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Heerwaarden, J. van

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Heerwaarden
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J. van
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Heerwaarden, J. van
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0000-0002-4959-3914

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    The tricot approach: an agile framework for decentralized on-farm testing supported by citizen science. A retrospective
    (Springer Science + Business Media, 2024) de Sousa, K.; Etten, J. van; Manners, R.; Erna Abidin; Abdulmalik, R.O.; Bello Abolore; Kwabena Acheremu; Angudubo, S.; Aguilar, A.; Arnaud, E.; Adventina Babu; Barrios, M.; Benavente, G.; Boukar, O.; Cairns, J.E.; Carey, E.; Daudi, H.; Maryam Abba Dawud; Edughaen, G.; Ellison, J.; Esuma, W.; Sanusi Gaya Mohammed; van de Gevel, J.; Gomez, M.; Heerwaarden, J. van; Iragaba, P.; Kadege, E.; Assefa, T.; Kalemera, S.; Fadhili Salum Kasubiri; Kawuki, R.; Yosef Gebrehawaryat Kidane; Kilango, M.; Heneriko Kulembeka; Adofo Kwadwo; Madriz, B.; Masumba, E.; Mbiu, J.; Mendes, T.; Müller, A.; Moyo, M.; Kiddo Mtunda; Muzhingi, T.; Muungani, D.; Mwenda. E.T.; Nadigatla, G.R.; Ann Ritah Nanyonjo; Sognigbé, N.; Athanase Nduwumuremyi; Nshimiyimana, J.C.; Ephraim Nuwamanya; Hyacinthe Nyirahabimana; Occelli, M.; Olamide Olaosebikan; Ongom, P.O.; Ortiz-Crespo, B.; Oteng-Fripong, R.; Ozimati, A.; Durodola Owoade; Quiros, C.F.; Rosas, J.C.; Rukundo, P.; Rutsaert, P.; Milindi Sibomana; Sharma, N.; Nestory Shida; Steinke, J.; Ssali, Reuben; Suchini, J.G.; Teeken, B.; Theophilus Kwabla Tengey; Tufan, H.A.; Silver Tumwegamire; Tuyishime, E.; Ulzen, J.; Muhammad Lawan Umar; Onwuka, S.; Tessy Ugo Madu; Voss, R.C.; Yeye, M.; Zaman-Allah, M.
    Publication
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    Big data, small explanatory and predictive power: Lessons from random forest modeling of on-farm yield variability and implications for data-driven agronomy
    (Elsevier B.V., 2023) Silva, J.V.; Heerwaarden, J. van; Reidsma, P.; Laborte, A.G.; Tesfaye, K.; Ittersum, M.K. van
    Publication
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    Data-driven approaches can harness crop diversity to address heterogeneous needs for breeding products
    (National Academy of Sciences, 2023) Etten, J. van; de Sousa, K.; Cairns, J.E.; Dell'acqua, M.; Fadda, C.; Güereña, D.T.; Heerwaarden, J. van; Assefa, T.; Manners, R.; Müller, A.; Pè, M.E.; Polar, V.; Ramirez-Villegas, J.; Solberg, S.Ø.; Teeken, B.; Tufan, H.A.
    Publication
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    Big data, small explanatory power?: experiences with cereal yield variability across the globe
    (CIMMYT :, 2020) Silva, J.V.; Heerwaarden, J. van; Assefa, B.; Tesfaye, K.; Velasco, M.L.; Laborte, A.G.; Spätjens, L.; Reidsma, P.; Ittersum, M.K. van
    Publication
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    Maize crop nutrient input requirements for food security in sub-Saharan Africa
    (Elsevier, 2019) Berge, H.F.M. ten; Hijbeek, R.; Van Loon, M.P.; Rurinda, J.; Tesfaye, K.; Shamie Zingore; Craufurd, P.; Heerwaarden, J. van; Brentrup, F.; Schröder, J.J.; Boogaard, H.; De Groote, H.; Ittersum, M.K. van
    Nutrient limitation is a major constraint in crop production in sub-Saharan Africa (SSA). Here, we propose a generic and simple equilibrium model to estimate minimum input requirements of nitrogen, phosphorus and potassium for target yields in cereal crops under highly efficient management. The model was combined with Global Yield Gap Atlas data to explore minimum input requirements for self-sufficiency in 2050 for maize in nine countries in SSA. We estimate that yields have to increase from the current ca. 20% of water-limited yield potential to approximately 50–75% of the potential depending on the scenario investigated. Minimum nutrient input requirements must rise disproportionately more, with N input increasing 9-fold or 15-fold, because current production largely relies on soil nutrient mining, which cannot be sustained into the future.
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    Conservation agriculture with trees amplifies negative effects of reduced tillage on maize performance in East Africa
    (Elsevier, 2018) Ndoli, A.; Baudron, F.; Sida, T.S.; Schut, A.G.T.; Heerwaarden, J. van; Giller, K.E.
    Conservation agriculture (CA) is widely promoted in sub-Saharan Africa both in open fields and in agroforestry where the practice is known as ‘conservation agriculture with trees’ (CAWT). Although advantages and disadvantages of CA are well studied under sole cropping, less is known about its impact in agroforestry systems. The performance of open pollinated maize varieties under CA, CAWT, sole maize under conventional tillage (CT) and conventional tillage with trees (CTWT) was compared on-farm in equatorial savannah areas over four consecutive seasons in Rwanda and two seasons in Ethiopia. The tree species considered in the study were mature Grevillea robusta (A. Cunn.) and Senna spectabilis (DC.) in Rwanda and mature Acacia tortilis (Forssk.) in Ethiopia. Both CA and the presence of trees consistently reduced maize emergence, leaf area (LA), plant height, and maize yields. Crop emergence was significantly reduced under CAWT compared with CTWT. Maize emergence rates in CAWT and CTWT were respectively 46.9% and 70.1%, compared with 74.7% and 79.8% in sole maize under CA and CT. Grain yield in CAWT and CTWT were respectively 0.37 t dry matter (DM) ha−1 and 1.18 t DM ha−1 as compared with 1.65 t DM ha−1 and 1.95 t DM ha−1 in CA and CT. We conclude that CAWT strongly reduces crop yield in the equatorial savannah of East Africa. CA is incompatible with agroforestry under the conditions of our study. There is an urgent need for rigorous research to revisit if, when and where CAWT can generate benefits for smallholder farmers.
    Publication
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    Estimating maize genetic erosion in modernized smallholder agriculture
    (Springer, 2009) Heerwaarden, J. van; Hellin, J.; Visser, R.G.F.; Eeuwijk, F. van
    Replacement of crop landraces by modern varieties is thought to cause diversity loss. We studied genetic erosion in maize within a model system; modernized smallholder agriculture in southern Mexico. The local seed supply was described through interviews and in situ seed collection. In spite of the dominance of commercial seed, the informal seed system was found to persist. True landraces were rare and most informal seed was derived from modern varieties (creolized). Seed lots were characterized for agronomical traits and molecular markers. We avoided the problem of non-consistent nomenclature by taking individual seed lots as the basis for diversity inference. We defined diversity as the weighted average distance between seed lots. Diversity was calculated for subsets of the seed supply to assess the impact of replacing traditional landraces with any of these subsets. Results were different for molecular markers, ear- and vegetative/flowering traits. Nonetheless, creolized varieties showed lowdiversity for all traits. These varieties were distinct from traditional landraces and little differentiated from their ancestral stocks. Although adoption of creolized maize into the informal seed system has lowered diversity as compared to traditional landraces, genetic erosion was moderated by the distinct features offered by modern varieties.
    Publication