Different fruit thinning methods were tested on ‘Sensation’ mango trees over two seasons in a trial conducted in Northern Province, South Africa. The objective of the study was to select the best thinning intensity and method based on different parameters. Thinning was carried out in October prior to the occurrence of excessive natural fruit drop. When fruits were thinned to one and two fruits per panicle, fruit number, weight and yield per tree at harvest were all increased. When 50% of the panicles were thinned there was an increase in the fruit retention potential of the trees as well as in the size and quality of the fruit produced. Large fruits were, however, prone to certain physiological problems. Chemical thinning with Corasil.E produced very small fruits with an increased percentage of ‘mules’ (fruit without seed). Trees subjected to severe thinning intensities showed earlier recovery of starch reserves and better vegetative growth than the control.

Green manures (GM) as an alternative to inorganic fertilizer offer considerable potential as a source of plant nutrients and organic matter (OM). Hence, field experiments were carried out during 2015 and 2016 cropping seasons to compare impacts of GM and NPK (15:15:15) fertilizer on soil properties, growth, fruit yield, mineral, lycopene and vitamin C contents of tomato (Lycopersicon esculentum Mill). GMs were composed by green tender stems and leaves of pawpaw (Carica papaya L.), neem (Azadirachta indica A. Juss.), moringa (Moringa oleifera Lam.) or gliricidia (Gliricidia sepium (Jacq.) Kunth ex Walp.) and applied at 5 Mg ha−1, whereas NPK was applied at 300 kg ha−1 and there was a no fertilizer plot (control). Application of GMs reduced soil bulk density and increased soil OM, N, P, K, Ca, Mg, growth, number of fruits and fruit yield of tomato compared with the control. NPK fertilizer had no effect on soil bulk density and soil OM, but it increased soil fertility and tomato yield as compared with the control. When comparing treatments, the highest tomato yield and best cost:benefit ratio were obtained with gliricidia as GM. The GMs and NPK fertilizer increased mineral, lycopene and vitamin C contents in tomato fruits and the highest K, Ca, Fe, Zn, Cu, lycopene and vitamin C contents in tomato fruits were found with moringa as GM. Our results revealed that GM has potential to improve soil properties, tomato yield and quality, being an alternative for cropping management.

Long-term tillage and fertilizer experiments were conducted in rice in kharif followed by lentil in dry subhumid Inceptisols at Varanasi and Faizabad; horse gram at Phulbani and linseed at Ranchi in moist subhumid Alfisols in rabi during 2001 to 2010. The study was conducted to assess the effect of conventional tillage (CT), low tillage + interculture (LT1) and low tillage + herbicide (LT2) together with 100% N (organic) (F1), 50% N (organic) + 50% N (inorganic) (F2) and 100% N (inorganic) (F3) on productivity, profitability, rainwater and energy use efficiencies. The results at Varanasi revealed that CT was superior with mean yield of 2389 kg ha−1, while F1 was superior with 2378 kg ha−1 in rice. At Faizabad, CT was superior with mean rice yield of 1851 kg ha−1 and lentil yield of 977 kg ha−1, while F1 was superior with 1704 and 993 kg ha−1 of rice and lentil, respectively. At Phulbani, F2 was superior with rice yield of 1170 kg ha−1. At Ranchi, F2 with rice yield of 986 kg ha−1 and F3 with linseed yield of 224 kg ha−1 were superior. The regression model of crop seasonal rainfall and yield deviations indicated an increasing trend in rice yield over mean (positive deviation) with increase in rainfall at all locations; while a decreasing trend (negative deviation) was found for lentil at Faizabad, horse gram at Phulbani and linseed at Ranchi. Based on economic analysis, CTF1 at Varanasi and Faizabad, CTF2 at Phulbani and LT2F2 at Ranchi were superior.

The literature on ‘stability analysis’, which is better called ‘sensitivity analysis’, leaves much to be desired. This paper attempts to clarify the issues, particularly the effect of the non-linearity of the standard model relating variety yields to mean yields over sites. The model is extended from its original applications in the analysis of crop yields to the analysis of measurements that cannot be considered Normally distributed, such as disease assessments expressed as percentages or proportions. Modern computer software offers a method that is theoretically sound and can be applied routinely to data of many different distributional types. Graphical methods of displaying the results of the analysis of non-Normal data are discussed.

