Asynchrony between nitrogen (N) released by organic materials and N demand by the crop leads to low N use efficiency. Optimizing the time of application could increase the N recovery. A field experiment was designed to determine the effects of time of application of Gliricidia sepium prunings and of the addition of small doses of inorganic N fertilizer on N recovery and yield of maize. Six split applications of gliricidia prunings (in October, December and February) were compared. The prunings were incorporated into the soil while fresh. The application in October was done four weeks before planting the maize. Higher N uptake and maize yields were obtained when gliricidia prunings were applied in October than when applied in December and February. The corresponding substitution values were 0.66, 0.32 and 0.20. Split applications of prunings prolonged mineral N availability in the soil until March but did not increase N uptake and maize grain yield compared to a sole application in October. Combinations of gliricidia prunings and inorganic fertilizer increased N uptake and maize yield over prunings alone but the effect was only additive. We concluded that application of gliricidia prunings in October was more efficient than application in December and February.

Nitrogen deficiency severely limits production of the bean–maize association grown by small-scale farmers in upland Peru. Sixty-four bean Rhizobium isolates were evaluated for induction of a plant growth response in pots of soil from the area and 14 of the most promising strains of these were tested on farmers' fields in 13 trials over a three year period. Bean yields were increased by inoculation with at least one Rhizobium strain in seven of the trials, with increases ranging from 0.21 to 0.68 t ha−1. Bean yields were not increased by the application of 120 kg N ha−1 to the intercrop. Maize yields were increased by Rhizobium inoculation in nine of the 13 trials by between 0.34 and 1.85 t ha−1. Maize responded to nitrogen fertilizer on the same nine farms. This Rhizobium selection strategy, although laborious, was effective in identifying strains that can be recommended for use as inoculants by farmers in the region.

The effects of temperature and soil water potential on maize germination were investigated in controlled environment conditions and the effects of depth of planting and a mulch on maize emergence were studied in a field experiment in eastern Kenya. The rate of germination increased to an optimum temperature of 33.6°C above a base temperature of 6.1°C and decreased above the optimum to zero germination at 42.9°C. The thermal time for median germination increased from 51.5°Cd to 56.4°Cd as soil matric potential decreased from -5 to -40 kPa. Soil water content, depth of planting, and their interaction had significant (P < 0.001) effects on final germination and emergence but mulch, or any interactions involving mulch, had no such effects. Increasing depth of planting by 1 cm increased the thermal time required for emergence by 2.8°Cd, and decreasing water content by 1% increased the thermal time required for emergence by 3.2°Cd.

Germinación y emergencia del maíz

The growth of roots and shoots was measured in stands of groundnut grown at a number of populations on stored water in central India. Total weight and length of roots per unit land area increased with population density, but the proportional increases were much less than for shoot weight. Consequently the root:total weight ratio increased from 0.3 in the densest stand to almost 0.5 in the widely spaced crop. The denser stands produced a greater proportion of their roots at depth. In wide rows there was little change in rooting density across the inter-row space.

Total dry matter per unit land area increased with population, although the weight per plant was less in denser stands. Although the crops were harvested prematurely, pod yield per unit land area, unlike total dry matter, was no greater in dense stands than in more widely spaced crops. The greatest number of pods per unit land area was recorded at an intermediate population density.

Onion bulbs were stored at 30°C at relative humidities of 50, 80 and 95 per cent in 1971–72 and at the same temperature at 35, 50, 60 and 70 per cent RH in 1972–73. Losses from rotting, sprouting and desiccation were recorded. The latter were lowest at 95 per cent RH and not correlated with humidity in the range 35–80 per cent RH. Rotting losses similarly were not correlated with humidity but were highest at the highest humidity.

Preliminary evidence is presented in this study for the existence of (1) intraspecific physiological variants of Striga hermonthica, with Gabob population as the most responsive strain to a range of Sorghum bicolor cultivars, and (2) a local Sudanese sorghum cultivar called Tetron with broad-spectrum resistance to striga. Thus Tetron may be recommended as another standard resistant cultivar with reference to Framida of East Africa.

Cotton (Gossypium hirsutum) is the main agricultural export commodity from Tanzania. The most significant disease of the crop is fusarium wilt caused by Fusarium oxysporum f.sp. vasinfectum. Phytosanitary measures instituted at the cotton ginneries to prevent the distribution, for planting, of seed infected with the wilt fungus have become difficult to apply since economic liberalization and the entry of the private sector into cotton ginning and lint marketing. Surveys of cotton fields, ginneries and cotton buying posts were conducted in order to determine the factors affecting disease incidence and spread. In affected fields, disease incidence was generally less than 5%. Where it was greater than this, wilt symptoms were associated with root damage caused by the root-knot nematode (Meloidogyne incognita). At a number of ginneries, herdsmen were allowed to remove seed husks that accumulate at the ginneries as a byproduct of oil extraction. The husks are used as cattle feed and this was identified as a potential source of disease spread. At the buying posts visited, there was no system for separating cotton varieties or for identifying seed cotton purchased from villages infected with fusarium wilt. As a result, seed subsequently distributed for planting is likely to be a source of infection for the spread of this disease. The implications of economic liberalization in the cotton sector are discussed with respect to seed distribution and management of fusarium wilt.

