WHARF:

World Hunger Alleviation through Response Farming

J. Ian STEWART, President
640 Portsmouth Ave.
Davis, CA 95616
530-753-1422
wharf@cal.net or ian@responsefarming.org

WHARF is a 501(c)(3) scientific, educational and charitable trust, founded in 1984 in Davis, California. WHARF's mission is to extend "Response Farming" research and practice worldwide (wherever warranted). Support is welcomed from all who have an interest in reducing hunger and poverty among the World's rural poor, and in ending Slash & Burn Agriculture, the most pervasive destroyer of tropical forests and the wildlife which inhabit them.  Your contribution may be in the form of a tax exempt gift, grant, or contract for research, training or consulting services.

Founding directors & professional advisory council members

WHARF/Response Farming origins and methodology

Response Farming springs from research on rainfall behavior and its predictability in a "cropping systems design" project in Kenya, sponsored by USDA/USAID. The methodology also includes crop yield estimation procedures developed earlier by Dr. J. Ian Stewart and colleagues at UC Davis, plus subsequent findings in global research on rainfall behavior sponsored by WHARF. At UCD, Stewart and colleagues pioneered studies of crop water requirements, crop capabilities to extract soil water when under stress, and crop yield responses to water deficits - and developed practical field methods of estimating these and related "water production functions" to guide improvement in water management for crop production. Findings were substantiated and broadened in coordinated field studies carried out by university research teams in four western states (CA, UT, CO, AZ).

In Kenya the project goal was to design sustainable cropping systems for low resource farmers in marginal rainfall zones, characterized by great seasonal rainfall variability, uncertainty, and recurrent drought. Despite the complete swing from large scale hi-tech irrigated farming in the western USA, to small scale lo-tech rainfed farming in Kenya, crop interactions with the soil-water-weather environment held to the same principles, and Western USA estimation procedures worked equally well in Africa. However, great rainfall variation soon made it clear that no fixed set of cropping procedures could both minimize the crop failure rate in poor seasons and produce above average yields to lift the family from utter poverty in good seasons. A need for flexibility in crop management implied a need also for some useful level of predictability of season rains. The selected predictor was the date of onset of the rainy season and research was focused on ways cropping season rainfall behavior (amount, duration, daily intensity, etc), or rain behavior in any particularly sensitive crop growth stage, changes with the date of onset of the rains. In other words, for any given crop(s), how do localized rainfall probabilities differ between seasons in which onset of the rains is "late" versus seasons when onset is "early"? Do probabilities differ enough to warrant changes in how farmers proceed in late vs. early seasons? If so, flexible or "opportunity cropping" can greatly reduce risks from insufficient seasonal rain, or its duration, or aberrant behavior in critical crop growth stages.

The answer is yes in most locations enjoying monsoonal or Mediterranean type rainfall regimes, i.e. the globe girdling belt termed the tropics and semi-tropics, plus all Mediterranean countries, California, Western Australia, South Africa's Capetown area, etc. This means Response Farming is applicable through all the developing world and certain areas located in the more advanced countries.

Response Farming analyses require localized daily rainfall records for farms, groups of farms, or a village, or groups of records representing projects, areas, regions, etc. Generally speaking, early seasons are superior to late seasons. Early seasons last longer and produce more water, usually also more water per day on average.

The initial analysis determines an onset date for each season of record - defined in terms of rainfall adequacy to start a crop within acceptable limits of risk - and then determines rainfall duration thereafter, quantifying amounts and daily intensities throughout the season, divided as desired into shorter time periods. Graphical analysis follows, illustrating how season duration, water amount, average daily intensity, amounts and intensities in specified growth stages, etc, have historically related to onset dates. The graphs show quantitatively how probabilities of different rainfall characteristics worsen with later onset.

The critical date separating early seasons from late seasons is selected arbitrarily by visual inspection of the graphs - usually the graph of season rainfall duration versus date of onset which clarifies when one should shift from a longer growing period variety to one with earlier maturity. The graph of season water amount and/or average water amount per day, is then used to determine if there should also be a change in the acreage apportionments of crops being grown, or even a change in the types of crops.

