Numerous technologies have contributed to the recent development of agriculture, especially the advancement in hyperspectral remote sensing (HRS) constituted a revolution in crop monitoring. The widespread use of HRS to obtain crop parameters suggests the need for a review of research advances in this area. HRS offers new theories and methods for studying crop parameters, but much work needs to be done both experimentally and theoretically before we can truly understand the physical and chemical processes that predict these crop parameters. The study focuses on the following elements: 1) The article provides a relatively comprehensive introduction to HRS and how it can be applied to crop monitoring; 2) Current state-of-the-art techniques are summarized and analyzed to inform further advances in crop monitoring; 3) Opportunities and challenges for crop monitoring applications using HRS are discussed, and future research is summarized. Finally, through a comprehensive discussion and analysis, the article proposes new directions for using HRS to study crop characteristics, such as new data mining techniques including deep learning provide opportunities for efficient processing of large amounts of HRS data; combining the temporal and dynamic characteristics of crop parameters and vegetation growth processes will greatly improve the accuracy of crop parameter detection and monitoring; multidata fusion and multiscale data assimilation will become HRS monitoring. Multidata fusion and multiscale data assimilation will become another research hotspot for HRS monitoring of crop parameters.

The efficiency of many intercropping research programmes could be improved if research workers made fuller use of modern statistical knowledge about experimental design. Important statistical considerations for experimental design and plot sampling are reviewed and their relevance to intercropping research assessed. The general philosophy of factorial structure and blocking, and specific ideas on the use of systematic designs and monocrop plots, are discussed.

Groundnuts given a mixture of S35-labelled ground rock phosphate and sulphur at planting were radioactive 14 days later, when go per cent of the seedlings had emerged. Forty days after planting one-third of the total plant-S was from the fertilizer, and the mean recovery of fertilizer-S was 18 per cent by harvest. In field experiments the mixture outyielded ground rock phosphate and was as good as single superphosphate, though drought diminished yields generally. At three sites which were harvested the percentages of applied-S recovered were 12, 20 and 27 per cent. Significantly more P was taken up by the crop receiving the mixture than was recovered from the ground rock phosphate alone.

The yield responses of clonal tea (Clone 6/8) to irrigation and fertilizer were studied in a field experiment (based on the line-source technique) at a high altitude site (1840 m) in the Southern Highlands of Tanzania over a three-year period. In this area (latitude 8°33′S) the annual dry season can last up to six months with potential soil water deficits reaching 600 to 700 mm. In the third year of the experiments yields for the fully irrigated, well fertilized (375 kg N ha−1) treatments had reached 4.9 t ha−1 of made tea. These were reduced by about 2.9 kg ha−1 for each mm increase in the potential soil water deficit. For tea with little or no fertilizer applied the loss of yield was about 1.4 kg ha−1 mm−1. These figures provide a basis for assessing the potential benefits from irrigation where other factors, such as large saturation deficits of the air, do not restrict shoot extension and yield. Yield responses to nitrogen (applied as N:P:K 20:10:10) were essentially linear up to a maximum of about 375 kg N ha−1 in the fully irrigated plots, and 300 kg N ha−1 for the unirrigated plots. Irrigation increased the proportion of crop harvested during the dry season, up to 45% in the fully irrigated treatments. The commercial implications of these results for ‘high’ and ‘low’ input producers are discussed.

Improving farmers’ knowledge of new technologies and creating conducive learning opportunities, with particular attention to the marginalized poor (women and youth), are major factors in the move towards sustainable agriculture. To explore the gender gap in agricultural knowledge acquisition and adoption in West Africa, we used baseline data collected in 2013 and 2014 in five countries (Benin, Côte d'Ivoire, Niger, Nigeria and Togo) with 499 surveyed households. The t-test and Kruskal–Wallis test were used for analysis. The most quoted source for acquiring knowledge on rice farming methods was ‘other farmers’, showing the importance of social capital for rural African farmers. In Benin, a gender gap was noted in rice farmers’ access to agricultural knowledge sources, with women being more advantaged. In Côte d'Ivoire, Niger, Nigeria and Togo, no significant gender gap was observed in rice farmers’ access to agricultural knowledge sources. Regarding the level of knowledge and use of rice farming methods in Côte d'Ivoire and Niger, significant gender gaps were observed. The gender approach to rural development is having impact in West Africa with regard to farmers’ access to agricultural information. However, interactive rural learning approaches (such as farmer-to-farmer video) need to be resorted to make the technologies’ principles well known and improve the ability of marginalized poor to adopt and or innovate with local or limited resources. This study leads to a better understanding of the relationship between gender, knowledge and use of agricultural technologies in order to enhance marginalized farmers’ adoption of improved innovations.