Análisis de la sensibilidad de ensayos con variedades

On-farm nutrient management practices were evaluated in the irrigated rice-wheat cropping system (RWCS) in northwestern India. Large farmers used comparatively higher doses of nutrients than small and medium farmers for both rice and wheat crops. On average, a field is treated with organic manure after every 15 years for rice and 53 years for wheat. Nitrogen use was generally more than the recommended dose for both crops. Phosphorus use in wheat was nearly as per recommendation, while in rice it was below the recommended dose. Potassium use was almost nil; however, the use of Zn (particularly in rice) is becoming common. Use of biofertilizers was negligible. Overall, farmers applied higher doses of organic manures, K, Zn and biofertilizers in rice than wheat, and there was increasing trend in their use with increase in the size of land holdings. Grain yield increased significantly with increase in the size of land holding in rice but remained almost same in wheat. This study generated comprehensive data on nutrient use pattern in the RWCS, thus providing necessary input to researchers, planners and developmental agencies who wish to enhance food security.

Some agronomic, economic and ecological aspects of an agroforestry system combining Grevillea robusta trees, bananas (Musa spp.) and beans (Phaseolus vulgaris) were studied in the subhumid highlands of Burundi. Three densities of G. robusta, 208, 313 and 625  trees  ha−1 were interplanted in plots of bananas, beans and a banana–bean mixture. When G. robusta was interplanted with bananas, the tree had a positive effect on banana yield with maximum yield occurring at 300  trees  ha−1. In the presence of beans, banana yield was not influenced by the densities of the tree. Under low fertility regimes, the yields of beans interplanted with G. robusta were equal to or greater than those of the no-tree plots. Maximum bean yields were observed at between 283 and 295  trees  ha−1, representing a 25–135% yield increase above the no-tree control. When soil fertility was raised by the application of fertilizers, bean yields declined with an increasing density of G. robusta. Three years after planting, the growth of G. robusta was not affected by tree density. Mean height and mean basal diameter were 7.1   m and 13.2   cm respectively. Below ground competition between beans on the one hand, and bananas or bananas and G. robusta on the other, was more important than competition for light. Compared with the crops alone treatments, cumulative net present values of tree plots improved from being negative in the first year to being positive in the third year. Net present value was highest in two of three instances when the density of G. robusta was 625  trees  ha−1. A multistrata arrangement of bananas and beans with G. robusta is viable for the low input agriculture system of the highlands of Burundi.

Deficiencies of micro (Zn, B) and secondary (S) nutrients are well-documented in soil as well as in cereal crops, leading to decreased crop yields and low nutritional quality of food. We evaluated the effects of coated urea on maize yield, N and Zn uptake, and input cost relationships. Field experiments were conducted on maize to test boron-coated (BCU), sulphur-coated (SCU) and zinc-coated urea (ZnCU) during 2013 and 2014. On the basis of 2 years’ average data, the highest grain yield was achieved with 0.5% BCU, 5% SCU and 2.5% ZnCU as zinc sulphate hepta hydrate. These treatments increased yields by 5.4, 12.8 and 9.9% over prilled urea (PU), respectively. Application of 0.5% BCU (supplying 1.4 kg B ha−1), 5% SCU (supplying 14.1 kg S ha−1) and 2.5% ZnCU (supplying 7.05 kg Zn ha−1) registered the highest N concentrations and uptake in grain and stover. Total N uptake (grain + stover) was increased by 7.6, 16.7 and 17.1% with BCU, SCU and ZnCU treatments over PU. As compared to PU, Zn concentration in maize grain was significantly higher and total Zn uptake (grain + stover) increased by 32.4% with 2.5% ZnCU. Coated urea materials also enhanced the partial factor productivity (PFPN), agronomic efficiency (AEN), recovery efficiency (REN) and harvest index (HIN) over those of PU. From the economic viewpoint this study suggests that coating of urea with 0.3% boron, 5% sulphur or 2% zinc gives maximum net returns and benefit-cost ratio. Our data indicate that coating of B, Zn and S onto urea increases maize yield, profitability and nitrogen use efficiency in the western Indo-Gangetic plains of India.

