In the Central Rift Valley (CRV) of Ethiopia, low productive cereal systems and a declining resource base call for options to increase crop productivity and improve resource use efficiency to meet the growing demand of food. We compiled and analysed a large amount of data from farmers’ fields (>10,000) and experimental data across the CRV from 2004–2009 to quantify yield gaps (Yg) between actual (average and best performing farmers) and experimental (water-limited potential (Yw)) yields of maize and wheat in homogenous farming zones (HFZs). Resource use efficiencies (nutrients and water) of maize and wheat were also analysed to assess spatial variation and scope for improvements. The average (2004–2009) yield gap of maize and wheat in the CRV ranged between 4.2 t ha−1 and 9.2 t ha−1, and 2.5 t ha−1 and 4.7 t ha−1, respectively, across farming zones. The yield gap was lowest in the Central lowlands, where Yw was also lowest, i.e. 6.5 t ha−1 for maize and 4.4 t ha−1 for wheat, compared with Yw in the Eastern highlands (11 t ha−1 for maize and 6.7 t ha−1 for wheat) and Western highlands (10.8 t ha−1 for maize and 5.7 t ha−1 for wheat). The actual nitrogen (N) and phosphorus (P) application in farmers’ fields was low, as about 46% of maize and 27% of wheat fields did not receive fertilizers, while the average applied mineral fertilizer rates across all farmers (2.6–16.5 kg N ha−1 and 2.2–17.3 kg P ha−1 across HFZs and crops) were far below the recommended rate. On average, the best performing farmers applied 8–20 kg N ha−1 and 5–21 kg P ha−1 ranging across HFZs and crops. Increasing N application to recommended rates had only a small effect on narrowing the yield gap under current farmers’ management. Therefore, the yield gap closure strongly depends on improving other aspects of crop management while paying attention to the interaction with nutrient management. Since rain water use efficiency (seasonal rainfall) of water-limited yields was 12–17.3 kg mm−1 for maize and 7.4–10.6 kg mm−1 for wheat and much higher than that of actual yields (2.7–4.3 kg mm−1 for maize and 2.3–3.5 kg mm−1 for wheat), improving the input use and crop management can increase water use efficiency. A large set of experimental and survey data enabled us to gain insight in the spatial and temporal variation in yield gaps and input rates and in differences between average and the best performing farmers.

The depth to ground water is increasing in several regions of the world due to use of high-yielding, but also high water-requiring crops such as rice (Oryza sativa) and wheat (Triticum aestivum), in order to maintain food security for an ever increasing world population. There is a need not only to increase the water productivity of food crops, but also to find less water-requiring crops. Irrigated chickpea (Cicer arietinum L.), traditionally grown without irrigation, may provide an alternative crop to irrigated wheat in some regions. Two field experiments were conducted to determine the effects of irrigation on chickpea yields, yield components and grain and biomass water productivity (based on irrigation (WPI) and irrigation + rainfall (WPI+R)) grown in a loamy sand soil. In the first year, 75 mm of irrigation at the vegetative stage and at the vegetative plus podding stages resulted in a 59% and a 73% increase in grain yield, respectively, compared to no irrigation, but with little change in WPI+R. Overall yields in the second year were significantly higher due to warmer temperatures and fewer frosts during flowering and podding. Compared to no irrigation, 75 mm of irrigation at flowering or at podding resulted in a 7% and a 27% increase in grain yield, but a decrease in grain and biomass water productivity (WPI+R). Irrigation had a significant effect on the number of pods plant−1 in both the years and on 100-seed weight in the first year. We conclude that application of a single irrigation during podding to chickpea grown in a loamy sand soil will reliably increase yields and may provide a water-saving alternative to wheat in water-scarce environments.

