Trials in Kenya have shown that yields of tea clones can be increased significantly by grafting onto suitable rootstocks, with the best combinations giving profitable yield increases compared to straight cuttings. However, stock × scion interactions were significant, and not all clones gave useful responses to grafting even onto the best rootstocks, so combinations must be tested individually before commercial planting is considered. The effect of grafting was to increase the number of shoots harvested, with little change in mean shoot weight. Grafting had little or no effect on quality of the tea produced. Attempts to find a method of identifying good rootstocks without testing them in grafting trials were inconclusive.

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.

The goal of this study was to evaluate the effects of thinning eucalyptus trees on yield and nutritive value of corn for silage and palisadegrass in a crop–livestock–forest integrated system and to evaluate the total aboveground biomass yield in systems with and without trees. Plant variables, as well as the incidence of photosynthetically active radiation (PAR) and soil moisture, were evaluated between October 2016 and March 2018 in São Carlos, Brazil, in a crop–livestock–forest and a crop–livestock system. In the crop–livestock–forest system, eucalyptus trees (Eucalyptus urograndis clone GG100) were planted in April 2011, in single rows, with 15 × 2 m spacing. In 2016, the trees were thinned, and the spacing was changed to 15 × 4 m. The treatments comprised measurements at 0.00, 3.75, 7.50, and 11.25 m from the trees of the North row in the integrated crop–livestock–forest (iCLF) system and integrated crop–livestock (iCL) system. Palisadegrass (Urochloa brizantha) was sown after harvesting the corn. Corn yields were similar between treatments, with an average of 13.6 Mg ha−1. Corn for silage presented a higher percentage of grain in total biomass in the crop–livestock–forest positions (41.4 and 42.1%) than in the crop–livestock system (35.6%). No differences in forage accumulation were observed. Crude protein content in corn for silage and palisadegrass was higher in the crop–livestock–forest treatments than in the crop–livestock system. Such results indicate that thinning was favorable to production in the crop–livestock–forest system. Total aboveground biomass yield was higher in the iCLF system, indicating better land use for this type of integrated system.

We describe the insertion and reinstatement of a simple lined access pit that allows for the permanent installation of tensiometers, piezometers, etc. in soil that is cultivated annually. The presence of the access pit did not affect the hydrology of the soil in its vicinity. We give an example of the application of results from tensiometers permanently installed in this way.

Established plants of bermudagrass (Cynodon dactylon (L.) Pers.), johnsongrass (Sorghum halepense (L.) Pers.) and purple nutsedge (Cyperus rotundus L.), grown in containers, were repeatedly clipped to the ground from spring to winter, at monthly and bi-weekly intervals. Regrowth of bermudagrass was markedly reduced after monthly clippings, but all plants regrew in the following March; there was no regeneration in March of bi-weekly clipped plants. Severe decrease of regrowth of clipped johnsongrass occurred after bi-weekly or monthly clippings, but a quarter of the clipped plants regenerated in the following March. Nutsedge was more resistant to clipping than the other two species and all clipped plants regrew vigorously in the following March. Repeated clipping reduced the rhizome length or tuber number and the dry matter content in the regrown plants in proportion to the frequency of clipping.

A micrometeorological experiment was carried out in an area of soyabean cultivation located in northeastern Para state, Brazil, in order to evaluate impacts on the local energy balance due to replacement of forests by soyabean. The meteorological data from forest ecosystems were collected in Caxiuanã forests located in central Para. The energy balance components were obtained using the Bowen ratio technique. Differences in energy balance components between ecosystems were significant during the soyabean growing season and more significant between growing seasons. During the soyabean growing season mean impacts of −15%, −9% and −27% on net radiation, latent heat flux (LE) and sensible heat flux (H), respectively, were observed. At specific soyabean stages, LE was higher than in the forest because of the high soyabean surface conductance of water vapour. However, during the production off-season the impacts were more significant (p < 0.05), showing a reduction of 78% in LE and a substantial increase in H (84%) because of the absence of vegetation cover over this period.

