Shortages of hired labour are leading to greater interest in mechanisation for crop establishment in smallholder agriculture. Due to small field sizes, mechanised planters mounted on four-wheel tractors are not a suitable technology. The Versatile Multi-crop Planter (VMP) was developed for zero tillage (ZT), strip planting (SP) or single pass shallow tillage (SPST) on flat land and for forming and planting on tops of beds, each in a single pass operation, when mounted on a two-wheel tractor (2WT). The aim of the present study was to evaluate the field performance of the VMP in comparison to conventional broadcast seeding and full rotary tillage (2 to 4 passes; called CT) for establishing chickpea (Cicer arietinum L.), jute (Corchorus olitorius L.), lentil (Lens culinaris Medikus), maize (Zea mays L.), mung bean (Vigna radiata L. R. Wilczek), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) in 15 locations of Bangladesh. Plant populations emerging from all single pass operations viz. SP, ZT, and bed planting (BP) were generally satisfactory and in 12 out of 15 experiments plant populations after SP were similar to or greater than after CT. In addition, SP gave comparable or greater plant populations than SPST and BP planting methods. Overall, the SP planting achieved comparable yields and lower costs of establishment than CT. We conclude that effective and reliable planters are now available for sowing a range of crop species on small fields with minimum soil disturbance. This opens up realistic options for the development of mechanised conservation agriculture suited to small field sizes.

In an experiment on genotype × environment interactions in tea (Camellia sinensis), yield differed between the genotypes at all sites. The highest yield in the third year after planting was 3760 kg ha−1 for clone S15/10 at site 4 (1800 m altitude), while the lowest was 1610 kg ha−1 for clone 6/8 at site 1 (2200 m). The dry matter contents of harvested shoots from each clone ranged from 0.24 for clone TN14-3 down to 0.19 for clone S15/10. Yield response to soil water deficits was more pronounced at site 4, where larger deficits were observed. Hail damage affected the yield of two sites and a temperature influence on recovery was evident.

Genotype by environment (G x E) interactions for grain yield were investigated in 13 perennial rice (Oryza sativa L./Oryza longistaminata) derivatives over three sites and 2 years in Lao PDR. Genotype accounted for 29.0% of the total sum of squares, with environment and the G x E interaction responsible for 60.2 and 10.8%, respectively. Cluster analysis identified three environment and six genotype groups, which accounted for 49.7, 98.0 and 42.8% of the E, G and G x E sums of squares, respectively. Principal component axes 1, 2 and 3 accounted for 54.0, 30.6 and 11.7% of the G x E sum of squares, respectively, with PCA1 indicating yield potential, PCA2 timing of cessation of rainfall in the 2011 wet season, and PCA3 environmental stresses affecting regrowth in the 2012 wet season. Genotype groups differed in adaptation to these contrasting conditions. G6 (Line 213, 240 and RD23) was widely adapted to all environments, with G5 (Line 248) being especially adapted to the 2012 environments. G3 and G4 were neutral, though G3 (Line 53) showed some preference for the Na Pok environments. G1 and G2 were poorly adapted everywhere, with the tall and late G1 (Line 11) being especially poor at Na Pok 2011 in a dry finish. While yields were lower in 2012, all derivatives survived the dry season with access to life-saving irrigation. This is promising, as the annual rice RD23 was unable to ratoon under these conditions, and had to be re-sown. Importantly, Line 213, 240 and 248 yielded comparably to RD23 from regrowth in 2012. Development of perennial rice should target rainfed and especially upland environments.

