCS), the first of its kind to enhance accuracy of survey results in an improved seed supply system through brokerage and linkages among diverse actors, this study assesses Ghanaian farmers’ access to improved hybrid cocoa seeds and provides evidence on the socio-cultural factors that affect field performance of such planting materials. Results show that farmers value a seed brokerage system (SBS), which is facilitated through group bulk purchase, timely acquisition and delivery of seeds. The study also revealed that farm size, land use type and gender have significant effect on survival rate of transplanted hybrid cocoa seedlings over two dry seasons. Regardless of the rehabilitation process, mean survival rate was high (79%) although an 11% (p < 0.000) difference occurred between gender with men recording a higher rate. The majority of farmers prefer cultivating cocoa on forest and fallow lands, implying continues degradation of forest areas. There is therefore an urgent need for a change of mind set, to advocate for land recycling to spare forest areas to thrive.

Grain sorghum [Sorghum bicolor (L.) Moench] is the major cereal crop used as staple crop in the arid and semi-arid regions of Ethiopia. Low sorghum yields are attributed to soil, climate and topographic factors. We investigated sorghum yield response to factorial combination of nitrogen and phosphorous (NP) as well as potassium (K), sulphur (S) and zinc (Zn), and how the position of farmers’ fields belonging to different landscape positions (i.e., upslope, mid-slope, and foot slope) could explain fertilizer response and yield variability. The analysis in this study made use of dataset from two sets of on-farm experiments where trials were set at two farmers’ fields for NPKS and three farmers’ fields for NPZn experiments in each landscape position. The experiments were implemented at two sorghum-growing locations (i.e., Hayk and Sirinka) in parts of the north-eastern Amhara region in Ethiopia. Sorghum yield response to fertilizer application was strongly linked to the spatial variation along landscape positions and varied over locations. Fertilizer response was significantly higher at foot slopes compared to mid-slopes and upslope positions, where fields at foot slopes exhibited relatively homogeneous responses. Application of combined nitrogen (N) and phosphorus (P) fertilizers, landscape position and the interaction of fertilizer application and landscape positions strongly affected sorghum yield. There was a linear and significant increase in sorghum yield with the increase in the NP rates. The combined application of NP with different levels of KS as well as NP with Zn fertilizer rates did not result in significant yield difference. The results indicated that local factors were much more influential when accounting for the heterogeneity in sorghum yield response to fertilizer. This further acknowledges the importance of a landscape-based fertilizer management approach to respond yield potential variability related with the farmers’ fields and landscape environment. Further investigation is needed to develop homogeneous fertilizer response units based on spatial variability of soil and topographic attributes along the landscape.

Improving water productivity depends on how local communal water and grazing resources are governed. This involves institutional and organizational issues. In the mixed farming systems of the Amhara Regional State, Ethiopia, non-participatory water users’ associations, neglect of traditional water rights, corruption, village power relations, inequitable allocation of irrigated land and free-grazing practice impact the governance of local common pool resources (CPR). Indigenous governance structures for CPR such as the kire are participatory and effective in terms of rule enforcement. Externally initiated governance structures lack acceptance by farmers and sufficient support from local government. In order to improve water productivity in the mixed farming systems, institutional deficiencies need attention and existing indigenous governance structures require recognition and support.

At doses of 75 mg./kg. given per os, Neguvon was ineffective against Sarcoples scabiei var. Auchenidae. Benzene hexachloride (BHC) per os was ineffective at doses of 20 mg./kg. and killed alpacas when the dose was increased. Spraying the lesions with BHC killed the acari and lesions quickly disappeared. Psoroptes communis, the cause of otitis in alpacas, was equally susceptible to spraying. Lesions and their location are described and attention is drawn to the possible role of acari in nostrils and perinea in the epidemiology of the disease. Dipping is, at present, the only method of cure worth using, but the search for systemic acaricides should be continued.

The presence of velvetleaf (Abutilon theophrasti) in crops is increasing in arid and semi-arid environments. Field experiments were conducted in Greece in 2009 and 2010 to determine the influence of velvetleaf emergence time and maize (Zea mays) hybrids with different growth rates on maize yield and velvetleaf growth and fecundity. Velvetleaf was uniformly seeded in order to emerge at the 1, 3, 5 and 7-leaf stage of maize (V1, V3, V5 and V7 growth stages, respectively). Velvetleaf biomass, canopy area and seed production were significantly affected by the date of velvetleaf emergence. Velvetleaf plants emerging just after maize (V1) produced 7–17 times lower seed number, compared with the V5 growth stage. Maximum maize grain yield loss ranged from 26 to 37% for early emerging velvetleaf, and less than 6% yield loss occurred from velvetleaf seedlings emerging at V7 growth stage. Maize hybrids with high initial growth rate seem to be more competitive than the other hybrids. The results of this study are essential in the development of an integrated weed management strategy for maize in semi-arid environments, since they highlight the importance of the careful selection of a competitive maize hybrid and avoidance of early velvetleaf emergence.