Horsegram (Macrotyloma uniflorum) is sown late in the rainy season by resource-poor farmers in marginal, drought-prone areas of India. Sowing and early crop growth coincide with declining rainfall so crop establishment is often poor and yields are low. Horsegram is a ‘neglected’ crop and farmers' choice of varieties to grow is limited to poor-yielding landraces or to modern varieties for which access to seed is limited. In on-station trials, we compared the yield and relative merits over three years of seven varieties potentially suited to conditions in Jharkhand State and sown with or without priming by soaking seeds in water prior to sowing. Yield stability of the varieties was tested using data from these and five additional trials. Farmers' opinions were recorded during six participatory exercises based on farmers' trials, and their rankings were compared with those from the on-station evaluations. Significant variety × year interactions were observed and yield was generally inversely proportional to drought. Both linear and non-linear genotype × environment interactions were significant for all varieties. Variety BK 1 was the most desirable with stable yields across environments and a higher overall mean grain yield. Variety VLG 1 was unresponsive to more favourable environments but yielded more in the low yielding environments. However, it was the earliest to mature and was identified as a promising variety, which farmers preferred for its grain and brown seeds. This could be used to diversify farming systems with additional options for farmers. Although soaking seeds for 12 h was most effective in increasing germination in an in vitro study, soaking for 8 h before sowing increased emergence and final stand by 11 % and grain yield by 10 % averaged over all varieties and years. Soaking advanced flowering by 1.3 d and maturity by 1.9 d. All varieties responded positively to soaking and did so in all three years, although the response was stronger in drier years.

Daily measurements of moisture by neutron probe showed an erratic pattern of ET in the Sudan Gezira, attributed to the redistribution of water and development of cracks in a drying profile. However, dividing an irrigation cycle into periods of 3–5 days revealed a unique trend of ET that was consistently low in the early period, increased to a maximum in the middle, and fell off at the end. Roots suffer from anaerobic conditions for about 5 days after flooding but subsequent drying and cracking improves soil aeration that leads to final depletion of profile moisture and depression of ET.

The objective of this study was to identify whether grain yield in four contrasting rice cultivars is limited by supply of assimilate to fill the grains or by sink capacity to accept the assimilate. Grain yield was limited mostly by sink capacity, with little variation in single grain weight among cultivars, but an old cultivar showed some ability to adjust single grain weight. Sink capacity was very sensitive to variation in assimilate supply immediately after anthesis. Reduction in assimilate supply in the anthesis to early grain filling period reduced filled grain percentage and grain yield, particularly in high yielding cultivars with a large number of grains per panicle.

Growth and water use of sole crops and intercrops of morphologically contrasting maize and pea cultivars were measured in two years. The maize cultivars were Nancis with erectophile and Sophy with planophile leaves and the pea cultivars Maro a leafy pea and Princess a semi-leafless pea. In the first part of the season water use was lower for sole maize but intercrops and sole pea used similar amounts of water. By 90 days after sowing, when peas had matured, all crops had used similar amounts of water. Maize had slightly greater water use efficiency than peas. Cultivars Nancis and Princess tended to have greater water use efficiency than Sophy and Maro respectively. Intercrops produced more dry matter than sole crops and therefore had consistently greater water use efficiencies.

Competition from weeds is one of the major biophysical constraints to rice (Oryza spp.) production in sub-Saharan Africa. Smallholder rice farmers require efficient, affordable and labour-saving weed management technologies. Mechanical weeders have shown to fit this profile. Several mechanical weeder types exist but little is known about locally specific differences in performance and farmer preference between these types. Three to six different weeder types were evaluated at 10 different sites across seven countries – i.e., Benin, Burkina Faso, Côte d'Ivoire, Ghana, Nigeria, Rwanda and Togo. A total of 310 farmers (173 male, 137 female) tested the weeders, scored them for their preference, and compared them with their own weed management practices. In a follow-up study, 186 farmers from Benin and Nigeria received the ring hoe, which was the most preferred in these two countries, to use it during the entire crop growing season. Farmers were surveyed on their experiences. The probability of the ring hoe having the highest score among the tested weeders was 71%. The probability of farmers’ preference of the ring hoe over their usual practices – i.e., herbicide, traditional hoe and hand weeding – was 52, 95 and 91%, respectively. The preference of this weeder was not related to gender, years of experience with rice cultivation, rice field size, weed infestation level, water status or soil texture. In the follow-up study, 80% of farmers who used the ring hoe indicated that weeding time was reduced by at least 31%. Of the farmers testing the ring hoe in the follow-up study, 35% used it also for other crops such as vegetables, maize, sorghum, cassava and millet. These results suggest that the ring hoe offers a gender-neutral solution for reducing labour for weeding in rice as well as other crops and that it is compatible with a wide range of environments. The implications of our findings and challenges for out-scaling of mechanical weeders are discussed.