Firstly, I would like to say that it is a great honour to take over the position of Editor-in-chief of Experimental Agriculture, one of the most important journals devoted to publishing original and high quality papers addressing the many facets of agricultural sciences in subtropical and tropical areas. Tradition! I would say that this single word has an enormous meaning for me. I am proud in serving Experimental Agriculture, a journal published by the Cambridge University Press since 1933. Originally titled The Empire Journal of Experimental Agriculture (1933-1964), the publication's mission was ambitious “every new fruit of discovery and invention in the agricultural field”, publishing critical information for improving agricultural systems. So pertinent was the Journal's remit that it was recognised in an article published in Nature in May 27th, 1933. Currently, Experimental Agriculture has an Impact Factor of 1.079 (ISI Thomson Reuters) and stands as a Q1 journal in ‘Agronomy and Crop Science’ (SCImago Journal and Country Rank). In 2015, we received submissions from the five continents, with the majority coming from Asia and Africa. Thank you for considering Experimental Agriculture as a potential journal to publish your paper!

Intensification of maize production is imperative to improve food security for the rising population in the central rift valley (CRV) of Ethiopia, whose livelihood is principally based on rainfed maize that operates under shrinking landholding and high seasonal rainfall variability. This study examined different levels of intensification options in maize production by sequentially introducing minimum tillage and seed priming, phosphorus (P) fertilizer microdosing, surface mulching and nitrogen (N) fertilizer microdosing. Field experiments were conducted with five treatments, steps or levels consisting of conventional tillage (farmers practice as a control); minimum tillage + seed priming, unfertilized (step 1); step 1 + microdosing 53 kg ha−1 P (step 2); step 2 + 4 ton ha−1 maize stover as surface mulch (step 3) and step 3 + 53 kg ha−1 N (step 4). These steps represented increasing levels of intensification. Except at the lowest level (step 1), agronomic and economic responses improved with increasing levels of inputs. Relative to the very high and increasing gross margin, production costs were low but slowly increased with increasing levels of inputs. Except at the lowest level, the value cost ratio was above 4 even at the highest levels of inputs, demonstrating that such kind of intensification can be achieved with low risk. Likewise, the fertilizer use efficiency was quite high even at the highest of levels of inputs signifying the efficiency of the pocket application of fertilizer through the microdosing method. The improvement in maize establishment and yield and the reduction in the days to maturity could contribute to make maize production more adaptive to the existing seasonal rainfall variability. Depending on the affordability to the external inputs and their feasibilities, the different technology packages in the intensification ladder may give different choices for the farmers to improve maize production in the CRV of Ethiopia.

To quantify the effect of thermal stress and photothermal quotient (PTQ) on yield components, eleven years experimental data of three cultivars (HD-2285, K-8804 and K-9107) under three sowing dates at Kanpur centre were analysed. Number of grains per ear (NG), grain weight per ear (GW) and 1000-grain weight (TG) were identified as prime yield contributing components in HD-2285, K-8804 and K-9107, respectively. GW was highly sensitive to maximum temperature (MXT) while NG was sensitive to minimum temperature (MNT) during jointing (JNT) to anthesis (ATS) as well as the total growing season in all the cultivars. In both HD-2285 and K-8804, optimum MXT and MNT during JNT to ATS are 22.7–24.6 and 7.0–7.9 °C, respectively for obtaining maximum NG. Optimum MXT for GW ranged from 15.8–17.3 °C during tillering (TLR) to JNT stage in K-8804 and K-9107 while it was 20.4 °C during JNT to ATS stage in HD-2285. MXT, MNT and PTQ of 23.6 °C, 9.2 °C and 25 MJ/m2/day/ °C, respectively during JNT to ATS in K-9107 were found optimum for higher TG.

Eucalyptus spp. is the main tree used in cellulose production worldwide, cultivated mostly in extensive monocrop plantations. However, due to concerns on environmental impacts, fear on decrease of food production related to the size of cultivated area, its location near human settlements with few jobs generation, eucalypt cultivation is no longer encouraged in many places. At the same time, large plantations hold the opportunity to integrate eucalypt into agroforestry systems (AFS) in a variety of production systems with many social, economical and environmental advantages. In this study we studied canopy modifications of E. camaldulensis sprouts under different degrees of shade. The plants were located on a gradient of available solar irradiation ranging from 51 to 94%. E. camaldulensis showed canopy plasticity with modified radiation interception patterns under diverse irradiations. Most of these variations were of small amplitude with some important variables remaining almost unchanged (leaf density, canopy percentage, tree, trunk and canopy height) or increasing only slightly (leaf area index and canopy opening). The main changes presented by E. camaldulensis, with a steep increase towards full sun, were: foliage area, canopy surface, canopy volume and area of canopy projection. In order to design appropriate agroforestry systems with young eucalypt growing under the shade of other crops, it is necessary to determine at which point the observed variable changes can support reasonable production.