Land and crop management practices were studied to determine yield stability and feasible measures to improve productivity of dry-seeded rice. Variability of yields among farms that had grown dry-seeded rice on the entire farm every season during the period 1991–95 was lower than among farms that had consistently grown transplanted rice during the same period. Weed control is a major challenge for dry-seeded rice and almost all farmers used herbicides to control weeds. Farmers who grew a non-rice crop before the rice season had better weed control than those who did not. Ploughing intensity and the type of implement used for land preparation were not significant factors for weed control. Field bund management was one determinant of productivity differences among farmers. The use of cross-bunds or periphery- and cross-bunds improved the efficiency of rainwater conservation and input use, and increased yields. Fields with higher levelling precision had lower water stress and produced better yields. On average, a farmer lost 0.93 t ha−1 yield due to land-levelling deficiency. The division of large and medium farms into a number of smaller plots improved levelling precision and water control, resulting in higher yields.

Most previous studies focused on intercropping systems involving two-crop associations. However, there is much scope to improve existing cropping systems by devising and evaluating modifications that allow more effective use of the season. To this effect, experiments were conducted to quantify efficiency of sequential intercropping consisting of maize (Zea mays L.), common bean (Phaseolus vulgaris L.) and mung bean (Vigna radiata (L.) Wilczek) during 2007 and 2009 cropping seasons, in southern Ethiopia. Treatments included three- and two-crop associations and equivalent sole crops of components. Land equivalent ratio (LER) and area time equivalency ratio (ATER) were used to estimate intercropping advantage. Maize had the highest partial LER, 0.95, whenever mung bean comes first in the sequence. Comparable partial LERs were observed in common bean irrespective of planting times while mung bean had greater partial LERs from simultaneous rather than sequential planting. Maize had the highest competitive ratio (1.56) followed by common bean (0.67) and mung bean (0.53). The three-crop association involving simultaneous planting of maize with mung bean followed by common bean (MZ + MB − CB) gave the highest mean total LER of 1.66. This combination also had the highest combined productivity and maximum monetary gain, which is above the minimum acceptable marginal rate of return. It exceeded advantages from intercrops of maize–common bean by 41% and maize–mung bean by 23%. Thus, farmers would get greater advantage from practicing sequential intercropping in areas where the season is sufficient to grow long-duration maize.

Initial and residual effects of phosphorus, lime and potassium were studied on Natal Common and Dodoma Bold groundnuts. Double superphosphate (D.S.P., 42% P2O5) considerably increased yields of the first two crops. Lime was noticeably beneficial on Dodoma Bold but less so on Natal Common, while K depressed yields of both when applied without P. The LPK treatment yielded best with each variety, but initially P alone was most economic. Comparing D.S.P., Tororo superphosphate (T.S.P., 21% P2O5, 13% S) and Minjingu phosphate (M.P., 15% citric soluble P2O5), T.S.P. gave the best response (625 lb/acre over 3 years), more than double that of equivalent P2O5 as D.S.P. T.S.P.'s superiority is attributed mainly to its sulphur content. Though initially inferior, M.P. proved as good as D.S.P. over 3 years. 224 lb/acre T.S.P. in alter-nate years is recommended. After two or three crops, light applications of lime and potassium together would be beneficial.

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.