Application of biochar to rice has shown to elicit positive environmental and agricultural impacts due to its physicochemical properties. However, the relationship between greenhouse gas (GHG) emissions, rice yield, and soil nutrient status under biochar amendment remains unclear. In this study, rice yield and methane (CH4) and nitrous oxide (N2O) emissions were quantified in response to biochar application rate (0, 10, 20, and 40 t ha−1) to early and late subtropical rice cropping systems. We found that application of 10 t of biochar ha−1 to early rice reduced average CH4 emission fluxes, while all biochar application rates diminished average emissions in late rice paddy. Total global warming potential (GWP) and GHG intensity (GHGI) were inherently greater in late rice than early rice cropping. In early rice, GWP and GHGI were found to be similar between soil control, 10 and 20 t of biochar ha−1 treatments, although the largest occurred in the 40 t of biochar ha−1 treatment, whereas in late rice cropping, they were not affected by biochar application rates. Compared to the nil-biochar application, biochar application at varied rates did not affect rice yield. However, compared to 10 t biochar ha−1, increasing biochar application rate to 40 t ha−1 significantly decreased total rice yield (sum of early and late cropping). Generally, application of biochar increased soil salinity and total Fe and Fe2+ content while reducing soil bulk density. Temporal effects of biochar application were noted on CH4 emission flux, soil temperature, and soil Fe2+ and Fe3+ in early rice; and soil temperature, salinity, NH4+-N, NO3−-N, and soil Fe2+ and Fe3+ in late rice. This study confirms that the application of biochar at the lower rate of 10 t ha−1 is optimal for maintaining rice yield while reducing GHG emissions. Moreover, the study demonstrates the potential benefit of biochar in sustainable subtropical rice production.

Growth and developmental stages of Alaska peas, from planting to dry seed maturity, were examined and described. Node counts were determined by designating the cotyledonary node as 0 and counting successive nodes up the plant to the highest visible one with unexpanded stipules. Five additional nodes are already determined in the shoot apex beyond the highest one with unexpanded stipules, indicating that damage to the shoot apex would result in losses of flowers and fruits that would have developed later if damage had not occurred.

A four-year study from 1958 to 1962 showed that time of application of fertilizer nitrogen greatly influenced the yield of grain, the percentage of nitrogen and the crude protein of the grain under Nigerian conditions characteristic of the early maize cropping season from March to July. Split applications of nitrogen fertilizer significantly increased maize grain yield by 35 per cent when two equal doses were given one month and two months after planting; and by 31 per cent when four equal doses were supplied at planting and one month, two months and three months after seeding. Yield was significantly reduced when application was delayed two months after planting. High yields of maize were not obtained by supplying the whole of nitrogen fertilizer at one time, eidier at sowing or any time later during the growing season. However, applying all of the nitrogen fertilizer one month after planting significantly increased the percentage of nitrogen and of the crude protein content of the grain. The maize ear weight was favourably influenced by spreading the nitrogen application over the three-month period of the maize growth.

Continuous cropping of a tropical Ultisol with or without nitrogen fertilizer increased soil acidification and reduced soil organic matter and productivity. Addition of nitrogen fertilizer failed to increase yields. This was apparently due to the decline in soil pH, an increase in the amount of soluble aluminium, and consequent inefficient utilization of added nutrients. Continuous use of ammonium sulphate as a nitrogen source hastened the development of both surface and subsoil exchange acidity.