Instructions are given for the presentation of the results of statistical analyses in Experimental Agriculture. Statistical codes accepted by the journal are defined. Appropriate styles of presentation are illustrated for estimated parameters and variances for a selection of standard statistical analyses. The value of presentations of results of significance tests is discussed. Formats for acceptable tables and graphs are shown. References to further guiding texts are included for non-standard situations.

Abscisic acid (ABA) accumulation in leaves of drought-stressed coconut palms and its involvement with stomatal regulation of gas exchange during and after stress were investigated. Two Brazilian Green Dwarf coconut ecotypes from hot/humid and hot/dry environments were submitted to three consecutive drying/recovery cycles under greenhouse conditions. ABA accumulated in leaflets before significant changes in pre-dawn leaflet water potential (ΨPD) and did not recover completely in the two ecotypes after 8 days of rewatering. Stomatal conductance was influenced by ABA under mild drought and by ΨPD under severe drought. There were no significant differences between the ecotypes for most variables measured. However, the ecotype from a hot/dry environment showed higher water use efficiency after repeated cycles of water stress.

The objective of this study was to investigate the user communities' understanding and interpretation of changes in rangeland use and productivity in the communal lands of Zimbabwe. While external knowledge has been instrumental in defining the drivers and effects of ecological changes hitherto, the role of local knowledge is becoming increasingly important in explaining factors that inform user community perceptions and guide their decisions on the use of rangeland resources. Data on community perceptions were collected in four villages, using Participatory Rural Appraisals in each village and household surveys with a total of 104 households. This study showed that user communities in Nkayi district differentiate rangelands among seven categories of livestock feed resources and how these have changed over time. Communities viewed rangelands not as one continuous, designated and specialized land parcel, but differentiated the land by location, productivity, management and uses in different times of the year. Although land use changes affecting these livestock feed resources were considered to be widespread and multi-directional (both negative and positive) they did not cause widespread degradation. Rangelands converted to croplands were not completely lost, but became important dual purpose land parcels fulfilling both household food security needs and dry season livestock feed requirements. The importance of croplands as a feed resource is reflected in the emergence of new institutions governing their use for livestock grazing and to guarantee security of tenure. On the other hand institutions governing the use of common property rangelands decreased or weakened in their application. The study concludes that while this situation presents ecological challenges for the rangelands, it offers opportunities to find innovative ways of utilizing croplands as the new frontier in the provision of dry season feed resources to smallholder farmers in highly variable environments. Implications for livestock water productivity need to be investigated and water saving technologies should be promoted in the land use intensification processes.

Scores of assessments of the impacts of agricultural research have been carried out over the years. However, few appear to have been used to improve decision making and the effectiveness of research programmes. The Institutional Learning and Change (ILAC) Initiative emerged within the Consultative Group on International Agricultural Research (CGIAR), with the goal of strengthening learning from experience and using lessons to improve pro-poor innovation. It is testing approaches for expanding the contributions of impact assessment and evaluation to learning, decision making and improvement.

Striga gesnerioides is a serious parasite of cowpea (Vigna unguiculata) on the Abomey plateau of southern Bénin. S. gesnerioides in southern Bénin has been characterized as a race that is different from those found in the dry savanna of West Africa. IITA breeding line IT93KZ-4-5-6-1-5 was used in a trial to study fertilizer response of cowpea on two farmers' fields in 1998. No emerged S. gesnerioides plants were observed on this breeding line while heavy parasite loads were observed on local cultivars growing in adjacent fields. In 1999, IT93KZ-4-5-6-1-5 was grown again on seven fields and no emerged S. gesnerioides plants were observed. In 2000 the same line was grown on 18 farmers' fields with local cowpea cultivars in adjacent control plots. The mean number of S. gesnerioides plants on the local cultivars was 0.92 per cowpea plant (s.d. 0.72) while the improved line carried none. The mean yield gain from the improved cowpea line was 156% and varied from 20 to 680 kg pods ha−1. Thus it appears that progress has been made in developing cowpea lines that are resistant to S. gesnerioides and the potential impact of adoption of resistant cowpea is high.