A study was conducted to evaluate performance of two rice (Oryza sativa L.) varieties under water saving irrigation through alternate wetting and drying in sandy clay loams of Southern Malawi. The varieties, Nunkile and NERICA 4, are adapted to upland and lowland irrigated conditions, individually, and commonly grown by farmers. Four irrigation regimes were used in the study: (1) continuous flooding with surface water level kept at approximately 5 cm throughout crop duration (CFI), (2) alternate wetting and drying up to start of flowering after which continuous flooding was applied (AWD1), (3) alternate wetting and drying up to start of grain filling after which continuous flooding was applied (AWD2) and (4) alternate wetting and drying throughout the crop duration (AWD3). While seasonal crop water requirement was 690 mm, total irrigation depths were 1923.61, 1307.81, 1160.61 and 807.87 mm for the four regimes respectively. The CFI treatment used 32%, 40% and 58% more water than AWD1, AWD2, and AWD3 regimes respectively. In the same treatment order, the average yields per treatment for Nunkile were 4.92, 4.75, 4.74, and 4.47 t ha−1 with significant yield differences among CFI, AWD2 and AWD3 treatments. The average yields per treatment for NERICA 4 were 3.93, 3.75, 3.75, and 3.71 t ha−1 with significant yield differences only between CFI and all AWD treatments. Crop water productivity (CWP) was higher for Nunkile compared with NERICA 4 across all irrigation treatments, while CWP for CFI treatment was superior to all three AWD treatments grown under either variety. Thus, CWP was not increased with AWD irrigations. AWD till flowering and grain filling did not significantly differ with respect to yield and CWP. It is suggested that for similar conditions and where water is scarce, rice can be grown by AWD till grain filling as it saved more water. An important part of the research is to extend the initial results beyond the climate and soils of study.

Conservation agriculture (CA) practices are becoming more important in Mediterranean rainfed areas due to their potential to minimize climatic risk, reduce soil erosion, and improve soil quality and water availability. Due to minimum soil disturbance and crop residue retention, the soil environment for crop growth and development can differ between CA and conventional tillage (CT) practice. However, breeding targets for improving yield performance in CA system remain poorly explored. The objective of this study was to assess the performance of elite genotypes of barley, chickpea, lentil, and wheat grown under CA, a promising alternative agricultural practice in the Mediterranean rainfed conditions. A three-year field study, with contrasting rainfall pattern, was conducted in the International Center for Agriculture Research in the Dry Areas’s research field in Morocco to evaluate the tillage × genotype interaction and its consequence for yield performance of barley, chickpea, lentil, and wheat. Thirteen elite genotypes for each crop were planted under both CA and CT systems. Wheat and chickpea produced significantly higher grain yield (+62% for wheat and +43% for chickpea) under CA than in CT, while lentil and barley performed equally under both systems. Significant effect of tillage × genotype was more frequent for chickpea and wheat than for barley and lentil. Increased yield under CA, mainly in dry year, was associated with higher harvest index (HI). For each crop species yield was mainly influenced by rainfall amount and distribution (75–88% yield variation), and tillage × genotype was of little importance. The overall results suggest that a specific breeding program for CA in lentil, chickpea, wheat, and barley may not be efficient. Few tillage × genotype interaction, especially in dry years, indicated that breeding target on increasing HI, tolerance to drought (high yield in dry years), and potential yield (high yield in wet year) can help to improve yield performance of chickpea, lentil, and wheat genotypes in CA system. Varieties with wider adaptability considering drought tolerance, higher yield with stability, and adoption of CA practices are important in the context of the Mediterranean rainfed environment. Integrating trade-off analysis between yield potential and stability in a rainfall gradient in both CT and CA in the national certification scheme of varieties may be more efficient than developing breeding programs for each type of tillage system.

In marginal lands Opuntia ficus-indica (OFI) could be used as an alternative fruit and forage crop. The plant vigour and the biomass production were evaluated in Portuguese germplasm (15 individuals from 16 ecotypes) by non-destructive methods, 2 years following planting in a marginal soil and dryland conditions. Two Italian cultivars (Gialla and Bianca) were included in the study for comparison purposes. The biomass production and the plant vigour were estimated by measuring the cladodes number and area, and the fresh (FW) and dry weight (DW) per plant. We selected linear models by using the biometric data from 60 cladodes to predict the cladode area, the FW and the DW per plant. Among ecotypes, significant differences were found in the studied biomass-related parameters and several homogeneous groups were established. Four Portuguese ecotypes had higher biomass production than the others, 3.20 Mg ha−1 on average, a value not significantly different to the improved ‘Gialla’ cultivar, which averaged 3.87 Mg ha−1. Those ecotypes could be used to start a breeding program and to deploy material for animal feeding and fruit production.