Improved upland rice cultivars introduced in Volta Region, Ghana, have been perceived to store poorly compared to farmers' traditional cultivars. A survey was conducted in 2003 in the Hohoe district of this region, where a Participatory Varietal Selection programme had started in 1997, to gain insight into farmers' seed production and storage practices that are likely to affect seed quality in storage. Farmers rated keeping quality (p < 0.001), tolerance to storage pests (p < 0.001), seed quality (p < 0.001) and establishment of their local cultivars Kawomo, Viono and Wuwulili as much better than the improved cultivar IDSA 85. Initial seed moisture content ranged from 12.8 to 18% and germination from 0 to 82%. There was a significant relationship between seed moisture content and duration of drying prior to storage (p < 0.001) and storage method (p = 0.015). Germination loss in storage was rapid at high moisture content and slow at low moisture content. Between 60 and 80% of seeds germinated after six months storage at 12.8% moisture content. The viability equation predicted accurately germination of farmer-saved seed stored under ambient temperature in Ghana. Except for the japonica rice cultivar WAB 126-18-HB, the traditional cultivars Kawomo, Viono and Wuwulili survived better in storage than improved cultivars. There is a need to improve seed quality of improved cultivars if farmers are to benefit from their higher yields and grain quality and to improve storage practices.

Seed-oriented planting provides a manner to influence canopy structure. The purpose of this research was to improve maize light interception using seed-oriented planting to manipulate leaf azimuth across the row thereby minimizing leaf overlap. To achieve leaf azimuths oriented preferentially across the row, seeds were planted: (i) upright with caryopsis pointed down, parallel to the row (upright); and (ii) laying flat, embryo up, perpendicular to the row (flat). These treatments were compared to conventionally planted seeds with resulting random leaf azimuth distribution. Seed orientation effects were contrasted with three levels of plant population and two levels of hybrid specific canopy structures. Increased plant population resulted in greater light interception but yield tended to decrease as plant population increased. The planophile hybrid produced consistently greater yields than the erectophile hybrid. The difference between planophile and erectophile hybrids ranged from 283 to 903 kg ha−1. Overall, mean grain yield for upright and flat seed placement increased by 351 and 463 kg ha−1 compared to random seed placement. Greater cumulative intercepted photosynthetically active radiation (CIPAR) was found for oriented seeds rather than random-oriented seeds. At physiological maturity upright, flat and random-oriented seeds intercepted 555, 525 and 521 MJ m−2 of PAR, respectively. Maize yield responded positively to improved light interception and better radiation use efficiency. Under irrigated conditions, precision planting of maize increased yield by 9 to 14% compared to random-oriented seeds.

Low genetic diversity acts as a major bottleneck in garden pea breeding, and diverse parents are required to generate new genetic material. The diversity of parents utilized in hybridization programme was ascertained following simple sequence repeats (SSR) markers. Thirty-six homozygous F7 progenies were isolated from three intervarietal crosses through shuttle breeding programme over a period of 6 years (2009–2014). Two experiments were conducted for two consecutive years 2014/15 and 2015/16, for evaluating the agronomic performance of progenies along with four commercial control cultivars. Analysis of variance (ANOVA) revealed that genotype, growing year and their interaction had significant effects on most of the traits. Line ‘DPP-SP-6’ recorded significantly higher pod yield/plant in comparison to all other genotypes in 2014/15, 2015/16 and for pooled over years. In addition, ‘DPP-SP-22’, ‘DPP-SP-7’ and ‘DPP-SP-17’ also performed statistically at par with best-performing check ‘Pb-89’ during both the years. These superior lines, in general, showed better pod filling, green pod colour, high shelling, sweetness and resistance to powdery mildew disease. These superior progenies could act as an alternative to the popular check varieties after their exhaustive evaluation over environments.

Trees are important sources of food in both the humid and semi-arid tropics. Some species have been exploited for centuries and are widely distributed around the world, others have been cultivated only in limited areas, while most are still essentially wild. The potential for rapid genetic improvement by clonal selection is enormous and well-proven by the recent history of some species. Trees can yield as much food per hectare as most C3 annual crops – although special problems may have to be overcome to ensure regular bearing of fruit and nut trees. Trees also offer great ecological and social benefits.