The hydraulic press was compared with the dew point psychrometer and the pressure chamber methods for measuring leaf water potential (Ψ) in groundnuts (Arachis hypogaea L.). For measurements on the same leaf, regression analysis revealed that the slopes did not differ significantly from unity. An analysis of functional relations between measurements made by the press and the dew point psychrometer or the press and the pressure chamber showed that the error variance of the press was similar to those of the two other methods. Therefore, we conclude that for groundnuts the performance of the press, the dew point psychrometer and the pressure chamber are similar.

Eight triticale lines were evaluated in Cyprus during the period 1977–82 and compared with the best other cereal varieties grown locally. One triticale line was selected which outyielded Athenais barley by 8.3% and Pitic 62 aestivum wheat by 11.4% in drylands, and durum and aestivum wheat by 20% in irrigated areas. Regression analysis showed that Athenais was the best yielding crop in the least productive environments while under medium or favourable conditions triticale gave maximum yields. Number of grains per spike, harvest index and the N content of grain were larger but ear number, 1000-grain weight and N content of straw were smaller in triticale than in barley. The yield component most sensitive to drought was 1000-grain weight.

Trials were conducted in 1987 and 1988 to test methods of intercropping annual Ethiopian clovers, Trifolium spp, with wheat. Several different clover varieties, sowing methods, plant spacings, planting dates and rates of phosphorus application were compared. Planting in single or double alternative rows 20 cm apart did not affect wheat grain and straw yield but broadcast sowing of Trifolium in wheat rows 20 cm apart reduced wheat yield. The Trifolium species used significantly affected legume yield. Phosphorus fertilizer increased yield significantly, especially that of the legume component. The trials indicated that the intercropping of Ethiopian clovers in wheat has potential under African highland conditions.

Siembra simultanea de trigo/ Trifolium en Etiopía

Dodoma Edible outyielded Natal Common groundnut, due to varietal effects associated with differences in pod number, leaf area duration, crop growth rate, number of grains/pod and m2, and weight of individual grain. Increase in plant density led to an increase in grain yield. There was a close and positive relation between stem and pod dry weight; grain yield and leaf area duration; and crop growth rate, grain yield and grain number/m2 of land surface. A greater proportion of total dry matter was diverted into the stems of Dodoma Edible than Natal Common.

Two experiments were conducted over a two year period at the International Rice Research Institute (IRRI) in the Philippines to evaluate the effect of a soyabean green manure intercrop on the grain yield of maize. Three rows of soyabeans were interplanted at 50 cm spacing between maize rows 1.5 m apart. Forty two days after planting the two outside soyabean rows were ploughed into the maize rows in a traditional ‘hilling up’ operation. At the zero and lower nitrogen rates, the soyabean green manure resulted in significantly larger maize yields than when maize was grown without green manure, providing the equivalent of 28 kg N ha−1 on the zero nitrogen plots. A response to green manure was also seen at 25 and 50 kg N ha−1. Allowing the central soyabean row to grow to maturity provided additional yield and protein.

Data from mulched tea show that an earlier defined ratio of temperature fluctuations in thermally homogeneous soil can be successfully used in rating the thermal efficiency of artificial grass mulches. The efficiency of a natural mulch of growing grass is also determined for comparison. It is demonstrated that the use of the ratio is more precise than using average temperatures in assessing the effects of the mulches.

In the dry areas of Nicaragua, white-grain sorghum is an important subsistence crop for resource-poor farmers. From 2002 to 2007, participatory varietal selection (PVS) was implemented in three regions with the aim of identifying new varieties matching small farmers' needs. This paper describes the general approach, the partnership and the methods used to identify farmers' selection criteria (FSC), as well as the evaluation of new germplasm using the scoring method. Data analysis involved relating farmers' evaluation data to agronomic data and farmers' selection decisions (FSD), using Spearman correlations and the chi-square test. In the three regions, higher grain yield and good grain quality for making tortillas were identified as the two main FSCs for both the ‘tortillero’ and ‘millón’ sorghum types; the ranking of the other important FSC differed between the sites and the sorghum types. Our data shows that farmers' scores for earliness were highly correlated with breeder's observations while farmers' assessments of grain yield were correlated with measured yield in half the cases, depending on their knowledge of the crop. The study shows that in evaluating grain quality the farmers used several specific traits which were not considered by breeders. Overall appreciation, grain yield and grain quality were the key farmers' criteria that contributed to FSD. The PVS work enabled breeders to obtain a better understanding of farmers' criteria as well as identifying new progenitors, which should be useful for the sorghum breeding schemes in Central America in the future. Furthermore, by exploring wide genetic diversity, it was possible to release several farmer-preferred and high-performing varieties within a fairly short period.