Although triple cropping in inland valleys of Nigeria is technically feasible, the third crop between the main crop and dry season non-rice crop has been considered not to be economically viable because of poor crop establishment due to soil inundation. The identification of an appropriate technology with low input, such as ratooning, would allow this niche to be utilized. Field experiments were conducted at the University of Agriculture, Abeokuta, Nigeria in 2007–2008 and 2008–2009 cropping seasons to evaluate the performance of the main and ratooned crops of lowland NERICA (New Rice for Africa) rice (Oryza sativa L.) varieties in a lowland rice–ratooned rice–fluted pumpkin (Telfairia occidentalis Hook F.) sequence. The experiment was laid out in a randomized complete block design with three replicates. The lowland rice varieties used were NERICA-L 19, NERICA-L 20, NERICA-L 22, NERICA-L 24, OFADA, NERICA-L 26, NERICA-L 41, NERICA-L 42, NERICA-L 44 and NERICA-L 47. The grain yield of the main rice crop ranged from 5.0 to 7.3 t ha−1 in 2007–2008 cropping season and from 4.1 to 9.1 t ha−1 in 2008–2009. The ratooned rice had a grain yield of 1.0–4.7 t ha−1 in 2007–2008 and 1.2–3.4 t ha−1 in 2008–2009. The total grain yield obtained in 2007–2008 from the main and ratooned rice crops in seven months was 6.7–11.6 t ha−1, while in 2008–2009 it was 5.3–2.6 t ha−1. The fresh leaf yield of fluted pumpkin ranged from 14.6 to 16.9 t ha−1 in 2007–2008 and from 18.3 to 19.8 t ha−1 in 2008–2009, similar to previously reported rainy season unfertilized yields. Thus, a ratooned rice crop appears to be a feasible technology capable of boosting rice production and consequently increasing the overall productivity of the inland valley in a rice–rice–vegetable cropping sequence.

In addition to latex and timber, the rubber tree is useful in the alleviation of rural poverty and also in the mitigation of climate change through fixing atmospheric CO2 as biomass. For developing any rubber-based carbon projects, protocols for quantifying biomass and carbon fixed are required. In this context, the present study was aimed at building up allometric models using simple growth indicators (i.e. tree diameter and total height) to assess the timber, biomass and carbon in rubber trees and also to quantify their ontogenetic variation under average growth conditions in two major climatic regimes (i.e. wet and intermediate) of Sri Lanka. All models developed were in the accuracy level of over 88%. The mean absolute percentage error in the validation of allometric models was only 12.9% for timber and less than 5% for biomass and carbon. Under average growth conditions, 1 ha of rubber could produce 208 m3 timber, 191 MT biomass and fix 78 MT carbon during its 30-year lifespan in the wet zone and ca. 16% lesser values in the intermediate zone. The applicability of the findings in carbon trading is discussed.

Yield gaps have become a useful tool for guiding development-related agronomy, especially in the global South. While critics have challenged some aspects of the yield gap methodology, and the relevance of food security advocacy based on yield gaps, very few studies question the actual relevance, application and scalability of yield gaps for smallholder farmers (and researchers) in the tropics. We assess these limitations using two contrasting case studies: maize-based farming systems in Western Kenya and rice-based farming systems in Central Luzon, the Philippines. From these two cases, we propose improvements in the use of yield gaps that would acknowledge both the riskiness of crop improvement options and the role that yield increases might play within local livelihoods. Participatory research conducted in Western Kenya calls into question the actual use and up-scaling of yield measurements from on-station agronomic trials to derive estimates of actual and water-limited yields in the region. Looking at maize yield gaps as cumulative probabilities demonstrates the challenges of assessing the real magnitude of yield gaps in farmers’ fields and of deciding whose yield gaps count for agricultural development in Kenya. In the case of rice-based farming systems, we use a historical dataset (1966–2012) to assess changes in rice yields, labour productivity, gross margin and rice self-sufficiency in Central Luzon, the Philippines. While large rice yield gaps persist here, there appear to be few incentives to close that gap once we consider the position of crop production within local livelihoods. In this context, economic returns to labour for farm work were marginal: labour productivity increased over time in both wet and dry seasons, but gross margins decreased in the wet season while no trend was observed for the dry season. Since most households were rice self-sufficient and further increases in crop production would offer minimal returns while relying increasingly on hired labour, we question who should close which yield gap. Our case studies show the importance of contextualising yield gaps within the broader livelihood context in which farmers operate. We propose that this should be done at farm and/or farming systems level while considering the risks associated with narrowing yield gaps and looking into multiple performance indicators.