Biochar application appears to be a promising method to improve soil physicochemical and biological properties by increasing soil carbon. Along with the influence of hardwood biochar on wheat growth, yield and soil quality for a period of two years, this study also evaluates the major soil parameters to be taken as minimum data set while assessing the impact of hardwood biochar in an acidic sandy loam soil. Five fertilizer treatments combining inorganic fertilizers and biochar were applied: unfertilized control (T1); 100% NPK (T2); 5 Mg ha−1 biochar (T3); 100% NPK + 5 Mg ha−1 biochar (T4); and 50% N + 100% PK + 5 Mg ha−1 biochar (T5). Biochar application (T3 vs. T1; T4 and T5 vs. T2) significantly increased leaf chlorophyll content, net photosynthesis rate, leaf N concentration and above and below-ground biomass, with improved wheat yield and grain quality (total grain protein and carbohydrate). Soil pH, water-holding capacity, available nutrients (N, P and K), organic carbon and its fractions also enhanced in biochar applied plots with reduced bulk density. Increased activities of soil enzymes urease, phosphatase, dehydrogenase, fluorescein di-acetate and arylsulphatase were recorded in biochar treatment along with significant increase in N recovery index (22%) and agronomic efficiency (40%). Multivariate analysis identified activity of phosphatase, pH and humic acid to fulvic acid ratio as the indicators to explain the total variance from biochar addition in acidic sandy loam soil under wheat cultivation. Soil quality index showed a significant improvement when biochar was added with reduced N doses (T5). This study confirms the efficacy of biochar as a soil conditioner when applied with reduced N fertilizer and would be a sustainable option to improve wheat production and soil quality in acidic sandy loam soils of northeast India.

Aerobic rice is considered a viable agro-technology to cope with the looming crisis of water supply that threatens the sustainability of irrigated rice production systems. Rice adapted to aerobic conditions requires less water than that grown under conventional irrigation management. A field study was conducted at Cuttack, India, during the dry season (January–May) in 2005 and 2006 to determine the critical soil moisture regime at the root-zone depth (30 cm) for sustaining optimum growth and grain yield of aerobic rice variety ‘Apo’ (IR 55423-01). Irrigation at 0, 20 and 40 kPa soil moisture tension resulted in similar grain yields (4.90–5.25 t ha−1 in 2005 and 4.35–4.50 t ha−1 in 2006). The seasonal water requirement in treatments receiving irrigation at 20, 40 and 60 kPa soil moisture tensions was 28.4, 42.8 and 60.7% lower than that at 0 kPa soil moisture tension, but the yield declined significantly at 60 kPa, i.e. by 42.8% in 2005 and 36.7% in 2006. Irrigation at 40 kPa soil moisture tension ensured maximum water productivity of 0.90, 0.47 and 0.53 g grain kg−1 water with respect to evapotranspiration, irrigation plus rainfall and irrigation alone, respectively. Thus, irrigation at 40 kPa soil moisture tension may be considered critical for optimum grain yield and maximum water productivity of aerobic rice in Indian cultivation conditions.

The after effects of three years' continuous cropping with sole millet, sole cowpea or a traditional millet/cowpea intercrop were compared using five levels of nitrogen fertilizer. The continuous sole cowpea system had reduced the carbon to nitrogen ratio more than the continuous sole millet or the traditional intercrop. The test crop millet yielded much more, and its uptake of nitrogen and phosphorus was greater, when it followed sole cowpea than when it followed sole millet or the traditional millet/cowpea intercrop. The three years' continuous sole cowpea had an effect equivalent to the application of 205 kg N ha−1 on the test crop of millet. It also caused the greatest reduction in Striga infestation in the test crop. It is therefore recommended that cowpea cultivation be increased in the Sahel.

Trials on leaf abscission of cassava led to the conclusion that the leaf lamina is necessary, and must receive light, to prevent abscission of the petiole. The abscission rate of old leaves is increased by the presence of an active apex, but is not affected by the carbohydrate requirements of the roots.

A field technique to screen large numbers of pearl millet and sorghum lines for seedling emergence through soil crusts is described. Seeds were sown on raised broad beds in an Alfisol field. The beds were smoothed after sowing with a bed shaper. Thirty five mm of water was applied from two parallel lines of sprinklers at a rate of 14 mm per hour. A crust of relatively constant strength in different tests developed as the surface dried out. The crust was broken in the control treatment with a crust breaker. The ratio of emergence under crust to that under control (c/u ratio) was used to classify the test materials.