Long-term field experiments were conducted at Agra, Solapur and Hisar from 2000 to 2008 to identify efficient tillage and nutrient management practices and to develop predictive models that would describe the relationship between crop yields and monthly rainfall for rainfed pearl millet grown on arid and semi-arid Inceptisol, Vertisol and Aridisol soils. Nine treatments comprising a factorial combination of three tillage practices, viz., conventional tillage (CT), low tillage + interculture (LT1) and low tillage + herbicide (LT2) and three fertilizer treatments viz., 100% N from an organic source (F1), 50% organic N + 50% inorganic N (F2) and 100% inorganic N (F3) were tested in a split-plot design at the three locations. Studies revealed that tillage and fertilizer treatments, and their interactions, significantly influenced pearl millet grain yields at the three locations. Prediction models describing the relation between grain yield and monthly rainfall indicated that rainfall occurring in June, July and August at Agra; June and July at Solapur; and June and August at Hisar significantly influenced pearl millet grain yield attained by different treatments. The R2 values of the model ranged from 0.64 to 0.81 at Agra; 0.63 to 0.92 at Solapur, and 0.75 to 0.89 at Hisar. When averaged over all the treatment combinations, mean pearl millet grain yields varied from 1590 to 1744 kg ha−1 at Agra; 1424 to 1786 kg ha−1 at Solapur; and 1675 to 1766 kg ha−1 at Hisar while their corresponding sustainability yield indice (SYI) varied from 35.4 to 42.2%, 19.9 to 45.6% and 64.1 to 68.3%, respectively. At Agra (Inceptisol), CTF3 resulted in significantly higher mean net returns (Rs 11 439 ha−1), benefit-cost ratio (2.33), rainwater use efficiency (RWUE) (3.52 kg ha−1 mm−1) and the second best SYI (39.9%). At Solapur (Vertisol), the LT1F3 resulted in significantly higher net returns (Rs 12 818 ha−1), benefit-cost ratio (3.52), RWUE (3.89 kg ha−1 mm−1) and the fourth best SYI (42.6%). At Hisar (Aridisol), the LT1F3 treatment gave higher net returns (Rs 3866 ha−1), benefit-cost ratio (1.26), RWUE (5.05 kg ha−1 mm−1) and the fourth best SYI (67.8%). These treatment combinations can be recommended for their respective locations to achieve maximum RWUE, productivity and profitability.

Many smallholder farm systems in Uganda produce coffee as an important cash crop. Yet coffee yields are poor. To increase farmers’ production, a range of agronomic practices have been recommended by national and international agencies. Yet the adoption potential of recommendations differs between farm systems. To understand the differences in adoption potential of recommended coffee management practices in Uganda, we provide a typology of farm systems with coffee, assess the diversity between the farm types, and evaluate the current use of existing management recommendations for each farm type. Through factor analysis and cluster analysis of farms producing coffee, we identified five farm types: large coffee farms, farms with off-farm activities, coffee-dependent farms, diversified farms, and banana–coffee farms. The farm types were based on differences in size, and on the relative contributions of coffee, banana and off-farm labour to total household income. They also differ in the availability of the resources labour, land and cash, in coffee production and revenue, and in current use of most recommended practices. Qualitative analysis indicates that farm types have different constraints and opportunities to adopt recommendations. Our results highlight that an analysis of different farm systems with coffee production, a degree of definition beyond the ‘smallholder coffee farmer’ as a homogenous entity, is important in order to understand the scope for success or failure of recommended practices.

A model predicting biomass production and water use in tea plantations is described. Biomass production is calculated from the amount of light intercepted and a radiation conversion efficiency. Available assimilate (current production plus reserves) is distributed according to the ‘potential’ demand of each of the shoots, stems and roots. Any excess is stored in the stem and root reserve pool. In the case of the demand for assimilate exceeding the supply, allocation is according to the relative demands of each component. Simulations with the model suggest that assimilate supply is unlikely to limit shoot growth under most conditions. Soil water movement and crop water uptake are simulated using the water balance sub-model used by the CERES crop growth models. The model calculates a water stress factor (Φ) as the ratio of actual to potential crop transpiration, and uses this factor to adjust various crop processes such as dry matter production and shoot development and extension rates. Predicted yields match observed yields well across a range of watering treatments and for different years at sites in Tanzania and Zimbabwe, providing some degree of confidence in the model's ability to predict tea yields for environments in East Africa.

Maize (Zea mays)-mucuna (Mucuna pruriens) systems have been promoted to the smallholder farmers of the Los Tuxtlas region of southeastern Veracruz, Mexico. To determine on-farm performance, an agronomic assessment was conducted in 1995–97 replicating farmer conditions in four fields. Treatments were first- and second-season maize with first-season mucuna (system Zm-Mp/Zm), first-season maize with first- and second-season mucuna (system Zm-Mp/Mp), second-season maize following first-season mucuna (system Mp/Zm), and first- and second-season maize, no mucuna control. Data on mucuna biomass amount and quality as well as maize yield, yield components, and nutrient status were collected. Highest mucuna biomass was obtained in system Mp/Zm (leaf-stem-mulch biomass in 1996/97, 7.34 t ha−1, 147 kg ha−1 N), followed by systems Zm-Mp/Mp (5.06 t ha−1, 101 kg N ha−1) and Zm-Mp/Zm (2.75 t ha−1, 50 kg N ha−1). Second-season maize yield was increased over that of the control by 45–58% (0.15–0.23 t ha−1) in system Zm-Mp/Zm and by 118% (0.60 t ha−1) in system Mp/Zm. Mucuna did not increase first-season maize yield. Climatic constraints make second-season maize production risky and yield increases due to mucuna are low in absolute terms, perhaps not offsetting labour costs (systems Zm-Mp/Zm and Mp/Zm) or loss of first-season maize (Mp/Zm).