Bambara groundnut (Vigna subterranea) is one of the most promising food legumes in Africa, due to its agronomic and nutritional potential. To take advantage of these attributes, several research programmes gathering agronomic and genetic data are being implemented throughout Africa. In this context, the response of yield and yield components to sowing density and seedbed type were tested in a three-year (2005, 2006 and 2007) field experiment using a bambara groundnut landrace with a semi-bunch growth habit. Three plant population densities: 13 900 plants ha−1, 62 500 plants ha−1 and 250 000 plants ha−1 were coupled with two seedbed types – raised and flat. A factorial trial using a split-plot design with three replicates was set up to analyse seed yield and plant biomass, as well as nine yield components. Sowing density influenced significantly (p < 0.05) seed yield (direct relationship) and most of the yield components (inverse relationship). The highest seed yields were observed on high-density plots (4.11 ± 1.05 ha−1). In contrast, seedbed type and year of experiment did not influence significantly the marketable yield and plant biomass (p > 0.05). This result has been attributed to the suitability of the amount and distribution of rainfall and temperature for the production of bambara groundnut at the target site. Based on the trend of yield response, cultivation of landraces of bambara groundnut characterized by a semi-bunch growth habit at high density on flat seedbeds was suggested in woodland savannas of Côte d'Ivoire to enhance seeds yield and reduce labour.

There is a quest for resource-conserving technologies that can save water, reduce production costs and improve production to address the slow down in productivity growth in the Indo-Gangetic Plains, the cereal bowl of South Asia. Findings from farm surveys are used to evaluate the farm household factors that affect the adoption of zero tillage (ZT) wheat in the rice-wheat systems of India's Haryana State and Pakistan's Punjab province. Three adoption classes are distinguished in each site: ZT adopters, dis-adopters and non-adopters. Bivariate analysis shows that adopters typically have the most favourable values for most of the indicators compiled and the non-adopters the least favourable, with dis-adopters often taking an intermediate position. The study highlights that ZT adoption in the initial diffusion stage is strongly linked to the wealth of the farm household. This indicates the need for closer consideration of equity implications in future research and development. The structural differences between adoption categories also easily confound the assessment of ZT impact.

Enset [Ensete ventricosum (Welw.) Cheesman (Musaceae)] is a multi-purpose and drought-tolerant crop, traditionally grown in Ethiopia. Food from enset has nutritive values similar to potato; it could improve food and livelihood security for many in larger geographical areas. Agronomical advice is needed which requires increased knowledge of management techniques. The purposes of this study were to (i) compare traditional corm pre-treatments when planting for sucker production, (ii) compare all six officially released cultivars regarding sprouting and (iii) investigate the effect of watering on newly buried corms. Emergence rate and number and characteristics of sprouts were recorded. Corms, from 63 two year old plants, were buried in local soil supplied with cow manure in Wolaita Sodo, Ethiopia. Emergence was recorded daily. After nine months, including one rainy season, all suckers (totally 4405) were harvested and individually recorded. Regardless of cultivar, minimum time to emergence was 50 days. Sprouts from split parent corms emerged earlier than from entire. Emergence occurred from 100% of corms, number of sprouts was strongly correlated to cultivar: average 28–106. The cultivars responded similarly to corm splitting: the more pieces the corm was split into, the more sprouts per parent corm. Average pseudostem diameter of the seven largest per parent corm: 8–10 cm for all cultivars, leaf length: 3.1–3.7 m, remaining 2700 smaller suckers: diameter 3 cm (SD 1.8). Watering decreased the average time to emergence and levelled out the differences between pre-treatments. The traditional belief is that watering as well as manure on corm cause rotting; manure is therefore usually put on the soil surface. On the contrary, full emergence and unexpected large suckers may be a result of careful soil preparation with manure applied on corm directly; watering resulted in an even emergence and growth. In conclusion, vegetative propagation of enset is efficient, but methods used and agronomical advice can be improved.

Potato is an important source of food and income in the highlands of East Africa. Identification of superior genotypes for improved agronomic characteristics will enhance tuber yield. Seven promising clones from population B potato selections (quantitative resistance to late blight) obtained from the International Potato Center, two genotypes from population A (qualitative resistance) and three control cultivars were evaluated for three cropping seasons at four locations in western Uganda in order to determine performance and yield stability. The additive main effects and multiplicative interactive (AMMI) model was used for the analysis. The analysis of variance of yield data for genotypes × locations, genotypes × seasons and genotypes × locations × seasons was significant (p < 0.05) showing the variable response of genotypes and the need for stability analysis. The AMMI statistical model showed that the most stable genotypes were 392618.250 (B5) and 392127.270 (B6) (high yield) and 392618.256 (B1), 391049.255 (B2) and 392127.256 (B7) (low yield) and had negligible interactions with the environments. Across environments, the ranking of genotypes for tuber yield was not consistent. The clones 381471.18 (A2), 387121.4 (A1) and cultivar Victoria had high average yields, but these yields were below average in a few environments. Selective deployment of cultivars can improve tuber yield in the highland tropics.