Long-term in situ soil and water conservation experiments are rare in sub-Saharan Africa, particularly in Eastern Africa. A long-term experiment was conducted (2005–2013) on a Vertisol to quantify the impacts of resource-conserving agriculture (RCA) on runoff, soil loss, soil fertility and crop productivity and economic profitability in northern Ethiopia. Two RCA practices were developed from traditional furrow tillage practices: (i) derdero+ (DER+) and terwah+ (TER+). DER+ is a furrow and permanent raised bed planting system, tilled once at planting time by refreshing the furrow and 30% of crop residue is retained. TER+ is ploughed once at planting, furrows are made at 1.5 m intervals and 30% crop residue is retained. The third treatment was a conventional tillage (CT) with a minimum of three tillage operations and complete removal of crop residues. Wheat, teff, barley and grass pea crops were grown in rotation. Runoff, and soil and nutrient loss were measured in plastic sheet-lined collector trenches. Significantly different (P < 0.05) runoff coefficients (%) and soil losses (t ha−1) averaged over 9 yrs were 14 and 3, 22 and 11 and 30 and 17 for DER+, TER+ and CT, respectively. Significant improvements in crop yield and gross margin were observed after a period of three years of cropping This study demonstrated that RCA systems in semi-arid agro-ecosystems constitute a field rainwater conservation and soil fertility improvement strategy that enhances crop productivity and economic profitability. Adoption of RCA systems (DER+ and TER+) in the study area requires further work to improve smallholder farmers’ awareness on benefits, to guarantee high standards during implementation and to design appropriate weed management strategies.

The short term nutrient supply of Leucaena leucocephala, Calliandra calothyrsus, Acacia angustissima and Acacia karoo prunings with or without supplemental inorganic nitrogen were tested using rape (Brassica napus L.) in a field trial. Prunings were applied at a rate of 5 t ha−1 to soil, alone or with supplemental N at 37.5 kg N ha−1 (¼ of recommended N). The respective decomposition and N release constants of the prunings were 9.15 and 9.70% for L. leucocephala; 6.15 and 6.40 for A. angustissima; 4.50 and 4.90 for C. calothyrsus; and 2.20 and 2.10 for A. karoo. These constants were best described by the (lignin+polyphenol)-to-nitrogen ratio of the prunings. Total biomass over the two seasons ranged from 1.40 to 17.28 t DM ha−1 and total growth rates ranged from 2.34–26.70 g plant−1 week−1. The cumulative N recovery at week 9 ranged from 21.1–66.1 %. Legume tree leaves can be used as a source of N for vegetable production. Farmers who use high tannin leaf litter are recommended to supplement with mineral N in order to assure adequate N availability during plant growth.

Innovation Platforms (IPs) are seen as a promising vehicle to foster a paradigm shift in agricultural research for development (AR4D). By facilitating interaction, negotiation and collective action between farmers, researchers and other stakeholders, IPs can contribute to more integrated, systemic innovation that is essential for achieving agricultural development impacts. However, successful implementation of IPs requires institutional change within AR4D establishments. The objective of this paper is to reflect on the implementation and institutionalisation of IPs in present AR4D programmes. We use experiences from sub-Saharan Africa to demonstrate how the adoption and adaptation of IPs creates both opportunities and challenges that influence platform performance and impact. Niche-regime theory is used to understand challenges, and anticipate on how to deal with them. A key concern is whether IPs in AR4D challenge or reinforce existing technology-oriented agricultural innovation paradigms. For example, stakeholder representation, facilitation and institutional embedding determine to a large extent whether the IP can strengthen systemic capacity to innovate that can lead to real paradigm change, or are merely ‘old wine in new bottles’ and a continuation of ‘business as usual’. Institutional embedding of IPs and – more broadly – the transition from technology-oriented to system-oriented AR4D approaches requires structural changes in organisational mandates, incentives, procedures and funding, as well as investments in exchange of experiences, learning and capacity development.