Echinacea purpurea has been introduced in to Taiwan and grown successfully. However, information regarding the effects of the growing climate on its active constituents (e.g. caffeoyl derivatives) and biomass production is very limited. In this study the biomass of field-grown E. purpurea plants harvested during three different crop seasons was compared. The content of caffeoyl phenols and the production of aerial plant parts were also assayed. The results indicated that both morphological and agronomic traits were affected by crop season, with spring-grown plants producing more stems and flowers but fewer leaves than autumn-grown plants. Autumn-grown plants produced more caffeoyl phenols, particularly cichoric acid and caftaric acid, in leaf and flower tissues than spring grown plants. Thus, transplanting E. purpurea seedlings in the autumn and harvesting the aerial parts at the beginning of winter first, and then harvesting the rhizome-regenerated plants again in the following summer are technically feasible. This farming system would give commercial cultivation of E. purpurea in Taiwan a great competitive advantage over other growing regions, provided that an environmentally suitable population is selected and established in Taiwan.

Common bean (Phaseolus vulgaris L.) germplasm was screened for resistance to charcoal rot (Macrophomina phaseolina) under field conditions at Kiboko and Katumani, eastern Kenya. Of the 313 bean accessions evaluated, 50 lines were resistant and six were tolerant to M. phaseolina, the charcoal rot incidence was less than 25% and between 25% and 50% for the resistant and tolerant lines respectively. Yields ranged from 135 to 1051 kg ha−1 compared with 55 kg for the susceptible control A464. Time to maturity did not seem to influence or affect the susceptibility or resistance to M. phaseolina of the various bean accessions.

Three alternate-row intercrop experiments of sorghum (Sorghum bicolor)–cowpea (Vigna unguiculata) and/or millet (Pennisetum glaucum)–cowpea were grown at plant densities of 20 000 to 80 000 plants ha−1 at two locations in northern Nigeria between 1990 and 1992 to examine relations between yield and plant density. These relations were examined using the reciprocals of yield per plant to determine effects of environment, species and genotype on the theoretical maximum yield and optimum plant density. The intercrops were dominated by cereals, and cowpea biomass (BY) and seed yield (SY) were <10% of cereal BY and SY. Cowpea yields decreased as cereal plant density (D) increased, whereas cereal and total intercrop yields increased asymptotically with increasing D. Biomass yield of all intercrops responded to increasing D in a similar manner and the theoretical maximum intercrop BY was 12 290 kg ha−1 in all experiments. The response of SY to D varied among intercrops and was greatest and least with early and late maturing cereals respectively. The optimum D required to produce 90% maximum intercrop BY and SY varied between 15 600 and 30 000 plants ha−1, and 0 (no response to D) and 120 000 plants ha−1 respectively, and was higher for sorghum than for millet intercrops. The implications of these responses for agronomic management and germplasm improvement of cereal–cowpea intercrops are discussed.

Smallholder farmers in Malawi are faced with the challenge of managing complex and dynamic farming systems while also adapting to change within volatile agroecological conditions. Moreover, management decisions are influenced by a combination of local knowledge, expert recommendations and on-farm experimentation. Although many smallholder farmers actively experiment with new crops and technologies, little is known about the prevalence of experimentation or the types of experiments farmers conduct. This study examined the decision-making processes of experimenting farmers to explore the drivers of on-farm experimentation. Using a mixed-methods design that incorporated field observations, survey data and in-depth interviews, we identified numerous examples of experiments with new crops, varieties and techniques that had been executed either independently or through participation in an agricultural development project. Results of quantitative and qualitative analysis reveal that smallholder farmers in Malawi across a range of socioeconomic characteristics are inclined to experiment, and gender roles in agricultural experimentation vary widely. While experimental methods differ between farmers, there are commonalities in the drivers of experimentation, including adapting to climate change, improving soil health, improving nutrition and generating income. Smallholders have a great capacity for experimentation, and their knowledge, experience, preferences and priorities – if properly understood and incorporated – could ultimately benefit both future agricultural development projects and their participants.