Note: Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation for endorsement by the US Department of Agriculture, Makerere University or Kachwekano Agricultural Research and Development Center.

In a short-term competition experiment in large containers, growth of cotton planted 3 weeks after bermudagrass (Cynodon dactylon), johnsongrass (Sorghum halepense) or purple nutsedge (Cyperus rotundus), was severely reduced; after 10 weeks of competition, weedy cotton weighed only 15 per cent of the weed-free control. Cotton sown before weeds, or weeds planted before cotton, were only slightly affected by competition. Highly significant negative correlations were found between growth parameters of cotton and weeds. Inhibiting effects, and in some cases transitory stimulation, were produced on mustard seedlings by leachate from weed-infested soil and by extracts from subterranean weed parts, suggesting that the competitive effects of perennial weeds are due to nutrient depletion and to biologically active substances.

The line-source sprinkler irrigation system provides a continuously variable water application rate, which depends on distance from the line-source. The system is simple to set up and minimizes the amount of land required for experimental work. As the irrigation treatments are allocated systematically, the assumptions of analysis of variance are not satisfied. It is proposed that the effects of irrigation treatments be assessed using analysis of covariance, with distance from the sprinkler line as covariate, thus adjusting for a linear fertility trend. This method of analysis provides an approximate residual mean square for the fitting of response curves, but could be vulnerable to a quadratic fertility trend.

Forty different cultivars of cassava were grown in unreplicated plots at a plant population of 20,000 plants/ha in fertile soil. Harvests were taken at 4, 6, 8, 10 and 12 months after planting 18 varieties. The characteristics of the two highest yielding varieties, M Colombia 113 (66 t/ha) and M Colombia 22 (32 t/ha), were compared with the other types. M Colombia 22 is an early type (25 t/ha after 6 months) with a very high harvest index; M Colombia 113 yields little better than average 6 months after planting. High yield is associated with a balance between leaf production and root production, so that leaf area index does not decline excessively in the later growth stages. Changing canopy structure is unlikely to increase yields.

In order to understanding the changes in morpho-physiological traits of wheat cultivars released from 1940 to 2000 in Iran and to determine the association of these traits with grain yield, an experiment was conducted with 15 wheat cultivars released over the past 60 years using an randomized complete block design with four replications. The experiment was conducted on an experimental farm of Arsanjan Islamic Azad University in 2005/6 and 2006/7. Results indicated that cultivar grain yield was significantly correlated with year of release over the 60 years (r = 0.878, p < 0.01). Harvest index and biological yield increased significantly with increasing grain yield. The change in the photosynthesis rate was not significant during this period but transpiration rate and stomatal conductance and chlorophyll index increased significantly. Among yield components, grain number per ear increased significantly but increase in ear number was not significant. Plant height decreased significantly in new cultivars. In conclusion the results showed that wheat yield improvement in Iran is associated with increasing harvest index, grain number per ear, transpiration rate, stomatal conductance and decreasing plant height.

A simple Stress Time Index (STI) for predicting yield loss in the tea crop due to drought is proposed, based on the daily summation of the difference between the potential soil water deficit and a specified limiting value. Validation of the technique with results from a line-source irrigation experiment with a single clone in the Southern Highlands of Tanzania suggests that there is a linear relationship between STI and relative yield loss during the warm dry season. As a result of changes in the composition of the shoot population at each harvest the apparent critical deficit at which shoot growth is restricted increases from below 20 to 300 mm as the dry season progresses. The rate of yield loss with increasing STI also varies through the dry season for the same reason.

Potassium (K) is an essential nutrient and abundant cation in plant cells. The application of K+ could alleviate abiotic stress. However, it was reported that the alleviation of K+ on salt-stressed plants only happened when K+ concentration was low. Most studies were focused on effects of sodium salts on plants in salty soils, and little information was reported about potassium salts, especially a higher level of potassium in alkaline salts. To explore the effects of K+ in alkaline salts on plant growth, and whether it had a same destructive impact as Na+, we mixed two alkaline sodium salts (ASS) (NaHCO3:Na2CO3 = 9:1) and two alkaline potassium salts (APS) (KHCO3:K2CO3 = 9:1) to treat 10-day-old wheat seedlings. Effects of ASS and APS on growth, photosynthesis, ions absorption and solutes accumulation were compared. Results indicated that effects of potassium salts in soil on plants growth were related to K+ concentration. Both growth and photosynthesis of wheat seedlings decreased, and the reduction was higher in APS treatment than in ASS treatment at 40 mM alkalinity. ASS treatment absorbed Na+, competing with K+ and free Ca2+, and inhibited the absorption of inorganic anions. APS treatments accumulated K+ and reduced the absorption of anions, with no competition with other cations. Both APS and ASS treatments promoted free Mg2+ accumulation and inhibited H2PO4−uptake. The reduction of H2PO4− promoted organic acid synthesis indirectly. Soluble sugar and proline accumulation were also related to the alkaline condition and extra K+ addition. In conclusion, excess potassium ions in soil, especially in alkaline soils, were harmful to plants. APS was another severe salt stress, intensity of which was higher than ASS. The growth and physiological response mechanisms of wheat seedlings to APS were similar to ASS. Both inorganic ions and organic solutes took part in the osmotic adjustment. Differences for APS depended on K+, but ASS on Na+.