Twenty one genotypes belonging to Spanish, Valencia and Virginia groups of groundnut were studied at Patancheru and a further seventeen at Delhi. Their relative performance based on a large number of characters spanning the entire growth phase was assessed. Nitrogenase activity and nodule mass were measured at three stages of crop growth starting from first flowering, and these two characters alone when measured at 30 days after flowering closely matched the measure of relative performance based on the entire set of characters.

The complex dynamics of the sulphur (S) cycle has prompted several questions concerning its bioavailability and evaluation by different extraction methods, and few studies under field conditions have been performed to elucidate available S on Brazilian soils under no-till (NT) cropping systems. A field experiment examined the effects of phosphogypsum (PG) applications on nutrient uptake and availability of S to maize and wheat crops under an NT system aiming to establish critic levels of S on an Oxisol (clay, kaolinitic, Rhodic Hapludox) in Parana state, Brazil. PG at the rates of 0, 3, 6 and 9 t ha−1 was applied on the surface of the plots in 1998 upon conversion from pasture to an NT cropping system, and in 2004 subplots received either 0 or 6 t ha−1 of PG on the surface. Effects of PG applications on nutrient uptake and available soil SO4-S to the maize and wheat crops were evaluated in 2004–2005. Increasing the surface-applied PG rate in 1998 increased Mg uptake by maize, and N, K, Ca and Mg uptake by wheat plants. Reapplication of PG in 2004 increased the uptake of N and P by maize, and the uptake of N, K, Ca and Mg by wheat plants. The PG rates surface-applied in 1998 have resulted in a long-term residual effect on soil by increasing SO4-S in surface and subsoil layers 6.5 and 7.5 years after application, affecting aboveground biomass, S uptake and S content in the leaves of the wheat crop. The reapplication of PG in 2004 increased maize S uptake, S content in leaves and grains and S exported by maize harvest, and increased wheat aboveground biomass, S uptake and S content in leaves. These effects were due to increasing available soil SO4-S from different depths extracted by 0.5 M ammonium acetate (NH4OAc) along with 0.25 M acetic acid (HOAc) and 0.01 M calcium phosphate (Ca(H2PO4)2). Both extractants were very similar in their ability to assess available soil S in these crops, and the 0–0.20-m layer is shown to be adequate for evaluating the concentration of available SO4-S in maize and wheat cultivated under NT.

Agricultural research and development (R&D) would benefit from reliable yet cheap technology uptake indicators to guide decision making. The paper explores the use of village surveys to monitor technology use and illustrates this through two empirical case studies into tillage dynamics in the Trans-Gangetic Plains in northwest India. The first case study is a revisit of 50 communities surveyed earlier in Haryana State. The second case study is a new and wider representative sample of 120 villages across Haryana and Punjab States. The case studies illustrate that after an initial rapid spread of tractor-drawn zero tillage drills for wheat seeding in these intensive systems, the zero + reduced tillage area seems to have stabilized there at between a fifth and a quarter of the wheat area. Conventional tillage for wheat continues to decline, with an increased use of rotavators making up the difference – but its intensive shallow tillage goes against the conservation agriculture tenets. The paper illustrates the potential of village surveys to provide timely and cost-effective feedback to agricultural R&D.

Prior on-station research showed that sowing dates, sowing density and applications of fungicide and phosphorus (P) increased groundnut (Arachis hypogaea) pod yield by 60–80%. Farmer-managed trials were conducted in the Wa district of the Upper West Region of Ghana from 2004 to 2007 to test the yield response to sowing density, fungicide and P and to assess economic returns of these technologies to farmers. Treatments included: an early maturing groundnut cultivar, Chinese, sown at farmers' density (5–8 plant m−2) without fungicide and without P application (T1, control), with fungicide sprays alone (T2), or with fungicide and P application (T3), cultivar Chinese sown at recommended (higher) density (20 plant m−2) with fungicide and P application (T4), and a full season cultivar, Manipinter, with fungicide and P application (T5). Soil fertility, sowing density, days from sowing to first weeding, incidence and severity of leaf-spot disease and plant population at final harvest were recorded. Relative to farmers' practice, pod yield of cultivar Chinese was significantly increased by 80% with fungicide sprays alone, 108% with fungicide and P application, and 113% with fungicide and P application at higher sowing density. Cultivar Manipinter treated with fungicide and P gave 107% increase in pod yield relative to farmers' practice. Correlation and stepwise regression analyses suggested that major determinants of groundnut pod yield in farmers' fields were plant density, leaf-spot disease and P availability. The increase in yield with fungicide and P application translated into a 4–5-fold increase in gross margin for farmers in the region. Returns to labour and labour productivity were doubled with combined use of fungicide and P fertilizer.