Reanalysis of the rainfall record, based on the above selected crops and their growing periods then allows determination of rainfall probabilities for each stage of growth. For example, early onset at some locations is often followed by relatively long dry periods before the rains gain strength again. Were seed planted and germinated by onset rains, the seedlings could die and require replanting. This risk is easily mitigated or even eliminated by redefining onset to require sufficient buildup of soil water (prior to seeding) to assure both germination and seedling survival. Similarly, should rain historically show too much weakness in the pollination period of growth, imposition of an "earliest acceptable planting date" (perhaps a week or so after onset) may shift that growth stage to a more secure rainfall period.

Having decided on crops, varieties, and acceptable planting criteria, the next step is to decide on slopes of plant rows to balance desired rainfall runoff (if any) with capture and infiltration of rain where it falls. For example, in Sri Lanka early onset rainfall intensities seldom threaten waterlogging of the root zone, so call for essentially flat rows to capture all of the rain. However, late seasons, though short, are unusually intense, often requiring surface drainage of the excess to prevent waterlogging. This fact has led to the ancient and ongoing practice of maintaining tanks (reservoirs) in each village to collect runoff and, following cessation of the rains, irrigating with it to extend the growing period for crops. Thus, seedbed preparation, particularly slopes, may differ in late seasons from that in early seasons.

The next decision concerns plant numbers and row spacings which, respectively, affect seasonal crop water requirements and time sequences of soil water extraction. Published water requirements and estimation methods, are predicated on relatively high plant populations - enough to reach a "Leaf Area Index" (LAI) of 3.0 or greater. But in many areas of low or uncertain rainfall, LAI seldom reaches 3.0, and may be only 1.0 or even less. When LAI is 1.0, the crop water requirement is about 70% or so of published figures. Reducing plant numbers in drier seasons - by lower seed rates and/or thinning of seedlings - may be crucial to the health of each plant left in the field, and its ability to produce a near-normal component of yield. Late season onset dates may dictate lower seeding rates. Then seedling period rains, say rains in the first 30 days after germination, become the best indicator as to whether to thin the crop or not.

Another key factor is fertilizer, especially nitrogen (N), which is costly, yet essential to markedly increase yields in good rainfall years. N should be used to attain target yields, based on expected rainfall. Happily, N applications may be split, with a portion applied at seeding time and a second portion at thinning time, but only if justified by good rains in the seedling period. If seedling period rains are weak, the second N application may be reduced or eliminated, and plant numbers reduced by thinning. To carry out the above described rainfall analyses and flexible cropping system design procedures for early versus late rainfall seasons, WHARF has gathered daily rainfall data representative of farming areas worldwide. Additionally, WHARF has created three highly specialized computer programs:

(1) "CONVERT" transforms ASCII files of daily rainfall and other meteorological parameters from collaborating scientists' data banks to WHARF format;

(2) "WHARFDAT" checks data quality, permits hand entry of data and/or error correction as required, adjusts data for desired units, stores, retrieves and prints them out in several forms useful for understanding of weather patterns. WHARFDAT also converts WHARF data files to ASCII format for export to collaborating scientists who so desire.

(3) "WHARF" analyzes daily rainfall records from the past as they would have impacted on crop production - determining onset/germination dates for each past season, and quantifying extractable water stored in the soil at germination - whether dryplanting or seeding only after attainment of a user defined "onset" of the rains - then quantifying rainfall amounts and intensities through any specified sequence of growth stages until maturity. If days to maturity are unspecified, the WHARF program will determine the general suitability of the rainfall regime for cropping, quantifying viable lengths of growing seasons for varietal selection, and season water supplies (germ soil water + all subsequent rainfall) which, when compared to known water requirements of alternative crops, facilitates selection of crop types to receive closer scrutiny. The unique aspect of the WHARF program is a highly sophisticated and accurate bare soil (or stubble-mulched) water balance algorithm which can track rains through fallow periods exceeding two years, quantifying amounts of water stored in the (future) root zone versus losses to evaporation.

PRACTICING RESPONSE FARMING AT THE FIELD LEVEL - Rainfall analyses will have revealed the critical date separating "early" from "late" seasons, and guided us in designing an early season cropping system (Plan A) with suitable modifications for late seasons (Plan B). Full details will have been communicated to farmers, who prepare in advance to follow either plan as soon as the current season date of onset is revealed. This may be done at a central point for all farmers in a localized area by WHARF program analysis of realtime rain events in the budding new season, using measurements from a representative met station nearby. After germination, seedling stage rains may be tracked to determine whether or not an additional application of N fertilizer is called for, and whether or not to reduce plant numbers by thinning.

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Web construction by: Don Lotter. / dwlotter@dcn.davis.ca.us