The soil health of rubber (Hevea brasiliensis) plantations shows a declining trend, mainly due to the continuous mono crop cultivation and the ‘clean-weeding’ practices. Another weeding approach which allows the under-flora to grow profusely after closing up of the rubber canopy (no-weeding) can establish a multi-flora system that can improve soil health. A case study was undertaken to test this hypothesis. Rubber fields with and without control of under-flora were investigated for different soil properties, biomass and nutrients of under-flora and rubber yield. The ‘no-weeding’ practice for about 10 years in the rubber fields significantly improved the soil OC, N, available forms K and Mg, respiration rate and moisture status. The biomass and associated nutrients of under-flora also were much higher while the rubber yield was not negatively affected in the ‘no-weeding’ fields. The new weed management system is of great significance in improving soil quality, carbon sequestration and biodiversity conservation, besides the economic and energy savings without affecting crop yield.

Hand-planted plots of across-row-oriented corn seeds (Zeamays L.) produce highly structured leaf canopies and have shown significant yield advantage over randomly planted plots in prior studies. For further investigation of the phenomenon by simulation, the objective of this study was to develop a probabilistic model for the correlation between seed orientation and initial plant orientation. In greenhouse trials, the azimuthal orientation of kernels of four different hybrids was recorded at planting. At collar setting of the seed leaf, the orientation of the seed leaf was determined and the angular data subjected to the analytical methods of circular statistics. The results indicate that the correlation between seed azimuth and seed leaf azimuth can be described by a von Mises distribution. The probabilistic seed to seed leaf azimuth model described herein may be implemented in simulation models to investigate the effect of canopy architecture, canopy closure and light interception efficiency of corn under conditions of seed oriented planting.

During growth, several cereals store significant amounts of fructo-oligosaccharides (FOS), which have important prebiotic properties. Cereal forage crops are also essential components of many Mediterranean agricultural systems, although little information is available on their dynamics of accumulation and partitioning of dry matter and FOS during growth. Oat (Avena sativa L., cv. ‘Flavia’ and cv. ‘Genziana’), emmer wheat (Triticum dicoccum Schrank, cv. ‘Giovanni Paolo’), barley (Hordeum vulgare L., cv. ‘Diomede’) and triticale (xTriticosecale Wittmack, cv. ‘Rigel’) were investigated for their synthesis of FOS, with a view to development of management approaches for harvesting high-quality forage, and to determine whether these species can be used as natural sources of FOS for commercial use. The study was conducted at Foggia (Italy) and Bella (Potenza, Italy) over two growing seasons (2008–2009; 2009–2010). Dry-matter accumulation and FOS contents were determined for plant fractions from heading to kernel-hard stages. There were large variations across these species for dry-matter partitioning and dry-matter yield (greatest for triticale: 1.24 kg m−2), and for FOS levels of total plants and plant fractions. Emmer wheat and triticale showed greater FOS production (52.0, 41.1 g m−2, respectively). Barley, emmer wheat and triticale showed higher FOS levels in total plants (4.11%, 5.93%, 4.33% dry matter, respectively). Barley, emmer wheat and triticale appear to be the most interesting species for production of forage biomass rich in FOS and as natural FOS sources for industrial use.

