Jacques Lançon

An improved methodology for integrated crop management systems

Designing innovative combinations of techniques to improve the sustainability of a cropping system is a major challenge in many regions of the world. The available techniques are often added together, and assessed for yield only, rather than combined in an integrated approach. We than developed here a methodology to design and assess a sustainable crop management system adapted to a specific set of constraints. Based on the prototyping approach, this methodology takes advantage of expert knowledge on cotton cropping techniques such as no-till, cover crop, varieties and growth regulator, with innovative potential but which are not yet properly simulated by actual crop models. It involves four successive steps: (1) identification of the local sets of constraints to crop production, and selection of relevant criteria for sustainability assessment, (2) elaboration of a cropping system prototype and its assessment indicators adapted to a target set of constraints, (3) on-station assessment and adjustment of the prototype, and (4) on-farm evaluation and adjustment of the prototype. We describe here the methodology, and how its first three steps were implemented to build and test a prototype for late-planted cotton with low input availability in West Africa. A new cropping system was designed, which included new genotypes, increased plant stand, lower rates of fertilisers and the use of herbicides and growth regulators. Fourteen indicators were selected to assess the economic, environmental and social performance of the prototype. The prototype was then tested in Mali, Cameroon, and Benin in 2002 and 2003. Our findings show that this prototype improved farmers’ income by about +35% in 2002 and +20% in 2003, and increased labour productivity by about +5 to +20%. It achieved a satisfactory environmental performance, similar to the control, with positive mineral balances. The prototype still requires extra labour, skill and money to implement, and therefore requires further adjustment.

BREEDING NEW COTTON VARIETIES TO FIT THE DIVERSITY OF CROPPING CONDITIONS IN AFRICA: EFFECT OF PLANT ARCHITECTURE, EARLINESS AND EFFECTIVE FLOWERING TIME ON LATE-PLANTED COTTON PRODUCTIVITY

SUMMARY In most cotton-growing regions of West and Central Africa where rainfed conditions prevail, cropping conditions are highly diversified since the crop is planted over an extended period. We studied production and development patterns in 10 cotton (Gossypiumhirsutum) varieties to determine the most efficient strategies that could be transformed into breeding traits. Four trials were carried out between 2002 and 2003 in two cotton-growing areas in Benin to compare the 10 varieties at three stand densities and two planting dates. The parameters monitored were the mean first flower opening date (FF), effective flowering time (EFT), plant height at harvest (HH), height to node ratio (HNR), length of fruiting branch (LFB), number of vegetative branches (NVB) and average boll retention at the first position of the fruiting branches (RP1). We identified two ideotypes that yielded better than the others: (i) Mar 88-214 performed well under late planting–high stand density conditions and was characterized by low vegetative growth and early flowering onset, a short flowering period and low RP1; (ii) H 279-1 performed especially well under early planting–low stand density conditions and was characterized by high vegetative growth, late flowering, long EFT and high RP1. We propose a breeding strategy for both ideotypes based on seven indicators with high heritability (FF, HH, HNR, and LFB) or medium heritability (NVB, EFT, and RP1).

Experiment-based prototyping to design and assess cotton management systems in West Africa

Designing innovative combinations of techniques to improve the sustainability of cropping systems in poor countries is a major challenge. Here, we developed a prototyping methodology to design, assess and adapt a crop management system for a specific set of constraints. It was applied in Mali with the aim of designing innovative prototypes of cotton management systems to be further tested and adapted by farmers. The prototype aimed at shortening the cotton cycle to overlap the rainy season. The prototype is particularly suited for late sowing and for regions where rainfall is often insufficient. We propose a conceptual model that organizes technical interventions to shorten the cotton cycle. We developed a set of indicators to evaluate the relevance of each modified technical intervention, by comparison with current farmer practices. We evaluated the overall performances of the prototype by taking into account economic, environmental and social factors. The prototype was tested and adjusted in six trials between 2002 and 2004. Our results show that the cotton growth cycle was reduced by 15 days on average, mainly through the shortening of the flowering period. The combination of much higher stand density than currently applied in the region and application of the growth regulator mepiquat chloride produced a much higher number of bolls per hectare of +69%. The prototype produced higher seed-cotton yields, of +44% on average, and much higher gross margin than the standard cotton management system. The method was therefore successful in designing a new cotton management system that helps farmers to adapt to diverse cropping conditions.

EFFECTIVE FLOWERING TIME VARIATIONS IN UPLAND COTTON (GOSSYPIUM HIRSUTUM) AT DIFFERENT PLANTING DATES AND STAND DENSITIES IN BENIN

Effective flowering time in Gossypium hirsutum cotton plants was studied with the aim of enhancing decision making on the best varieties to plant according to the planting date under rainfed cropping conditions. Trials were conducted at two sites in a cotton-growing area of Benin in 2002 and 2003. A split-split plot design with three replicates was used to compare 10 cotton varieties, with different growth cycle lengths and morphology, at three stand densities (42 000, 125 000, 167 000 plants ha-I) and two planting dates (standard planting in June and late planting). The flowering period was characterized by the mean first flower opening date (FF), which is an indicator of flowering earliness, and by the opening date of the last flower giving rise to a first-position boll on fruiting branches (LFP1). Effective flowering time (EFT) was calculated as the difference between LFP1 and FE EFTs differed markedly in the 10 cotton varieties tested and this parameter could not be predicted on the basis of flowering earliness. Late planting and high planting rates delayed first-flower opening, accelerated last-boll development and reduced the effective flowering time. This latter factor should be taken into account in cotton breeding programmes so that varieties adapted to local rainfall constraints can be recommended to growers while also enhancing crop management sequences. (Resume dauteur)

A SIMPLE METHOD FOR ESTIMATING THE END OF EFFECTIVE FLOWERING IN UPLAND COTTON (GOSSYPIUM HIRSUTUM)

SUMMARY In cotton (Gossypium hirsutum), it is hard to determine the exact date when reproductive growth ceases on the basis of field observations, as compared to more visible factors such as the onset of flowering or boll opening. It is, however, essential to characterize the growth cycle in order to determine what varieties are suitable for planting in different climatic and local cropping conditions. We estimated the end of the effective flowering period on the basis of the opening date of the last flower giving rise to a first-position boll on fruiting branches (LFP1), and propose a simple method for estimating this date. This study, conducted in 2002 and 2003 at Okpara, Benin, involved a comparison of six cotton varieties planted at two different dates (June and July). Plants were monitored to determine the dates when flowers opened at each position on fruiting branches. The LFP1 indicator made a clear distinction between varieties. This highly heritable trait, which was found to be closely correlated with other earliness criteria, could be used to characterize the length of the growth cycle in cotton varieties.