Two maize cvs, FARZ 23 and FARZ 25, were grown at three densities (37,000, 53,000 and 80,000 plants/ha) in 1979 and 1980. Leaf area index (LAI) increased with increase in plant population and was at a maximum at mid-silk. Grain yield was highest at 53,000 plants/ha. There was no relation between LAI and grain yield but there was a positive correlation between LAI and total dry matter yield.

This study demonstrates a relationship between earliness of ripening and stalk elongation which could be useful in a sugarcane selection programme. Sixty-four sugarcane genotypes with contrasting ripening behaviour were grown in a quadruple-lattice design and ordinary logistic curves were shown to give the best fit between stalk height and time. Genotypes with early high sucrose contents gave logistic curves with earlier inflection points and steeper slopes at the point of inflection. The inflection point was shown to be a reliable indicator of time of ripening and it was suggested that stalk height per se could be considered as a selection criterion for earliness of ripening in sugarcane.

Soil fertility decline and fallow effects were studied in Ferralsol-Acrisol catenas of plantations of sisal (Agave sisalana) in north-east Tanzania. The fertility of Ferralsols that had been subject to continuous sisal cultivation in the absence of fertilizers was extremely low but that of Ferralsols that had been under 18 years of bush fallow or under secondary forest was slightly better. Acrisols that had been under continuous sisal cultivation were less depleted than the Ferralsols because of greater intrinsic fertility. A comparison of soil analytical data from the 1950s and 1960s with recent data from the same sisal fields showed that the topsoil pH of the Ferralsols had decreased by 1.5 (r2 = 0.807) and that of the Acrisols by 1.2 (r2 = 0.494) under continuous sisal cultivation. Thus there had been a serious decline in soil fertility under sisal cultivation, and this decline was not adequately reversed by fallowing.

Soil nutrient constraints coupled with erratic rainfall have led to poor crop yields and occasionally to crop failure in sole cropping in the Guinea savanna of West Africa. We explored different maize-grain legume diversification and intensification options that can contribute to mitigating risks of crop failure, increase crop productivity under different soil fertility levels, while improving soil fertility due to biological N2-fixation by the legume. There were four relay patterns with cowpea sown first and maize sown at least 2 weeks after sowing (WAS) cowpea; two relay patterns with maize sown first and cowpea sown at least 3 WAS maize in different spatial arrangements. These were compared with groundnut-maize, soybean–maize, fallow-maize and continuous maize rotations in fields high, medium and poor in fertility at a site each in the southern (SGS) and northern (NGS) Guinea savanna of northern Ghana. Legumes grown in the poorly fertile fields relied more on N2-fixation for growth leading to generally larger net N inputs to the soil. Crop yields declined with decreasing soil fertility and were larger in the SGS than in the NGS due to more favourable rainfall and soil fertility. Spatial arrangements of relay intercrops did not have any significant impact on maize and legume grain yields. Sowing maize first followed by a cowpea relay resulted in 0.18–0.26 t ha−1 reduction in cowpea grain yield relative to cowpea sown from the onset. Relaying maize into cowpea led to a 0.29–0.64 t ha−1 reduction in maize grain yield relative to maize sown from the onset in the SGS. In the NGS, a decline of 0.66 and 0.82 t ha−1 in maize grain yield relative to maize sown from the onset was observed due to less rainfall received by the relay maize. Groundnut and soybean induced 0.38–1.01 t ha−1 more grain yield of a subsequent maize relative to continuous maize, and 1.17–1.71 t ha−1 more yield relative to relay maize across both sites. Accumulated crop yields over both years suggest that sowing maize first followed by cowpea relay is a promising ecological intensification option besides the more common legume–maize rotation in the Guinea savanna, as it was comparable with soybean–maize rotation and more productive than the other treatments.

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.

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.