Recent studies have reported the benefits of fertilizer microdosing in increasing crop yields in low input cropping systems. Little information is however available on the mechanisms underlying this effect. The objective of this study was therefore to explore the root-based mechanisms governing the growth enhancing phenomena of the fertilizer microdosing technology. A two-year experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Research Station in Niger. Four treatments comprising (i) 2 g hill−1 of diammonuim phosphate (DAP), (ii) 6 g hill−1 of compound fertilizer NPK, (iii) broadcasting of 200 kg ha−1 of compound fertilizer NPK (recommended rate) and (iv) unfertilized control was arranged in a randomized complete block design with four replications. On average, fertilizer microdosing treatments (2-g DAP hill−1 and 6-g NPK hill−1) achieved 86% and 79% of the grain yields recorded from broadcasting of 200-kg NPK ha−1, respectively, in 2013 and 2014. The leaf area index and leaf chlorophyll content significantly increased with fertilizer microdosing at the early stage of millet growth. At the same stage, fertilizer microdosing enhanced the lateral root length density in the topsoil (0–20 cm) by 72% and 40% at respective lateral distances of 25 cm and 50 cm from the centre of the hill compared with broadcast of 200-kg NPK ha−1. Fertilizer microdosing did not significantly change soil pH in the root zone. It is concluded that the positive effect of fertilizer microdosing in increasing millet yield results from the better exploitation of soil nutrients due to early lateral roots proliferation within the topsoil.

Conservation agriculture (CA) is a promising technology for controlling soil degradation, mitigating drought, increasing crop yield and reducing production costs. We hypothesized that adopting CA system would improve system productivity and efficiency, hence resulting in higher profits. To test the hypothesis, we designed a study to evaluate water use efficiency (WUE) and the economic benefits (yield and gross margins) of CA in the upper and lower midlands agro-ecological zones of eastern Kenya. Four tillage treatments, including farmers’ practice (residues removed), conventional tillage (residues removed) and two CA practices with residue retention (zero tillage and furrow–ridge), were laid out in 22 farmers’ fields where each farm was treated as a replicate. The results are based on four consecutive seasons farmer–researcher managed trials during the period 2010 and 2012. CA significantly improved crop yields after the first season of experimentation. Joint use of zero tillage and furrow–ridge provided higher WUE and yield advantage (25–34%) in the third and fourth seasons compared to the conventional practices. The lower midlands zone gave higher WUE values, which can be explained by the effects of water harvesting and retention for longer period on CA treatments. CA practices have increased income on average by 12% resulted from labour cost reduction and yield increment. Weeding costs for conventional tillage were USD 88 ha−1 compared to USD 24 ha−1 for herbicide application under CA. Practicing CA will certainly increase crop yields, WUE, generate more revenue and diversify risks during poor seasons. However, these benefits may not necessarily be earned in the first season, but will accrue in subsequent seasons.

When water stress develops post-anthesis, wheat (Triticum aestivum L.) plants have to rely increasingly on remobilization of previously stored assimilates to maintain grain filling. In two-year field trials, we studied more than 20 agronomic and developmental traits in 61 wheat genotypes (27 F4:5 families, 17 parents used for the crosses and 17 standards), comparing plants that were defoliated (DP) by cutting off all leaf blades 10 days after anthesis with intact control plants (CP). Estimated contributions of stem and sheath assimilate reserves to grain weight/spike were from 10–54% and from 24–84% in CP and DP plants, respectively. Stem-related traits were among key traits determining stem reserve contribution (SRC). The most important genetic variables in differentiating genotypes for stress tolerance were biomass/stem, stem reserves mobilization efficiency and grain filling rate (GFR). Balance among traits related to yield maintenance in DP were more important than their high values. In general F4:5 families (FAM), that had been crossed to combine typical breeding traits such as biomass and yield components, showed better tolerance under moderate stress than standards and parents.

The systematic rather than random entry arrangement of honeycomb designs (HDs) has been deployed to sample the spatial heterogeneity. This hypothesis was studied in fairly homogeneous populations, assuming that their phenotypic variability stemmed absolutely from spatial rather than genetic heterogeneity. It was based on single plant performance in two separate trials of a maize hybrid and a wheat cultivar reflecting different level of spatial heterogeneity. In general, the HDs counteracted spatial heterogeneity well, particularly when the number of evaluated entries was limited. There was a suggestion that they do well even in a high number of entries with many replicates per entry. Distribution and layout of spatial heterogeneity across the experimental area did not affect the precision of the HDs. Standardized configuration, which ensures implementation of essential principles met in other experimental models such as blocking, replication and nearest-neighbour (NN) adjustment on the same baseline, renders the honeycomb experimental pattern advantageous over the classical experimental designs like the randomized complete block (RCB), the NN method and the lattice model.