The yield gap has arisen again as a focus for agricultural research to ensure food security and economic growth for farmers around the world. To examine this renewed interest, we carried out a review of key literature in the field of yield gap analysis to identify important gaps in research and analysis. In so doing, both the complexities in yield gap studies emerged along with some significant omissions. Much of the literature and research on the yield gap has been framed by larger concerns and initiatives to raise agricultural productivity. This focus has led to an emphasis on technical solutions such as crop breeding, fertilizer application and other methods to increase production. However, this concentration on the technical usually ignores the wider social, economic and political context that shapes farmer decision-making about agricultural production. This context can either discourage or enable farmers to close their yield gap. Additionally, the impact of increased agricultural production through certain technical solutions also often overlooks the wider impact on the landscape and the ecosystem services which underpin agricultural production and livelihoods. We argue that increasing agricultural productivity, and closing the yield gap, must be addressed with this broader approach.

The effect of the root hemiparasitic angiosperm Striga hermonthica on the gowth, photosynthesis and partitioning of biomass in maize was studied in glasshouse experiments in two seasons. In both seasons, nitrogen was applied to the plants at rates equivalent to 20, 60 and 120 kg ha−1. There was no significant Striga×nitrogen interaction on the responses measured. Averaged across all nitrogen treatments, maize plants infected with S. hermonthica had smaller leaf areas and accumulated less biomass, than did uninfected plants. The leaf area of infected and uninfected plants increased asymptotically from emergence to the final harvest (about the 18-leaf stage) at which time the leaf area of infected plants was 63% that of uninfected plants. The rates of photosynthesis of the youngest, fully expanded leaves of infected plants, averaged across N treatments, were significantly lower than for uninfected plants. However, stomatal conductance and the sub-stomatal CO2 concentration were unaffected by Striga infection. Although infection with Striga significantly reduced shoot biomass (dry weight at final harvest was 37% that of uninfected plants in 1995 and 63% in 1996), there were no significant effects of Striga infection on root biomass so that the infected plants partitioned a significantly greater proportion of their total biomass to roots compared with the uninfected plants. The allometric coefficients, though, were similar for both infected and uninfected plants. Averaged across infected and uninfected plants, application of nitrogen increased total leaf area per plant and root and shoot biomass but did not change the proportion of total biomass partitioned to roots. These results did not show a major effect of nitrogen on the relative growth response of maize to infection with Striga.

Barley (Hordeum sativum) and field beans (Vicia faba) were grown in pure stands, alternate-row mixtures and within-row mixtures in two field experiments. In both experiments the Land Equivalent Ratio (LER), based on seed yield, was consistently greater than 1.0 only when the crops were grown in alternate rows. The LER was greatest (1.8) when the mixture included more barley than beans. Reasons for the yield advantage of alternate row planting are discussed. Barley was more competitive than beans in mixtures, but this was not significantly affected by planting pattern.

Water use efficiency of maize (Zea mays) and cowpea (Vigna unguiculata) was investigated, with and without tillage, under four irrigation frequencies in which 12 mm of water was applied at 2, 4, 8 and 12 day intervals, using a sprinkler system. Both maize and cowpea under no-tillage yielded more than with conventional ploughing. Water use efficiency of maize without tillage was 18·3, 17·5, 57·8 and 100% greater than with tillage at irrigation frequencies of 2, 4, 8 and 12 days respectively. Whereas the leaf water potential of cowpea was not affected by tillage, that of maize was generally higher for no-tillage compared with conventional ploughing.

The Agricultural Technology Improvement Project (ATIP) has been conducting on-farm research in Botswana with the goal of identifying improved arable production technologies. In an effort to increase the role of farmers in technology design and assessment, ATIP set up farmer groups that meet on a regular basis to discuss farming problems and on-farm trials. This article reviews and evaluates ATIP's experiences with farmer groups. A typology of technology development groups is proposed and group management issues are discussed.