A growth analysis study involving monthly excavation of Dioscorea esculenta plants revealed that the root system developed fully in the period before tuber initiation, and extended radially for a distance between 2.3 and 4.3 m. Primary roots initially remained in the top 10 cm of the soil profile, but descended to approximately 30 cm near their full extension. Tuber number increased from initiation around 21 weeks after planting (WAP) until maximum vine growth was reached around 33 WAP, but tuber dry weight continued to increase throughout the senescence period of the vine, to 45 WAP. Tubers lost dry matter but not fresh weight during dormancy in the soil, to 55 WAP. The results indicate that a distance of at least 4.5 m is required to separate experimental fertilizer treatments, and that post-establishment burial of fertilizers around the mound or ridge risks damage to roots near their base, while inter-row application is accessible to roots and may be preferable.

Relay intercropping of maize with fodder crops is a promising option for sustainable intensification of dairy small-scale farms in the Cerrado of Brazil. Twenty-six intercropping trials were conducted on farmers’ fields with the following experimental treatments: sole maize crop cropping (MS), maize-Brachiaria intercropping (MB) and maize-pigeon pea intercropping (MP). The trials were managed by the farmers, i.e. choice of conventional tillage (CT) versus no-tillage (NT), sowing dates, fertilization and weed control. Maize grain yield varied strongly across the farmer fields, from 100 to 5900 kg ha−1 in the MS treatment, 500 to 6900 kg ha−1 in MP and 300 to 5500 kg ha−1 in MB. Intercropping did not significantly affect maize grain yields under NT, but yields were reduced under CT in one out of two seasons. Maize yields in the intercropped systems were also higher under NT than CT. Total biomass productivity was significantly higher in the maize-fodder than in the sole maize system. An increased interval between sowing of maize and fodder crop significantly reduced the fodder crop biomass. Relay intercropping, especially in combination with NT, is a promising option if crop calendars and fertilization are properly managed by farmers to reduce interspecific competition between the maize and fodder crop.

The effects of weeds on coffee productivity and the methods used for their control are discussed. The more common weeds are listed, together with the control methods that can be used at various phases of coffee production.

Malezas y control de las mismas en el café

In southern Bénin, the legume cover crop Mucuna pruriens var. utilis has been widely promoted for soil fertility improvement. Recent findings have shown, however, that the majority of farmers have not adopted it, and that alternative technologies are needed that are both attractive to farmers and beneficial in terms of soil fertility. A survey was carried out in southern Bénin to determine farmer perception and use of traditional grain legumes and to assess the adoption potential of new low-harvest-index grain legumes. Grain legumes were shown to be integral components of traditional cropping systems and constituted farmers' most important technology for soil fertility maintenance. More than 80% of respondents expressed interest in testing new, low-harvest-index varieties. Preferred grain characteristics and farmers' culinary preferences for grain legumes varied between locations and need to be taken into account if new germplasm is to be introduced. It is argued that farmers' interest and experience in legume cultivation provide an opportunity for the introduction of alternative legume-based technologies such as low-harvest-index grain legumes and techniques for the detoxification of mucuna seed. In addition, efforts should be made to increase the productivity of current legume production systems and to develop mucuna cultivars with reduced L-dopa content.

A replicated field study was conducted during 1979 and 1980 in the Karnal district of Haryana, India to investigate the effects of three rates of gypsum (0, 5.2 and 10.4 t ha−1) on the performance of five forage grass species (Rhodes grass (Chloris gayana), blue panic (Panicum antidotale), Panicum laevifolium, Karnal grass (Diplachne fusca) and coastal Bermuda (Cynodon dactylon)) on an extremely sodic soil. The soils used had a large exchangeable sodium concentration and pH in the top 15 cm (94% and 10.6, respectively). For comparison, the same grasses were also planted in a normal soil. The results showed that the relative tolerance of these species to increasing sodicity was in the order of Karnal grass > Rhodes grass > coastal Bermuda > blue panic ≥ Panicum laevifolium.

The development and influence of crop drought stress was examined in winter-planted small-grain cereals under Mediterranean environmental conditions. In two average or wetter than average years crop drought stress in the grain-filling period was greatly exacerbated by the addition of fertilizer (N and P) and this usually resulted in significantly lower kernel weights. Yet this reduction was not so substantial as to seriously affect crop yields. Total grain yields were largest in treatments receiving fertilizer, due to greater spike numbers and numbers of kernels per spike. But heavy nitrogen applications may promote the risk of a large proportion of small or shrivelled grains in a dry year.