Conservation agriculture (CA) was introduced to farmers in Malawi to address soil degradation, declining crop productivity and the need to adapt to climate variability and change. This research from 2005 to 2014 aimed at analysing the effects of CA on longer-term productivity and profitability compared with conventional systems as practiced in two communities of Central Malawi. CA treatments outyielded conventional ridge tilled control plots in Mwansambo and Zidyana on average by between 22 and 31%, respectively. An economic analysis from 2011 to 2014 found that, on average, income was 50 and 83% greater in CA systems than in conventional systems. The crops were produced with 28 -39 less labour days ha−1 compared with the conventional practice, leading to greater net benefits. Despite the higher returns with CA, there are still challenges with residue retention, weed control, adequate rotations, management of pests and diseases as well as other socio-economic constraints. At the same time, there are opportunities to address these challenges through site-specific and adaptive research using innovation systems approaches.

To evaluate the impact of trash management on sugarcane production and N fertiliser requirements in environmental conditions of Brazilian coastal tablelands, a simulation was conducted with APSIM-Sugar cropping systems model. The model was parameterised for, and validated against results from a long term (over 23 years) experiment comparing the system-burnt trash and green cane trash blanketing (GCTB), in Linhares-ES. Simulations were conducted over two crop cycles (14 years) with different management (100%, 75%, 50%, 25% GCTB and burnt trash), and N fertiliser rates from 0 to 240 kg ha−1 (in 40 kg ha−1 increments) on the ratoon crops, and 75% of these rates on the plant crops. Measured cane yields and soil carbon were simulated well by the model. The RMSE (root mean square error) of predictions in burnt and GCTB treatments were 14.02 Mg ha−1 and 13.45 Mg ha−1 for yield, and 0.09 and 0.13% for soil carbon. In the simulation, the cane yield responded positively to the GCTB systems. Optimum N rates were higher in the 100%, 75% and 50% GCTB than with burnt trash and 25% GCTB reflecting the greater yields under GCTB systems. The response to trash retention was dependent on N fertiliser, and it was smaller or even negative at lower N rates. With adequate N, the positive responses were predicted to occur in all crops after the imposition of GCTB system. The removal of any proportion of the trash reduced the potential sugarcane yield. The simulations showed that average environmental losses of N are likely to be greater from trash-retained systems at all N fertiliser rates.

To evaluate the effects of defoliation on green forage performance and grain yield (GY) variation in barley, five barley genotypes were imposed on three levels of defoliation treatments over two consecutive growing seasons in this study. The results indicated that green forage yields were significantly improved by repeated defoliation. The traits of green forage quality, including the ratio of dry weight to fresh weight, crude ash and calcium content were improved, while crude protein and crude fat were reduced, and crude fiber and phosphorus contents appeared not to be influenced by repeated defoliation. Plant height (PH), GY and other yield components, grain number per spike and thousand kernel weight, were significantly reduced by defoliation over the two growing seasons, while internode length below spike was less affected. Reduction in spike length and the number of spikes per plant were identified in only one year. Correlation analysis revealed that only PH exhibited a positive correlation with GY. Effects of genotype, interaction between genotype and defoliation, and environments on changes of forage yield and quality and GY were also discussed. Our current work provides a feasible approach to select elite barley cultivars with optimal defoliation treatments for both forage and grain uses in barley breeding programme.

Aluminium toxicity is an important abiotic factor limiting the growth and yield of oat plants (Avena sativa L.) and other cultivated species. The objectives of this study were to evaluate the response of oat cultivars at the reproductive stage to aluminium under acid soil conditions and to compare with the responses observed at seedling stage under hydroponic conditions. In the soil, the damage to the above-ground part of the plant was estimated by the morphological response to aluminium, shoot length, shoot dry mass and plant height and, to the below-ground part of the plant as the length of roots and root dry mass. In hydroponics, the primary root regrowth was used to define the level of tolerance. The comparison of the results obtained in acid soil with those obtained in hydroponics demonstrated that both conditions produced essentially the same responses. The use of hydroponic solution can be a valuable tool for phenotyping large populations, especially useful for breeding programmes located in regions were aluminium is not present at toxic levels in the soil.